这项工作得到了科学进步研究公司 (科特雷尔学院学者奖 #22548) 和三生物技术 (ResearchReward 赠款 #G139) 的支持。

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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=Directed+evolution+of+DNA+polymerases+for+next-generation+sequencing.">Directed evolution of DNA polymerases for next-generation sequencing.</a> Angew Chem Int Ed Engl. 49 (34), 5921-5924 (2010).</li><li>Xia, G., 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=Directed+evolution+of+novel+polymerase+activities:+mutation+of+a+DNA+polymerase+into+an+efficient+RNA+polymerase.">Directed evolution of novel polymerase activities: mutation of a DNA polymerase into an efficient RNA polymerase.</a> Proc Natl Acad Sci U S A. 99 (10), 6597-6602 (2002).</li><li>Chen, T., 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=Evolution+of+thermophilic+DNA+polymerases+for+the+recognition+and+amplification+of+C2'-modified+DNA.">Evolution of thermophilic DNA polymerases for the recognition and amplification of C2'-modified DNA.</a> Nat Chem. 8 (6), 556-562 (2016).</li><li>Thirunavukarasu, D., Chen, T., Liu, Z., Hongdilokkul, N., Romesberg, F. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selection+of+2'-Fluoro-Modified+Aptamers+with+Optimized+Properties.">Selection of 2'-Fluoro-Modified Aptamers with Optimized Properties.</a> J Am Chem Soc. 139 (8), 2892-2895 (2017).</li><li>Taylor, A. I., 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=Catalysts+from+synthetic+genetic+polymers.">Catalysts from synthetic genetic polymers.</a> Nature. 518 (7539), 427-430 (2015).</li><li>Alves Ferreira-Bravo, I., Cozens, C., Holliger, P., DeStefano, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selection+of+2'-deoxy-2'-fluoroarabinonucleotide+(FANA)+aptamers+that+bind+HIV-1+reverse+transcriptase+with+picomolar+affinity.">Selection of 2'-deoxy-2'-fluoroarabinonucleotide (FANA) aptamers that bind HIV-1 reverse transcriptase with picomolar affinity.</a> Nucleic Acids Res. 43 (20), 9587-9599 (2015).</li><li>Schultz, H. J., 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=Taq+DNA+Polymerase+Mutants+and+2'-Modified+Sugar+Recognition.">Taq DNA Polymerase Mutants and 2'-Modified Sugar Recognition.</a> Biochemistry. 54 (38), 5999-6008 (2015).</li><li>Rosenblum, S. L., 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=Design+and+discovery+of+new+combinations+of+mutant+DNA+polymerases+and+modified+DNA+substrates.">Design and discovery of new combinations of mutant DNA polymerases and modified DNA substrates.</a> Chembiochem. 18 (8), 816-823 (2017).</li><li>Creighton, S., Goodman, M. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gel+kinetic+analysis+of+DNA+polymerase+fidelity+in+the+presence+of+proofreading+using+bacteriophage+T4+DNA+polymerase.">Gel kinetic analysis of DNA polymerase fidelity in the presence of proofreading using bacteriophage T4 DNA polymerase.</a> J Biol Chem. 270 (9), 4759-4774 (1995).</li><li>Joyce, C. M., Benkovic, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+polymerase+fidelity:+kinetics,+structure,+and+checkpoints.">DNA polymerase fidelity: kinetics, structure, and checkpoints.</a> Biochemistry. 43 (45), 14317-14324 (2004).</li><li>Leconte, A. 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=Discovery,+characterization,+and+optimization+of+an+unnatural+base+pair+for+expansion+of+the+genetic+alphabet.">Discovery, characterization, and optimization of an unnatural base pair for expansion of the genetic alphabet.</a> J Am Chem Soc. 130 (7), 2336-2343 (2008).</li><li>Sanger, F., Nicklen, S., Coulson, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+sequencing+with+chain-terminating+inhibitors.">DNA sequencing with chain-terminating inhibitors.</a> Proc Natl Acad Sci U S A. 74 (12), 5463-5467 (1977).</li><li>Karger, B. L., Guttman, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+Sequencing+by+Capillary+Electrophoresis.">DNA Sequencing by Capillary Electrophoresis.</a> Electrophoresis. 30 (Suppl 1), S196-S202 (2009).</li><li>Lawyer, F. 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C., 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=Isolation,+characterization,+and+expression+in+Escherichia+coli+of+the+DNA+polymerase+gene+from+Thermus+aquaticus.">Isolation, characterization, and expression in Escherichia coli of the DNA polymerase gene from Thermus aquaticus.</a> J Biol Chem. 264 (11), 6427-6437 (1989).</li><li>Carroll, S. S., Cowart, M., Benkovic, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+mutant+of+DNA+polymerase+I+(Klenow+fragment)+with+reduced+fidelity.">A mutant of DNA polymerase I (Klenow fragment) with reduced fidelity.</a> Biochemistry. 30 (3), 804-813 (1991).</li><li>Shendure, J., Ji, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Next-generation+DNA+sequencing.">Next-generation DNA sequencing.</a> Nat Biotechnol. 26 (10), 1135-1145 (2008).</li><li>Larsen, A. C., 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=A+general+strategy+for+expanding+polymerase+function+by+droplet+microfluidics.">A general strategy for expanding polymerase function by droplet microfluidics.</a> Nat Commun. 7, 11235 (2016).</li><li>Cozens, C., 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=Enzymatic+Synthesis+of+Nucleic+Acids+with+Defined+Regioisomeric+2'-5'+Linkages.">Enzymatic Synthesis of Nucleic Acids with Defined Regioisomeric 2'-5' Linkages.</a> Angew Chem Int Ed Engl. 54 (51), 15570-15573 (2015).</li></ol>

作者没有什么可透露的。

在这里, 我们描述了一种测定 dna 聚合酶介导的 M dna 的合成。利用近红外标记的 DNA 引物, 利用变性聚丙烯酰胺凝胶电泳解决不同大小的寡核苷酸, 可以获得核苷酸的单核苷酸分辨力, 从而实现对合成的精确测量。这些方法可以用来测量酶的整体活性 (2.1 节) 或测量单个步骤的蔑氏参数 (注意以下步骤 2.1)。我们的实验室最近使用这些来表征以前进化的酶9以及合理设计的酶10。
我们在这里所描述的分析不同于以前的方法使用放射性 DNA 标签。从历史上看, 放射性已被用来跟踪 DNA 合成由于高灵敏度, 可以获得使用放射性磷标签11,18。不幸的是, 昂贵的处置费用以及放射性标签的货架寿命有限, 可以使放射性标签的使用望而却步。在这里, 我们描述了使用近红外线荧光标记的 DNA, 这并不遭受这些缺点。值得注意的是, 与近红外荧光染料, 我们看到类似的检测限制放射性标记的 DNA (未发表的结果)。然而, 由于荧光染料在可见光范围内, 我们无法观察到类似的检测限制 (未发表的结果)。虽然我们的小组通常使用商业制备的 DNA 轴承近红外荧光, 这些染料是兼容的一些已建立的合成 5 ' 修改化学试剂, 可用于安装这些标签。
近红外荧光染料也有好处, 有多种商业可用的颜色, 这可以使更复杂的实验, 监测合成的两个标记的寡核苷酸在一个单一的实验。与放射性标签, 这些类型的多组分实验是不容易执行。这可能会使一些更复杂的实验, 特别是正交复制实验。
这种方法, 以及任何使用变性聚丙烯酰胺凝胶电泳法, 主要是受技术挑战, 执行电泳, 这些实验的低吞吐量, 以及有限的大小范围, 可观察到单核苷酸分辨率。我们希望这一详细的协议能够让小组克服这些化验的技术挑战。值得注意的是, 虽然检测的吞吐量是有限的, 但使用近红外荧光标签确实增加了吞吐量, 因为它不要求用户开发放射。然而, 凝胶仍然需要大约4-6 小时来设置和运行, 限制了每天可以运行的实验次数。有限的范围是由聚丙烯酰胺的电泳能力造成的。实际上, 这些限制意味着这些分析最适合需要单核苷酸分辨率的重点研究问题。
最近,高通量 dna 测序19已被越来越多地用作表征 dna 聚合2021的方法。这些分析是值得注意的显著增加的吞吐量, 这使得更广泛的问题集中在序列偏差和错误谱。重要的是, 虽然高通量测序可以使许多并行实验, 它可能是挑战的解释单核苷酸基础上。这为使用聚丙烯酰胺凝胶电泳技术的酶检测提供了一个令人振奋的机会, 以填补高通量测序中的空白, 确保本文所描述的方法在今后的许多年内都是相关的。

dna 聚合进行准确和有效的 dna 合成, 是维持基因组完整性的关键。在不出错的情况下, 每秒合成数百个核苷酸的能力也使 DNA 聚合了分子生物学和生物技术的基本工具。然而, 这些属性也限制了 M DNA 基板的应用;一般而言, 天然 dna 聚合不能合成许多潜在的有价值的 M dna 基质, 可能是由于对使用非标准基质的高选择性压力在体内。许多小组开发了有针对性的进化方法来产生突变的 dna 聚合能够进行 M dna 合成1a,2,3,4,5;这些努力扩大了 DNA 的生物技术效用6,7,8。
为了评估突变 dna 聚合合成 M dna 的能力, 我们9,10, 其他11,12,13通常使用体外测量 dna聚合酶活性, 这是在这篇手稿中描述。在这些实验中, DNA 聚合是 co-incubated 与标记的底漆/模板复式和核苷三磷酸基板;用凝胶电泳法对产品进行评价。根据具体的实验问题, 突变的 DNA 聚合, 改良引物, 改良的模板, 或改性的核苷 triphosphates 可以使用, 使突变酶活性的系统生化评价。
从历史上看, 这些化验都依赖于5的放射性标签来跟踪 DNA 合成;最常见的是, 使用了32p 和33p。通常, 使用 T4 核苷酸激酶11实现标记。然而, 由于放射性标签的寿命有限, 成本相对较高, 安全处置, 我们组改用合成5的近红外荧光标记 DNA。使用相对低成本的近红外凝胶成像仪, 我们观察到了使用放射性标签 (未发表的结果) 之前研究的类似检测限制。我们已经成功地重现了过去的观测值9, 我们没有观察到与以前测量的速率常数 (未发布的结果) 有任何大的定量差异。
为了分析 dna 的大小, 因此, 我们依靠聚丙烯酰胺凝胶电泳方法, 在毛细管电泳15问世之前为桑格测序14 。分离或移动的距离可以用作分子量的测量;大格式, 垂直聚丙烯酰胺凝胶可以实现单核苷酸的分辨率, 使定量观察的 DNA 寡核苷酸的长度不等。
总的来说, 这些实验是一种用于聚合酶表征的健壮方法。由于反应的时间敏感性, 准备和护理是必要的, 以达到重现的结果。此外, 虽然丙烯酰胺凝胶是一种非常有效的方法来测量 dna 合成, 以及许多其他的 dna 修饰反应, 单核苷酸分辨率, 它可以在技术上具有挑战性。这里的协议有望使用户能够执行这些实验, 同时避免最常见的错误。

<table>
	<tbody>
		<tr>
			<td>Tris HCl</td>
			<td>Promega</td>
			<td>H5123</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris Base</td>
			<td>Promega</td>
			<td>H5131</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Fisher Scientific</td>
			<td>BP214-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetylated BSA</td>
			<td>Promega</td>
			<td>PR-R3961</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma</td>
			<td>P4504</td>
			<td></td>
		</tr>
		<tr>
			<td>Dithiothreitol (i.e. DTT)</td>
			<td>Research Products International</td>
			<td>D11000</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylenediaminetetraacetic acid (i.e. EDTA) (0.5M solution)</td>
			<td>Sigma</td>
			<td>03690-100mL</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sigma</td>
			<td>G5516</td>
			<td></td>
		</tr>
		<tr>
			<td>Formamide</td>
			<td>Acros</td>
			<td>AC42374-5000</td>
			<td></td>
		</tr>
		<tr>
			<td>Orange G</td>
			<td>Sigma Aldrich</td>
			<td>O3756</td>
			<td></td>
		</tr>
		<tr>
			<td>Bromophenol blue</td>
			<td>Fisher Scientific</td>
			<td>50-701-6973</td>
			<td></td>
		</tr>
		<tr>
			<td>dNTPs</td>
			<td>Fisher Scientific</td>
			<td>FERR0191</td>
			<td></td>
		</tr>
		<tr>
			<td>M-dNTPs (riboNTPs)</td>
			<td>Fisher Scientific</td>
			<td>45-001-341 (343, 345, 347)</td>
			<td></td>
		</tr>
		<tr>
			<td>M-dNTPs (all other modified NTPs)</td>
			<td>TriLink Biotechnologies</td>
			<td>assorted</td>
			<td></td>
		</tr>
		<tr>
			<td>primer 1</td>
			<td>IDT DNA / TriLink Biotechnologies</td>
			<td>Custom Syntheses</td>
			<td>We use the IR700 dye which can be purchased as a custom synthesis. We typically purchase the oligonucleotides HPLC purified. Sequence is 5&#8217;-dTAATACGACTCACTATAGGGAGA</td>
		</tr>
		<tr>
			<td>template 1</td>
			<td>IDT DNA / TriLink Biotechnologies</td>
			<td>Custom Syntheses</td>
			<td>We typically purchase the oligonucleotides HPLC purified. Sequence is 5&#8217;-dCGCTAGGACGGCATTGGATCAGTCTCCCTATAGTGAGTCGTATTA</td>
		</tr>
		<tr>
			<td>Acrylamide</td>
			<td>Research Products International</td>
			<td>A11405</td>
			<td>38.67% acrylamide and 1.33% bis-acrylamide</td>
		</tr>
		<tr>
			<td>Tris/Borate/EDTA (TBE) solid</td>
			<td>Research Products International</td>
			<td>T22020</td>
			<td></td>
		</tr>
		<tr>
			<td>Urea ultrapure</td>
			<td>Research Products International</td>
			<td>U20200</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel tape</td>
			<td>CBS Scientific</td>
			<td>GT-72-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Large white spring clamp polypropylene</td>
			<td>CBS Scientific</td>
			<td>GPC-0001</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium persulfate (APS)</td>
			<td>Fisher Scientific</td>
			<td>BP179</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetramethylethylenediamine (TEMED)</td>
			<td>Fisher Scientific</td>
			<td>BP15020</td>
			<td></td>
		</tr>
		<tr>
			<td>0.75 mm spacers</td>
			<td>CBS Scientific</td>
			<td>SGS-20-0740A</td>
			<td></td>
		</tr>
		<tr>
			<td>33x42 Notched Glass Plate Set</td>
			<td>CBS Scientific</td>
			<td>SGP33-040A</td>
			<td></td>
		</tr>
		<tr>
			<td>Wedge plate separator</td>
			<td>CBS Scientific</td>
			<td>WPS-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Comb for gel electrophoresis</td>
			<td>CBS Scientific</td>
			<td>SG33-0734</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel electrophoresis rig</td>
			<td>CBS Scientific</td>
			<td>SG-400-33</td>
			<td></td>
		</tr>
		<tr>
			<td>ultrapure water</td>
			<td></td>
			<td></td>
			<td>we use a Milli-Q system from Millipore</td>
		</tr>
		<tr>
			<td>DNA polymerases</td>
			<td></td>
			<td></td>
			<td>we prepare these in our laboratory using published protocols.</td>
		</tr>
	</tbody>
</table>

dna polymerase activity assay using near-infrared fluorescent labeled dna visualized by acrylamide gel electrophoresis

对于任何酶, 都需要有健壮的、定量的方法来表征本地和工程酶。对于 dna 聚合, dna 合成可以用一种体外dna 合成方法进行表征, 然后采用聚丙烯酰胺凝胶电泳法。该方法的目的是量化合成的天然 dna 和修饰 dna (M-dna)。这些方法是特别有用的解决单核苷酸分解寡核苷酸, 使观察的个别步骤在酶寡核苷酸合成。这些方法已被用于评价的一系列生物化学和生物物理特性, 如测量的稳态速率常数的个别步骤的 dna 合成, 错误率的 dna 合成, 和 dna 结合的亲和力。通过修改后的核苷 triphosphates (NTP)、m-dna 和/或突变的 dna 聚合, 可以有效地评价基质 dna 聚合酶对的相对效用。在这里, 我们详细的分析本身, 包括必须作出的改变, 以适应非传统的底漆 dna 标记策略, 如近红外线荧光标记 dna。此外, 我们有详细的关键技术步骤, 丙烯酰胺凝胶浇注和运行, 这往往是技术上的挑战。

一个成功的聚丙烯酰胺凝胶分析的总体活动的定性描述 (在2.1 节,图 1) 和稳态动力学 (说明在说明中的 2.1,图 2) 显示。还显示了不成功的聚丙烯酰胺凝胶分析 (图 3)。
请注意, 没有商业可用的梯子或分子标记使用。有时, 我们将使用已知的聚合酶-基质结合物来创建分子标记;然而, 重要的是要注意, 不同的修饰核苷酸有非常不同的电泳迁移, 使比较的相同长度, 但不同的核苷酸结构不适当的寡核苷酸。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56228/56228fig1.jpg"> 
图 1: 成功的聚丙烯酰胺凝胶分析的例子整体活动的定性描述.请注意, 各个频带是定义良好和定期的。带代表不同长度的寡核苷酸;这种凝胶可以方便地比较聚合。没有酵素控制车道用 "-" 表明。活动由产品的长度和被标记的底漆的部分判断被转换成更大的产品。从这个分析中, E6 和 E5 是最活跃的。E3 和 E2 在活动中近似相等, 但少于 E6 或 E5, E4 和 E1 是活性最低的酶。
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56228/56228fig2.jpg"> 
图 2: 使用稳态动力学定量分析成功的凝胶的例子.请注意, 乐队是很好的解决和明确定义。为了测量寡核苷酸合成过程中各个步骤的稳态速率常数, 用不同数量的三磷酸核苷 (在本例中为桩) 孵育酶;请注意, 只有 n 和 (n+1) 产品是合成的, 从而能够量化奇异事件。
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56228/56228fig3.jpg"> 
图 3: 用于整体活动的不成功凝胶的示例.在处理过程中, 凝胶被撕裂, 导致了带内可见的间隙。请注意, 凝胶带不规则形状, 使量化和分析困难。

Watch this Scientific Journal Video about DNA Polymerase Activity Assay Using Near-infrared Fluorescent Labeled DNA Visualized by Acrylamide Gel Electrophoresis at JoVE.com

DNA Polymerase Activity Assay Using Near-infrared Fluorescent Labeled DNA Visualized by Acrylamide Gel Electrophoresis

用丙烯酰胺凝胶电泳法可视化近红外荧光标记 dna 聚合酶活性

本议定书描述了 dna 聚合酶合成的修饰 dna 通过观察的变化近红外荧光标记 dna 使用凝胶电泳和凝胶显像。丙烯酰胺凝胶用于高分辨率成像分离的短核酸, 这是根据大小不同的速率迁移。

For any enzyme, robust, quantitative methods are required for characterization of both native and engineered enzymes. For DNA polymerases, DNA synthesis ...

dna-polymerase-activity-assay-using-near-infrared-fluorescent-labeled

Nanyang Technological University

Research

JoVE Journal

Biochemistry

14.0K 次观看.  W.M. Keck Science Department of Claremont Mckenna, Pitzer, and Scripps College. 本议定书描述了 dna 聚合酶合成的修饰 dna 通过观察的变化近红外荧光标记 dna 使用凝胶电泳和凝胶显像。丙烯酰胺凝胶用于高分辨率成像分离的短核酸, 这是根据大小不同的速率迁移。

视频: DNA Polymerase Activity Assay Using Near-infrared Fluorescent Labeled DNA Visualized by Acrylamide Gel Electrophoresis

Characterization of Multi-subunit Protein Complexes of Human MxA Using Non-denaturing Polyacrylamide Gel-electrophoresis

The formation of oligomeric complexes is a crucial prerequisite for the proper structure and function of many proteins. The interferon-induced antiviral effector protein MxA exerts a broad antiviral activity against many viruses. MxA is a dynamin-like GTPase and has the capacity to form oligomeric structures of higher order. However, whether oligomerization of MxA is required for its antiviral activity is an issue of debate. We describe here a simple protocol to assess the oligomeric state of endogenously or ectopically expressed MxA in the cytoplasmic fraction of human cell lines by non-denaturing polyacrylamide gel electrophoresis (PAGE) in combination with Western blot analysis. A critical step of the protocol is the choice of detergents to prevent aggregation and/or precipitation of proteins particularly associated with cellular membranes such as MxA, without interfering with its enzymatic activity. Another crucial aspect of the protocol is the irreversible protection of the free thiol groups of cysteine residues by iodoacetamide to prevent artificial interactions of the protein. This protocol is suitable for a simple assessment of the oligomeric state of MxA and furthermore allows a direct correlation of the antiviral activity of MxA interface mutants with their respective oligomeric states.

This article describes a simple and rapid protocol to evaluate the oligomeric state of the dynamin-like GTPase MxA protein from lysates of human cells using a combination of non-denaturing PAGE with western blot analysis.

使用非变性聚丙烯酰胺凝胶电泳人的MxA多亚基蛋白复合物的表征

The formation of oligomeric complexes is a crucial prerequisite for the proper structure and function of many proteins. The interferon-induced antiviral ...

科研

生物化学

An Optimized Protocol for Electrophoretic Mobility Shift Assay Using Infrared Fluorescent Dye-labeled Oligonucleotides

Electrophoretic Mobility Shift Assays (EMSA) are an instrumental tool to characterize the interactions between proteins and their target DNA sequences. Radioactivity has been the predominant method of DNA labeling in EMSAs. However, recent advances in fluorescent dyes and scanning methods have prompted the use of fluorescent tagging of DNA as an alternative to radioactivity for the advantages of easy handling, saving time, reducing cost, and improving safety. We have recently used fluorescent EMSA (fEMSA) to successfully address an important biological question. Our fEMSA analysis provides mechanistic insight into the effect of a missense mutation, G73E, in the highly conserved HMG transcription factor SOX-2 on olfactory neuron type diversification. We found that mutant SOX-2G73E protein alters specific DNA binding activity, thereby causing olfactory neuron identity transformation. Here, we present an optimized and cost-effective step-by-step protocol for fEMSA using infrared fluorescent dye-labeled oligonucleotides containing the LIM-4/SOX-2 adjacent target sites and purified SOX-2 proteins (WT and mutant SOX-2G73E proteins) as a biological example.

We describe here an optimized protocol of fluorescent Electrophoretic Mobility Shift Assays (fEMSA) using purified SOX-2 proteins together with infrared fluorescent dye-labeled DNA probes as a case study to tackle an important biological question.

一种优化的协议电泳迁移分析使用红外荧光染料标记的寡核苷酸

Electrophoretic Mobility Shift Assays (EMSA) are an instrumental tool to characterize the interactions between proteins and their target DNA sequences. ...

Real-time Tracking of DNA Fragment Separation by Smartphone

Slab gel electrophoresis (SGE) is the most common method for the separation of DNA fragments; thus, it is broadly applied to the field of biology and others. However, the traditional SGE protocol is quite tedious, and the experiment takes a long time. Moreover, the chemical consumption in SGE experiments is very high. This work proposes a simple method for the separation of DNA fragments based on an SGE chip. The chip is made by an engraving machine. Two plastic sheets are used for the excitation and emission wavelengths of the optical signal. The fluorescence signal of the DNA bands is collected by smartphone. To validate this method, 50, 100, and 1,000 bp DNA ladders were separated. The results demonstrate that a DNA ladder smaller than 5,000 bp can be resolved within 12 min and with high resolution when using this method, indicating that it is an ideal substitute for the traditional SGE method.

Traditional slab gel electrophoresis (SGE) experiments require a complicated apparatus and high chemical consumption. This work presents a protocol that describes a low-cost method to separate DNA fragments within a short timeframe.

通过智能手机实时跟踪DNA片段分离

Slab gel electrophoresis (SGE) is the most common method for the separation of DNA fragments; thus, it is broadly applied to the field of biology and ...

Horizontal Gel Electrophoresis for Enhanced Detection of Protein-RNA Complexes

Native polyacrylamide gel electrophoresis is a fundamental tool of molecular biology that has been used extensively for the biochemical analysis of RNA-protein interactions. These interactions have been traditionally analyzed with polyacrylamide gels generated between two glass plates and samples electrophoresed vertically. However, polyacrylamide gels cast in trays and electrophoresed horizontally offers several advantages. For example, horizontal gels used to analyze complexes between fluorescent RNA substrates and specific proteins can be imaged multiple times as electrophoresis progresses. This provides the unique opportunity to monitor RNA-protein complexes at several points during the experiment. In addition, horizontal gel electrophoresis makes it possible to analyze many samples in parallel. This can greatly facilitate time course experiments as well as analyzing multiple reactions simultaneously to compare different components and conditions. Here we provide a detailed protocol for generating and using horizontal native gel electrophoresis for analyzing RNA-Protein interactions.

Native polyacrylamide gel electrophoresis is a fundamental tool for analyzing RNA-protein interactions. Traditionally most experiments have used vertical gels. However, horizontal gels provide several advantages, such as the opportunity to monitor complexes during electrophoresis. We provide a detailed protocol for generating and using horizontal native gel electrophoresis.

水平凝胶电泳用于增强蛋白质 -  RNA复合物的检测

Native polyacrylamide gel electrophoresis is a fundamental tool of molecular biology that has been used extensively for the biochemical analysis of ...

Analysis of AtHIRD11 Intrinsic Disorder and Binding Towards Metal Ions by Capillary Gel Electrophoresis and Affinity Capillary Electrophoresis

Plants are strongly dependent on their environment. In order to adjust to stressful changes (e.g., drought and high salinity), higher plants evolve classes of intrinsically disordered proteins (IDPs) to reduce oxidative and osmotic stress. This article uses a combination of capillary gel electrophoresis (CGE) and mobility shift affinity electrophoresis (ACE) in order to describe the binding behavior of different conformers of the IDP AtHIRD11 from Arabidopsis thaliana. CGE is used to confirm the purity of AtHIRD11 and to exclude fragments, posttranslational modifications, and other impurities as reasons for complex peak patterns. In this part of the experiment, the different sample components are separated by a viscous gel inside a capillary by their different masses and detected with a diode array detector. Afterward, the binding behavior of the sample towards various metal ions is investigated by ACE. In this case, the ligand is added to the buffer solution and the shift in migration time is measured in order to determine whether a binding event has occurred or not. One of the advantages of using the combination of CGE and ACE to determine the binding behavior of an IDP is the possibility to automate the gel electrophoresis and the binding assay. Furthermore, CGE shows a lower limit of detection than the classical gel electrophoresis and ACE is able to determine the manner of binding a ligand in a fast manner. In addition, ACE can also be applied to other charged species than metal ions. However, the use of this method for binding experiments is limited in its ability to determine the number of binding sites. Nevertheless, the combination of CGE and ACE can be adapted for characterizing the binding behavior of any protein sample towards numerous charged ligands.

This protocol combines the characterization of a protein sample by capillary gel electrophoresis and a fast-binding screening for charged ligands by affinity capillary electrophoresis. It is recommended for proteins with a flexible structure, such as intrinsically disordered proteins, to determine any differences in binding for different conformers.

毛细管电泳与亲和毛细管电泳对金属离子 AtHIRD11 固有紊乱与结合的分析

Plants are strongly dependent on their environment. In order to adjust to stressful changes (e.g., drought and high salinity), higher plants evolve ...

Proofreading and DNA Repair Assay Using Single Nucleotide Extension and MALDI-TOF Mass Spectrometry Analysis

The maintenance of the genome and its faithful replication is paramount for conserving genetic information. To assess high fidelity replication, we have developed a simple non-labeled and non-radio-isotopic method using a matrix-assisted laser desorption ionization with time-of-flight (MALDI-TOF) mass spectrometry (MS) analysis for a proofreading study. Here, a DNA polymerase [e.g., the Klenow fragment (KF) of Escherichia coli DNA polymerase I (pol I) in this study] in the presence of all four dideoxyribonucleotide triphosphates is used to process a mismatched primer-template duplex. The mismatched primer is then proofread/extended and subjected to MALDI-TOF MS. The products are distinguished by the mass change of the primer down to single nucleotide variations. Importantly, a proofreading can also be determined for internal single mismatches, albeit at different efficiencies. Mismatches located at 2-4-nucleotides (nt) from the 3' end were efficiently proofread by pol I, and a mismatch at 5 nt from the primer terminus showed only a partial correction. No proofreading occurred for internal mismatches located at 6 - 9 nt from the primer 3' end. This method can also be applied to DNA repair assays (e.g., assessing a base-lesion repair of substrates for the endo V repair pathway). Primers containing 3' penultimate deoxyinosine (dI) lesions could be corrected by pol I. Indeed, penultimate T-I, G-I, and A-I substrates had their last 2 dI-containing nucleotides excised by pol I before adding a correct ddN 5'-monophosphate (ddNMP) while penultimate C-I mismatches were tolerated by pol I, allowing the primer to be extended without repair, demonstrating the sensitivity and resolution of the MS assay to measure DNA repair.

A non-labeled, non-radio-isotopic method for DNA polymerase proofreading and a DNA repair assay was developed by using high-resolution MALDI-TOF mass spectrometry and a single nucleotide extension strategy. The assay proved to be very specific, simple, rapid, and easy to perform for proofreading and repair patches shorter than 9-nucleotides.

单核苷酸延长和 MALDI 质谱分析校对及 DNA 修复方法

The maintenance of the genome and its faithful replication is paramount for conserving genetic information. To assess high fidelity replication, we have ...

Analysis of Thylakoid Membrane Protein Complexes by Blue Native Gel Electrophoresis

Photosynthetic electron transfer chain (ETC) converts solar energy to chemical energy in the form of NADPH and ATP. Four large protein complexes embedded in the thylakoid membrane harvest solar energy to drive electrons from water to NADP+ via two photosystems, and use the created proton gradient for production of ATP. Photosystem PSII, PSI, cytochrome b6f (Cyt b6f) and ATPase are all multiprotein complexes with distinct orientation and dynamics in the thylakoid membrane. Valuable information about the composition and interactions of the protein complexes in the thylakoid membrane can be obtained by solubilizing the complexes from the membrane integrity by mild detergents followed by native gel electrophoretic separation of the complexes. Blue native polyacrylamide gel electrophoresis (BN-PAGE) is an analytical method used for the separation of protein complexes in their native and functional form. The method can be used for protein complex purification for more detailed structural analysis, but it also provides a tool to dissect the dynamic interactions between the protein complexes. The method was developed for the analysis of mitochondrial respiratory protein complexes, but has since been optimized and improved for the dissection of the thylakoid protein complexes. Here, we provide a detailed up-to-date protocol for analysis of labile photosynthetic protein complexes and their interactions in Arabidopsis thaliana.

A protocol for the elucidation of plant thylakoid protein complex organization and composition with blue native polyacrylamide gel electrophoresis (BN-PAGE) and 2D-SDS-PAGE is described. The protocol is optimized for Arabidopsis thaliana, but can be used for other plant species with minor modifications.

蓝色本机凝胶电泳法分析囊体膜蛋白配合物

Photosynthetic electron transfer chain (ETC) converts solar energy to chemical energy in the form of NADPH and ATP. Four large protein complexes embedded ...

High Sensitivity Measurement of Transcription Factor-DNA Binding Affinities by Competitive Titration Using Fluorescence Microscopy

Accurate quantification of transcription factor (TF)-DNA interactions is essential for understanding the regulation of gene expression. Since existing approaches suffer from significant limitations, we have developed a new method for determining TF-DNA binding affinities with high sensitivity on a large scale. The assay relies on the established fluorescence anisotropy (FA) principle but introduces important technical improvements. First, we measure a full FA competitive titration curve in a single well by incorporating TF and a fluorescently labeled reference DNA in a porous agarose gel matrix. Unlabeled DNA oligomer is loaded on the top as a competitor and, through diffusion, forms a spatio-temporal gradient. The resulting FA gradient is then read out using a customized epifluorescence microscope setup. This improved setup greatly increases the sensitivity of FA signal detection, allowing both weak and strong binding to be reliably quantified, even for molecules of similar molecular weights. In this fashion, we can measure one titration curve per well of a multi-well plate, and through a fitting procedure, we can extract both the absolute dissociation constant (KD) and active protein concentration. By testing all single-point mutation variants of a given consensus binding sequence, we can survey the entire binding specificity landscape of a TF, typically on a single plate. The resulting position weight matrices (PWMs) outperform those derived from other methods in predicting in vivo TF occupancy. Here, we present a detailed guide for implementing HiP-FA on a conventional automated fluorescent microscope and the data analysis pipeline.

Here we present a novel method for determining binding affinities at equilibrium and in solution with high sensitivity on a large scale. This improves the quantitative analysis of transcription factor-DNA binding. The method is based on automated fluorescence anisotropy measurements in a controlled delivery system.

荧光显微镜竞争滴定法测定转录机-dna 结合感的高灵敏度

Accurate quantification of transcription factor (TF)-DNA interactions is essential for understanding the regulation of gene expression. Since existing ...

DNA Electrophoresis Using Thiazole Orange Instead of Ethidium Bromide or Alternative Dyes

DNA gel electrophoresis using agarose is a common tool in molecular biology laboratories, allowing separation of DNA fragments by size. After separation, DNA is visualized by staining. This article demonstrates how to use thiazole orange to stain DNA. Thiazole orange compares favorably to common staining methods, in that it is sensitive, inexpensive, excitable with UV or blue light (to prevent sample damage), and safer than ethidium bromide. Labs already equipped to run DNA electrophoresis experiments using ethidium bromide can generally switch dyes with no additional changes to existing protocols, using UV light for detection. Blue-light detection to avoid sample damage can additionally be achieved with a blue-light source and emission filter. Labs already equipped for blue-light detection can simply switch dyes with no additional changes to existing protocols.

Here, we present a protocol to use thiazole orange for the detection of DNA in gel electrophoresis experiments. The use of thiazole orange allows elimination of ethidium bromide, and fluorescence detection can be achieved with either UV or blue light.

用噻唑橙代替溴代或替代染料进行 DNA 电泳

DNA gel electrophoresis using agarose is a common tool in molecular biology laboratories, allowing separation of DNA fragments by size. After separation, ...

DNA Sequence Recognition by DNA Primase Using High-Throughput Primase Profiling

DNA primase synthesizes short RNA primers that initiate DNA synthesis of Okazaki fragments on the lagging strand by DNA polymerase during DNA replication. The binding of prokaryotic DnaG-like primases to DNA occurs at a specific trinucleotide recognition sequence. It is a pivotal step in the formation of Okazaki fragments. Conventional biochemical tools that are used to determine the DNA recognition sequence of DNA primase provide only limited information. Using a high-throughput microarray-based binding assay and consecutive biochemical analyses, it has been shown that 1) the specific binding context (flanking sequences of the recognition site) influences the binding strength of the DNA primase to its template DNA, and 2) stronger binding of primase to the DNA yields longer RNA primers, indicating higher processivity of the enzyme. This method combines PBM and primase activity assay and is designated as high-throughput primase profiling (HTPP), and it allows characterization of specific sequence recognition by DNA primase in unprecedented time and scalability.&#160;

Protein binding microarray (PBM) experiments combined with biochemical assays link the binding and catalytic properties of DNA primase, an enzyme that synthesizes RNA primers on template DNA. This method, designated as high-throughput primase profiling (HTPP), can be used to reveal DNA-binding patterns of a variety of enzymes.

DNA序列识别利用高通量原酶分析的DNAPrimase

DNA primase synthesizes short RNA primers that initiate DNA synthesis of Okazaki fragments on the lagging strand by DNA polymerase during DNA replication. ...