MCV is member of the CIB Intramural Program &#8220;Molecular Machines for Better Life&#8221; (MACBET). The research leading to these results has received funding from the Spanish Instituto de Salud Carlos III (PI12/01667 to MCV), the Spanish Ministerio de Econom&#237;a y Competitividad (CTQ2015-66206-C2-2-R and SAF2015-72961-EXP to MCV), the Regional Government of Madrid (S2010/BD-2316 to MCV), and the European Commission (Framework Programme 7 (FP7)) project ComplexINC (Contract No. 279039 to MCV). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Caution: Consult all relevant material safety data sheets (MSDS) before use. Several of the chemicals used in this protocol are toxic and corrosive. Use appropriate practices when performing the extraction of tRNA using phenol, including the use of a fume hood and personal protective equipment (safety glasses, gloves, lab coat, full-length pants, closed-toe shoes, etc.). This protocol uses a non-toxic nucleic acid stain. The use of alternative stains may require additional precautions and specialized disposal of...

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	<li>Scott, V., Clark, A. R., Docherty, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+gel+retardation+assay.">The gel retardation assay.</a> Methods Mol Biol. 31, 339-347 (1994).</li><li>L&#243;pez-Estepa, 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=The+crystal+structure+and+small-angle+X-ray+analysis+of+CsdL/TcdA+reveal+a+new+tRNA+binding+motif+in+the+MoeB/E1+superfamily.">The crystal structure and small-angle X-ray analysis of CsdL/TcdA reveal a new tRNA binding motif in the MoeB/E1 superfamily.</a> Plos One. 10 (4), e0118606 (2015).</li><li>Miyauchi, K., Kimura, S., Suzuki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+cyclic+form+of+N6-threonylcarbamoyladenosine+as+a+widely+distributed+tRNA+hypermodification.">A cyclic form of N6-threonylcarbamoyladenosine as a widely distributed tRNA hypermodification.</a> Nat Chem Biol. 9 (2), 105-111 (2013).</li><li>Bolstad, H. M., Botelho, D. J., Wood, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomic+analysis+of+protein-protein+interactions+within+the+Cysteine+Sulfinate+Desulfinase+Fe-S+cluster+biogenesis+system.">Proteomic analysis of protein-protein interactions within the Cysteine Sulfinate Desulfinase Fe-S cluster biogenesis system.</a> J Proteome Res. 9 (10), 5358-5369 (2010).</li><li>Loiseau, L., Ollagnier-de Choudens, S., Lascoux, D., Forest, E., Fontecave, M., Barras, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+the+heteromeric+CsdA-CsdE+cysteine+desulfurase,+assisting+Fe-S+cluster+biogenesis+in+Escherichia+coli.">Analysis of the heteromeric CsdA-CsdE cysteine desulfurase, assisting Fe-S cluster biogenesis in Escherichia coli.</a> J Biol Chem. 280 (29), 26760-26769 (2005).</li><li>Fried, M. G., Crothers, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Equilibrium+studies+of+the+cyclic+AMP+receptor+protein-DNA+interaction.">Equilibrium studies of the cyclic AMP receptor protein-DNA interaction.</a> J Mol Biol. 172 (3), 241-262 (1984).</li><li>Garner, M. M., Revzin, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+gel+electrophoresis+method+for+quantifying+the+binding+of+proteins+to+specific+DNA+regions:+application+to+components+of+the+Escherichia+coli+lactose+operon+regulatory+system.">A gel electrophoresis method for quantifying the binding of proteins to specific DNA regions: application to components of the Escherichia coli lactose operon regulatory system.</a> Nucleic Acids Res. 9 (13), 3047-3060 (1981).</li><li>Rio, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophoretic+mobility+shift+assays+for+RNA-protein+complexes.">Electrophoretic mobility shift assays for RNA-protein complexes.</a> Cold Spring Harb Protoc. 2014 (4), 435-440 (2014).</li><li>Ryder, S. P., Recht, M. I., Williamson, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+analysis+of+protein-RNA+interactions+by+gel+mobility+shift.">Quantitative analysis of protein-RNA interactions by gel mobility shift.</a> Methods Mol Biol. 488, 99-115 (2008).</li><li>Yakhnin, A. V., Yakhnin, H., Babitzke, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gel+mobility+shift+assays+to+detect+protein-RNA+interactions.">Gel mobility shift assays to detect protein-RNA interactions.</a> Methods Mol Biol. 905, 201-211 (2012).</li><li>Ream, J. A., Lewis, L. K., Lewis, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+agarose+gel+electrophoretic+mobility+shift+assay+for+quantitating+protein:+RNA+interactions.">Rapid agarose gel electrophoretic mobility shift assay for quantitating protein: RNA interactions.</a> Anal Biochem. 511, 36-41 (2016).</li><li>Hagel, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gel-filtration+chromatography.">Gel-filtration chromatography.</a> Curr Protoc Mol Biol. , (2001).</li></ol>

The authors have nothing to disclose.

The protein-tRNA agarose gel retardation assay described herein can be modified in a number of ways. First, the percentage of agarose in the gel can be reduced to allow the separation and visualization of protein-tRNA complexes significantly larger than the one analyzed here (120 kDa). Second, if the target protein is thermolabile, extra precautions must be taken to ensure that the temperature is kept below the maximum acceptable temperature by moving the electrophoresis apparatus to a cold room or by using ice packs ins...

The gel retardation assay1 (also known as electrophoretic mobility shift assay, EMSA) is an electrophoretic method designed to study and characterize protein-nucleic acid interactions. It allows the analysis of protein-DNA as well as protein-RNA interactions and in particular, interactions between tRNA and tRNA-binding proteins, using either purified components or complex mixtures of proteins (e.g., cell lysates) or nucleic acids (e.g., tRNA pools). We have applied gel retardation assays to the study of the interaction between purified tRNA(UUU) and TcdA, an N6-threonylcarbamoyladenosine (t6A) dehydratase, which cyclizes the threonylcarbamoyl side chain attached to A37 in the anticodon stem loop (ASL) of tRNAs to cyclic t6 (ct6A)2,3. TcdA is also known as CsdL3,4. The tcdA/csdL gene forms a cluster with the csdA and csdE genes5, which encode the cysteine desulfurase and the sulfur acceptor of the cysteine sulfinase desulfinate (CSD) system and is required to sustain TcdA function in vivo3.
The rationale behind the gel retardation assays is that, while free nucleic acid molecules migrate rapidly to the front of acrylamide or agarose gels by virtue of their large negative charge, the electrophoretic mobility of protein complexes of the same nucleic acids is dramatically reduced. The reduction in mobility is visualized as a &#34;shift&#34; in the nucleic acid-protein complexes, which resolve as discrete bands. Positively charged and larger nucleic acid-protein complex show a greater shift or reduction in mobility on a gel.
Since charge neutralization of the complex is a universal phenomenon for protein-nucleic acid complexes, the gel retardation assay can be applied to a wide range of complexes and nucleic acid types. The method is simple, inexpensive, and can be conducted in laboratories with minimum equipment. It requires only small amounts of proteins and tRNA. This is an advantage over alternative biophysical techniques, which usually consume larger quantities of sample.
The gel retardation assay has been widely used for the study of transcription factors. The assay has been used to analyze binding kinetics, strength, and specificity of transcription factors for many different DNA sequences. It was indeed in this field that the EMSA was first developed6,7. Gel retardation assays with RNA8,9,10,11 and tRNA molecules have also been used in ribosome research and to analyze, as we do here, the enzymes that modify tRNA nucleosides post-transcriptionally.
Many different parameters affect the result of a gel retardation assay such as temperature, quality of the protein and tRNA sample, and the strength of the binding. Careful planning and execution of the experiment is crucial for the interpretation of the results of the free nucleic acid and protein-bound species. Here, we used the synthetic gene encoding tRNA(UUU) cloned into an expression vector whose promoter lacks the Shine-Dalgarno ribosome binding site, leading to the synthesis of large amounts of the tRNA2. This detailed protocol is intended to provide a clear guide for performing tRNA gel retardation experiments while avoiding common mistakes.

<table border="0" cellpadding="0" cellspacing="0" width="1054">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:433px;">E. coli BL21(DE3)</td>
			<td style="width:135px;">Novagen</td>
			<td style="width:119px;">70235</td>
			<td style="width:367px;">DE3 lysogen contains T7 polymerase upon IPTG induction.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">pET23d</td>
			<td style="width:135px;">Novagen</td>
			<td style="width:119px;">69748-3</td>
			<td style="width:367px;">pET23d confers resistance to ampicillin; T7 promoter.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">LB Broth, Low Salt (Lennox L Broth), Granulated</td>
			<td style="width:135px;">Melford</td>
			<td style="width:119px;">GL1703</td>
			<td style="width:367px;">Conventional LB Broth, High Salt, can also be used.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Ampicillin</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td style="width:119px;">10419313</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:433px;">Incubator Shaker (Thermostated)</td>
			<td style="width:135px;">NBS</td>
			<td style="width:119px;">Excella E24&#160;</td>
			<td style="width:367px;">Any shaker incubator with temperature control can be used.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Isopropyl-beta-D-thiogalactopyranoside (IPTG), &#62;=99%</td>
			<td style="width:135px;">Acros Organics</td>
			<td style="width:119px;">BP1755</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Sodium acetate, anhydrous, &#62;99%</td>
			<td style="width:135px;">Melford</td>
			<td style="width:119px;">B4017</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Ethylenediaminetetraacetic acid (EDTA), Disodium salt, &#62;99%</td>
			<td style="width:135px;">Acros Organics</td>
			<td style="width:119px;">AC327205000</td>
			<td style="width:367px;">Harmful if inhaled.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Centrifuge (refrigerated)</td>
			<td style="width:135px;">Eppendorf</td>
			<td style="width:119px;">5430</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Centrifuge (refrigerated) rotor</td>
			<td style="width:135px;">Eppendorf</td>
			<td style="width:119px;">5430/5430P</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Centrifuge</td>
			<td style="width:135px;">Sorvall</td>
			<td style="width:119px;">RC5C</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Centrifuge rotor</td>
			<td style="width:135px;">Sorvall</td>
			<td style="width:119px;">SLA-3000</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:433px;">Phenol solution, Saturated with 0.1 M citrate buffer, pH 4.3 &#177; 0.2</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td style="width:119px;">P4682</td>
			<td style="width:367px;">Acute toxicity (oral, dermal, inhalation), corrosive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Ethanol absolute for analysis, 100% v/v</td>
			<td style="width:135px;">Merck Millipore</td>
			<td style="width:119px;">100983</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Sodium phosphate dibasic dihydrate, Na2HPO4, &#62;=99%</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td style="width:119px;">71643</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Potassium dihydrogen phosphate, KH2PO4</td>
			<td style="width:135px;">Merck</td>
			<td style="width:119px;">48,730,250</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">HiLoad 16/60 Superdex 75&#160;</td>
			<td style="width:135px;">GE Healthcare</td>
			<td style="width:119px;">28989333</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Agarose</td>
			<td style="width:135px;">Melford</td>
			<td style="width:119px;">MB1200</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Tris [Tris(hydroxymethyl) aminomethane HCl]</td>
			<td style="width:135px;">Melford</td>
			<td style="width:119px;">T1513</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Boric Acid</td>
			<td style="width:135px;">Melford</td>
			<td style="width:119px;">B0503</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Microwave</td>
			<td style="width:135px;">Haier</td>
			<td style="width:119px;">HDA-2070M</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">TCEP [Tris(2-carboxyethyl)phosphine hydrochloride]</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td style="width:119px;">C4706</td>
			<td style="width:367px;">Corrosive to metals and skin.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:433px;">ATP [Adenosine 5&#8242;-triphosphate disodium salt hydrate], Grade I, &#62;=99%</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td style="width:119px;">A2383</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:433px;">Magnesium chloride (MgCl2), anhydrous, &#62;=98%</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td style="width:119px;">M8266</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Sodium chloride (NaCl), &#62;99%</td>
			<td style="width:135px;">Fisher Bioreagents</td>
			<td style="width:119px;">BP358</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Potassium chloride (KCl), &#62;99%</td>
			<td style="width:135px;">Melford</td>
			<td style="width:119px;">P0515</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">NZYDNA Ladder VI</td>
			<td style="width:135px;">NZYtech</td>
			<td style="width:119px;">MB8901</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Power supply</td>
			<td style="width:135px;">Consort</td>
			<td style="width:119px;">EV261</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Electrophoresis unit</td>
			<td style="width:135px;">Real Laboratory</td>
			<td style="width:119px;">RELSMINI10</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Real Safe nucleic acid staining</td>
			<td style="width:135px;">Real Laboratory</td>
			<td style="width:119px;">RBMSAFE</td>
			<td style="width:367px;">20,000X stock</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">UV Transilluminator (G:Box/EF)</td>
			<td style="width:135px;">Syngene</td>
			<td style="width:119px;">2216498</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Coomassie Brilliant Blue G</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td style="width:119px;">B0770</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Rocker (Gyro-Rocker)</td>
			<td style="width:135px;">Stuart</td>
			<td style="width:119px;">SSL3</td>
			<td style="width:367px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:433px;">Mixer Vortex&#160;</td>
			<td style="width:135px;">Fisher brand</td>
			<td style="width:119px;">13214789</td>
			<td style="width:367px;"></td>
		</tr>
	</tbody>
</table>

protein-trna agarose gel retardation assays for the analysis of the n6-threonylcarbamoyladenosine tcda function

We demonstrate methods for the expression and purification of tRNA(UUU) in Escherichia coli and the analysis by gel retardation assays of the binding of tRNA(UUU) to TcdA, an N6-threonylcarbamoyladenosine (t6A) dehydratase, which cyclizes the threonylcarbamoyl side chain attached to A37 in the anticodon stem loop (ASL) of tRNAs to cyclic t6A (ct6A). Transcription of the synthetic gene encoding tRNA(UUU) is induced in E. coli with 1 mM isopropyl &#946;-D-1-thiogalactopyranoside (IPTG) and the cells containing tRNA are harvested 24 h post-induction. The RNA fraction is purified using the acid phenol extraction method. Pure tRNA is obtained by a gel filtration chromatography that efficiently separates the small-sized tRNA molecules from larger intact or fragmented nucleic acids. To analyze TcdA binding to tRNA(UUU), TcdA is mixed with tRNA(UUU) and separated on a native agarose gel at 4 &#176;C. The free tRNA(UUU) migrates faster, while the TcdA-tRNA(UUU) complexes undergo a mobility retardation that can be observed upon staining of the gel. We demonstrate that TcdA is a tRNA(UUU)-binding enzyme. This gel retardation assay can be used to study TcdA mutants and the effects of additives and other proteins on binding.

Large amounts of tRNA(UUU) can be obtained by expressing the tRNA gene in E. coli under the control of a strong inducible T7 promoter. The expressed tRNA(UUU) accumulates in the cytoplasm and is enriched over the pool of naturally abundant tRNAs. A two-step purification process consisting of a capture/extraction step and a gel filtration/polishing step was utilized to obtain EMSA-grade tRNA. The capture/extraction step uses pH 4.3 phenol to achieve the simultaneous precipitation ...

Watch this Scientific Journal Video about Protein-tRNA Agarose Gel Retardation Assays for the Analysis of the N6-threonylcarbamoyladenosine TcdA Function at JoVE.com

Protein-tRNA Agarose Gel Retardation Assays for the Analysis of the N6-threonylcarbamoyladenosine TcdA Function

A protocol is presented for the production of tRNA(UUU) and the analysis of tRNA(UUU) in complex with the enzyme TcdA by agarose gel retardation assays.

Protein-tRNA Agarose Gel Retardation Assays for the Analysis of the N6-threonylcarbamoyladenosine TcdA Function

We demonstrate methods for the expression and purification of tRNA(UUU) in Escherichia coli and the analysis by gel retardation assays of the binding of ...

The overall goal of this procedure is to demonstrate an RNA gel retardation assay designed for the discovery and characterization of RNA-binding proteins. Application of this assay is used to investigate the interaction between TcdA and transfer RNA. The agarose gel retardation method can provide answers to key questions in the field of RNA biology.For example, whether a certain protein interacts with RNA, whether the interaction is sequences-specific, and the strength of the interaction. The main advantages of this technique are that it uses various small amounts of protein and RNA samples, and yields very informative results about the protein-RNA interactions quite quickly. Though this method can provide insight into protein-tRNA complexes, it can also be applied to many other systems such as ribosomal RNA, messenger RNA, and any other kinds of RNA molecule.In the morning, retrieve a vial of frozen E coli BL21 DE3 transformed with the expression vector pET-23D EC triple-U. Streak a low salt luria broth or LB plate supplemented with 100 micrograms per milliliter ampicillin. Invert the plate and place it into a 37 degrees Celsius incubator until colonies appear in the late afternoon.Inoculate one well-grown single colony in five milliliters of LB plus 100 micrograms per milliliter of ampicillin and grow overnight. The next morning, pellet the cells. Following centrifugation, replace the medium with five milliliters of fresh LB plus 100 micrograms per milliliter of ampicillin and re-suspend.Use this suspension to inoculate 200 milliliter of LB plus 100 micrograms per milliliter of ampicillin. Grow the cells for five hours at 220 RPM and 37 degrees Celsius. When the optical density of the culture at 590 nanometers has reached 0.6 to 0.8, atdd1 millimolar IPTG to the culture to trigger the expression of the tRNA triple-U gene.After incubating the cells at 37 degrees Celsius for three hours, harvest the cells by centrifuging the culture at 6500 times g for 10 minutes at four degrees Celsius. To perform lysis, first re-suspend the cell pellet in five milliliters of lysis buffer. Add one volume of acid phenol to the re-suspended cell pellet in the fume hood and mix for one minute by inversion to lyse the cells.Then, centrifuge at 10 thousand times g for 10 minutes at 4 degrees Celsius. Collect the upper aqueous phase containing the soluble tRNA triple-U using a pipette. Take care not to aspirate the organic bottom phase.Precipitate the tRNA by thoroughly mixing the soluble phase with 2.5 volumes of 100%volume per volume ethanol by inversion for one hour at four degrees Celsius. Then, centrifuge at 15 thousand times g for 30 minutes at four degrees Celsius. Decant the supernatant carefully, then resuspend the tRNA-rich pellet in four milliliters of gel filtration buffer.Following standard chromatographic practice, load the re-suspended tRNA triple-U onto a high-resolution preparative gel filtration column previously equilibrated in gel filtration buffer. Set the flow rate to 1 milliliter per minute to elute the samples. To begin sample preparation, pipette the corresponding amount of TcdA as indicated in the text protocol into properly labeled 1.5 milliliter centrifuge tubes.Add a final concentration of 1.6 millimolar TCEP and gently mix using a pipette. Close the lid and incubate the mixture at room temperature for five minutes. Following incubation, add adenosine triphosphate and magnesium chloride.Mix with a pipette before incubating the mixture for five minutes at room temperature. Next, add purified tRNA triple-U according to the text protocol and mix the sample with a pipette. After incubating the sample at room temperature for five minutes, add phosphate buffered saline up to a 100 microliter final volume.Mix properly and add glycerol to a final concentration of 10%Vortex the sample before briefly spinning down the contents of the tube. Prepare the agarose gel as described in the text protocol. Place the electrophoresis unit into a tray filled with crushed ice to maintain the chamber at four degrees Celsius during the electrophoresis run.Carefully pipette five microliters of each sample into the corresponding well. Also add a suitable DNA size marker. Then, plug the electrodes into the corresponding slots of the power supply unit.After turning on the power supply unit, set the voltage to 100 volts and run the gel for 90 minutes. Next, prepare the staining solution by mixing 50 milliliters of TBE with 1X of a suitable DNA stain. After 90 minutes of electrophoresis, carefully remove the gel from the tray and place it in a container with staining solution.Place the container on a rocker at low rocking speed and rock at room temperature for 30 minutes. Remove the agarose gel from the staining container and tap it carefully on a piece of cellulose paper to remove excess liquid. Then, place the gel directly on a transilluminator.Switch on the UV light to visualize bands containing tRNA. Finally, take a photograph of the gel. Shown here are representative results of tRNA purification for gel retardation assays.In the chromatogram the absorbance of the elution fractions at 254 nanometers is recorded. The tRNA pool, enriched in over-expressed tRNA triple-U elutes at the highest peak. The quality and quantity of the tRNA pool is examined by agarose gel electrophoresis.The RNA gel retardation assay reveals that TcdA forms a stable complex with tRNA triple-U in tRNA concentration-dependent manner, which results in a protein-tRNA band that migrates more slowly than the free tRNA at the front of the gel. Once mastered, this technique can be done in less than two hours. While attempting this protocol, it's important to remember to follow strict laboratory techniques to ensure the chemical stability of tRNA.After watching this video, you should have a good understanding how to use agarose gel retardation assay to investigate the interaction of your protein of choice with tRNA, as in the case of TcdA or with any other type of RNA.

protein-trna-agarose-gel-retardation-assays-for-analysis-n6

Research

JoVE Journal

Biochemistry

9.7K 次观看.  Spanish National Research Council (CSIC). The overall goal of this procedure is to demonstrate an RNA gel retardation assay designed for the discovery and characterization of RNA-binding proteins. Application of this assay is used to investigate the interaction between TcdA and transfer RNA. The agarose gel retardation method can provide answers to key questions in the field of RNA biology.For example, whether a certain protein interacts with RNA, whether the interaction is sequences-specific, and the strength of the interacti...