Name: large-scale production of recombinant rnas on a circular scaffold using a viroid-derived system in escherichia coli
Uploaded: 2018-11-30T14:00:00
Description: Watch this Scientific Journal Video about Large-scale Production of Recombinant RNAs on a Circular Scaffold Using a Viroid-derived System in Escherichia coli at JoVE.com

This work was supported by grants BIO2017-83184-R and BIO2017-91865-EXP from the Spanish Ministerio de Ciencia, Innovaci&#243;n y Universidades (co-financed FEDER funds).

1. Plasmid Construction
<ol>
	<li>Amplify by PCR (or by reverse transcription PCR if starting from an RNA template) the cDNA corresponding to the RNA of interest using primers with 5&#8217; extension to allow assembly into the expression plasmid.&#160;To avoid undesired mutations, use a high-fidelity DNA polymerase.
	<ol>
		<li>To insert the cDNA in the expression plasmid by Gibson assembly20, add the following 5&#8217; extensions to the PCR primers: forward, 5&#8217;-tctccccctc...

<ol>
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A., Aragon&#233;s, V., Cordero, 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+viroid-derived+system+to+produce+large+amounts+of+recombinant+RNA+in+Escherichia+coli.">A viroid-derived system to produce large amounts of recombinant RNA in Escherichia coli.</a> Scientific Reports. 8 (1), 1904 (1904).</li><li>Dar&#242;s, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viroids:+small+noncoding+infectious+RNAs+with+the+remakable+ability+of+autonomous+replication.">Viroids: small noncoding infectious RNAs with the remakable ability of autonomous replication.</a> Current Research Topics in Plant Virology. , 295-322 (2016).</li><li>Flores, R., Hern&#225;ndez, C., Mart&#237;nez de Alba, A. E., Dar&#242;s, J. A., Di Serio, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viroids+and+viroid-host+interactions.">Viroids and viroid-host interactions.</a> Annual Review of Phytopathology. 43, 117-139 (2005).</li><li>Di Serio, F., 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=ICTV+Virus+Taxonomy+Profile:+Avsunviroidae.">ICTV Virus Taxonomy Profile: Avsunviroidae.</a> The Journal of General Virology. 99 (5), 611-612 (2018).</li><li>Nohales, M. A., Flores, R., Dar&#242;s, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viroid+RNA+redirects+host+DNA+ligase+1+to+act+as+an+RNA+ligase.">Viroid RNA redirects host DNA ligase 1 to act as an RNA ligase.</a> Proceedings of the National Academy of Sciences of the United States of America. 109 (34), 13805-13810 (2012).</li><li>Nohales, M. A., Molina-Serrano, D., Flores, R., Dar&#242;s, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Involvement+of+the+chloroplastic+isoform+of+tRNA+ligase+in+the+replication+of+viroids+belonging+to+the+family+Avsunviroidae.">Involvement of the chloroplastic isoform of tRNA ligase in the replication of viroids belonging to the family Avsunviroidae.</a> Journal of Virology. 86 (15), 8269-8276 (2012).</li><li>Dar&#242;s, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eggplant+latent+viroid:+a+friendly+experimental+system+in+the+family+Avsunviroidae.">Eggplant latent viroid: a friendly experimental system in the family Avsunviroidae.</a> Molecular Plant Pathology. 17 (8), 1170-1177 (2016).</li><li>Cordero, T., Ortol&#224;, B., Dar&#242;s, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mutational+Analysis+of+Eggplant+Latent+Viroid+RNA+Circularization+by+the+Eggplant+tRNA+Ligase+in+Escherichia+coli.">Mutational Analysis of Eggplant Latent Viroid RNA Circularization by the Eggplant tRNA Ligase in Escherichia coli.</a> Frontiers in Microbiology. 9 (635), (2018).</li><li>Gibson, D. 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=Enzymatic+assembly+of+DNA+molecules+up+to+several+hundred+kilobases.">Enzymatic assembly of DNA molecules up to several hundred kilobases.</a> Nature Methods. 6 (5), 343-345 (2009).</li><li>Timmons, L., Court, D. L., Fire, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ingestion+of+bacterially+expressed+dsRNAs+can+produce+specific+and+potent+genetic+interference+in+Caenorhabditis+elegans.">Ingestion of bacterially expressed dsRNAs can produce specific and potent genetic interference in Caenorhabditis elegans.</a> Gene. 263 (1-2), 103-112 (2001).</li><li>Schumacher, J., Randles, J. W., Riesner, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+two-dimensional+electrophoretic+technique+for+the+detection+of+circular+viroids+and+virusoids.">A two-dimensional electrophoretic technique for the detection of circular viroids and virusoids.</a> Analytical Biochemistry. 135 (2), 288-295 (1983).</li><li>Hansen, J. N., Pheiffer, B. H., Boehnert, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+and+electrophoretic+properties+of+solubilizable+disulfide+gels.">Chemical and electrophoretic properties of solubilizable disulfide gels.</a> Analytical Biochemistry. 105 (1), 192-201 (1980).</li><li>Gigu&#232;re, T., Adkar-Purushothama, C. R., Bolduc, F., Perreault, J. 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While researching the ELVd sequence and structure requirements involved in the recognition by the eggplant tRNA ligase, we noticed that co-expression of both molecules in the non-host E. coli led to an unexpected large accumulation of viroid circular forms in bacterial cells19. We understood that the large accumulation of viroid RNA in E. coli most probably was the consequence of co-expressing a highly stable RNA molecule, such as the relatively small (333 nt), highly based-paire...

In contrast to DNA and proteins, protocols for easy, efficient and cost-effective production of large amounts of RNA are not abundant. However, research and industry demand increasing amounts of these biomolecules to investigate their unique biological properties1, or to be employed in sophisticated biotechnological applications, including their use as highly specific aptamers2, therapeutic agents3, or selective pesticides4. In vitro transcription and chemical synthesis are commonly used in research to produce RNA. However, these methods entail important limitations when large amounts of the products are required. The logical alternative is to use the endogenous transcription machinery of living cells, followed by a purification process to separate the RNAs of interest from the cellular companions. Following this strategy, methods have been developed to produce recombinant RNAs in bacterial cells, such as the lab-friendly Escherichia coli5 or the marine purple phototrophic alpha-proteobacterium Rhodovolum sulfidophilum6. Most methods to produce recombinant RNA in bacteria rely on the expression of a native highly stable RNA scaffold, such as a tRNA or an rRNA, in which the RNA of interest is inserted7. This imposes the necessity of releasing the RNA of interest out of the chimeric molecule, if the presence of extra RNA is a problem for the downstream applications8. Another concept in recombinant RNA biotechnology is the production of recombinant ribonucleoprotein complexes that may be the desired product per se or used as a protective strategy to increase the stability of the RNA of interest9,10. Similarly, the production of circular RNAs has also been suggested as a strategy to generate more stable products11.
We have recently developed a new method to produce large amounts of recombinant RNA in E. coli that participates in three of the above concepts: the insertion of the RNA of interest in a highly stable circular RNA scaffold and the co-expression of the recombinant RNA with an interacting protein to likely produce a stable ribonucleoprotein complex that accumulates in remarkable amounts in bacterial cells12. In contrast to previous developments, we used an RNA scaffold completely alien to E. coli, namely a viroid. Viroids are a very particular type of infectious agents of higher plants that are exclusively constituted by a relatively small (246-401 nt) highly base-paired circular RNA13. Interestingly, viroids are non-coding RNAs and, with no help from their own proteins, they are able to complete complex infectious cycles in the infected hosts14. These cycles include the RNA-to-RNA replication in the nuclei or chloroplasts, depending on the viroid family &#8212;Pospiviroidae or Avsunviroidae, respectively&#8212;&#160;movement through the infected plant and evasion of the host defensive response. Viroids must be ranked among the most stable RNAs in nature, as a consequence of being a naked circular RNA and having to survive in the hostile environment of plant infected cells. This property may make viroids particularly suitable as scaffolds to stabilize recombinant RNA in biotechnological approaches. In addition, the new method is based on co-expression of the viroid scaffold with an interacting plant protein. Viroids replicate through a rolling-circle mechanism in which host enzymes are recruited to catalyze the different steps of the process. Notably some viroids, more specifically those that belong to the family Avsunviroidae15, contain ribozymes that are also involved in replication. Depending on the viroid species, transcription of viroid RNAs is mediated by the host RNA polymerase II or the chloroplastic nuclear-encoded RNA polymerase (NEP). Viroid RNA processing seems to be catalyzed by a host type-III RNase, although in viroids with ribozymes oligomeric RNA intermediates self-cleave during replication. Finally, the resulting viroid monomers are circularized, depending on the viroid family, by the host DNA ligase 1 or the chloroplastic isoform of tRNA ligase16,17. This last enzyme is involved in ligation of the monomeric forms of the viroids in the family Avsunviroidae, such as Eggplant latent viroid (ELVd)18.
In the course of a work to analyze the sequence and structural requirements of ELVd that determine recognition by the eggplant (Solanum melongena L.) tRNA ligase, we set up an experimental system based on co-expression of both molecules in E. coli19. We noticed that longer-than-unit ELVd transcripts self-cleave efficiently in E. coli cells through the embedded hammerhead ribozymes and that the resulting viroid monomers with 5&#39;-hydroxyl and 2&#39;,3&#39;-phosphodiester termini were efficiently circularized by the co-expressed eggplant tRNA ligase. Even more, the resulting circular viroid RNA reached an unexpected high concentration in E. coli, exceeding those of the endogenous rRNAs12. Absence of replication intermediates indicated lack of ELVd RNA-to-RNA amplification in these bacterial cells. Interestingly, insertion of heterologous RNAs in a particular position of the viroid molecule had a moderate effect on accumulation of the circular viroid-derived RNAs12. These observations made us envision a method to produce large amounts of recombinant RNAs in bacteria. In this method, the cDNAs corresponding to the RNAs of interest are inserted in the ELVd cDNA and the resulting chimeric RNA is expressed in E. coli through a strong constitutive promoter. For the system to work, E. coli must be co-transformed with a plasmid to express the eggplant tRNA ligase. The ELVd-derived longer-than-unit transcript is processed by the embedded hammerhead ribozymes and the resulting monomers with the appropriate termini are recognized and circularized by the co-expressed tRNA ligase. This way, the RNA of interest is inserted into a very stable circular scaffold consisting of the viroid circular molecule. This recombinant chimeric RNA is most probably further stabilized inside the E. coli cells by formation of a ribonucleoprotein complex through interaction with tRNA ligase. Using this method (see protocol below), RNA aptamers, hairpin RNAs and other structured RNAs have been easily produced in amounts of tens of milligrams per liter of E. coli culture in regular laboratory conditions and purified to homogeneity taking advantage of circularity12.

<table>
	<tbody>
		<tr>
			<td>Phusion High-Fidelity DNA polymerase</td>
			<td>Thermo Scientific</td>
			<td>F530S</td>
			<td></td>
		</tr>
		<tr>
			<td>Bpi I</td>
			<td>Thermo Scientific</td>
			<td>ER1011</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Conda</td>
			<td>8010</td>
			<td>D1 low EEO</td>
		</tr>
		<tr>
			<td>Tris</td>
			<td>PanReac AppliChem</td>
			<td>A1086,1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>PanReac AppliChem</td>
			<td>131008.1214</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Sigma-Aldrich</td>
			<td>E5134-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethidium bromide</td>
			<td>PanReac AppliChem</td>
			<td>A1152,0025</td>
			<td>1%</td>
		</tr>
		<tr>
			<td>Zymoclean Gel DNA Recovery</td>
			<td>Zymo Research</td>
			<td>D4001</td>
			<td></td>
		</tr>
		<tr>
			<td>NanoDrop</td>
			<td>ThermoFisher Scientific</td>
			<td>ND-3300</td>
			<td></td>
		</tr>
		<tr>
			<td>NEBuilder HiFi DNA Assembly Master Mix</td>
			<td>New England BioLabs</td>
			<td>E2621S</td>
			<td></td>
		</tr>
		<tr>
			<td>DNA Clean &#38; Concentrator</td>
			<td>Zymo Research</td>
			<td>D4003</td>
			<td></td>
		</tr>
		<tr>
			<td>Eporator</td>
			<td>Eppendorf</td>
			<td>4309000019</td>
			<td></td>
		</tr>
		<tr>
			<td>Escherichia coli DH5&#945;</td>
			<td>Invitrogen</td>
			<td>18265-017</td>
			<td></td>
		</tr>
		<tr>
			<td>Tryptone</td>
			<td>Intron Biotechnology</td>
			<td>Ba2014</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast extract</td>
			<td>Intron Biotechnology</td>
			<td>48045</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>PanReac AppliChem</td>
			<td>131659.1211</td>
			<td></td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>Intron Biotechnology</td>
			<td>25999</td>
			<td></td>
		</tr>
		<tr>
			<td>Ampicillin</td>
			<td>PanReac AppliChem</td>
			<td>A0839,0010</td>
			<td></td>
		</tr>
		<tr>
			<td>X-gal</td>
			<td>Duchefa</td>
			<td>X1402.1000</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N-Dimethylformamide</td>
			<td>PanReac AppliChem</td>
			<td>131785.1611</td>
			<td></td>
		</tr>
		<tr>
			<td>NucloSpin Plasmid</td>
			<td>Macherey-Nagel</td>
			<td>22740588.250</td>
			<td></td>
		</tr>
		<tr>
			<td>Escherichia coli BL21(DE3)</td>
			<td>Novagen</td>
			<td>69387-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Escherichia coli HT115(DE3)</td>
			<td></td>
			<td></td>
			<td>Ref. Timmons et al., 2001</td>
		</tr>
		<tr>
			<td>Chloramphenicol</td>
			<td>Duchefa</td>
			<td>C 0113.0025</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>PanReac AppliChem</td>
			<td>122329.1211</td>
			<td>87%</td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>PanReac AppliChem</td>
			<td>131509.1210</td>
			<td></td>
		</tr>
		<tr>
			<td>K2HPO4</td>
			<td>PanReac AppliChem</td>
			<td>122333.1211</td>
			<td></td>
		</tr>
		<tr>
			<td>HCl</td>
			<td>PanReac AppliChem</td>
			<td>131020.1211</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenol</td>
			<td>Scharlau</td>
			<td>FE04791000</td>
			<td>90%</td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>PanReac AppliChem</td>
			<td>A3691,1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Filtropur S 0.2</td>
			<td>Sarstedt</td>
			<td>83.1826.001</td>
			<td></td>
		</tr>
		<tr>
			<td>HiTrap DEAE Sepharose FF column</td>
			<td>GE Healthcare Life Sciences</td>
			<td>17-5055-01</td>
			<td></td>
		</tr>
		<tr>
			<td>&#196;KTAprime plus liquid chromatography system</td>
			<td>GE Healthcare Life Sciences</td>
			<td>11001313</td>
			<td></td>
		</tr>
		<tr>
			<td>Acrylamyde</td>
			<td>PanReac AppliChem</td>
			<td>A1089,1000</td>
			<td>2K</td>
		</tr>
		<tr>
			<td>N,N&#8217;-methylenebisacrylamide</td>
			<td>Sigma-Aldrich</td>
			<td>M7279-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Urea</td>
			<td>PanReac AppliChem</td>
			<td>146392.1211</td>
			<td></td>
		</tr>
		<tr>
			<td>Boric acid</td>
			<td>PanReac AppliChem</td>
			<td>A2940,1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Formamide</td>
			<td>PanReac AppliChem</td>
			<td>A0937,2500</td>
			<td></td>
		</tr>
		<tr>
			<td>Bromophenol blue</td>
			<td>Sigma-Aldrich</td>
			<td>B8026-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylene cyanol</td>
			<td>Sigma-Aldrich</td>
			<td>X4126-10G</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N&#8242;-Bis(acryloyl)cystamine</td>
			<td>Sigma-Aldrich</td>
			<td>A4929-5G</td>
			<td></td>
		</tr>
	</tbody>
</table>

large-scale production of recombinant rnas on a circular scaffold using a viroid-derived system in escherichia coli

With increasing interest in RNA biology and the use of RNA molecules in sophisticated biotechnological applications, the methods to produce large amounts of recombinant RNAs are limited. Here, we describe a protocol to produce large amounts of recombinant RNA in Escherichia coli based on co-expression of a chimeric molecule that contains the RNA of interest in a viroid scaffold and a plant tRNA ligase. Viroids are relatively small, non-coding, highly base-paired circular RNAs that are infectious to higher plants. The host plant tRNA ligase is an enzyme recruited by viroids that belong to the family Avsunviroidae, such as Eggplant latent viroid (ELVd), to mediate RNA circularization during viroid replication. Although ELVd does not replicate in E. coli, an ELVd precursor is efficiently transcribed by the E. coli RNA polymerase and processed by the embedded hammerhead ribozymes in bacterial cells, and the resulting monomers are circularized by the co-expressed tRNA ligase reaching a remarkable concentration. The insertion of an RNA of interest into the ELVd scaffold enables the production of tens of milligrams of the recombinant RNA per liter of bacterial culture in regular laboratory conditions. A main fraction of the RNA product is circular, a feature that facilitates the purification of the recombinant RNA to virtual homogeneity. In this protocol, a complementary DNA (cDNA) corresponding to the RNA of interest is inserted in a particular position of the ELVd cDNA in an expression plasmid that is used, along the plasmid to co-express eggplant tRNA ligase, to transform E. coli. Co-expression of both molecules under the control of strong constitutive promoters leads to production of large amounts of the recombinant RNA. The recombinant RNA can be extracted from the bacterial cells and separated from the bulk of bacterial RNAs taking advantage of its circularity.

To produce recombinant RNA in E. coli using the ELVd-derived system12, the RNA of interest is grafted into an ELVd RNA scaffold. This chimeric RNA is co-expressed along the eggplant tRNA ligase in E. coli. Once processed, cleaved and circularized, the chimeric circular RNA, from which the RNA of interest protrudes, likely forms a ribonucleoprotein complex with the co-expressed eggplant enzyme that reaches remarkable concentration in the bacterial ...

Watch this Scientific Journal Video about Large-scale Production of Recombinant RNAs on a Circular Scaffold Using a Viroid-derived System in Escherichia coli at JoVE.com

Large-scale Production of Recombinant RNAs on a Circular Scaffold Using a Viroid-derived System in Escherichia coli

Here, we present a protocol to produce large amounts of recombinant RNA in Escherichia coli by co-expressing a chimeric RNA that contains the RNA of interest in a viroid scaffold and a plant tRNA ligase. The main product is a circular molecule that facilitates purification to homogeneity.

Large-scale Production of Recombinant RNAs on a Circular Scaffold Using a Viroid-derived System in Escherichia coli

With increasing interest in RNA biology and the use of RNA molecules in sophisticated biotechnological applications, the methods to produce large amounts ...

This method can help to produce large amounts of recombinant RNAs of interest for application in research or industry. The main advantage is that recombinant RNA is produced in Escherichia coli in a cheap process that can be easily scaled up. Importantly, the RNA is produced on a circular RNA scaffold, which facilitates purification to homogeneity.In contrast to DNA or proteins, RNAs of interest are not easily produced in large amounts in biofactory systems, such an Escherichia coli culture. Our method is based on co-expression of the RNA of interest inserted into a highly stable circular scaffold and applying a ligase that mediates RNA circularization. The circular RNA scaffold derives from a patented viroid.Viroids are relatively small, non-coiling, highly base-paired circular RNAs that are infectious to some higher plants. We can produce tens of milligrams of the recombinant RNA per liter of bacterial culture in regular laboratory conditions. To begin this procedure, amplify the cDNA by PCR as outlined in the text protocol.Next, add 100 nanograms of the plasmid pLELVd-BZB to a 0.5 milliliter tube. Add 10 U of the type IIS restriction enzyme BpiI and enough of buffer G to create a 20 microliter reaction. Incubate at 37 degrees Celsius for one hour to digest the plasmid.After this, separate the PCR and digestion products by electrophoresis in a one percent agarose gel in TAE buffer. Stain the gel by shaking it in 200 milliliters ethidium bromide at a concentration of 0.5 micrograms per milliliter. Using a UV transilluminator, visualize the DNA.Use a scalpel to cut out the bands corresponding to the amplified cDNA and the BpiI digested plasmid. Using silica gel columns, elute the DNAs from the gel fragments. Quantify the concentration of the DNA by spectrophotometric analysis.Set up a Gibson Assembly reaction using the amplified cDNA and the digested plasmid. Incubate at 50 degrees Celsius for one hour. Then, use a silica gel column to purify the reaction.After electroporating competent E.coli DH5-Alpha Cells, pick several white colonies and transfer them to liquid LB medium. Grow the colonies overnight at 37 degrees Celsius. Next, use a miniprep kit to purify the plasmids, and analyze their sizes by electrophoresis in a one percent agarose gel in TAE buffer.First, co-electroporate the selected E.coli strain with both the pLELVd-BZB derivative that contains the cDNA corresponding to the RNA of interest and the plasmid P15LTRNISM to co-express the eggplant tRNA ligase. Transfer SOC liquid medium into the electroporation cuvette to recover the cells, and incubate at 37 degrees Celsius for one hour. Then, plate the bacteria on LB solid medium containing 50 micrograms per milliliter ampicillin, and 34 micrograms per milliliter chloramphenicol.Incubate at 37 degrees Celsius overnight. The next day, add 250 milliliters of liquid TB medium, containing 50 micrograms per milliliter ampicillin, and 34 micrograms per milliliter chloramphenicol, to a one liter baffled Erlenmeyer flask. Retrieve the incubated E.Coli, and then pick a colony and inoculate the medium in the flask.Incubate at 37 degrees Celsius with vigorous shaking at 180 RPM for 12 to 16 hours before harvesting the bacteria. Pour the harvested E.Coli culture into a 250 milliliter centrifuge bottle and spin down the cells at 14, 000 G for 10 minutes. Discard the supernatant and resuspend the cells in 30 milliliters of water.Transfer this suspension to a centrifuge tube, and spin down the cells again using the previous conditions. Discard the supernatant and add 10 milliliters of chromatography buffer to the cell pellet. Vortex to resuspend the cells in the buffer.Add one volume of phenol:chloroform and vortex vigorously to break the cells. Then, centrifuge at 12, 000 G for 10 minutes. Recover the aqueous phase, add one volume of chloroform, and vortex vigorously.Centrifuge at 12, 000 G for 10 minutes. After this, filter the RNA preparation through a 45 micrometer syringe filter. Purify the RNA using a one milliliter diethyl ethanol amine column connected to a liquid chromatography system.Adjust the flow rate to one milliliter per minute, and equilibrate the column with 10 milliliters of chromatography buffer. Then, load the sample and wash the column with 10 milliliters of chromatography buffer. Elute the RNA with 20 milliliters of elution buffer, and collect one milliliter aliquots.Using two-dimensional polyacrylamide gel electrophoresis, separate the circular RNAs from their linear counterparts. First, prepare a five percent polyacrylamide gel in TBE buffer and containing eight molar urea as outlined in the text protocol. Mix 20 microliters of the RNA preparations with one volume of loading buffer.Incubate at 95 degrees Celsius in a heating block for 1.5 minutes, and then snap-cool on ice. Load the samples in the polyacrylamide gel and run the electrophoresis at the appropriate conditions for the gel dimension. After this, stain the gel in 0.5 microgram per milliliter ethidium bromide for 15 minutes.Wash the stained gel with water, and then visualize the RNA under UV light. Electrophoretic analysis of several recombinant plasmids in which different cDNAs are inserted show different migrations when compared to pLELVd-BZB. Note that pLELVd-BZB contains the lacZ marker, which is replaced by the cDNA corresponding to the RNA of interest, so while the migration does depend on the size of the inserted cDNA, the recombinant plasmids will usually migrate faster than the control plasmid.Production of the recombinant RNA in co-electroporated bacterial cultures is monitored by breaking the cells and analyzing the RNA by denaturing PAGE. Strong bands can be seen, which correspond to empty ELVd and chimeric ELVd forms, in which different RNAs of interest were inserted. Interestingly, a major fraction of the recombinant RNA is seen as a circular form.The circularity of the main fraction is observed by using a combination of two PAGEs under denaturing conditions at high and low ionic strength. The RNA preparation can be further purified by anion exchange chromatography. As seen here, the E.Coli RNA is efficiently retained at low ionic strength, and subsequently eluted at high ionic strength, with most of the RNA being collected in fractions two and three.Recombinant RNA can be further purified to homogeneity by 2-D electrophoresis. This protocol allows the easy production of large amounts of recombinant RNA in Escherichia coli and purification to homogeneity thanks to the circularity of the final product. Remember that the RNA of interest results embedded into a circular RNA scaffold derived from a plant viroid.If you wish to separate both moieties, you need to use a standard strategy, such as ribozymes, DNAzymes, or RNase H.The yield of this protocol depends on the particular RNA of interest, as small RNAs are likely to be produced in higher amounts than larger ones. For larger scale expressions, take into consideration that optimum time to harvest bacteria depends on many factors including the E.Coli strain, culture medium, and growing conditions. We recommend a preliminary time course assay to find the optimal production window in your particular conditions.Remember that the recombinant RNAs accumulate in bacterial cells transiently, and that they completely disappear at the late-growing phase.

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Research

JoVE Journal

Biochemistry

Directed Protein Packaging within Outer Membrane Vesicles from Escherichia coli: Design, Production and Purification

An increasing interest in applying synthetic biology techniques to program outer membrane vesicles (OMV) are leading to some very interesting and unique applications for OMV where traditional nanoparticles are proving too difficult to synthesize. To date, all Gram-negative bacteria have been shown to produce OMV demonstrating packaging of a variety of cargo that includes small molecules, peptides, proteins and genetic material. Based on their diverse cargo, OMV are implicated in many biological processes ranging from cell-cell communication to gene transfer and delivery of virulence factors depending upon which bacteria are producing the OMV. Only recently have bacterial OMV become accessible for use across a wide range of applications through the development of techniques to control and direct packaging of recombinant proteins into OMV. This protocol describes a method for the production, purification, and use of enzyme packaged OMV providing for improved overall production of recombinant enzyme, increased vesiculation, and enhanced enzyme stability. Successful utilization of this protocol will result in the creation of a bacterial strain that simultaneously produces a recombinant protein and directs it for OMV encapsulation through creating a synthetic linkage between the recombinant protein and an outer membrane anchor protein. This protocol also details methods for isolating OMV from bacterial cultures as well as proper handling techniques and things to consider when adapting this protocol for use for other unique applications such as: pharmaceutical drug delivery, medical diagnostics, and environmental remediation.

Directed Protein Packaging within Outer Membrane Vesicles from Escherichia coli: Design, Production and Purification

A protocol for the production, purification, and use of enzyme packaged outer membrane vesicles (OMV) providing for enhanced enzyme stability for implementation across diverse applications is presented.

An increasing interest in applying synthetic biology techniques to program outer membrane vesicles (OMV) are leading to some very interesting and unique ...

Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo

Bacteria are frequently exposed to environmental changes, such as alterations in pH, temperature, redox status, light exposure or mechanical force. Many of these conditions cause protein unfolding in the cell and have detrimental impact on the survival of the organism. A group of unrelated, stress-specific molecular chaperones have been shown to play essential roles in the survival of these stress conditions. While fully folded and chaperone-inactive before stress, these proteins rapidly unfold and become chaperone-active under specific stress conditions. Once activated, these conditionally disordered chaperones bind to a large number of different aggregation-prone proteins, prevent their aggregation and either directly or indirectly facilitate protein refolding upon return to non-stress conditions. The primary approach for gaining a more detailed understanding about the mechanism of their activation and client recognition involves the purification and subsequent characterization of these proteins using in vitro chaperone assays. Follow-up in vivo stress assays are absolutely essential to independently confirm the obtained in vitro results.
This protocol describes in vitro and in vivo methods to characterize the chaperone activity of E. coli HdeB, an acid-activated chaperone. Light scattering measurements were used as a convenient read-out for HdeB&#39;s capacity to prevent acid-induced aggregation of an established model client protein, MDH, in vitro. Analytical ultracentrifugation experiments were applied to reveal complex formation between HdeB and its client protein LDH, to shed light into the fate of client proteins upon their return to non-stress conditions. Enzymatic activity assays of the client proteins were conducted to monitor the effects of HdeB on pH-induced client inactivation and reactivation. Finally, survival studies were used to monitor the influence of HdeB&#39;s chaperone function in vivo.

Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo

This study describes biophysical, biochemical and molecular techniques to characterize the chaperone activity of Escherichia coli HdeB under acidic pH conditions. These methods have been successfully applied for other acid-protective chaperones such as HdeA and can be modified to work for other chaperones and stress conditions.

Bacteria are frequently exposed to environmental changes, such as alterations in pH, temperature, redox status, light exposure or mechanical force. Many ...

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating these studies, reincorporation of detergent-solubilized membrane proteins into liposomes is a stochastic process where protein topology is impossible to enforce. This paper offers an alternative method to these challenging techniques that utilizes a liposome-based scaffold. Protein solubility is enhanced by deletion of the transmembrane domain, and these amino acids are replaced with a tethering moiety, such as a His-tag. This tether interacts with an anchoring group (Ni2+ coordinated by nitrilotriacetic acid (NTA(Ni2+)) for His-tagged proteins), which enforces a uniform protein topology at the surface of the liposome. An example is presented wherein the interaction between Dynamin-related protein 1 (Drp1) with an integral membrane protein, Mitochondrial Fission Factor (Mff), was investigated using this scaffold liposome method. In this work, we have demonstrated the ability of Mff to efficiently recruit soluble Drp1 to the surface of liposomes, which stimulated its GTPase activity. Moreover, Drp1 was able to tubulate the Mff-decorated lipid template in the presence of specific lipids. This example demonstrates the effectiveness of scaffold liposomes using structural and functional assays and highlights the role of Mff in regulating Drp1 activity.

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

This paper describes a method for assessing the interactions and assemblies of integral membrane proteins in vitro with various partner factors in a lipid-proximal environment.

Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating ...

Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. Hydrogen-Deuterium Exchange (HDX) measured at rapid time scales is uniquely suited to detect structures and hydrogen bonding networks that are briefly populated, allowing for the characterization of transient conformers in native ensembles. Coupling of HDX to mass spectrometry offers several key advantages, including high sensitivity, low sample consumption and no restriction on protein size. This technique has advanced greatly in the last several decades, including the ability to monitor HDX labeling times on the millisecond time scale. In addition, by incorporating the HDX workflow onto a microfluidic platform housing an acidic protease microreactor, we are able to localize dynamic properties at the peptide level. In this study, Time-Resolved ElectroSpray Ionization Mass Spectrometry (TRESI-MS) coupled to HDX was used to provide a detailed picture of residual structure in the tau protein, as well as the conformational shifts induced upon hyperphosphorylation.

Conformational flexibility plays a critical role in protein function. Herein, we describe the use of time-resolved electrospray ionization mass spectrometry coupled to hydrogen-deuterium exchange for probing the rapid structural changes that drive function in ordered and disordered proteins.

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. ...

Quantification of the Abundance and Charging Levels of Transfer RNAs in Escherichia coli

Transfer RNA (tRNA) is an essential part of the translational machinery in any organism. tRNAs bind and transfer amino acids to the translating ribosome. The relative levels of different tRNAs, and the ratio of aminoacylated tRNA to total tRNA, known as the charging level, are important factors in determining the accuracy and speed of translation. Therefore, the abundance and charging levels of tRNAs are important variables to measure when studying protein synthesis, for example under various stress conditions. Here, we describe a method for harvesting tRNA and directly measuring both the relative abundance and the absolute charging level of specific tRNA species in Escherichia coli. The tRNA is harvested in such a way that the labile bond between the tRNA and its amino acid is preserved. The RNA is then subjected to gel electrophoresis and Northern blotting, which results in separation of the charged and uncharged tRNAs. The levels of specific tRNAs in different samples can be compared due to the addition of spike-in cells for normalization. Prior to RNA purification, we add 5% of E. coli cells that overproduce the rare tRNAselC to each sample. The amount of the tRNA species of interest in a sample is then normalized to the amount of tRNAselC in the same sample. Addition of spike-in cells prior to RNA purification has the advantage over addition of purified spike-in RNAs that it also accounts for any differences in cell lysis efficiency between samples.

Quantification of the Abundance and Charging Levels of Transfer RNAs in Escherichia coli

Here we present a method for directly measuring transfer RNA charging levels from purified Escherichia coli RNA as well as a way to compare relative levels of transfer RNA, or any other short RNA, across different samples based on the addition of spike-in cells expressing a reference gene.

Transfer RNA (tRNA) is an essential part of the translational machinery in any organism. tRNAs bind and transfer amino acids to the translating ribosome. ...

A Simple Method for High Throughput Chemical Screening in Caenorhabditis Elegans

Caenorhabditis elegans is a useful organism for testing chemical effects on physiology. Whole organism small molecule screens offer significant advantages for identifying biologically active chemical structures that can modify complex phenotypes such as lifespan. Described here is a simple protocol for producing hundreds of 96-well culture plates with fairly consistent numbers of C. elegans in each well. Next, we specified how to use these cultures to screen thousands of chemicals for effects on the lifespan of the nematode C. elegans. This protocol makes use of temperature sensitive sterile strains, agar plate conditions, and simple animal handling to facilitate the rapid and high throughput production of synchronized animal cultures for screening.

A Simple Method for High Throughput Chemical Screening in Caenorhabditis Elegans

Here we describe a simple protocol for rapidly producing hundreds of nematode growth media agar, 96-well culture plates with consistent numbers of Caenorhhabditis elegans per well. These cultures are useful for the phenotypic screening of whole organisms. We focus here on using these cultures to screen chemicals for pro-longevity effects.

Caenorhabditis elegans is a useful organism for testing chemical effects on physiology. Whole organism small molecule screens offer significant advantages ...

Site-Directed Mutagenesis for In Vitro and In Vivo Experiments Exemplified with RNA Interactions in Escherichia Coli

Site-directed mutagenesis is a technique used to introduce specific mutations in DNA to investigate the interaction between small non-coding ribonucleic acid (sRNA) molecules and target messenger RNAs (mRNAs). In addition, site-directed mutagenesis is used to map specific protein binding sites to RNA. A 2-step and 3-step PCR based introduction of mutations is described. The approach is relevant to all protein-RNA and RNA-RNA interaction studies. In short, the technique relies on designing primers with the desired mutation(s), and through 2 or 3 steps of PCR synthesizing a PCR product with the mutation. The PCR product is then used for cloning. Here, we describe how to perform site-directed mutagenesis with both the 2- and 3-step approach to introduce mutations to the sRNA, McaS, and the mRNA, csgD, to investigate RNA-RNA and RNA-protein interactions. We apply this technique to investigate RNA interactions; however, the technique is applicable to all mutagenesis studies (e.g., DNA-protein interactions, amino-acid substitution/deletion/addition). It is possible to introduce any kind of mutation except for non-natural bases but the technique is only applicable if a PCR product can be used for downstream application (e.g., cloning and template for further PCR).

Site-Directed Mutagenesis for In Vitro and In Vivo Experiments Exemplified with RNA Interactions in Escherichia Coli

Site-directed mutagenesis is a technique used to introduce specific mutations in deoxyribonucleic acid (DNA). This protocol describes how to do site-directed mutagenesis with a 2-step and 3-step polymerase chain reaction (PCR) based approach, which is applicable to any DNA fragment of interest.

Site-directed mutagenesis is a technique used to introduce specific mutations in DNA to investigate the interaction between small non-coding ribonucleic ...

Use of Alu Element Containing Minigenes to Analyze Circular RNAs

In addition to linear mRNAs, many eukaryotic genes generate circular RNAs. Most circular RNAs are generated by joining a 5&#39; splice site with an upstream 3&#39; splice site within a pre-mRNA, a process called back-splicing. This circularization is likely aided by secondary structures in the pre-mRNA that bring the splice sites into close proximity. In human genes, Alu elements are thought to promote these secondary RNA structures, as Alu elements are abundant and exhibit base complementarities with each other when present in opposite directions in the pre-mRNA. Here, we describe the generation and analysis of large, Alu element containing reporter genes that form circular RNAs. Through optimization of cloning protocols, reporter genes with up to 20 kb insert length can be generated. Their analysis in co-transfection experiments allows the identification of regulatory factors. Thus, this method can identify RNA sequences and cellular components involved in circular RNA formation.

Use of Alu Element Containing Minigenes to Analyze Circular RNAs

We clone and analyze reporter genes generating circular RNAs. These reporter genes are larger than constructs to analyze linear splicing and contain Alu elements. To investigate the circular RNAs, the constructs are transfected into cells and resulting RNA is analyzed using RT-PCR after removal of linear RNA.

In addition to linear mRNAs, many eukaryotic genes generate circular RNAs. Most circular RNAs are generated by joining a 5&#39; splice site with an ...

Detergent-assisted Reconstitution of Recombinant Drosophila Atlastin into Liposomes for Lipid-mixing Assays

Membrane fusion is a crucial process in the eukaryotic cell. Specialized proteins are necessary to catalyze fusion. Atlastins are endoplasmic reticulum (ER) resident proteins implicated in homotypic fusion of the ER. We detail here a method for purifying a glutathione S-transferase (GST) and poly-histidine tagged Drosophila atlastin by two rounds of affinity chromatography. Studying fusion reactions in vitro requires purified fusion proteins to be inserted into a lipid bilayer. Liposomes are ideal model membranes, as lipid composition and size may be adjusted. To this end, we describe a reconstitution method by detergent removal for Drosophila atlastin into preformed liposomes. While several reconstitution methods are available, reconstitution by detergent removal has several advantages that make it suitable for atlastins and other similar proteins. The advantage of this method includes a high reconstitution yield and correct orientation of the reconstituted protein. This method can be extended to other membrane proteins and for other applications that require proteoliposomes. Additionally, we describe a FRET based lipid mixing assay of proteoliposomes used as a measurement of membrane fusion.

Detergent-assisted Reconstitution of Recombinant Drosophila Atlastin into Liposomes for Lipid-mixing Assays

Biological membrane fusion is catalyzed by specialized fusion proteins. Measuring the fusogenic properties of proteins can be achieved by lipid mixing assays. We present a method for purifying recombinant Drosophila atlastin, a protein that mediates homotypic fusion of the ER, reconstituting it to preformed liposomes, and testing for fusion capacity.

Membrane fusion is a crucial process in the eukaryotic cell. Specialized proteins are necessary to catalyze fusion. Atlastins are endoplasmic reticulum ...

Site Specific Lysine Acetylation of Histones for Nucleosome Reconstitution using Genetic Code Expansion in Escherichia coli

Acetylated histone proteins can be easily expressed in Escherichia coli encoding a mutant, N&#949;-acetyl-lysine (AcK)-specific Methanosarcina mazi pyrrolysine tRNA-synthetase (MmAcKRS1) and its cognate tRNA (tRNAPyl) to assemble reconstituted mononucleosomes with site specific acetylated histones. MmAcKRS1 and tRNAPyl deliver AcK at an amber mutation site in the mRNA of choice during translation in Escherichia coli. This technique has been used extensively to incorporate AcK at H3 lysine sites. Pyrrolysyl-tRNA synthetase (PylRS) can also be easily evolved to incorporate other noncanonical amino acids (ncAAs) for site specific protein modification or functionalization. Here we detail a method to incorporate AcK using the MmAcKRS1 system into histone H3 and integrate acetylated H3 proteins into reconstituted mononucleosomes. Acetylated reconstituted mononucleosomes can be used in biochemical and binding assays, structure determination, and more. Obtaining modified mononucleosomes is crucial for designing experiments related to discovering new interactions and understanding epigenetics.

Site Specific Lysine Acetylation of Histones for Nucleosome Reconstitution using Genetic Code Expansion in Escherichia coli

Here we present a method to express acetylated histone proteins using genetic code expansion and assemble reconstituted nucleosomes in vitro.

Acetylated histone proteins can be easily expressed in Escherichia coli encoding a mutant, N&#949;-acetyl-lysine (AcK)-specific Methanosarcina mazi ...