The Lundbeck Foundation, Aarhus University, Dandrite and Lundbeck A/S supported this work.

NOTE: Perform all steps at room temperature unless otherwise stated and keep buffers on ice or in the fridge (except from the Elution buffer containing SDS). The protocol is divided into 5 sections: Preparation of RNA samples; preparation of beads for IP; binding of BrU-labelled RNA to beads; elution and purification of bound BrU-labelled RNA by 3 steps phenol-phenol/chloroform-chloroform extraction; analysis of RNA (in this example using RT-qPCR)
1. Preparation of RNA Samples
<ol>
	<li>Count HEK293T cells using an automated cell counter and seed 3,500,000 cells in a 10 cm petri dish in 10 mL growth media (Dulbecco&#39;s Modified Eagle&#39;s Medium supplemented with 10% fetal calf serum and 50 &#181;g/mL penicillin/streptomycin) to obtain a total of &#62;40 &#181;g RNA upon extraction 48 h later. Maintain cells at 37 &#176;C and 5% CO2.</li>
	<li>48 h after seeding, aspirate 8 mL growth media and leave 2 mL behind to avoid drying out the cells. Add 2 mM BrU and any treatment to the 8 mL aspirated growth media, and remove the residual 2 mL from the cells before reapplying the 8 mL BrU containing growth media. Avoid the use of fresh media upon application of the BrU to the cells, since this can induce changes in gene expression.</li>
	<li>Incubate the cells for 1 h with BrU and treatment. Wash the cells in 5 mL Hank&#39;s buffer and trypsinize the cells using 2 mL 0.05% trypsin. Add 8 mL growth media to stop the reaction, transfer the cells to a 15 mL tube, and spin down the cells for 2 min at 1,000 x g.</li>
	<li>Remove the supernatant and extract total RNA from the cell pellet using an RNA isolation kit (see Table of Materials) or any other preferred method, and elute in RNase-free H2O. Store the RNA at -80 &#176;C until ready to proceed.</li>
</ol>
2. Preparation of Beads for IP
<ol>
	<li>Prepare beads in batches for the number of samples to be investigated plus one extra to account for loss during pipetting and whirl mixing. Resuspend anti-Mouse IgG magnetic beads thoroughly by whirl mixing and take out 20 &#181;L beads per sample in an RNase-free 1.5 mL tube. Place the 1.5 mL tube in a magnetic stand and leave approximately 20 s for the beads to collect on the side.</li>
	<li>Remove the supernatant, take out the tube from the magnetic stand, and resuspend in 400 &#181;L 1x BrU-IP buffer by pipetting. Spin the tube very briefly for 2 s in a table-top centrifuge, place it back in the magnetic stand, and remove the supernatant. Repeat the washing step once.</li>
	<li>Block unspecific binding to the beads using heparin. Resuspend the beads in 1 mL 1x BrU-IP+ 1 mg/mL heparin buffer, and leave rotating for 30 min. Wash the beads once, as in step 2.2. 
	NOTE: Heparin is a negatively charged polymer, which will compete with RNAs for binding. tRNA or other irrelevant RNAs can also be used if the downstream application is not sequencing.</li>
	<li>Resuspend the beads in 1 mL 1x BrU-IP buffer and add 1.25 &#181;g/sample anti-&#945;-Bromodeoxyuridine antibody, which also recognizes BrU. Incubate the beads for 1 h while rotating, or overnight at room temperature.</li>
	<li>Wash the beads three times as in step 2.2. Resuspend the beads in 50 &#181;L/sample 1x BrU-IP buffer supplemented with 1 mM BrU and leave rotating for 30 min to lower the sensitivity of the antibody bound to the beads and hereby the risk of unspecific binding during IP.</li>
	<li>Wash the beads three times as in step 2.2, and resuspend in 50 &#181;L/sample 1xBrU-IP buffer.</li>
</ol>
3. Binding of BrU-Labelled RNA to Beads
<ol>
	<li>Measure RNA concentrations in the RNA extracts from step 1.3 using ultraviolet-visible spectrophotometry, and dilute 40 &#181;g RNA from each sample in RNase-free H2O to a total volume of 200 &#181;L.</li>
	<li>Heat RNA samples for 2 min at 80 &#176;C to denature RNA and spin briefly in a tabletop centrifuge. Add 200 &#181;L 2x BrU-IP+BSA/RNAse inhibitor.</li>
	<li>Add 50 &#181;L resuspended and prepared beads from step 2.6 to each sample and leave rotating 1 h. Wash the beads four times as in step 2.2.</li>
</ol>
4. Elution and Purification of RNA by 3 Steps Phenol-phenol/Chloroform-chloroform Extraction
<ol>
	<li>Elute RNA and perform phenol extraction
	<ol>
		<li>Resuspend the beads in 200 &#181;L Elution buffer to elute RNA, and quickly thereafter add 200 &#181;L phenol, pH 6.6 (CAUTION: Toxic, see note below step 4.1.2) to remove any non-RNA molecules from the sample.</li>
		<li>Whirl mix the sample, and spin 3 min at 25,000 x g in a tabletop centrifuge. 
		NOTE: Phenol is toxic and should be handled in a fume hood wearing skin protection. The slightly acidic pH ensures that only RNA, and not DNA, is extracted. The RNA will remain in the upper aqueous phase due to the hydrophilic nature of charges. The hydrophobic cores of proteins will bind phenol and move to the lower organic phenol-phase.</li>
	</ol>
	</li>
	<li>Perform phenol-chloroform extraction
	<ol>
		<li>Aspirate as much upper-phase as possible (approximately 190 &#181;L of the 200 &#181;L, depending on experience in handling) and move it to a tube with 200 &#181;L phenol/chloroform, pH 6.6 (CAUTION: Toxic, see note). Make sure to aspirate the same amount across samples.</li>
		<li>Whirl mix the sample and spin for 3 min at 25,000 x g. 
		NOTE: Chloroform is toxic and should be handled in a fume hood wearing skin protection. Chloroform is added to remove phenol, which can affect the downstream analysis of RNA by inhibiting reverse transcription14 and polymerase chain reactions15.</li>
	</ol>
	</li>
	<li>Perform chloroform extraction by aspirating the aqueous upper phase as before (now approximately 180 &#181;L), and transfer to a tube containing 200 &#181;L chloroform. Whirl mix the sample and spin 3 min at 25,000 x g.</li>
	<li>Aspirate the aqueous upper phase as before (now approximately 170 &#181;L) and transfer it to a tube containing 17 &#181;L (1/10 volume) 3 M CH3COONa, pH 6.0. To neutralize and precipitate RNA from the aqueous solution, add 2 &#181;L glycogen (20 mg/mL), which precipitates together with RNA and makes the RNA pellet more visible.</li>
	<li>Add 500 &#181;L 96% ethanol to increase binding between the salt ions and RNA and mix by inverting the tube a couple of times. Leave the tube overnight at -20 &#176;C or 15 min on dry ice.</li>
	<li>Spin the sample at 25,000 x g, 4 &#176;C for 30 min. Discard supernatant without disturbing the pellet and wash the pellet in 185 &#181;L 75% ethanol to remove any residual salt. Spin at 25,000 x g, 4 &#176;C for 5 min.</li>
	<li>Discard supernatant completely without disturbing the pellet and leave the pellet to dry 5-10 min with an open lid. Resuspend in 10 &#181;L RNase-free H2O applied on the side of the tube to avoid disturbing the pellet.</li>
</ol>
5. Analysis of RNA
<ol>
	<li>Prepare cDNA using a cDNA reverse transcription kit (see Table of Materials) or any other preferred method using 2 &#181;L RNA sample and 1 &#181;g yeast total RNA as carrier RNA for the cDNA synthesis reaction (not used if cDNA is used for next generation sequencing). Use 1 &#181;g RNA without yeast RNA for cDNA preparation of corresponding input.</li>
	<li>Dilute cDNA 1:25 and mix 9 &#181;L diluted cDNA with 10 &#181;L qPCR Master mix and 1 &#181;L fluorogenic probe, both specified in the Table of Materials. 
	NOTE: The cDNA dilution depends on the cDNA preparation and qPCR method used.</li>
	<li>Run the following qPCR program (e.g., on a 7500 Fast Real-time PCR system or equivalent): 2 min at 50 &#176;C, 20 s at 95 &#176;C, 40 cycles of 3 s at 95 &#176;C and 30 s at 60 &#176;C.</li>
</ol>

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Dis. 106, 49-62 (2017).</li><li>Imamachi, N., 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=BRIC-seq:+A+genome-wide+approach+for+determining+RNA+stability+in+mammalian+cells.">BRIC-seq: A genome-wide approach for determining RNA stability in mammalian cells.</a> Methods. 67, 55-63 (2014).</li><li>Jacob, F., Monod, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+regulatory+mechanisms+in+the+synthesis+of+proteins.">Genetic regulatory mechanisms in the synthesis of proteins.</a> J. Mol. Biol. 3, 318-356 (1961).</li><li>Lee, T. I., Young, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptional+Regulation+and+its+Misregulation+in+Disease.">Transcriptional Regulation and its Misregulation in Disease.</a> Cell. 152, 1237-1251 (2014).</li><li>Farrer, 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=Comparison+of+kindreds+with+parkinsonism+and+&#945;-synuclein+genomic+multiplications.">Comparison of kindreds with parkinsonism and &#945;-synuclein genomic multiplications.</a> Ann. Neurol. 55, 174-179 (2004).</li><li>Khodr, C. E., Becerra, A., Han, Y., Bohn, M. 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The authors have nothing to disclose.

This protocol describes the use of BrU-IP for determination of RNA production by labelling of newly produced RNA for 1 h with BrU, followed by immediate RNA extraction and immunoprecipitation of BrU-labelled RNA. This method has previously been described in reference16, and this article includes some additional steps to increase IP specificity and RNA purity, by pre-treating beads with low concentrations of BrU as well as a phenol-chloroform purification step to increase RNA purity following IP. A...

5-Bromouridine (BrU) immunoprecipitation (IP) allows the study of RNA production in cells with no or very limited effects on cell physiology during the brief labelling period1,2. The method is based upon incorporation of the synthetic uridine derivative BrU into newly synthesized RNA followed by IP of labelled RNA using anti-BrU antibodies (Figure 1).
It has been known for decades that protein synthesis can be transcriptionally regulated, and the existence of transcription factors was hypothesized more than 50 years ago3. Today, it is known that several diseases are caused by dysregulation of transcription and RNA stability (Supplementary Figure S1 in reference4), and the ability to measure changes in RNA production is of great importance in understanding disease development.
On the other hand, tools to regulate RNA production provide new possibilities for treating diseases caused by too little or too much protein expression, or protein accumulation such as in Parkinson&#39;s disease (PD). The predominant protein accumulating as insoluble aggregates in PD is &#945;-synuclein, and the level of &#945;-synuclein is directly linked to the disease, as gene multiplication of the &#945;-synuclein gene causes familial PD5. Furthermore, &#945;-synuclein aggregates in a concentration dependent manner. Downregulation of &#945;-synuclein mRNA levels is therefore an interesting therapeutic strategy, which has been successfully achieved using RNA interference to decrease neuronal cell loss in PD rodent models6,7.
It is important to be able to measure the changes in RNA production caused by either disease or therapeutic interventions. State of the art methods for measuring steady state levels of RNA, such as reverse transcription followed by quantitative polymerase chain reaction (RT-qPCR), are not capable of distinguishing between changes caused by transcriptional regulation or by altered RNA stability. A widely used method for investigation of RNA decay rates is blocking of the transcriptional machinery using compounds such as &#945;-amanitin or actinomycin D followed by measurements of the decaying RNAs. However, there are some problems associated with an overall blockage of transcription in cells, such as induction of apoptosis8,9. Beside the cytotoxic effects, transcriptional inhibitors also present several technical issues, such as slow cellular uptake of &#945;-amanitin and lack of specificity of actinomycin D (reviewed in reference10).
To avoid the overall blockage of transcription, nucleotide analogues have been used, such as 5-ethynyl uridine (5-EU), 4-thiouridine (4-TU), and BrU. These are readily taken up by mammalian cells and incorporated into newly synthesized RNA, enabling pulse-labelling of RNA within a specific time-frame. BrU is less toxic than 5-EU and 4-TU, making it the preferred analogue of choice11,12.
BrU-IP can be used to investigate both the rate of RNA synthesis and stability, and thus distinguish between the underlying causes of changes in total RNA. This article will focus on the measurement of RNA synthesis and refers to reference2 for details on investigation of RNA stability. To investigate RNA synthesis, cells are briefly labelled with BrU e.g. for 1 h followed by BrU-IP1 (Figure 1C). This enables measurements of RNA synthesized within the short labelling time and observed changes will give a better estimate of regulations in RNA synthesis than by measuring changes in total RNA by RT-qPCR. It should be mentioned, however, that even though the labelling time is, for example, only 1 h, degradation can still have an influence on the RNA levels observed.
RNA from BrU-IP experiments are suitable for downstream analysis by both RT-qPCR1 or next generation sequencing2,13. Other standard RNA detection methods, such as northern blotting or ribonuclease protection assay, may also be applicable for certain RNAs.

<table>
	<tbody>
		<tr>
			<td>Ribolock Rnase inhibitor</td>
			<td>ThermoFisher</td>
			<td>EO0381</td>
			<td></td>
		</tr>
		<tr>
			<td>Dynabeads M-280 Sheep anti-mouse IgG</td>
			<td>Life Technologies</td>
			<td>11202D</td>
			<td></td>
		</tr>
		<tr>
			<td>&#945;-Bromodeoxyuridine mouse antibody</td>
			<td>BD Bioscience</td>
			<td>555627</td>
			<td></td>
		</tr>
		<tr>
			<td>Nanodrop 1000</td>
			<td>Thermo Fisher</td>
			<td></td>
			<td>Ultraviolet-visible spectrophotometry</td>
		</tr>
		<tr>
			<td>Water-Saturated Phenol pH 6.6</td>
			<td>ThermoFisher</td>
			<td>AM9712</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenol:Chloroform:IAA 25:24:1 pH 6.6</td>
			<td>ThermoFisher</td>
			<td>AM9732</td>
			<td></td>
		</tr>
		<tr>
			<td>High Pure RNA isolation Kit</td>
			<td>Roche</td>
			<td>11828665001</td>
			<td></td>
		</tr>
		<tr>
			<td>High Capacity cDNA Reverse Transcription Kit</td>
			<td>ThermoFisher</td>
			<td>4368814</td>
			<td></td>
		</tr>
		<tr>
			<td>Taqman Fast Advanced Master Mix</td>
			<td>ThermoFisher</td>
			<td>4444557</td>
			<td>qPCR Master Mix</td>
		</tr>
		<tr>
			<td>Taqman RNA probes</td>
			<td>ThermoFisher</td>
			<td>SNCA: Hs01103383_m1, 18sRNA: Hs03928985_g1, ACTB: Hs01060665_g1, HMBS: Hs00609296, NADH: Hs01072843_m1</td>
			<td>Flurogenic probes</td>
		</tr>
		<tr>
			<td>7500 Fast Real-Time PCR system</td>
			<td colspan="2">Applied Biosystems</td>
			<td></td>
		</tr>
		<tr>
			<td>HEK293T cell line</td>
			<td>ATCC</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle&#39;s Medium</td>
			<td>Lonza</td>
			<td>BE12-604F</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal calf serum</td>
			<td>Biochrom</td>
			<td>S0115</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>Biochrom</td>
			<td>A2213</td>
			<td></td>
		</tr>
		<tr>
			<td>Hank&#39;s buffer</td>
			<td></td>
			<td></td>
			<td>5,3 mM KCl, 0.44 mM KH2PO4, 0.2 mM Na2HPO4 and 136.8 mM NaCl pH 6.77, autoclaved.</td>
		</tr>
		<tr>
			<td>DEPC-H2O</td>
			<td></td>
			<td></td>
			<td>0.1% diethylpyrocarbonate treated H2O</td>
		</tr>
		<tr>
			<td>2xBrU-IP Buffer</td>
			<td></td>
			<td></td>
			<td>40 mM Tris-HCl pH 7.5 and 500 mM NaCl in DEPC H2O</td>
		</tr>
		<tr>
			<td>2xBrU-IP+BSA/RNAse inhibitor</td>
			<td></td>
			<td></td>
			<td>2xBrU-IP buffer supplemented with 1 &#956;g/&#956;L BSA and 80 U/mL Ribolock</td>
		</tr>
		<tr>
			<td>BrU-IP+ 1 mg/mL heparin</td>
			<td></td>
			<td></td>
			<td>2xBrU-IP buffer diluted 1:1 DEPC-H2O and supplemented with 1mg/mL heparin</td>
		</tr>
		<tr>
			<td>1xBrU-IP</td>
			<td></td>
			<td></td>
			<td>2xBrU-IP buffer diluted 1:1 in DEPC-H2O and supplemented with 0.5 &#956;g/&#956;L BSA and 20 U/mL Ribolock</td>
		</tr>
		<tr>
			<td>Elution buffer</td>
			<td></td>
			<td></td>
			<td>0.1% SDS in RNAse-free H2O</td>
		</tr>
	</tbody>
</table>

investigation of rna synthesis using 5-bromouridine labelling and immunoprecipitation

When steady state RNA levels are compared between two conditions, it is not possible to distinguish whether changes are caused by alterations in production or degradation of RNA. This protocol describes a method for measurement of RNA production, using 5-Bromouridine labelling of RNA followed by immunoprecipitation, which enables investigation of RNA synthesized within a short timeframe (e.g., 1 h). The advantage of 5-Bromouridine-labelling and immunoprecipitation over the use of toxic transcriptional inhibitors, such as &#945;-amanitin and actinomycin D, is that there are no or very low effects on cell viability during short-term use. However, because 5-Bromouridine-immunoprecipitation only captures RNA produced within the short labelling time, slowly produced as well as rapidly degraded RNA can be difficult to measure by this method. The 5-Bromouridine-labelled RNA captured by 5-Bromouridine-immunoprecipitation can be analyzed by reverse transcription, quantitative polymerase chain reaction, and next generation sequencing. All types of RNA can be investigated, and the method is not limited to measuring mRNA as is presented in this example.

Our initial tests of BrU-labelling time were performed in AsPC-1 cells. The cells were treated with BrU for 0, 1, 2, and 4.5 h, followed by total RNA extraction and BrU-IP. GAS5 and GAPDH were measured in BrU-IP RNA, which demonstrated that 1 h labelling was sufficient to reach an approximately 9- and 44-fold change compared to background (0 h) for GAPDH and GAS5, respectively.
BrU-IP and the analysis described above were used t...

Watch this Scientific Journal Video about Investigation of RNA Synthesis Using 5-Bromouridine Labelling and Immunoprecipitation at JoVE.com

Investigation of RNA Synthesis Using 5-Bromouridine Labelling and Immunoprecipitation

This method can be used to measure RNA synthesis. 5-Bromouridine is added to cells and incorporated into synthesized RNA. RNA synthesis is measured by RNA extraction immediately after labelling, followed by 5-Bromouridine-targeted immunoprecipitation of labelled RNA and analysis by reverse transcription and quantitative polymerase chain reaction.

When steady state RNA levels are compared between two conditions, it is not possible to distinguish whether changes are caused by alterations in ...

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9.4K Views.  Aarhus University. This method can be used to measure RNA synthesis. 5-Bromouridine is added to cells and incorporated into synthesized RNA. RNA synthesis is measured by RNA extraction immediately after labelling, followed by 5-Bromouridine-targeted immunoprecipitation of labelled RNA and analysis by reverse transcription and quantitative polymerase chain reaction.

Video: Investigation of RNA Synthesis Using 5-Bromouridine Labelling and Immunoprecipitation

RNA Interference-based Investigation of the Function of Heat Shock Protein 27 during Corneal Epithelial Wound Healing

Small interfering RNA (siRNA) is among the most widely used RNA interference methods for the short-term silencing of protein-coding genes. siRNA is a synthetic RNA duplex created to specifically target a mRNA transcript to induce its degradation and it has been used to identify novel pathways in various cellular processes. Few reports exist regarding the role of phosphorylated heat shock protein 27 (HSP27) in corneal epithelial wound healing. Herein, cultured human corneal epithelial cells were divided into a scrambled control-siRNA transfected group and a HSP27-specific siRNA-transfected group. Scratch-induced directional wounding assays, and western blotting, and flow cytometry were then performed. We conclude that HSP27 has roles in corneal epithelial wound healing that may involve epithelial cell apoptosis and migration. Here, step-by-step descriptions of sample preparation and the study protocol are provided.

Herein, we present a protocol to use heat shock protein 27 (HSP27)-specific small interfering RNA to assess the function of HSP27 during corneal epithelial wound healing. RNA interference is the best method for effectively knocking-down gene expression to investigate protein function in various cell types.

Small interfering RNA (siRNA) is among the most widely used RNA interference methods for the short-term silencing of protein-coding genes. siRNA is a ...

Mapping RNA-RNA Interactions Globally Using Biotinylated Psoralen

Knowing how RNAs interact with themselves and with others is key to understanding RNA based gene regulation in the cell. While examples of RNA-RNA interactions such as microRNA-mRNA interactions have been shown to regulate gene expression, the full extent to which RNA interactions occur in the cell is still unknown. Previous methods to study RNA interactions have primarily focused on subsets of RNAs that are interacting with a particular protein or RNA species. Here, we detail a method named Sequencing of Psoralen crosslinked, Ligated, and Selected Hybrids (SPLASH) that allows genome-wide capture of RNA interactions in vivo in an unbiased manner. SPLASH utilizes in vivo crosslinking, proximity ligation, and high throughput sequencing to identify intramolecular and intermolecular RNA base-pairing partners globally. SPLASH can be applied to different organisms including bacteria, yeast and human cells, as well as diverse cellular conditions to facilitate the understanding of the dynamics of RNA organization under diverse cellular contexts. The entire experimental SPLASH protocol takes about 5 days to complete and the computational workflow takes about 7 days to complete.

Here, we detail the method of Sequencing of Psoralen crosslinked, Ligated, and Selected Hybrids (SPLASH), which enables genome-wide mapping of intramolecular and intermolecular RNA-RNA interactions in vivo. SPLASH can be applied to study RNA interactomes of organisms including yeast, bacteria and humans.

Knowing how RNAs interact with themselves and with others is key to understanding RNA based gene regulation in the cell. While examples of RNA-RNA ...

Analysis of the c-KIT Ligand Promoter Using Chromatin Immunoprecipitation

Multiple cellular processes, including DNA replication and repair, DNA recombination, and gene expression, require interactions between proteins and DNA. Therefore, DNA-protein interactions regulate multiple physiological, pathophysiological, and biological functions, such as cell differentiation, cell proliferation, cell cycle control, chromosome stability, epigenetic gene regulation, and cell transformation. In eukaryotic cells, the DNA interacts with histone and nonhistone proteins and is condensed into chromatin. Several technical tools can be used to analyze DNA-protein interactions, such as the Electrophoresis (gel) Mobility Shift Assay (EMSA) and DNase I footprinting. However, these techniques analyze the protein-DNA interaction in vitro, not within the cellular context. Chromatin immunoprecipitation (ChIP) is a technique that captures proteins at their specific DNA binding sites, thereby allowing for the identification of DNA-protein interactions within their chromatin context. It is done by fixation&#160;of the DNA-protein interaction, followed by&#160;immunoprecipitation of the protein of interest. Subsequently, the genomic site that the protein was bound to is characterized. Here, we describe and discuss ChIP and demonstrate its analytical value for the identification of the Transforming Growth Factor-&#946; (TGF-&#946;)-induced binding of the transcription factor SMAD2 to SMAD Binding Elements (SBE) within the promoter region of the tyrosine-protein kinase Kit (c-KIT) receptor ligand Stem Cell Factor (SCF).

DNA-protein interactions are essential for multiple biological processes. During the evaluation of cellular functions, the analysis of DNA-protein interactions is indispensable for understanding gene regulation. Chromatin immunoprecipitation (ChIP) is a powerful tool to analyze such interactions in vivo.

Multiple cellular processes, including DNA replication and repair, DNA recombination, and gene expression, require interactions between proteins and DNA. ...

Investigation of Protein Recruitment to DNA Lesions Using 405 Nm Laser Micro-irradiation

The DNA Damage Response (DDR) uses a plethora of proteins to detect, signal, and repair DNA lesions. Delineating this response is critical to understand genome maintenance mechanisms. Since recruitment and exchange of proteins at lesions are highly dynamic, their study requires the ability to generate DNA damage in a rapid and spatially-delimited manner. Here, we describe procedures to locally induce DNA damage in human cells using a commonly available laser-scanning confocal microscope equipped with a 405 nm laser line. Accumulation of genome maintenance factors at laser stripes can be assessed by immunofluorescence (IF) or in real-time using proteins tagged with fluorescent reporters. Using phosphorylated histone H2A.X (&#947;-H2A.X) and Replication Protein A (RPA) as markers, the method provides sufficient resolution to discriminate locally-recruited factors from those that spread on adjacent chromatin. We further provide ImageJ-based scripts to efficiently monitor the kinetics of protein relocalization at DNA damage sites. These refinements greatly simplify the study of the DDR dynamics.

Studying DNA damage repair kinetics requires a system to induce lesions at defined sub-nuclear regions. We describe a method to create localized double-stranded breaks using a laser-scanning confocal microscope equipped with a 405 nm laser and provide automated procedures to quantify the dynamics of repair factors at these lesions.

The DNA Damage Response (DDR) uses a plethora of proteins to detect, signal, and repair DNA lesions. Delineating this response is critical to understand ...

Rare Event Detection Using Error-corrected DNA and RNA Sequencing

Conventional next-generation sequencing techniques (NGS) have allowed for immense genomic characterization for over a decade. Specifically, NGS has been used to analyze the spectrum of clonal mutations in malignancy. Though far more efficient than traditional Sanger methods, NGS struggles with identifying rare clonal and subclonal mutations due to its high error rate of ~0.5&#8211;2.0%. Thus, standard NGS has a limit of detection for mutations that are &#62;0.02 variant allele fraction (VAF). While the clinical significance for mutations this rare in patients without known disease remains unclear, patients treated for leukemia have significantly improved outcomes when residual disease is &#60;0.0001 by flow cytometry. In order to mitigate this artefactual background of NGS, numerous methods have been developed. Here we describe a method for Error-corrected DNA and RNA Sequencing (ECS), which involves tagging individual molecules with both a 16 bp random index for error-correction and an 8 bp patient-specific index for multiplexing. Our method can detect and track clonal mutations at variant allele fractions (VAFs) two orders of magnitude lower than the detection limit of NGS and as rare as 0.0001 VAF.

Next-generation sequencing (NGS) is a powerful tool for genomic characterization that is limited by the high error rate of the platform (~0.5&#8211;2.0%). We describe our methods of error-corrected sequencing that allow us to obviate the NGS error rate and detect mutations at variant allele fractions as rare as 0.0001.

Conventional next-generation sequencing techniques (NGS) have allowed for immense genomic characterization for over a decade. Specifically, NGS has been ...

Quantitative Analysis of Alternative Pre-mRNA Splicing in Mouse Brain Sections Using RNA In Situ Hybridization Assay

Alternative splicing (AS) occurs in more than 90% of human genes. The expression pattern of an alternatively spliced exon is often regulated in a cell type-specific fashion. AS expression patterns are typically analyzed by RT-PCR and RNA-seq using RNA samples isolated from a population of cells. In situ examination of AS expression patterns for a particular biological structure can be carried out by RNA in situ hybridization (ISH) using exon-specific probes. However, this particular use of ISH has been limited because alternative exons are generally too short to design exon-specific probes. In this report, the use of BaseScope, a recently developed technology that employs short antisense oligonucleotides in RNA ISH, is described to analyze AS expression patterns in mouse brain sections. Exon 23a of neurofibromatosis type 1 (Nf1) is used as an example to illustrate that short exon-exon junction probes exhibit robust hybridization signals with high specificity in RNA ISH analysis on mouse brain sections. More importantly, signals detected with exon inclusion- and skipping-specific probes can be used to reliably calculate the percent spliced in values of Nf1 exon 23a expression in different anatomical areas of a mouse brain. The experimental protocol and calculation method for AS analysis are presented. The results indicate that BaseScope provides a powerful new tool to assess AS expression patterns in situ.

Quantitative Analysis of Alternative Pre-mRNA Splicing in Mouse Brain Sections Using RNA In Situ Hybridization Assay

An in situ hybridization (ISH) protocol that uses short antisense oligonucleotides to detect alternative pre-mRNA splicing patterns in mouse brain sections is described.

Alternative splicing (AS) occurs in more than 90% of human genes. The expression pattern of an alternatively spliced exon is often regulated in a cell ...

Chromatin Immunoprecipitation of Murine Brown Adipose Tissue

Most cellular processes are regulated by transcriptional modulation of specific gene programs. Such modulation is achieved through the combined actions of a wide range of transcription factors (TFs) and cofactors mediating transcriptional activation or repression via changes in chromatin structure. Chromatin immunoprecipitation (ChIP) is a useful molecular biology approach for mapping histone modifications and profiling transcription factors/cofactors binding to DNA, thus providing a snapshot of the dynamic nuclear changes occurring during different biological processes.
To study transcriptional regulation in adipose tissue, samples derived from in vitro cell cultures of immortalized or primary cell lines are often favored in ChIP assays because of the abundance of starting material and reduced biological variability. However, these models represent a limited snapshot of the actual chromatin state in living organisms. Thus, there is a critical need for optimized protocols to perform ChIP on adipose tissue samples derived from animal models.
Here we describe a protocol for efficient ChIP-seq of both histone modifications and non-histone proteins in brown adipose tissue (BAT) isolated from a mouse. The protocol is optimized for investigating genome-wide localization of proteins of interest and epigenetic markers in the BAT, which is a morphologically and physiologically distinct tissue amongst fat depots.

Here we describe a protocol for efficient chromatin immunoprecipitation (ChIP) followed by high-throughput DNA sequencing (ChIP-seq) of brown adipose tissue (BAT) isolated from a mouse. This protocol is suitable for both mapping histone modifications and investigating genome-wide localization of non-histone proteins of interest in vivo.

Most cellular processes are regulated by transcriptional modulation of specific gene programs. Such modulation is achieved through the combined actions of ...

Chromatin Immunoprecipitation Assay Using Micrococcal Nucleases in Mammalian Cells

To express cellular phenotypes in organisms, living cells execute gene expression accordingly, and transcriptional programs play a central role in gene expression. The cellular transcriptional machinery and its chromatin modification proteins coordinate to regulate transcription. To analyze transcriptional regulation at the molecular level, several experimental methods such as electrophoretic mobility shift, transient reporter and chromatin immunoprecipitation (ChIP) assays are available. We describe a modified ChIP assay in detail in this article because of its advantages in directly showing histone modifications and the interactions between proteins and DNA in cells. One of the key steps in a successful ChIP assay is chromatin shearing. Although sonication is commonly used for shearing chromatin, it is difficult to identify reproducible conditions. Instead of shearing chromatin by sonication, we utilized enzymatic digestion with micrococcal nuclease (MNase) to obtain more reproducible results. In this article, we provide a straightforward ChIP assay protocol using MNase.

Chromatin immunoprecipitation (ChIP) is a powerful tool for understanding the molecular mechanisms of gene regulation. However, the method involves difficulties in obtaining reproducible chromatin fragmentation by mechanical shearing. Here, we provide an improved protocol for a ChIP assay using enzymatic digestion.

To express cellular phenotypes in organisms, living cells execute gene expression accordingly, and transcriptional programs play a central role in gene ...

Identification of Footprints of RNA:Protein Complexes via RNA Immunoprecipitation in Tandem Followed by Sequencing (RIPiT-Seq)

RNA immunoprecipitation in tandem (RIPiT) is a method for enriching RNA footprints of a pair of proteins within an RNA:protein (RNP) complex. RIPiT employs two purification steps. First, immunoprecipitation of a tagged RNP subunit is followed by mild RNase digestion and subsequent non-denaturing affinity elution. A second immunoprecipitation of another RNP subunit allows for enrichment of a defined complex. Following a denaturing elution of RNAs and proteins, the RNA footprints are converted into high-throughput DNA sequencing libraries. Unlike the more popular ultraviolet (UV) crosslinking followed by immunoprecipitation (CLIP) approach to enrich RBP binding sites, RIPiT is UV-crosslinking independent. Hence RIPiT can be applied to numerous proteins present in the RNA interactome and beyond that are essential to RNA regulation but do not directly contact the RNA or UV-crosslink poorly to RNA. The two purification steps in RIPiT provide an additional advantage of identifying binding sites where a protein of interest acts in partnership with another cofactor. The double purification strategy also serves to enhance signal by limiting background. Here, we provide a step-wise procedure to perform RIPiT and to generate high-throughput sequencing libraries from isolated RNA footprints. We also outline RIPiT&#39;s advantages and applications and discuss some of its limitations.

Identification of Footprints of RNA:Protein Complexes via RNA Immunoprecipitation in Tandem Followed by Sequencing RIPiT-Seq

Here, we present a protocol to enrich endogenous RNA binding sites or &#34;footprints&#34;&#160;of RNA:protein (RNP) complexes from mammalian cells. This approach involves two immunoprecipitations of RNP subunits and is therefore dubbed RNA immunoprecipitation in tandem (RIPiT).

RNA immunoprecipitation in tandem (RIPiT) is a method for enriching RNA footprints of a pair of proteins within an RNA:protein (RNP) complex. RIPiT ...

High-Density DNA and RNA microarrays - Photolithographic Synthesis, Hybridization and Preparation of Large Nucleic Acid Libraries

Photolithography is a powerful technique for the synthesis of DNA oligonucleotides on glass slides, as it combines the efficiency of phosphoramidite coupling reactions with the precision and density of UV light reflected from micrometer-sized mirrors. Photolithography yields microarrays that can accommodate from hundreds of thousands up to several million different DNA sequences, 100-nt or longer, in only a few hours. With this very large sequence space, microarrays are ideal platforms for exploring the mechanisms of nucleic acid&#183;ligand interactions, which are particularly relevant in the case of RNA. We recently reported on the preparation of a new set of RNA phosphoramidites compatible with in situ photolithography and which were subsequently used to grow RNA oligonucleotides, homopolymers as well as mixed-base sequences. Here, we illustrate in detail the process of RNA microarray fabrication, from the experimental design, to instrumental setup, array synthesis, deprotection and final hybridization assay using a template 25mer sequence containing all four bases as an example. In parallel, we go beyond hybridization-based experiments and exploit microarray photolithography as an inexpensive gateway to complex nucleic acid libraries. To do so, high-density DNA microarrays are fabricated on a base-sensitive monomer that allows the DNA to be conveniently cleaved and retrieved after synthesis and deprotection. The fabrication protocol is optimized so as to limit the number of synthetic errors and to that effect, a layer of &#946;-carotene solution is introduced to absorb UV photons that may otherwise reflect back onto the synthesis substrates. We describe in a step-by-step manner the complete process of library preparation, from design to cleavage and quantification.

In this article, we present and discuss new developments in the synthesis and applications of nucleic acid microarrays fabricated in situ. Specifically, we show how the protocols for DNA synthesis can be extended to RNA and how microarrays can be used to create retrievable nucleic acid libraries.

Photolithography is a powerful technique for the synthesis of DNA oligonucleotides on glass slides, as it combines the efficiency of phosphoramidite ...