This work was supported by the Natural Sciences and Engineering Council of Canada and the Ontario Ministry of Research and Innovation.

1. Preparations for Cell Culture
<ol>
	<li>Purchase commercially available stocks of human cells. 
	NOTE: This protocol utilizes HCT116 colorectal carcinoma and primary human renal proximal tubular epithelial cells (HRPTEC).</li>
	<li>Make 500 ml medium for culture of HCT116: Dulbecco&#39;s Modified Eagle Medium (DMEM)/High glucose medium supplemented with 7.5% Fetal Bovine Serum (FBS) and 1% Penicillin/Streptomycin (P/S).</li>
	<li>Make 500 ml medium for culture of HRPTEC: Epithelial cell medium supplemented with 5% FBS, 1% epithelial cell growth supplement, and 1% P/S.</li>
	<li>Prepare 500 ml of 1x Phosphate-Buffered Saline (PBS): 140 mM NaCl, 3 mM KCl, 10 mM Na2HPO4, 15 mM KH2PO4. Adjust pH to 7.4 and sterilize by autoclaving for 40 min at 121 &#176;C.</li>
</ol>
2. Initiation of Cell Culturing
<ol>
	<li>Carefully aspirate the medium from a 80-90% confluent dish without disturbing the cells.</li>
	<li>Aliquot 3-5 ml of 1x PBS per culture dish, gently rock each flask to coat the surface area of the dish, and carefully aspirate the 1x PBS. Repeat for a second 1x PBS wash.</li>
	<li>Aliquot 3 ml of 0.05% trypsin-ethylenediaminetetraacetic acid (EDTA) into each culture dish and gently rock to evenly coat the cells with trypsin-EDTA. Incubate at 37 &#176;C for 2-3 min.</li>
	<li>Transfer the detached cells into a 15 ml centrifuge tube and centrifuge at 4,000 x g for 90 sec.</li>
	<li>Resuspend cell pellet in 1 ml of complete DMEM.</li>
	<li>Count cells using a haemocytometer. Calculate how many non-pyrogenic and polystyrene 100 mm cell culture dishes are required to achieve an initial seeding density of approximately 2,500-5,000 cells per cm2.</li>
	<li>Pre-warm complete cell culture medium made in steps 1.2 or 1.3 in a 37 &#176;C water bath for 30-45 min.</li>
	<li>Decontaminate the medium bottle and cell vial with 70% ethanol. From this point forward all operations should be performed aseptically.</li>
	<li>Aliquot 6 ml of complete DMEM into as many 100 mm cell culture dishes required to use the entire volume of frozen cells within the seeding density mentioned in step 2.6.</li>
	<li>Transfer the volume of cell suspension calculated in step 2.6 to each of the 100 mm culture dishes. Rock each plate manually to evenly distribute the cells over the surface of the plate.</li>
	<li>Place the seeded 100 mm cell culture dish in the incubator at 37 &#176;C in a 5% CO2 atmosphere. Allow cells to incubate at least 24 hr before the next steps.</li>
</ol>
3. Subculturing
<ol>
	<li>View each cell culture dish under a microscope to determine the percentage of cell confluency (% cells covering the area of the dish). Return cells to the incubator and pre-warm complete medium and 1x PBS. Proceed to the next step if the cells are 80-100% confluent.</li>
	<li>Carefully aspirate the spent medium without disturbing the cells in each culture dish.</li>
	<li>Aliquot 3-5 ml of 1x PBS per culture dish, gently rock each flask to coat the surface area of the dish, and carefully aspirate the 1x PBS. Repeat for a second 1x PBS wash.</li>
	<li>Aliquot 3 ml of 0.05% trypsin-EDTA into each culture dish and gently rock to evenly coat the cells with trypsin-EDTA. Incubate at 37 &#176;C for 2-3 min.</li>
	<li>During this incubation, aliquot 10 ml of complete medium into as many culture dishes are required to obtain cell density of 2,500-5,000 cells per cm2.</li>
	<li>When the cells have detached from the plate, quickly add 3 ml of 1x defined trypsin inhibitor and gently swirl the dish for 1 min to ensure that all of the trypsin-EDTA has been neutralized.</li>
	<li>Transfer the detached cells into a sterile 15 ml centrifuge tube and set aside. Add 3 ml 1x PBS to the dish to gather any remaining cells, and transfer that to the same 15 ml centrifuge tube.</li>
	<li>Pellet the cells by centrifuging 150 x g for 5 min.</li>
	<li>Aspirate the supernatant and resuspend the cell pellet in 3 ml of complete medium.</li>
	<li>Count cells using a haemocytometer and seed 150 mm culture dishes containing 15 ml of complete medium to obtain a cell density of 2,500-5,000 cells per cm2. Use two 150 mm for each cap-binding assay. 
	NOTE: Oxygen diffusion to cells through liquid media is dependent on the volume36. It is recommended to keep the volume of the media consistent between experiments whether adherent cells or cells in suspension are used. Media can be pre-conditioned (incubated in the workstation for 24 hr as discussed in Discussion) to avoid these variabilities in diffusion.</li>
	<li>Place the seeded-culture dishes in the incubator at 37 &#176;C in a 5% CO2 atmosphere. Allow cells to incubate at least 24 hr before proceeding to the next steps.</li>
</ol>
4. Physioxic Exposure
<ol>
	<li>View the cells under the microscope. For best results, ensure that cells are 70-80% confluent for a 24 hr exposure, 50-60% confluent for a 48 hr exposure, and 40-50% confluent for a 72 hr exposure.</li>
	<li>Place the cells into a hypoxia workstation for the desired time (24, 48, or 72 hr depending on the experiment).</li>
	<li>Set the workstation to the appropriate physioxia. 
	NOTE: For example, a 3% O2 setting would be accompanied by 5% CO2 and 92% N2. 
	NOTE: If oxygen fluctuations within a dynamic range are desired over a specific timeline, program the schedule into the instrument or manually adjust the oxygen settings at the desired intervals.</li>
	<li>Set the humidity to 60%. The workstation atmosphere is very dry nonetheless, and media will noticeably evaporate during long experiments (&#62;48 hr). Keep a media reserve in a cell culture flask within the workstation (so that the media is equilibrated with the workstation atmosphere) to replenish the media in the cell culture dishes. 
	NOTE: Any solution that will interact with the cells prior to lysis (such as PBS and trypsin-EDTA) should be pre-conditioned for 24 hr before use within the hypoxia workstation so that the dissolved oxygen equilibrates with the atmospheric oxygen36.</li>
	<li>Keep cells within the workstation until lysis.</li>
</ol>
5. Preparing Buffers for Cap-binding Assay
<ol>
	<li>Prepare 1x Tris-buffered Saline (TBS).
	<ol>
		<li>In 800 ml of dH2O, dissolve 8.76 g NaCl and 6.05 g Tris Base.</li>
		<li>Bring the solution to a final pH of 7.4 using 1 M HCl.</li>
		<li>Bring the final volume to 1 L using dH2O.</li>
	</ol>
	</li>
	<li>Prepare non-denaturing lysis buffer. Prepare lysis buffer the day of the cap-binding assay. Make extra lysis buffer to wash the blank agarose beads and the &#947;-aminophenyl-m7GTP agarose C10-linked beads (steps 7.9 and 7.13).
	<ol>
		<li>In 7 ml of dH2O, add 160 &#181;l 5 M NaCl, 160 &#181;l 1 M Tris-HCl pH 7.4, 40 &#181;l 200 mM NaF, 40 &#181;l 1 M MgCl2, and 40 &#181;l 1 mM sodium orthovanadate.</li>
		<li>Add 40 &#181;l of Igepal to the 7 ml solution. Cut the tip of the pipette to help retrieve Igepal as it is extremely viscous.</li>
		<li>Mix by pipetting up and down, or vortex, the 7 ml solution until all of the Igepal has been dissolved.</li>
		<li>Raise the final volume of the solution to 8 ml and keep on ice.</li>
	</ol>
	</li>
	<li>Prepare 4x Sodium Dodecyl Sulfate (SDS)-PAGE Sample Buffer.
	<ol>
		<li>In a beaker, combine 16 ml 1 M Tris-HCl pH 6.8, 12.64 ml glycerol, and 8 ml dithiothreitol (DTT).</li>
		<li>Add 3.2 g of SDS and 0.16 g of bromophenol blue. Allow powder to fully dissolve by mixing with a magnetic stir bar.</li>
		<li>Aliquot into 1.5 ml microcentrifuge tubes and store at -20 &#176;C.</li>
	</ol>
	</li>
</ol>
6. Cell Lysis
<ol>
	<li>Prepare non-denaturing lysis buffer and keep on ice the day of the cap-binding assay.</li>
	<li>Pre-warm 1x PBS and trypsin in a 37 &#176;C water bath for 30 min.</li>
	<li>Aliquot 980 &#181;l of lysis buffer into a 1.5 ml microcentrifuge tube for each cap-binding assay being performed.</li>
	<li>Add 10 &#181;l of 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride and 10 &#181;l of 100x protease inhibitor cocktail to the 980 &#181;l of lysis buffer. Keep on ice.</li>
	<li>Discard the media from each 150 mm dish in a waste container within the hypoxia workstation.</li>
	<li>Wash the cells with 3-4 ml of warm 1x PBS and discard all of the liquid.</li>
	<li>Add 1 ml of warm 0.05% trypsin-EDTA to each dish and let sit for 2 min or until cells are no longer adhered to the plate.</li>
	<li>Using a pipette, transfer the cells of one plate to a 1.5 ml microcentrifuge tube. Repeat as needed so that each plate of cells is transferred to a separate 1.5 ml microcentrifuge tube.</li>
	<li>Centrifuge the 1.5 ml microcentrifuge tubes at 6,000 x g for 90 sec to pellet the cells.</li>
	<li>Aspirate the trypsin using a pipette without disturbing the pellet. If the pellet is disturbed, re-centrifuge the 1.5 ml microcentrifuge tube at 6,000 x g for 90 sec.</li>
	<li>Wash the cells with warm 1x PBS by gently pipetting 200 &#181;l of PBS into the tube just above the pellet. Re-centrifuge if the pellet is disturbed.</li>
	<li>Aspirate the PBS without disturbing the pellet.</li>
	<li>Pipette 500 &#181;l from the 1 ml prepared lysis buffer solution onto the first cellular pellet. Resuspend the pellet entirely by pipetting up and down.</li>
	<li>Combine the resuspended cells with the second cell pellet and resuspend the second pellet by pipetting up and down. Repeat this process until all pellets have been combined and resuspended for each sample.</li>
	<li>Combine the lysate with the remaining 500 &#181;l of lysis buffer in a 1.5 ml microcentrifuge tube.</li>
	<li>Remove samples from the hypoxia workstation. 
	NOTE: After adding lysis buffer, all subsequent steps are to be performed in ambient air as the hypoxia workstation is set to 37 &#176;C and the following steps are to be performed cold (4 &#176;C or on ice).</li>
	<li>Lyse the cells using gentle agitation by rotating the samples at 4 &#176;C for 1.5-2 hr.</li>
	<li>Centrifuge the lysed cells at 12,000 x g for 15 min at 4 &#176;C to remove cellular debris.</li>
	<li>Transfer the lysate to a new 1.5 ml microcentrifuge tube and discard the pellet.</li>
	<li>Reserve a portion (5-10%) of the supernatant to be used as a whole cell lysate input control for future western blot analysis.</li>
</ol>
7. Cap-binding Assay
<ol>
	<li>For each sample, transfer 50 &#181;l of the blank agarose bead control slurry and 50 &#181;l of the &#947;-aminophenyl-m7GTP agarose C10-linked bead slurry to separate 1.5 ml microcentrifuge tubes. Use scissors to remove the tip of the pipette to facilitate collection of the bead slurry.</li>
	<li>Pellet the beads by centrifuging the slurry at 500 x g for 30 sec.</li>
	<li>Remove the supernatant carefully and resuspend the beads in 500 &#181;l of TBS.</li>
	<li>Repeat steps 7.2 and 7.3. Pellet the beads at 500 x g for 30 sec and remove the supernatant.</li>
	<li>Transfer the supernatant containing the lysate from step 6.19 to the 1.5 ml microcentrifuge tube containing the blank agarose beads. 
	NOTE: The blank agarose beads act as a pre-clearing step to remove proteins from the lysate that non-specifically interact with the bead.</li>
	<li>Incubate for 10 min at 4 &#176;C with gentle agitation.</li>
	<li>Pellet the blank agarose beads by centrifuging at 500 x g for 30 sec.</li>
	<li>Transfer the lysate to the 1.5 ml microcentrifuge tube containing the &#947;-aminophenyl-m7GTP agarose C10-linked beads.</li>
	<li>Wash the blank agarose beads by resuspending the beads in 500 &#181;l of lysis buffer, pelleting the beads by centrifuging at 500 x g for 30 sec, and discarding the supernatant. Repeat this four times for a total of five washes.</li>
	<li>Resuspend the blank agarose beads in 1x SDS-PAGE sample buffer, and boil the beads for 90 sec at 95 &#176;C. Store at -20 &#176;C for future western blot analysis to observe whether the protein of interest binds non-specifically to the bead.</li>
	<li>Incubate the lysate with the &#947;-aminophenyl-m7GTP agarose C10-linked beads with gentle agitation for 1 hr at 4 &#176;C to capture cap-binding proteins.</li>
	<li>Pellet the &#947;-aminophenyl-m7GTP agarose C10-linked beads by centrifuging at 500 x g for 30 sec. Discard the supernatant.</li>
	<li>Wash the &#947;-aminophenyl-m7GTP agarose C10-linked beads by repeating step 7.9.</li>
	<li>Resuspend the beads in 600 &#181;l of lysis buffer.</li>
	<li>Add GTP to a final concentration of 1 mM.</li>
	<li>Incubate the &#947;-aminophenyl-m7GTP agarose C10-linked beads + 1 mM GTP with gentle agitation for 1 hr at 4 &#176;C. Note: This will disassociate proteins that non-specifically interact with m7GTP (i.e., also interact with non-methylated GTP).</li>
	<li>Pellet the &#947;-aminophenyl-m7GTP agarose C10-linked beads by centrifuging at 500 x g for 30 sec.</li>
	<li>Transfer the supernatant to a new 1.5 ml microcentrifuge tube and add 200 &#181;l of 4x SDS-PAGE sample buffer (50 mM Tris-HCl, 100 mM DTT, 2% SDS, 0.1% bromophenol blue, and 10% glycerol). Store the GTP control sample at -20 &#176;C for future western blot analysis37. Wash the beads by repeating step 7.9.</li>
	<li>Resuspend the beads in 1x SDS-PAGE sample buffer (50 mM Tris-HCl, 100 mM DTT, 2% SDS, 0.1% bromophenol blue, and 10% glycerol), and boil at 95 &#176;C for 90 sec. Store the m7GTP-bound fraction at -20 &#176;C for future western blot analysis37.</li>
</ol>

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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liver+tissue+partial+pressure+of+oxygen+and+carbon+dioxide+during+partial+hepatectomy.">Liver tissue partial pressure of oxygen and carbon dioxide during partial hepatectomy.</a> Br J Anaesth. 92 (5), 735-737 (2004).</li><li>Muller, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Renocortical+tissue+oxygen+pressure+measurements+in+patients+undergoing+living+donor+kidney+transplantation.">Renocortical tissue oxygen pressure measurements in patients undergoing living donor kidney transplantation.</a> Anesth Analg. 87 (2), 474-476 (1998).</li><li>Richardson, R. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+skeletal+muscle+intracellular+oxygenation:+the+impact+of+ambient+oxygen+availability.">Human skeletal muscle intracellular oxygenation: the impact of ambient oxygen availability.</a> J Physiol. 571 (Pt 2), 415-424 (2006).</li><li>Harrison, J. S., Rameshwar, P., Chang, V., Bandari, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxygen+saturation+in+the+bone+marrow+of+healthy+volunteers.">Oxygen saturation in the bone marrow of healthy volunteers.</a> Blood. 99 (1), 394 (2002).</li><li>Gleadle, J., Ratcliffe, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Hypoxia. , (2001).</li><li>Gluckman, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hematopoietic+reconstitution+in+a+patient+with+Fanconi's+anemia+by+means+of+umbilical-cord+blood+from+an+HLA-identical+sibling.">Hematopoietic reconstitution in a patient with Fanconi's anemia by means of umbilical-cord blood from an HLA-identical sibling.</a> N Engl J Med. 321 (17), 1174-1178 (1989).</li><li>Parrinello, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxygen+sensitivity+severely+limits+the+replicative+lifespan+of+murine+fibroblasts.">Oxygen sensitivity severely limits the replicative lifespan of murine fibroblasts.</a> Nat Cell Biol. 5 (8), 741-747 (2003).</li><li>Jewell, U. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+HIF-1alpha+in+response+to+hypoxia+is+instantaneous.">Induction of HIF-1alpha in response to hypoxia is instantaneous.</a> FASEB J. 15 (7), 1312-1314 (2001).</li><li>Newby, D., Marks, L., Lyall, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissolved+oxygen+concentration+in+culture+medium:+assumptions+and+pitfalls.">Dissolved oxygen concentration in culture medium: assumptions and pitfalls.</a> Placenta. 26 (4), 353-357 (2005).</li><li>Towbin, H., Staehelin, T., Gordon, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophoretic+transfer+of+proteins+from+polyacrylamide+gels+to+nitrocellulose+sheets:+procedure+and+some+applications.">Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications.</a> Proc Natl Acad Sci U S A. 76 (9), 4350-4354 (1979).</li><li>Haghighat, A., Mader, S., Pause, A., Sonenberg, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Repression+of+cap-dependent+translation+by+4E-binding+protein+1:+competition+with+p220+for+binding+to+eukaryotic+initiation+factor-4E.">Repression of cap-dependent translation by 4E-binding protein 1: competition with p220 for binding to eukaryotic initiation factor-4E.</a> EMBO J. 14 (22), 5701-5709 (1995).</li><li>Pyronnet, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+eukaryotic+translation+initiation+factor+4G+(eIF4G)+recruits+mnk1+to+phosphorylate+eIF4E.">Human eukaryotic translation initiation factor 4G (eIF4G) recruits mnk1 to phosphorylate eIF4E.</a> EMBO J. 18 (1), 270-279 (1999).</li><li>Okumura, F., Zou, W., Zhang, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ISG15+modification+of+the+eIF4E+cognate+4EHP+enhances+cap+structure-binding+activity+of+4EHP.">ISG15 modification of the eIF4E cognate 4EHP enhances cap structure-binding activity of 4EHP.</a> Genes Dev. 21 (3), 255-260 (2007).</li><li>Kedersha, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+that+ternary+complex+(eIF2-GTP-tRNA(i)(Met))-deficient+preinitiation+complexes+are+core+constituents+of+mammalian+stress+granules.">Evidence that ternary complex (eIF2-GTP-tRNA(i)(Met))-deficient preinitiation complexes are core constituents of mammalian stress granules.</a> Mol Biol Cell. 13 (1), 195-210 (2002).</li><li>Gu, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insights+into+the+structure,+mechanism,+and+regulation+of+scavenger+mRNA+decapping+activity.">Insights into the structure, mechanism, and regulation of scavenger mRNA decapping activity.</a> Mol Cell. 14 (1), 67-80 (2004).</li><li>Szczepaniak, S. A., Zuberek, J., Darzynkiewicz, E., Kufel, J., Jemielity, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Affinity+resins+containing+enzymatically+resistant+mRNA+cap+analogs--a+new+tool+for+the+analysis+of+cap-binding+proteins.">Affinity resins containing enzymatically resistant mRNA cap analogs--a new tool for the analysis of cap-binding proteins.</a> RNA. 18 (7), 1421-1432 (2012).</li><li>Joshi, B., Cameron, A., Jagus, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+mammalian+eIF4E-family+members.">Characterization of mammalian eIF4E-family members.</a> Eur J Biochem. 271 (11), 2189-2203 (2004).</li></ol>

The authors declare that they have no competing financial interests.

The analysis of cap-binding proteins in human cells exposed to physiological oxygen conditions can allow for the identification of novel oxygen-regulated translation initiation factors. The affinity of these factors for the 5&#39; cap of mRNA or other cap-associated proteins can be measured by the strength of their association to m7GTP-linked Agarose beads. One caveat of this technique is that it measures the cap-binding potential of proteins post-lysis, but it is performed under non-denaturing conditions that...

Translational control is emerging as an equally important step to transcriptional regulation in gene expression, especially during periods of cellular stress1. A focal point of translation control is at the rate-limiting step of initiation where the first steps of protein synthesis involve the binding of the eukaryotic initiation factor 4E (eIF4E) to the 7-methylguanosine (m7GTP) 5&#39; cap of mRNAs2. eIF4E is part of a trimeric complex named eIF4F that includes eIF4A, an RNA helicase, and eIF4G, a scaffolding protein required for the recruitment of other translation factors and the 40S ribosome3. Under normal physiological conditions, the vast majority of mRNAs are translated via a cap-dependent mechanism, but under periods of cellular stress approximately 10% of human mRNAs contain 5&#39; UTRs that could allow cap-independent translation intiation1,4. Cap-dependent translation has been historically synonymous with eIF4F, however, stress-specific variations of eIF4F have become a trending topic5-8.
Various cellular stresses cause eIF4E activity to be repressed via the mammalian target of rapamycin complex 1 (mTORC1). This kinase becomes impaired under stress, which results in the increased activity of one of its targets, the 4E-binding protein (4E-BP). Non-phosphorylated 4E-BP binds to eIF4E and blocks its ability to interact with eIF4G causing the repression of cap-dependent translation9,10. Interestingly, a homolog of eIF4E named eIF4E2 (or 4EHP) has a much lower affinity for 4E-BP11, perhaps allowing it to evade stress-mediated repression. Indeed, initially characterized as a repressor of translation due to its lack of interaction with eIF4G12, eIF4E2 initiates the translation of hundreds of mRNAs that contain RNA hypoxia response elements in their 3&#39; UTR during hypoxic stress6,13. This activation is achieved through interactions with eIF4G3, RNA binding protein motif 4, and the hypoxia inducible factor (HIF) 2&#945; to constitute a hypoxic eIF4F complex, or eIF4FH6,13. As a repressor under normal conditions, eIF4E2 binds with GIGYF2 and ZNF59814. These complexes were, in part, identified through Agarose-linked m7GTP affinity resins. This classic method15 is standard in the field of translation and is the best and most commonly used technique to isolate cap-binding complexes in pull down and in vitro binding assays16-19. As the cap-dependent translation machinery is emerging as flexible and adaptable with inter-changing parts6-8,13, this method is a powerful tool to rapidly identify novel cap-binding proteins involved in the stress response. Furthermore, variations in eIF4F could have broad implications as several eukaryotic model systems appear to use an eIF4E2 homolog for stress responses such as A. thaliana20, S. Pombe21, D. melanogaster22, and C. elegans23.
Evidence suggests that variations in eIF4F may not be strictly limited to stress conditions, but be involved in normal physiology24. The oxygen supply to tissues (at capillary ends) or within tissues (measured via microelectrodes) varies from 2-6% in the brain25, 3-12% in the lungs26, 3.5-6% in the intestine27, 4% in the liver28, 7-12% in the kidney29, 4% in muscle30, and 6-7% in bone marrow31. Cells and mitochondria contain less than 1.3% oxygen32. These values are much closer to hypoxia than the ambient air where cells are routinely cultured. This suggests that what were previously thought of as hypoxia-specific cellular processes may be relevant in a physiological setting. Interestingly, eIF4F and eIF4FH actively participate in the translation initiation of distinct pools or classes of mRNAs in several different human cell lines exposed to physiological oxygen or &#34;physioxia&#34;24. Low oxygen also drives proper fetal development33 and cells generally have higher proliferation rates, longer lifespans, less DNA damage and less general stress responses in physioxia34. Therefore, eIF4FH is likely a key factor in the expression of select genes under physiological conditions.
Here, we provide a protocol to culture cells in fixed physiological oxygen conditions or in a dynamic fluctuating range that is likely more representative of tissue microenvironments. One advantage of this method is that cells are lysed within the hypoxia workstation. It is not often clear how the transition from hypoxic cell culture to cell lysis is performed in other protocols. Cells are often first removed from a small hypoxia incubator before lysis, but this exposure to oxygen could affect biochemical pathways as the cellular response to oxygen is rapid (one or two min)35. Certain cap-binding proteins require interactions with a second base or can hydrolyze the m7GTP, therefore some cap interactors may be missed in the purification process. Agarose-linked to enzymatically resistant cap analogs may be substituted in this protocol. Exploring the activity and composition of eIF4FH and other variations of eIF4F through the method described here will shed light on the intricate gene expression machineries that cells utilize during physiological conditions or stress responses.

<table border="0" cellpadding="0" cellspacing="0" width="901">
	<tbody>
		<tr height="26">
			<td height="26" style="height:26px;width:380px;">&#947;-aminophenyl-m7GTP agarose C10-linked beads</td>
			<td style="width:151px;">Jena Bioscience</td>
			<td style="width:165px;">AC-1555</td>
			<td style="width:205px;">Agarose-linked m7GTP</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">100 mm culture dish</td>
			<td>Corning</td>
			<td>877222</td>
			<td>10-cm culture dish</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">150 mm culture dish</td>
			<td>Thermofisher</td>
			<td>130183</td>
			<td>15-cm culture dish</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">AEBSF Hydrochloride</td>
			<td>ACROS Organics</td>
			<td>A0356829</td>
			<td>AEBSF</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Agarose Beads</td>
			<td>Jena Bioscience&#160;</td>
			<td>AC-0015</td>
			<td>Agarose bead control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bromophenol Blue</td>
			<td>Fisher</td>
			<td>BP112-25</td>
			<td>Component of SDS-PAGE loading buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1.5 mL Centrifuge Tubes</td>
			<td>FroggaBio</td>
			<td>1210-00S</td>
			<td>Used to centrifuge small volumes</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">15 mL Conical Centrifuge Tubes</td>
			<td>Fisher</td>
			<td>1495970C</td>
			<td>Used in culturing primary cells</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Defined trypsin inhibitor</td>
			<td>Fisher</td>
			<td>R007100</td>
			<td>DTI</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dithiothreital</td>
			<td>Fisher</td>
			<td>BP172-25</td>
			<td>DTT</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Epithelial cell medium (complete kit)</td>
			<td>ScienCell</td>
			<td>4101</td>
			<td>Includes serum and growth factor supplements)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glycerol</td>
			<td>Fisher</td>
			<td>BP229-1</td>
			<td>Component of SDS-PAGE loading buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">100 mM Guanosine 5&#39;-triphosphate, 1 mL</td>
			<td>Jena Bioscience</td>
			<td>272076-0251M</td>
			<td>GTP</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">HCT116 colorectal carcinoma</td>
			<td>ATCC</td>
			<td>CCL-247</td>
			<td>Human cancer cell line</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Human renal proximal tubular epithelial cells</td>
			<td>ATCC</td>
			<td>PCS-400-010</td>
			<td>HRPTEC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hyclone DMEM/High Glucose</td>
			<td>GE Life Sciences</td>
			<td>SH30022.01</td>
			<td>Standard media for human cell culture</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hyclone Penicillin-Streptomycin solution</td>
			<td>GE Life Sciences</td>
			<td>SV30010</td>
			<td>Antibiotic component of DMEM</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">H35 HypOxystation</td>
			<td>Hypoxygen</td>
			<td>N/A</td>
			<td>Hypoxia workstation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Igepal CA-630</td>
			<td>MP Biomedicals</td>
			<td>2198596</td>
			<td>Detergent component of lysis buffer</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Monopotassium phosphate</td>
			<td>Fisher</td>
			<td>P288-500</td>
			<td>KH2PO4</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Potassium chloride</td>
			<td>Fisher</td>
			<td>P217-500</td>
			<td>KCl</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Magnesium chloride</td>
			<td>Fisher</td>
			<td>M33-500</td>
			<td>MgCl2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium chloride</td>
			<td>Fisher</td>
			<td>BP358-10</td>
			<td>NaCl</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium fluoride</td>
			<td>Fisher</td>
			<td>5299-100</td>
			<td>NaF (phosphatase inhibitor component of lysis buffer)</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Disodium phosphate</td>
			<td>Fisher</td>
			<td>5369-500</td>
			<td>Na2HPO4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Premium Grade Fetal Bovine Serum</td>
			<td>Seradigm</td>
			<td>1500-500</td>
			<td>FBS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Protease Inhibitor Cocktail (100 x)</td>
			<td>Cell Signalling</td>
			<td>58715</td>
			<td>Component of lysis buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Dodecyl Sulfate</td>
			<td>Fisher</td>
			<td>BP166-100</td>
			<td>SDS</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;">Sodium Orthovanadate</td>
			<td>Sigma</td>
			<td>56508</td>
			<td>Na3VO4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tris Base</td>
			<td>Fisher</td>
			<td>BP152-5</td>
			<td>Component of buffers</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.05% Trypsin-EDTA (1x)</td>
			<td>Life Technologies</td>
			<td>2500-067</td>
			<td>Trypsin used to detach adherent cells</td>
		</tr>
	</tbody>
</table>

analysis of cap-binding proteins in human cells exposed to physiological oxygen conditions

Translational control is a focal point of gene regulation, especially during periods of cellular stress. Cap-dependent translation via the eIF4F complex is by far the most common pathway to initiate protein synthesis in eukaryotic cells, but stress-specific variations of this complex are now emerging. Purifying cap-binding proteins with an affinity resin composed of Agarose-linked m7GTP (a 5' mRNA cap analog) is a useful tool to identify factors involved in the regulation of translation initiation. Hypoxia (low oxygen) is a cellular stress encountered during fetal development and tumor progression, and is highly dependent on translation regulation. Furthermore, it was recently reported that human adult organs have a lower oxygen content (physioxia 1-9% oxygen) that is closer to hypoxia than the ambient air where cells are routinely cultured. With the ongoing characterization of a hypoxic eIF4F complex (eIF4FH), there is increasing interest in understanding oxygen-dependent translation initiation through the 5' mRNA cap. We have recently developed a human cell culture method to analyze cap-binding proteins that are regulated by oxygen availability. This protocol emphasizes that cell culture and lysis be performed in a hypoxia workstation to eliminate exposure to oxygen. Cells must be incubated for at least 24 hr for the liquid media to equilibrate with the atmosphere within the workstation. To avoid this limitation, pre-conditioned media (de-oxygenated) can be added to cells if shorter time points are required. Certain cap-binding proteins require interactions with a second base or can hydrolyze the m7GTP, therefore some cap interactors may be missed in the purification process. Agarose-linked to enzymatically resistant cap analogs may be substituted in this protocol. This method allows the user to identify novel oxygen-regulated translation factors involved in cap-dependent translation.

Analysis of Cap-binding Ability in Response to Oxygen of eIF4E and eIF4E2 in an m7GTP Affinity Column
Figures 1 and 2 represent western blots of typical m7GTP affinity purification of two major cap-binding proteins in response to oxygen fluctuations in two human cell lines: primary human renal proximal tubular epithelial cells (HRPTEC) in Figure 1 and colorect...

Watch this Scientific Journal Video about Analysis of Cap-binding Proteins in Human Cells Exposed to Physiological Oxygen Conditions at JoVE.com

Analysis of Cap-binding Proteins in Human Cells Exposed to Physiological Oxygen Conditions

Here, we present human cell culture protocols to analyze translation initiation factors that bind the 5' cap of mRNA during physiological oxygen conditions. This method utilizes an Agarose-linked m7GTP cap analog and is suitable to investigate cap-binding factors and their interacting partners.

Translational control is a focal point of gene regulation, especially during periods of cellular stress. Cap-dependent translation via the eIF4F complex ...

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7.7K Views.  University of Guelph. Here, we present human cell culture protocols to analyze translation initiation factors that bind the 5' cap of mRNA during physiological oxygen conditions. This method utilizes an Agarose-linked m7GTP cap analog and is suitable to investigate cap-binding factors and their interacting partners.

Video: Analysis of Cap-binding Proteins in Human Cells Exposed to Physiological Oxygen Conditions

siRNA Transfection and EMSA Analyses on Freshly Isolated Human Villous Cytotrophoblasts

Human primary villous cytotrophoblasts are a very useful source of primary cells to study placental functions and regulatory mechanisms, and to comprehend diseases related to pregnancy. In this protocol, human primary villous cytotrophoblasts freshly isolated from placentas through a standard DNase/trypsin protocol are microporated with small interfering RNA (siRNA). This approach provided greater efficiency for siRNA transfection when compared to a lipofection-based method. Transfected cells can subsequently be analyzed by standard Western blot within a time frame of 3-4 days post-transfection. In addition, using cultured primary villous cytotrophoblasts, Electrophoretic Mobility Shift Assay (EMSA) analysis was optimized and performed on extracts from days 1 to 4. The use of these cultured primary cells and the protocol described allow for an evaluation of the implication of specific genes and transcription factors in the process of villous cytotrophoblast differentiation into a syncytiotrophoblast-like cell layer. However, the limited time span allowable in culture precludes the use of methods requiring more time, such as generation of a stable cell population. Therefore testing of this cell population requires highly optimized gene transfer protocols.

This protocol describes a method for efficiently transfecting siRNA in freshly isolated human villous cytotrophoblasts using microporation and identifying DNA-protein complexes in these cells. Transfected cells can be monitored by Western blot and EMSA analyses during the 4-day culture time.

Human primary villous cytotrophoblasts are a very useful source of primary cells to study placental functions and regulatory mechanisms, and to comprehend ...

Conjugative Mating Assays for Sequence-specific Analysis of Transfer Proteins Involved in Bacterial Conjugation

The transfer of genetic material by bacterial conjugation is a process that takes place via complexes formed by specific transfer proteins. In Escherichia coli, these transfer proteins make up a DNA transfer machinery known as the mating pair formation, or DNA transfer complex, which facilitates conjugative plasmid transfer. The objective of this paper is to provide a method that can be used to determine the role of a specific transfer protein that is involved in conjugation using a series of deletions and/or point mutations in combination with mating assays. The target gene is knocked out on the conjugative plasmid and is then provided in trans through the use of a small recovery plasmid harboring the target gene. Mutations affecting the target gene on the recovery plasmid can reveal information about functional aspects of the target protein that result in the alteration of mating efficiency of donor cells harboring the mutated gene. Alterations in mating efficiency provide insight into the role and importance of the particular transfer protein, or a region therein, in facilitating conjugative DNA transfer. Coupling this mating assay with detailed three-dimensional structural studies will provide a comprehensive understanding of the function of the conjugative transfer protein as well as provide a means for identifying and characterizing regions of protein-protein interaction.

Here, we present a protocol to knockout a gene of interest involved in plasmid conjugation and subsequently analyze the impact of its absence using mating assays. The function of the gene is further explored to a specific region of its sequence using deletion or point mutations.

The transfer of genetic material by bacterial conjugation is a process that takes place via complexes formed by specific transfer proteins. In Escherichia ...

Engineering Artificial Factors to Specifically Manipulate Alternative Splicing in Human Cells

The processing of most eukaryotic RNAs is mediated by RNA Binding Proteins (RBPs) with modular configurations, including an RNA recognition module, which specifically binds the pre-mRNA target and an effector domain. Previously, we have taken advantage of the unique RNA binding mode of the PUF domain in human Pumilio 1 to generate a programmable RNA binding scaffold, which was used to engineer various artificial RBPs to manipulate RNA metabolism. Here, a detailed protocol is described to construct Engineered Splicing Factors (ESFs) that are specifically designed to modulate the alternative splicing of target genes. The protocol includes how to design and construct a customized PUF scaffold for a specific RNA target, how to construct an ESF expression plasmid by fusing a designer PUF domain and an effector domain, and how to use ESFs to manipulate the splicing of target genes. In the representative results of this method, we have also described the common assays of ESF activities using splicing reporters, the application of ESF in cultured human cells, and the subsequent effect of splicing changes. By following the detailed protocols in this report, it is possible to design and generate ESFs for the regulation of different types of Alternative Splicing (AS), providing a new strategy to study splicing regulation and the function of different splicing isoforms. Moreover, by fusing different functional domains with a designed PUF domain, researchers can engineer artificial factors that target specific RNAs to manipulate various steps of RNA processing.

This report describes a bioengineering method to design and construct novel Artificial Splicing Factors (ASFs) that specifically modulate the splicing of target genes in mammalian cells. This method can be further expanded to engineer various artificial factors to manipulate other aspects of RNA metabolism.

The processing of most eukaryotic RNAs is mediated by RNA Binding Proteins (RBPs) with modular configurations, including an RNA recognition module, which ...

Immunostaining for DNA Modifications: Computational Analysis of Confocal Images

For several decades, 5-methylcytosine (5mC) has been thought to be the only DNA modification with a functional significance in metazoans. The discovery of enzymatic oxidation of 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) as well as detection of N6-methyladenine (6mA) in the DNA of multicellular organisms provided additional degrees of complexity to the epigenetic research. According to a growing body of experimental evidence, these novel DNA modifications may play specific roles in different cellular and developmental processes. Importantly, as some of these marks (e. g. 5hmC, 5fC and 5caC) exhibit tissue- and developmental stage-specific occurrence in vertebrates, immunochemistry represents an important tool allowing assessment of spatial distribution of DNA modifications in different biological contexts. Here the methods for computational analysis of DNA modifications visualized by immunostaining followed by confocal microscopy are described. Specifically, the generation of 2.5 dimension (2.5D) signal intensity plots, signal intensity profiles, quantification of staining intensity in multiple cells and determination of signal colocalization coefficients are shown. Collectively, these techniques may be operational in evaluating the levels and localization of these DNA modifications in the nucleus, contributing to elucidating their biological roles in metazoans.

Newly discovered oxidized forms of 5-methylcytosine (oxi-mCs), 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) may represent distinct DNA modifications with unique functional roles. Here a semi-quantitative workflow for visualization of oxi-mCs' spatial distribution, signal intensity profiling and colocalization is described.

For several decades, 5-methylcytosine (5mC) has been thought to be the only DNA modification with a functional significance in metazoans. The discovery of ...

Adaptation of Hybridization Capture of Chromatin-associated Proteins for Proteomics to Mammalian Cells

The hybridization capture of chromatin-associated proteins for proteomics (HyCCAPP) technology was initially developed to uncover novel DNA-protein interactions in yeast. It allows analysis of a target region of interest without the need for prior knowledge about likely proteins bound to the target region. This, in theory, allows HyCCAPP to be used to analyze any genomic region of interest, and it provides sufficient flexibility to work in different cell systems. This method is not meant to study binding sites of known transcription factors, a task better suited for Chromatin Immunoprecipitation (ChIP) and ChIP-like methods. The strength of HyCCAPP lies in its ability to explore DNA regions for which there is limited or no knowledge about the proteins bound to it. It can also be a convenient method to avoid biases (present in ChIP-like methods) introduced by protein-based chromatin enrichment using antibodies. Potentially, HyCCAPP can be a powerful tool to uncover truly novel DNA-protein interactions. To date, the technology has been predominantly applied to yeast cells or to high copy repeat sequences in mammalian cells. In order to become the powerful tool we envision, HyCCAPP approaches need to be optimized to efficiently capture single-copy loci in mammalian cells. Here, we present our adaptation of the initial yeast HyCCAPP capture protocol to human cell lines, and show that single-copy chromatin regions can be efficiently isolated with this modified protocol.

This is a method to identify novel DNA-interacting proteins at specific target loci, relying on sequence-specific capture of crosslinked chromatin for subsequent proteomic analyses. No prior knowledge about potential binding proteins, nor cell modifications are required. Initially developed for yeast, the technology has now been adapted for mammalian cells.

The hybridization capture of chromatin-associated proteins for proteomics (HyCCAPP) technology was initially developed to uncover novel DNA-protein ...

Highly Efficient Gene Disruption of Murine and Human Hematopoietic Progenitor Cells by CRISPR/Cas9

Advances in the hematopoietic stem cell (HSCs) field have been aided by methods to genetically engineer primary progenitor cells as well as animal models. Complete gene ablation in HSCs required the generation of knockout mice from which HSCs could be isolated, and gene ablation in primary human HSCs was not possible. Viral transduction could be used for knock-down approaches, but these suffered from variable efficacy. In general, genetic manipulation of human and mouse hematopoietic cells was hampered by low efficiencies and extensive time and cost commitments. Recently, CRISPR/Cas9 has dramatically expanded the ability to engineer the DNA of mammalian cells. However, the application of CRISPR/Cas9 to hematopoietic cells has been challenging, mainly due to their low transfection efficiencies, the toxicity of plasmid-based approaches and the slow turnaround time of virus-based protocols.
A rapid method to perform CRISPR/Cas9-mediated gene editing in murine and human hematopoietic stem and progenitor cells with knockout efficiencies of up to 90% is provided in this article. This approach utilizes a ribonucleoprotein (RNP) delivery strategy with a streamlined three-day workflow. The use of Cas9-sgRNA RNP allows for a hit-and-run approach, introducing no exogenous DNA sequences in the genome of edited cells and reducing off-target effects. The RNP-based method is fast and straightforward: it does not require cloning of sgRNAs, virus preparation or specific sgRNA chemical modification. With this protocol, scientists should be able to successfully generate knockouts of a gene of interest in primary hematopoietic cells within a week, including downtimes for oligonucleotide synthesis. This approach will allow a much broader group of users to adapt this protocol for their needs.

A protocol for fast CRISPR/Cas9-mediated gene disruption in mouse and human primary hematopoietic cells is described in this article. Cas9-sgRNA ribonucleoproteins are introduced via electroporation with sgRNAs generated through in vitro transcription and commercial Cas9. High editing efficiencies are achieved with limited time and financial cost.

Advances in the hematopoietic stem cell (HSCs) field have been aided by methods to genetically engineer primary progenitor cells as well as animal models. ...

Differentiation, Maintenance, and Analysis of Human Retinal Pigment Epithelium Cells: A Disease-in-a-dish Model for BEST1 Mutations

Although over 200 genetic mutations in the human BEST1 gene have been identified and linked to retinal degenerative diseases, the pathological mechanisms remain elusive mainly due to the lack of a good in vivo model for studying BEST1 and its mutations under physiological conditions. BEST1 encodes an ion channel, namely BESTROPHIN1 (BEST1), which functions in retinal pigment epithelium (RPE); however, the extremely limited accessibility to native human RPE cells represents a major challenge for scientific research. This protocol describes how to generate human RPEs bearing BEST1 disease-causing mutations by induced differentiation from human pluripotent stem cells (hPSCs). As hPSCs are self-renewable, this approach allows researchers to have a steady source of hPSC-RPEs for various experimental analyses, such as immunoblotting, immunofluorescence, and patch clamp, and thus provides a very powerful disease-in-a-dish model for BEST1-associated retinal conditions. Notably, this strategy can be applied to study RPE (patho)physiology and other genes of interest natively expressed in RPE.

Differentiation, Maintenance, and Analysis of Human Retinal Pigment Epithelium Cells: A Disease-in-a-dish Model for BEST1 Mutations

Here we present a protocol to differentiate retinal pigment epithelium (RPE) cells from human pluripotent stem cells bearing patient-derived mutations. The mutant cell lines may be used for functional analyses including immunoblotting, immunofluorescence, and patch clamp. This disease-in-a-dish approach circumvents the difficulty of obtaining native human RPE cells.

Although over 200 genetic mutations in the human BEST1 gene have been identified and linked to retinal degenerative diseases, the pathological mechanisms ...

Single-cell RNA Sequencing and Analysis of Human Pancreatic Islets

Pancreatic islets comprise of endocrine cells with distinctive hormone expression patterns. The endocrine cells show functional differences in response to normal and pathological conditions. The goal of this protocol is to generate high-quality, large-scale transcriptome data of each endocrine cell type with the use of a droplet-based microfluidic single-cell RNA sequencing technology. Such data can be utilized to build the gene expression profile of each endocrine cell type in normal or specific conditions. The process requires careful handling, accurate measurement, and rigorous quality control. In this protocol, we describe detailed steps for human pancreatic islets dissociation, sequencing, and data analysis. The representative results of about 20,000 human single islet cells demonstrate the successful application of the protocol.

Here, we present a protocol to generate high-quality, large-scale transcriptome data of single cells from isolated human pancreatic islets using a droplet-based microfluidic single-cell RNA sequencing technology.

Pancreatic islets comprise of endocrine cells with distinctive hormone expression patterns. The endocrine cells show functional differences in response to ...

Generation of Defined Genomic Modifications Using CRISPR-CAS9 in Human Pluripotent Stem Cells

Human pluripotent stem cells offer a powerful system to study gene function and model specific mutations relevant to disease. The generation of precise heterozygous genetic modifications is challenging due to CRISPR-CAS9 mediated indel formation in the second allele. Here, we demonstrate a protocol to help overcome this difficulty by using two repair templates in which only one expresses the desired sequence change, while both templates contain silent mutations to prevent re-cutting and indel formation. This methodology is most advantageous for gene editing coding regions of DNA to generate isogenic control and mutant human stem cell lines for studying human disease and biology. In addition, optimization of transfection and screening methodologies have been performed to reduce labor and cost of a gene editing experiment. Overall, this protocol is widely applicable to many genome editing projects utilizing the human pluripotent stem cell model.

This protocol provides a method to facilitate the generation of defined heterozygous or homozygous nucleotide changes using CRISPR-CAS9 in human pluripotent stem cells.

Human pluripotent stem cells offer a powerful system to study gene function and model specific mutations relevant to disease. The generation of precise ...

Investigation of the Transcriptional Role of a RUNX1 Intronic Silencer by CRISPR/Cas9 Ribonucleoprotein in Acute Myeloid Leukemia Cells

The bulk of the human genome (~98%) is comprised of non-coding sequences. Cis-regulatory elements (CREs) are non-coding DNA sequences that contain binding sites for transcriptional regulators to modulate gene expression. Alterations of CREs have been implicated in various diseases including cancer. While promoters and enhancers have been the primary CREs for studying gene regulation, very little is known about the role of silencer, which is another type of CRE that mediates gene repression. Originally identified as an adaptive immunity system in prokaryotes, CRISPR/Cas9 has been exploited to be a powerful tool for eukaryotic genome editing. Here, we present the use of this technique to delete an intronic silencer in the human RUNX1 gene and investigate the impacts on gene expression in OCI-AML3 leukemic cells. Our approach relies on electroporation-mediated delivery of two preassembled Cas9/guide RNA (gRNA) ribonucleoprotein (RNP) complexes to create two double-strand breaks (DSBs) that flank the silencer. Deletions can be readily screened by fragment analysis. Expression analyses of different mRNAs transcribed from alternative promoters help evaluate promoter-dependent effects. This strategy can be used to study other CREs and is particularly suitable for hematopoietic cells, which are often difficult to transfect with plasmid-based methods. The use of a plasmid- and virus-free strategy allows simple and fast assessments of gene regulatory functions.

Investigation of the Transcriptional Role of a RUNX1 Intronic Silencer by CRISPR/Cas9 Ribonucleoprotein in Acute Myeloid Leukemia Cells

Direct delivery of preassembled Cas9/guide RNA ribonucleoprotein complexes is a fast and efficient means for genome editing in hematopoietic cells. Here, we utilize this approach to delete a RUNX1 intronic silencer and examine the transcriptional responses in OCI-AML3 leukemic cells.

The bulk of the human genome (~98%) is comprised of non-coding sequences. Cis-regulatory elements (CREs) are non-coding DNA sequences that contain binding ...