Name: protein-trna agarose gel retardation assays for the analysis of the n6-threonylcarbamoyladenosine tcda function
Uploaded: 2017-06-21T12:30:00.000+00:00
Duration: 8 min 3 s
Description: Watch this Scientific Journal Video about Protein-tRNA Agarose Gel Retardation Assays for the Analysis of the N6-threonylcarbamoyladenosine TcdA Function at JoVE.com

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 the staining agent if toxic and/or carcinogenic (e.g., ethidium bromide).
1. Preparation of the Agarose Gel
<ol>
	<li>Weigh 2 g of agarose and add it to a glass bottle to prepare a 2% w/v agarose gel.</li>
	<li>Add 100 mL of 1x tris-borate-ethylenediaminetetraacetic acid (EDTA) (TBE) running buffer to the agarose-containing bottle. Melt by heating in a microwave. At 30 s intervals, swirl the contents to mix well and repeat this step until the agarose is completely dissolved. Allow the agarose solution cool down to approximately 50-60 &#176;C.</li>
	<li>Tape the open edges of a gel tray to create a mold, place an appropriate comb to create the wells and cast the molten agarose into it. Avoid bubble formation and let it solidify at room temperature.</li>
	<li>Once solidified, place the gel tray in an electrophoresis unit and fill it with TBE buffer until the gel is fully covered.</li>
</ol>
2. Preparation of the tRNA
<ol>
	<li>Express tRNA(UUU) in E. coli
	<ol>
		<li>In the morning, use a vial of frozen E. coli BL21(DE3) transformed with the expression vector pET23d-EcUUU2 (harbors the gene encoding E. coli tRNA(UUU)), to streak a low-salt Luria Broth (LB) plate supplemented with 100 &#181;g/mL ampicillin. Invert the plate and place it into a 37 &#176;C incubator until colonies appear (late afternoon).</li>
		<li>Inoculate one well-grown, single colony in 5 mL LB plus 100 &#181;g/mL ampicillin and grow overnight at 220 rpm at 37 &#176;C.</li>
		<li>The next morning, pellet the cells (6,500 x g for 10 min at 4 &#176;C), replace medium with 5 mL fresh LB plus 100 &#181;g/mL ampicillin and resuspend. Use this suspension to inoculate 200 mL LB plus 100 &#181;g/mL ampicillin. Grow for 5 h at 220 rpm at 37 &#176;C.</li>
		<li>When the optical density of the culture at 590 nm (OD590) has reached 0.6 - 0.8, add 1 mM IPTG to the culture to trigger the expression of the tRNA(UUU) gene. Incubate at 37 &#176;C for 3 h.</li>
		<li>Harvest the cells by centrifuging the culture at 6,500 x g for 10 min at 4 &#176;C.</li>
	</ol>
	</li>
	<li>Lysis and extraction
	<ol>
		<li>Resuspend the cell pellet in 5 mL lysis buffer (0.3 M sodium acetate, 10 mM EDTA). From this point onward, used autoclaved buffers and keep all the tRNA-containing samples at 4 &#176;C to prevent tRNA degradation.</li>
		<li>Add 1 volume of acid phenol (pH 4.3) to the resuspended cell pellet in the fume hood. Mix for 1 min by inversion to lyse the cells and centrifuge at 10,000 x g (10 min, 4 &#176;C).</li>
		<li>Collect the upper aqueous phase containing the soluble tRNA(UUU) (and smaller concentrations of the other tRNA pools) using a pipette taking care not to aspirate the organic (bottom) phase. Discard the bottom layer and the pellet, which consists of the organic phase and cell debris, into an adequate container.</li>
		<li>Precipitate the tRNA by thoroughly mixing the soluble (aqueous) phase with 2.5 volume 100% v/v ethanol by inversion for 1 h at 4 &#176;C. Centrifuge the mixture at 15,000 x g (30 min, 4 &#176;C).</li>
		<li>Decant the supernatant carefully and resuspend the tRNA-rich pellet in 4 mL gel filtration buffer (20 mM sodium phosphate or potassium phosphate, pH 7.4, 0.1 mM EDTA). Run 5 &#181;L of the resuspended tRNA pool on a 2% w/v agarose gel. 
		NOTE: Good quality tRNA appears as a single band (molecular size between 50-100 bp).</li>
	</ol>
	</li>
	<li>Purification of tRNA(UUU)
	<ol>
		<li>Following standard chromatographic practice12, load the resuspended tRNA(UUU) onto a high-resolution preparative gel filtration column (dimensions: 16 x 600 mm, bed volume: 120 mL, resolution range: 1,000-70,000 Da) previously equilibrated in gel filtration buffer (mobile phase). Set the flow rate to 1 mL/min to elute the samples. 
		NOTE: The tRNA(UUU) peak elutes approximately at 75.5 mL. Typically, a yield of 0.5-1.0 mg/L tRNA of culture can be obtained.</li>
		<li>Analyze the samples at representative elution volumes by electrophoresing 5 - 10 &#181;L of each sample on a 2% w/v agarose gel.</li>
	</ol>
	</li>
</ol>
3. Sample Preparation
<ol>
	<li>Express and purify TcdA according to L&#243;pez-Estepa et al.2. 
	NOTE: Up to 250 &#181;M TcdA can be used for the study.</li>
	<li>Pipette the corresponding amount of TcdA as per Table 1 into properly labeled 1.5 mL centrifuge tubes. Add 1.6 mM tris(2-carboxyethyl)phosphine (TCEP) (final concentration) and gently mix using a pipette. Close the lid and incubate the mixture at room temperature for 5 min.</li>
	<li>Add 10 &#181;M of adenosine triphosphate (ATP) and 50 mM MgCl2 (final concentrations). Mix with a pipette and incubate the mixture for 5 min at room temperature.</li>
	<li>Add purified tRNA(UUU) (section 2.3) as per Table 1, mix with a pipette and incubate at room temperature for 5 min.</li>
	<li>Add phosphate buffered saline (PBS) up to 100 &#181;L final volume. Mix properly and add glycerol to a final concentration of 10% v/v.</li>
	<li>Vortex the sample and briefly spin down the contents of the tube (10,000 x g, 1 min, 4 &#176;C).</li>
</ol>
4. Gel Loading and Electrophoresis Development
<ol>
	<li>Place electrophoresis unit into a tray filled with crushed ice to maintain the chamber at 4 &#176;C during the electrophoresis run.</li>
	<li>Carefully, pipette 5 &#181;L of each sample into the corresponding well. Add a suitable DNA size marker.</li>
	<li>Plug the electrodes into the corresponding slots of the power supply unit. Turn on the power supply unit and set the voltage to 100 V and run the gel for 90 min.</li>
</ol>
5. Gel Staining to Observe tRNA-Protein Interaction
<ol>
	<li>Prepare the staining solution by mixing 50 mL of TBE with 1x of a suitable DNA stain. Avoid exposing the staining solution to sunlight by covering the staining container with aluminum foil. 
	NOTE: DNA stains are usually stored as 10,000 or 20,000x concentrated stocks.</li>
	<li>After 90 min of electrophoresis, carefully remove the gel from the tray and place it in a container with staining solution. Place it on a rocker at low rocking speed at room temperature for 30 min.</li>
	<li>Remove the agarose gel from the staining container, tap it carefully on a piece of cellulose tissue or filter paper to remove excess liquid, and place it directly on a transilluminator. Switch on the UV light to visualize bands containing tRNA. Take a photograph of the gel.</li>
	<li>Protein staining (optional).
	<ol>
		<li>Discard the DNA staining solution safely (according to safety procedures) and substitute it with 50 mL Coomassie Brilliant Blue (CBB) solution. Place the tray on a rocker at room temperature and stain overnight (&#62;12 h). Discard the CBB staining solution and replace it with 50 mL PBS to remove excess dye. Destain for 1 h on a rocker.</li>
	</ol>
	</li>
	<li>Visualize protein-containing tRNA complexes under a light transilluminator and take photographs of the gel to compare with the tRNA UV gel picture.</li>
</ol>

<ol>
	<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><tbody><tr><td>&lt;em&gt;E. coli&lt;/em&gt; BL21(DE3)</td><td>Novagen</td><td>70235</td><td>DE3 lysogen contains T7 polymerase upon IPTG induction.</td></tr><tr><td>pET23d</td><td>Novagen</td><td>69748-3</td><td>pET23d confers resistance to ampicillin; T7 promoter.</td></tr><tr><td>LB Broth, Low Salt (Lennox L Broth), Granulated</td><td>Melford</td><td>GL1703</td><td>Conventional LB Broth, High Salt, can also be used.</td></tr><tr><td>Ampicillin</td><td>Sigma-Aldrich</td><td>10419313</td><td></td></tr><tr><td>Incubator Shaker (Thermostated)</td><td>NBS</td><td>Excella E24&amp;nbsp;</td><td>Any shaker incubator with temperature control can be used.</td></tr><tr><td>Isopropyl-beta-D-thiogalactopyranoside (IPTG), &gt;=99%</td><td>Acros Organics</td><td>BP1755</td><td></td></tr><tr><td>Sodium acetate, anhydrous, &gt;99%</td><td>Melford</td><td>B4017</td><td></td></tr><tr><td>Ethylenediaminetetraacetic acid (EDTA), Disodium salt, &gt;99%</td><td>Acros Organics</td><td>AC327205000</td><td>Harmful if inhaled.</td></tr><tr><td>Centrifuge (refrigerated)</td><td>Eppendorf</td><td>5430</td><td></td></tr><tr><td>Centrifuge (refrigerated) rotor</td><td>Eppendorf</td><td>5430/5430P</td><td></td></tr><tr><td>Centrifuge</td><td>Sorvall</td><td>RC5C</td><td></td></tr><tr><td>Centrifuge rotor</td><td>Sorvall</td><td>SLA-3000</td><td></td></tr><tr><td>Phenol solution, Saturated with 0.1 M citrate buffer, pH 4.3 &amp;plusmn; 0.2</td><td>Sigma-Aldrich</td><td>P4682</td><td>Acute toxicity (oral, dermal, inhalation), corrosive</td></tr><tr><td>Ethanol absolute for analysis, 100% v/v</td><td>Merck Millipore</td><td>100983</td><td></td></tr><tr><td>Sodium phosphate dibasic dihydrate, Na&lt;sub&gt;2&lt;/sub&gt;HPO&lt;sub&gt;4&lt;/sub&gt;, &gt;=99%</td><td>Sigma-Aldrich</td><td>71643</td><td></td></tr><tr><td>Potassium dihydrogen phosphate, KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;</td><td>Merck</td><td>48,730,250</td><td></td></tr><tr><td>HiLoad 16/60 Superdex 75&amp;nbsp;</td><td>GE Healthcare</td><td>28989333</td><td></td></tr><tr><td>Agarose</td><td>Melford</td><td>MB1200</td><td></td></tr><tr><td>Tris [Tris(hydroxymethyl) aminomethane HCl]</td><td>Melford</td><td>T1513</td><td></td></tr><tr><td>Boric Acid</td><td>Melford</td><td>B0503</td><td></td></tr><tr><td>Microwave</td><td>Haier</td><td>HDA-2070M</td><td></td></tr><tr><td>TCEP [Tris(2-carboxyethyl)phosphine hydrochloride]</td><td>Sigma-Aldrich</td><td>C4706</td><td>Corrosive to metals and skin.</td></tr><tr><td>ATP [Adenosine 5&amp;prime;-triphosphate disodium salt hydrate], Grade I, &gt;=99%</td><td>Sigma-Aldrich</td><td>A2383</td><td></td></tr><tr><td>Magnesium chloride (MgCl&lt;sub&gt;2&lt;/sub&gt;), anhydrous, &gt;=98%</td><td>Sigma-Aldrich</td><td>M8266</td><td></td></tr><tr><td>Sodium chloride (NaCl), &gt;99%</td><td>Fisher Bioreagents</td><td>BP358</td><td></td></tr><tr><td>Potassium chloride (KCl), &gt;99%</td><td>Melford</td><td>P0515</td><td></td></tr><tr><td>NZYDNA Ladder VI</td><td>NZYtech</td><td>MB8901</td><td></td></tr><tr><td>Power supply</td><td>Consort</td><td>EV261</td><td></td></tr><tr><td>Electrophoresis unit</td><td>Real Laboratory</td><td>RELSMINI10</td><td></td></tr><tr><td>Real Safe nucleic acid staining</td><td>Real Laboratory</td><td>RBMSAFE</td><td>20,000X stock</td></tr><tr><td>UV Transilluminator (G:Box/EF)</td><td>Syngene</td><td>2216498</td><td></td></tr><tr><td>Coomassie Brilliant Blue G</td><td>Sigma-Aldrich</td><td>B0770</td><td></td></tr><tr><td>Rocker (Gyro-Rocker)</td><td>Stuart</td><td>SSL3</td><td></td></tr><tr><td>Mixer Vortex&amp;nbsp;</td><td>Fisher brand</td><td>13214789</td><td></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 ...

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JoVE Journal

Biochemistry

9.7K Views.  Spanish National Research Council (CSIC). 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.

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

Preparation and In Vivo Use of an Activity-based Probe for N-acylethanolamine Acid Amidase

Activity-based protein profiling (ABPP) is a method for the identification of an enzyme of interest in a complex proteome through the use of a chemical probe that targets the enzyme&#39;s active sites. A reporter tag introduced into the probe allows for the detection of the labeled enzyme by in-gel fluorescence scanning, protein blot, fluorescence microscopy, or liquid chromatography-mass spectrometry. Here, we describe the preparation and use of the compound ARN14686, a click chemistry activity-based probe (CC-ABP) that selectively recognizes the enzyme N-acylethanolamine acid amidase (NAAA). NAAA is a cysteine hydrolase that promotes inflammation by deactivating endogenous peroxisome proliferator-activated receptor (PPAR)-alpha agonists such as palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). NAAA is synthesized as an inactive full-length proenzyme, which is activated by autoproteolysis in the acidic pH of the lysosome. Localization studies have shown that NAAA is predominantly expressed in macrophages and other monocyte-derived cells, as well as in B-lymphocytes. We provide examples of how ARN14686 can be used to detect and quantify active NAAA ex vivo in rodent tissues by protein blot and fluorescence microscopy.

Preparation and In Vivo Use of an Activity-based Probe for N-acylethanolamine Acid Amidase

Here, we describe the preparation and use of an activity-based probe (ARN14686, undec-10-ynyl-N-[(3S)-2-oxoazetidin-3-yl]carbamate) that allows for the detection and quantification of the active form of the proinflammatory enzyme N-acylethanolamine acid amidase (NAAA), both in vitro and ex vivo.

Activity-based protein profiling (ABPP) is a method for the identification of an enzyme of interest in a complex proteome through the use of a chemical ...

In vitro tRNA Methylation Assay with the Entamoeba histolytica DNA and tRNA Methyltransferase Dnmt2 (Ehmeth) Enzyme

Protozoan parasites are among the most devastating infectious agents of humans responsible for a variety of diseases including amebiasis, which is one of the three most common causes of death from parasitic disease. The agent of amebiasis is the amoeba parasite Entamoeba histolytica that exists under two stages: the infective cyst found in food or water and the invasive trophozoite living in the intestine. The clinical manifestations of amebiasis range from being asymptomatic to colitis, dysentery or liver abscesses. E. histolytica is one of the rare unicellular parasite with 5-methylcytosine (5mC) in its genome. 1, 2 It contains a single DNA methyltransferase, Ehmeth, that belongs to the Dnmt2 family. 2 A role for Dnmt2 in the control of repetitive elements has been established in E. histolytica, 3 Dictyostelium discoideum 4,5 and Drosophila. 6 Our recent work has shown that Ehmeth methylates tRNAAsp, and this finding indicates that this enzyme has a dual DNA/tRNAAsp methyltransferase activity. 7 This observation is in agreement with the dual activity that has been reported for D. discoideum and D. melanogaster. 8 The functional significance of the DNA/tRNA specificity of Dnmt2 enzymes is still unknown. To address this question, a method to determine the tRNA methyltransferase activity of Dnmt2 proteins was established. In this video, we describe a straightforward approach to prepare an adequate tRNA substrate for Dnmt2 and a method to measure its tRNA methyltransferase activity.

In vitro tRNA Methylation Assay with the Entamoeba histolytica DNA and tRNA Methyltransferase Dnmt2 Ehmeth Enzyme

This protocol describes the preparation of a synthetic tRNA substrate for the Entamoeba histolytica DNA/tRNA methyltransferase 2 (Dnmt2) homolog Ehmeth and the measure of its methyltransferase activity. This experimental approach can be used for investigating the activity of other Dnmt2 proteins.

Protozoan parasites are among the most devastating infectious agents of humans responsible for a variety of diseases including amebiasis, which is one of ...

Immunology and Infection

Semi-quantitative Detection of RNA-dependent RNA Polymerase Activity of Human Telomerase Reverse Transcriptase Protein

Human telomerase reverse transcriptase (TERT) is the catalytic subunit of telomerase, and it elongates telomere through RNA-dependent DNA polymerase activity. Although TERT is named as a reverse transcriptase, structural and phylogenetic analyses of TERT demonstrate that TERT is a member of right-handed polymerases, and relates to viral RNA-dependent RNA polymerases (RdRPs) as well as viral reverse transcriptase. We firstly identified RdRP activity of human TERT that generates complementary RNA stand to a template non-coding RNA and contributes to RNA silencing in cancer cells. To analyze this non-canonical enzymatic activity, we developed RdRP assay with recombinant TERT in 2009, thereafter established in vitro RdRP assay for endogenous TERT. In this manuscript, we describe the latter method. Briefly, TERT immune complexes are isolated from cells, and incubated with template RNA and rNTPs including radioactive rNTP for RdRP reaction. To eliminate single-stranded RNA, reaction products are treated with RNase I, and the final products are analyzed with polyacrylamide gel electrophoresis. Radiolabeled RdRP products can be detected by autoradiography after overnight exposure.

Human telomerase reverse transcriptase (TERT) synthesizes not only telomeric DNA but also double-stranded RNA through RNA-dependent RNA polymerase activity. Here, we describe a newly established assay to detect RNA-dependent RNA polymerase activity of endogenous TERT.

Human telomerase reverse transcriptase (TERT) is the catalytic subunit of telomerase, and it elongates telomere through RNA-dependent DNA polymerase ...

Genetics

Efficient Purification and LC-MS/MS-based Assay Development for Ten-Eleven Translocation-2 5-Methylcytosine Dioxygenase

The epigenetic transcription regulation mediated by 5-methylcytosine (5mC) has played a critical role in eukaryotic development. Demethylation of these epigenetic marks is accomplished by sequential oxidation by ten-eleven translocation dioxygenases (TET1-3), followed by the thymine-DNA glycosylase-dependent base excision repair. Inactivation of the TET2 gene due to genetic mutations or by other epigenetic mechanisms is associated with a poor prognosis in patients with diverse cancers, especially hematopoietic malignancies. Here, we describe an efficient single step purification of enzymatically active untagged human TET2 dioxygenase using cation exchange chromatography. We further provide a liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach that can separate and quantify the four normal DNA bases (A, T, G, and C), as well as the four modified cytosine bases (5-methyl, 5-hydroxymethyl, 5-formyl, and 5-carboxyl). This assay can be used to evaluate the activity of wild type and mutant TET2 dioxygenases.

Here, we present a protocol for an efficient single step purification of the active untagged human ten-eleven translocation-2 (TET2) 5-methylcytosine dioxygenase using ion-exchange chromatography and its assay using a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based approach.

The epigenetic transcription regulation mediated by 5-methylcytosine (5mC) has played a critical role in eukaryotic development. Demethylation of these ...

An In Vitro Assay to Detect tRNA-Isopentenyl Transferase Activity

N6-isopentenyladenosine RNA modifications are functionally diverse and highly conserved among prokaryotes and eukaryotes. One of the most highly conserved N6-isopentenyladenosine modifications occurs at the A37 position in a subset of tRNAs. This modification improves translation efficiency and fidelity by increasing the affinity of the tRNA for the ribosome. Mutation of enzymes responsible for this modification in eukaryotes are associated with several disease states, including mitochondrial dysfunction and cancer. Therefore, understanding the substrate specificity and biochemical activities of these enzymes is important for understanding of normal and pathologic eukaryotic biology. A diverse array of methods has been employed to characterize i6A modifications. Herein is described a direct approach for the detection of isopentenylation by Mod5. This method utilizes incubation of RNAs with a recombinant isopentenyl transferase, followed by RNase T1 digestion, and 1-dimensional gel electrophoresis analysis to detect i6A modifications. In addition, the potential adaptability of this protocol to characterize other RNA-modifying enzymes is discussed.

An In Vitro Assay to Detect tRNA-Isopentenyl Transferase Activity

Here, we describe a protocol for the biochemical characterization of the yeast RNA-modifying enzyme, Mod5, and discuss how this protocol could be applied to other RNA-modifying enzymes.

N6-isopentenyladenosine RNA modifications are functionally diverse and highly conserved among prokaryotes and eukaryotes. One of the most highly conserved ...

Antibody-Free Assay for RNA Methyltransferase Activity Analysis

There are more than 100 chemically distinct modifications of RNA, two thirds of which consist of methylations. Interest in RNA modifications, and especially methylations, has re-emerged due to the important roles played by the enzymes that write and erase them in biological processes relevant to disease and cancer. Here, a sensitive in vitro assay for accurate analysis of RNA methylation writer activity on synthetic or in vitro transcribed RNAs is provided. This assay uses a tritiated form of S-adenosyl-methionine, resulting in direct labeling of methylated RNA with tritium. The low energy of tritium radiation makes the method safe, and pre-existing methods of tritium signal amplification, make it possible to quantify and to visualize the methylated RNA without the use of antibodies, which are commonly prone to artifacts. While this method is written for RNA methylation, few tweaks make it applicable to the study of other RNA modifications that can be radioactively labeled, such as RNA acetylation with 14C acetyl coenzyme A. Overall, this assay allows to quickly assess RNA methylation conditions, inhibition with small molecule inhibitors, or the effect of RNA or enzyme mutants, and provides a powerful tool to validate and expand results obtained in cells.

Here, an antibody-free in vitro assay for direct analysis of methyltransferase activity on synthetic or in vitro transcribed RNA is described.

There are more than 100 chemically distinct modifications of RNA, two thirds of which consist of methylations. Interest in RNA modifications, and ...

An In Vitro Enzymatic Assay to Measure Transcription Inhibition by Gallium(III) and H3 5,10,15-tris(pentafluorophenyl)corroles

Chemotherapy often involves broad-spectrum cytotoxic agents with many side effects and limited targeting. Corroles are a class of tetrapyrrolic macrocycles that exhibit differential cytostatic and cytotoxic properties in specific cell lines, depending on the identities of the chelated metal and functional groups. The unique behavior of functionalized corroles towards specific cell lines introduces the possibility of targeted chemotherapy.
Many anticancer drugs are evaluated by their ability to inhibit RNA transcription. Here we present a step-by-step protocol for RNA transcription in the presence of known and potential inhibitors. The evaluation of the RNA products of the transcription reaction by gel electrophoresis and UV-Vis spectroscopy provides information on inhibitive properties of potential anticancer drug candidates and, with modifications to the assay, more about their mechanism of action.
Little is known about the molecular mechanism of action of corrole cytotoxicity. In this experiment, we consider two corrole compounds: gallium(III) 5,10,15-(tris)pentafluorophenylcorrole (Ga(tpfc)) and freebase analogue 5,10,15-(tris)pentafluorophenylcorrole (tpfc). An RNA transcription assay was used to examine the inhibitive properties of the corroles. Five transcription reactions were prepared: DNA treated with Actinomycin D, triptolide, Ga(tpfc), tpfc at a [complex]:[template DNA base] ratio of 0.01, respectively, and an untreated control.
The transcription reactions were analyzed after 4 hr using agarose gel electrophoresis and UV-Vis spectroscopy. There is clear inhibition by Ga(tpfc), Actinomycin D, and triptolide.
This RNA transcription assay can be modified to provide more mechanistic detail by varying the concentrations of the anticancer complex, DNA, or polymerase enzyme, or by incubating the DNA or polymerase with the complexes prior to RNA transcription; these modifications would differentiate between an inhibition mechanism involving the DNA or the enzyme. Adding the complex after RNA transcription can be used to test whether the complexes degrade or hydrolyze the RNA. This assay can also be used to study additional anticancer candidates.

An In Vitro Enzymatic Assay to Measure Transcription Inhibition by GalliumIII and H3 5,10,15-trispentafluorophenylcorroles

Gallium(III) 5,10,15-(tris)pentafluorophenylcorrole and its freebase analogue exhibit low micromolar cell cytotoxicity. This manuscript describes an RNA transcription reaction, imaging RNA with an ethidium bromide-stained gel, and quantifying RNA with UV-Vis spectroscopy, in order to assess transcription inhibition by corroles and demonstrates a straightforward method of evaluating anticancer candidate properties.

Chemotherapy often involves broad-spectrum cytotoxic agents with many side effects and limited targeting. Corroles are a class of tetrapyrrolic ...

Bioengineering

Nucleocapsid Annealing-Mediated Electrophoresis (NAME) Assay Allows the Rapid Identification of HIV-1 Nucleocapsid Inhibitors

RNA or DNA folded in stable tridimensional folding are interesting targets in the development of antitumor or antiviral drugs. In the case of HIV-1, viral proteins involved in the regulation of the virus activity recognize several nucleic acids. The nucleocapsid protein NCp7 (NC) is a key protein regulating several processes during virus replication. NC is in fact a chaperone destabilizing the secondary structures of RNA and DNA and facilitating their annealing. The inactivation of NC is a new approach and an interesting target for anti-HIV therapy. The Nucleocapsid Annealing-Mediated Electrophoresis (NAME) assay was developed to identify molecules able to inhibit the melting and annealing of RNA and DNA folded in thermodynamically stable tridimensional conformations, such as hairpin structures of TAR and cTAR elements of HIV, by the nucleocapsid protein of HIV-1. The new assay employs either the recombinant or the synthetic protein, and oligonucleotides without the need of their previous labeling. The analysis of the results is achieved by standard polyacrylamide gel electrophoresis (PAGE) followed by conventional nucleic acid staining. The protocol reported in this work describes how to perform the NAME assay with the full-length protein or its truncated version lacking the basic N-terminal domain, both competent as nucleic acids chaperones, and how to assess the inhibition of NC chaperone activity by a threading intercalator. Moreover, NAME can be performed in two different modes, useful to obtain indications on the putative mechanism of action of the identified NC inhibitors.

Nucleocapsid Annealing-Mediated Electrophoresis NAME Assay Allows the Rapid Identification of HIV-1 Nucleocapsid Inhibitors

This protocol describes NAME, an assay that allows the rapid identification of molecules able to inhibit in vitro the chaperone activities of HIV-1 nucleocapsid protein.

RNA or DNA folded in stable tridimensional folding are interesting targets in the development of antitumor or antiviral drugs. In the case of HIV-1, viral ...

CD Spectroscopy to Study DNA-Protein Interactions

Circular dichroism (CD) spectroscopy is a simple and convenient method to investigate the secondary structure and interactions of biomolecules. Recent advancements in CD spectroscopy have enabled the study of DNA-protein interactions and conformational dynamics of DNA in different microenvironments in detail for a better understanding of transcriptional regulation in vivo. The area around a potential transcription zone needs to be unwound for transcription to occur. This is a complex process requiring the coordination of histone modifications, binding of the transcription factor to DNA, and other chromatin remodeling activities. Using CD spectroscopy, it is possible to study conformational changes in the promoter region caused by regulatory proteins, such as ATP-dependent chromatin remodelers, to promote transcription. The conformational changes occurring in the protein can also be monitored. In addition, queries regarding the affinity of the protein towards its target DNA and sequence specificity can be addressed by incorporating mutations in the target DNA. In short, the unique understanding of this sensitive and inexpensive method can predict changes in chromatin dynamics, thereby improving the understanding of transcriptional regulation.

The interaction of an ATP-dependent chromatin remodeler with a DNA ligand is described using CD spectroscopy. The induced conformational changes on a gene promoter analyzed by the peaks generated can be used to understand the mechanism of transcriptional regulation.

Circular dichroism (CD) spectroscopy is a simple and convenient method to investigate the secondary structure and interactions of biomolecules. Recent ...

Telomerase Activity in the Various Regions of Mouse Brain: Non-Radioactive Telomerase Repeat Amplification Protocol (TRAP) Assay

Telomerase, a ribonucleoprotein, is responsible for maintaining the telomere length and therefore promoting genomic integrity, proliferation, and lifespan. In addition, telomerase protects the mitochondria from oxidative stress and confers resistance to apoptosis, suggesting its possible importance for the surviving of non-mitotic, highly active cells such as neurons. We previously demonstrated the ability of novel telomerase activators to increase telomerase activity and expression in the various mouse brain regions and to protect motor neurons cells from oxidative stress. These results strengthen the notion that telomerase is involved in the protection of neurons from various lesions. To underline the role of telomerase in the brain, we here compare the activity of telomerase in male and female mouse brain and its dependence on age. TRAP assay is a standard method for detecting telomerase activity in various tissues or cell lines. Here we demonstrate the analysis of telomerase activity in three regions of the mouse brain by non-denaturing protein extraction using CHAPS lysis buffer followed by modification of the standard TRAP assay.
In this 2-step assay, endogenous telomerase elongates a specific telomerase substrate (TS primer) by adding TTAGGG 6 bp repeats (telomerase reaction). The telomerase reaction products are amplified by PCR reaction creating a DNA ladder of 6 bp increments. The analysis of the DNA ladder is made by 4.5% high resolution agarose gel electrophoresis followed by staining with highly sensitive nucleic acid stain.
Compared to the traditional TRAP assay that utilize 32P labeled radioactive dCTP&#39;s for DNA detection and polyacrylamide gel electrophoresis for resolving the DNA ladder, this protocol offers a non-toxic time saving TRAP assay for evaluating telomerase activity in the mouse brain, demonstrating the ability to detect differences in telomerase activity in the various female and male mouse brain region.

Telomerase Activity in the Various Regions of Mouse Brain: Non-Radioactive Telomerase Repeat Amplification Protocol TRAP Assay

Telomerase is expressed in the neonatal brain and also in distinct regions of the adult brain. We present a non-toxic time saving TRAP assay for the analysis of telomerase activity in various regions of the mouse brain and detection of differences in telomerase activity between male and female mouse brains.

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

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Preparation and In Vivo Use of an Activity-based Probe for N-acylethanolamine Acid Amidase

In vitro tRNA Methylation Assay with the Entamoeba histolytica DNA and tRNA Methyltransferase Dnmt2 (Ehmeth) Enzyme

Semi-quantitative Detection of RNA-dependent RNA Polymerase Activity of Human Telomerase Reverse Transcriptase Protein

Efficient Purification and LC-MS/MS-based Assay Development for Ten-Eleven Translocation-2 5-Methylcytosine Dioxygenase

An In Vitro Assay to Detect tRNA-Isopentenyl Transferase Activity

Antibody-Free Assay for RNA Methyltransferase Activity Analysis

An In Vitro Enzymatic Assay to Measure Transcription Inhibition by Gallium(III) and H₃ 5,10,15-tris(pentafluorophenyl)corroles

Nucleocapsid Annealing-Mediated Electrophoresis (NAME) Assay Allows the Rapid Identification of HIV-1 Nucleocapsid Inhibitors

CD Spectroscopy to Study DNA-Protein Interactions

Telomerase Activity in the Various Regions of Mouse Brain: Non-Radioactive Telomerase Repeat Amplification Protocol (TRAP) Assay