Name: ribo-seq in bacteria: a sample collection and library preparation protocol for ngs sequencing
Uploaded: 2021-08-07T14:00:00
Description: Watch this Scientific Journal Video about RIBO-seq in Bacteria: a Sample Collection and Library Preparation Protocol for NGS Sequencing at JoVE.com

ALS would like to acknowledge the financial support of EMBO Installation Grants IG 3914, and POIR. 04.04.00-00-3E9C/17-00 carried out within the First TEAM programme of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund.

1. Sample collection
<ol>
	<li>Prepare a bacterial culture. We recommend a culture volume of 100 mL per sample.</li>
	<li>Prepare equipment and reagents for sample collection: two scoopulas per sample, sterile 0.45 &#181;m mixed cellulose esters membrane (MCE) filters, 50 mL sterile tubes, liquid nitrogen, 50 mg/mL chloramphenicol in 70% (vol/vol) ethanol (optional). Puncture the lid of 50 mL tubes to allow liquid nitrogen evaporation and prevent the explosion of closed tubes. Decontaminate scoopulas with laboratory de...

The key technical challenge of the ribosome profiling is the need to rapidly inhibit translation in order to capture a snapshot of ribosomes on mRNAs at a particular physiological state of interest. To accomplish this, translation inhibitors, rapid harvesting and flash freezing in liquid nitrogen are commonly used. Applying antibiotics is optional since they can cause artifacts. Chloramphenicol is a commonly used drug to arrest elongating ribosomes in bacterial RIBO-seq. However, it does not prevent initiation, resulting...

The ribosome profiling technique (RIBO-seq) was developed in the laboratory of Jonathan Weissman at the University of California, San Francisco1. In comparison to other methods used to study gene expression at the translational level, RIBO-seq focuses on each ribosome binding to mRNA and provides information about its location and the relative number of ribosomes on a transcript. It enables monitoring the process of protein synthesis in vivo and can provide single codon resolution and accuracy allowing the measurement of the ribosome density on both, the individual mRNA and along the entire transcriptome in the cell. At the foundation of the RIBO-seq technique lies the fact that during translation the ribosome binds the mRNA molecule and thus protects the buried fragment of the transcript from a ribonuclease digestion. Upon addition of the ribonuclease, the unprotected mRNA is digested and the fragments enclosed by ribosomes - typically of ~28-30 nt long - remain intact. These fragments, called ribosomal footprints (RF), can then be isolated, sequenced and mapped onto the transcript they originated from resulting in the detection of the exact position of the ribosomes. In fact, the ribosome ability to protect mRNA fragments has been used since the 1960s to study ribosomal binding and translation initiation sites (TIS)2,3,4. However, with the advancement in deep sequencing technology, RIBO-seq has become a gold standard for translation monitoring5 which, through the ribosome engagement, can provide a genome-wide information on protein synthesis6. Ribosome profiling filled the technological gap that existed between quantifying the transcriptome and the proteome6.
To conduct ribosome profiling we need to obtain cell lysate of the organism that had grown under the investigated conditions. Disrupting these conditions during cell collection and lysis may provide unreliable data. To prevent this, translation inhibitors, rapid harvesting and flash freezing in liquid nitrogen are commonly used. Cells can be lysed by cryogenic grinding in a mechanical homogenizer like a mixer mill7,8 or a bead beater9, and by trituration through a pipette10 or with a needle11. The lysis buffer can be added just before or shortly after pulverization of the cells. In our protocol we use liquid nitrogen to precool mortar and pestle, as well as aluminum oxide as a gentler approach to disruption of the bacterial cell wall, which prevents RNA shearing often encountered when methods such as sonification are applied. After pulverization, we add an ice-cold lysis buffer into the cooled contents of the mortar. Selection of an appropriate lysis buffer is important for obtaining the best resolution of ribosomal footprints. Since ionic strength affects both the RF size and the reading frame precision, it is currently recommended to use lysis buffers with low ionic strength and buffer capacity, even if it appears that buffer composition does not affect ribosomal occupancy on mRNAs11,12. Important components of the lysis buffer are magnesium ions, the presence of which prevents dissociation of the ribosomal subunits and inhibits spontaneous conformational changes in the bacterial ribosomes11,13. Calcium ions also play a significant role and are essential for the activity of micrococcal nuclease (MNase) used in the bacterial ribosome profiling method14. Addition of guanosine 5&#8242;-[&#946;,&#947;-imido]triphosphate (GMP-PNP), a non-hydrolyzable analog of GTP, together with chloramphenicol inhibits translation during lysis15.
When the lysate is obtained, it is clarified by centrifugation and divided into two portions, each for a RIBO-seq and a high-throughput total mRNA sequencing (RNA-seq) since they are performed simultaneously (Figure 1). RNA-seq provides a point of reference which enables the comparison of data from both RIBO-seq and RNA-seq during data analysis. The investigated translatome is defined by normalization of ribosomal footprints to mRNA abundance16. Data from RNA-seq can also help identify cloning or sequencing artifacts17.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62544/62544fig01.jpg" /> 
Figure 1. Schematics of mRNA sample preparation for RIBO-seq and RNA-seq. For RIBO-seq library preparation, RNA is digested with MNase (A), followed by the size selection of RF of ~28-30 nt length (B); for RNA-seq RNA is isolated (C), depleted of rRNA (D), and the resulting mRNA is randomly fragmented into fragments of varying lengths (E). <a href="https://www.jove.com/files/ftp_upload/62544/62544fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Initial steps of the procedure of sample preparation for RIBO-seq and RNA-seq differ slightly (Figure 1). For the ribosomal profiling, the lysate needs to be digested by a specific endonuclease to degrade the mRNA molecules not protected by the ribosomes. In standard protocols, the obtained monosomes are recovered by a sucrose cushion ultracentrifugation or a sucrose gradient ultracentrifugation8,14. In this article, we show that this step is not necessary to isolate RF required for the RIBO-seq in bacteria, likewise for eukaryotic cells18, and that size selection of the appropriate length mRNA fragments from the polyacrylamide gel is sufficient.
For RNA-seq, mRNA is obtained by the depletion of rRNA from the total RNA - rRNA molecules hybridize to the biotinylated oligonucleotide probes which bind to the streptavidin-coated magnetic beads. The rRNA-oligonucleotide-bead complexes are then removed from the sample with a magnet resulting in a rRNA depleted sample19,20. The purified mRNA molecules are then randomly fragmented by alkaline hydrolysis. The obtained fragments of mRNA as well as the ribosomal footprints are converted into cDNA libraries and prepared for deep sequencing (Figure 2). This involves ends repair needed after alkaline hydrolysis (for mRNA) and enzymatic digestion (for RF): dephosphorylation of 3&#39; ends followed by phosphorylation of 5&#39; ends. The next steps are adaptors ligation and the reverse transcription to create cDNA inserts framed by sequences required for the next generation sequencing (NGS) using Illumina platform. The last phase of library preparation is a PCR reaction in which the constructs are amplified and labelled with sample specific barcodes to allow multiplexing and sequencing various samples on one channel. Before sequencing, the quality and quantity of the libraries are assessed by the high-sensitivity DNA on-chip electrophoresis. cDNA libraries with appropriate parameters can then be pooled and sequenced. Sequencing can be performed on different Illumina platforms, such as MiSeq, NextSeq or HighSeq, depending on the number of libraries, required read length and sequencing depth. After sequencing, the bioinformatic analysis is performed.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/62544/62544fig02.jpg" /> 
Figure 2. Library preparation. Library preparation includes the ends repair, adapters ligation, reverse transcription and amplification with barcoding. <a href="https://www.jove.com/files/ftp_upload/62544/62544fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The ribosome profiling is a universal method which can be easily modified and adjusted according to the scientific question. Originally it was used in yeast1, but shortly after it was applied to bacterial cells21 as well as eukaryotic model organisms including mouse10, zebrafish22, fruit fly23 and Arabidopsis thaliana24. It was also used for studying different ribosome types: cytoplasmic, mitochondrial25,26 and chloroplast27,28. In eukaryotes RIBO-seq is commonly adapted and refined to investigate specific aspects of translation, including initiation10,11,29,30,31,32, elongation1,10,11,31,33, ribosome stalling33 and conformation change33. Most of the modifications involve the use of different translation inhibitors. In bacteria however, analogous studies have been difficult to conduct because of the paucity of inhibitors with the required mechanism of action34. The most commonly used translation inhibitor in bacteria is chloramphenicol (CAM) which binds to the peptidyl transferase center (PTC) and prevents correct positioning of the aminoacyl-tRNA in the A-site. As a result, CAM prevents the formation of a peptide bond which leads to arresting the elongating ribosomes35. Other examples of translation inhibitors in bacteria are tetracycline (TET)36, retapamulin (RET)34 and Onc11237 which have been used to investigate translation initiation sites. TET, which prevents tRNA delivery to the ribosome by directly overlapping with the anticodon stem-loop of tRNA at the A-site, was originally applied to verify the results obtained from CAM treatment since they are both antibiotics inhibiting translation elongation38. TET was found to detect primary TIS, however was unable to reveal internal TIS36. RET binds in the PTC of the bacterial ribosome, and prevents formation of the first peptide bond by interfering with an elongator aminoacyl-tRNA in the A site. Applying RET results in ribosomes arrest at both primary as well as internal TISs34. Onc112, a proline-rich antimicrobial peptide, binds in the exit tunnel and blocks aminoacyl-tRNA binding in the ribosomal A site. As a result, Onc112 prevents initiation complexes from entering the elongation phase37.&#160;
The main information ribosome profiling provides is ribosomes density and their position on the mRNA. It was successfully applied to investigate differential gene expression at the level of translation in various growth conditions1,6, measure translational efficiency1,38,39 and detect translation regulation events such as ribosomal pausing10. RIBO-seq also allows for uncovering the translation of annotated ncRNA, pseudogenes and unannotated small open reading frames (ORF) leading to the identification of novel and/or very short protein coding genes10,12,22,30,37. In such cases, RIBO-seq can fine-tune and improve genome annotation. With its high sensitivity for the identification of translated ORFs and its quantitative nature, ribosome profiling can also serve as a proxy for the proteome determination or in aiding proteomics studies31,34,39. By mapping TIS, ribosome profiling reveals N-terminally extended and truncated isoforms of known proteins10,32. RIBO-seq was also adapted to study co-translational folding of proteins14,21,24. This&#160;method enables measuring of elongation rates1,10,39 or decoding speeds of individual codons6 and helps in developing quantitative models of translation17. The ribosome profiling method is also capable of providing mechanistic insights into the ribosome pausing in bacteria7,15,17, frameshifting40, stop-codon readthrough21, termination/recycling defects41,42 and ribosomal conformation changes33 in eukaryotes. RIBO-seq was also adapted to examine the impact of specific trans-acting factors on translation such as miRNAs6 and RNA-binding proteins in eukaryotes16,43. However, it is important to acknowledge that the experimental design and the obtained resolution of RIBO-seq determine the amount of information that can be extracted from the resulting sequencing data12.

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			<td>10X TBE (powder)</td>
			<td>Invitrogen</td>
			<td>AM9864</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Mercaptoethanol, 99%, pure</td>
			<td>Acros Organics</td>
			<td>125472500</td>
			<td></td>
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		<tr>
			<td>Adenosine 5&#39;-Triphosphate (ATP)</td>
			<td>New England Biolabs</td>
			<td>P0756S</td>
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			<td>Aluminium oxide calcinated pure p.a.</td>
			<td>Chempur</td>
			<td>114560600</td>
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			<td>Calcium chloride dihydrate</td>
			<td>Sigma-Aldrich</td>
			<td>C3881-500G</td>
			<td></td>
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			<td>Chloramphenicol</td>
			<td>MP Biomedicals</td>
			<td>190321</td>
			<td></td>
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			<td>DNA Clean &#38; Concentrator -5</td>
			<td>Zymo Research</td>
			<td>D4004</td>
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			<td>Dnase I recombinant, Rnase-free</td>
			<td>Roche</td>
			<td>4716728001</td>
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			<td>EDTA disodium salt</td>
			<td>Fisher Scientific</td>
			<td>E/P140/48</td>
			<td></td>
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		<tr>
			<td>Ethyl Alcohol Absolut 99,8%&#160; Pure-P.A.-Basic</td>
			<td>POCH Avantor Performance Materials Poland S.A</td>
			<td>BA6480111</td>
			<td></td>
		</tr>
		<tr>
			<td>Filtration apparatus</td>
			<td>VWR Collection</td>
			<td>511-0265</td>
			<td>all-glass filtration apparatus, with funnel, fritted base, cap, 47 mm &#216; spring clamp and ground joint flask</td>
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		<tr>
			<td>Gel 40 (19:1)</td>
			<td>Rotiphorese</td>
			<td>3030.1</td>
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			<td>Gel Loading Dye, Blue, 6X</td>
			<td>New England Biolabs</td>
			<td>E6138G</td>
			<td></td>
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			<td>Guanosine 5&#8242;-[&#946;,&#947;-imido]triphosphate trisodium salt hydrate</td>
			<td>Sigma-Aldrich</td>
			<td>G0635-25MG</td>
			<td></td>
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		<tr>
			<td>labZAP</td>
			<td>A&#38;A Biotechnology</td>
			<td>040-500</td>
			<td></td>
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			<td>Magnesium acetate tetrahydrate</td>
			<td>Sigma-Aldrich</td>
			<td>M5661-250G</td>
			<td></td>
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		<tr>
			<td>MCE membrane fiter</td>
			<td>Alfatec Technology</td>
			<td>M47MCE45GWS</td>
			<td>pore size: 0.45um</td>
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			<td>MICROBExpress Bacterial mRNA Purification</td>
			<td>Invitrogen</td>
			<td>AM1905</td>
			<td></td>
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			<td>Multiplex Small RNA Library Prep Set for Illumina</td>
			<td>New England Biolabs</td>
			<td>E7300S</td>
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			<td>Nuclease-Free Water</td>
			<td>Ambion</td>
			<td>AM9937</td>
			<td></td>
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		<tr>
			<td>Potassium Acetate Anhydrous Pure P.A.</td>
			<td>POCH Avantor Performance Materials Poland S.A</td>
			<td>744330113</td>
			<td></td>
		</tr>
		<tr>
			<td>Quick-Load pBR322 DNA-MspI Digest</td>
			<td>New England Biolabs</td>
			<td>E7323A</td>
			<td></td>
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			<td>RNA Clean &#38; Concentrator -25</td>
			<td>Zymo Research</td>
			<td>R1018</td>
			<td></td>
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			<td>Sodium acetate</td>
			<td>Sigma-Aldrich</td>
			<td>S2889-250G</td>
			<td></td>
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			<td>Sodium carbonate</td>
			<td>Sigma-Aldrich</td>
			<td>223530-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydrogen carbonate pure p.a.</td>
			<td>POCH Avantor Performance Materials Poland S.A</td>
			<td>810530115</td>
			<td></td>
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		<tr>
			<td>SYBR Gold nucleic acid gel stain</td>
			<td>Life Technologies</td>
			<td>S11494</td>
			<td></td>
		</tr>
		<tr>
			<td>T4 Polynucleotide Kinase</td>
			<td>New England Biolabs</td>
			<td>M0201L</td>
			<td></td>
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			<td>T4 Polynucleotide Kinase Reaction Buffer</td>
			<td>New England Biolabs</td>
			<td>B0201S</td>
			<td></td>
		</tr>
		<tr>
			<td>TBE-Urea Sample Buffer (2x)</td>
			<td>Invitrogen</td>
			<td>LC6876</td>
			<td></td>
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			<td>Tris(hydroxymethyl)amino-methane, ultrapure, 99,9%</td>
			<td>AlfaAesar</td>
			<td>J65594</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100, 98%</td>
			<td>Acros Organics</td>
			<td>327371000</td>
			<td></td>
		</tr>
		<tr>
			<td>Urea G.R.</td>
			<td>lach:ner</td>
			<td>40096-AP0</td>
			<td></td>
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ribo-seq in bacteria: a sample collection and library preparation protocol for ngs sequencing

The ribosome profiling technique (RIBO-seq) is currently the most effective tool for studying the process of protein synthesis in vivo. The advantage of this method, in comparison to other approaches, is its ability to monitor translation by precisely mapping the position and number of ribosomes on a mRNA transcript.
In this article, we describe the consecutive stages of sample collection and preparation for RIBO-seq method in bacteria, highlighting the details relevant to the planning and execution of the experiment.
Since the RIBO-seq relies on intact ribosomes and related mRNAs, the key step is rapid inhibition of translation and adequate disintegration of cells. Thus, we suggest filtration and flash-freezing in liquid nitrogen for cell harvesting with an optional pretreatment with chloramphenicol to arrest translation in bacteria. For the disintegration, we propose grinding frozen cells with mortar and pestle in the presence of aluminum oxide to mechanically disrupt the cell wall. In this protocol, sucrose cushion or a sucrose gradient ultracentrifugation for monosome purification is not required. Instead, mRNA separation using polyacrylamide gel electrophoresis (PAGE) followed by the ribosomal footprint excision (28-30 nt band) is applied and provides satisfactory results. This largely simplifies the method as well as reduces the time and equipment requirements for the procedure. For library preparation, we recommend using the commercially available small RNA kit for Illumina sequencing from New England Biolabs, following manufacturer&#39;s guidelines with some degree of optimization.
The resulting cDNA libraries present appropriate quantity and quality required for next generation sequencing (NGS). Sequencing of the libraries prepared according to the described protocol results in 2 to 10 mln uniquely mapped reads per sample providing sufficient data for comprehensive bioinformatic analysis. The protocol we present is quick and relatively easy and can be performed with standard laboratory equipment.

The exemplary results presented here were obtained in a study examining translation regulation in sporulating WT Bacillus subtilis cells. Overnight cultures were diluted to OD600 equal to 0.1 in 100 mL of rich medium and incubated at 37 &#176;C with vigorous shaking until OD600 reached 0.5-0.6. The rich medium was then replaced with minimal medium to induce sporulation process and the incubation was continued for up to four hours. Cells were harvested every hour beginning with T0 - sporulat...

Watch this Scientific Journal Video about RIBO-seq in Bacteria: a Sample Collection and Library Preparation Protocol for NGS Sequencing at JoVE.com

RIBO-seq in Bacteria: a Sample Collection and Library Preparation Protocol for NGS Sequencing

Here we describe the stages of sample collection and preparation for RIBO-seq in bacteria. Sequencing of the libraries prepared according to these guidelines results in sufficient data for comprehensive bioinformatic analysis. The protocol we present is simple, uses standard laboratory equipment and takes seven days from lysis to obtaining libraries.

The ribosome profiling technique (RIBO-seq) is currently the most effective tool for studying the process of protein synthesis in vivo. The advantage of ...

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