The work in this manuscript was supported by funds from Dept. of Radiation Oncology and Huntsman Cancer Institute and the National Institute of Health grant (R01-CA188520) to SB. I thank Danielle Johnson and Steven Bennett in my lab for demonstrating the protocol and explaining its benefits. I am grateful to Dr. Mahesh Chandrasekharan (Huntsman Cancer Institute) for critical comments on the manuscript.

1. Chromatin immunoprecipitation (ChIP) following BrdU Labeling
<ol>
	<li>Culture NIH3T3 cells in the presence of either DMSO or HDAC1,2-selective inhibitors as described previously6.</li>
	<li>Following treatment with DMSO or HDAC1,2 selective inhibitors, add BrdU to the cells in a sterile tissue culture hood. Incubate 2 x 106 NIH3T3 cells plated in 10 ml NIH3T3 media with a 20 &#181;M final concentration of bromodeoxyuridine (BrdU) for 60 min in a sterile 37 &#176;C tissue culture incubator.</li>
	<li>Crosslink intracellular proteins to DNA by adding formaldehyde directly to the culture media at a final concentration of 1%. Incubate 2 x 106 NIH3T3 cells with formaldehyde at RT&#160;for 10 min on a shaker.</li>
	<li>Quench the cross linking by the addition of glycine to a final concentration of 125 mM. Incubate at RT for 5 min on a shaker.</li>
	<li>Remove the media and collect cells in PBS in a 15 ml centrifuge tube. Spin cells at 956 x g for 5 min at 4 &#176;C. Wash the cell pellet twice with ice-cold PBS. Remove PBS from the tube. Store the cross-linked cell pellet without PBS (the supernatant) at -80 &#176;C until use.</li>
	<li>Prepare the lysate from the crosslinked cell pellet by adding 500 &#181;l FA140 buffer (50 mM of HEPES KOH pH 7.5, 140 mM of NaCl, 1 mM of EDTA (pH 8.0), 1% Triton-X-100 and 0.1% sodium deoxycholate) supplemented with protease inhibitor cocktail.</li>
	<li>Shear the chromatin by sonicating the samples five times at 35% power and with a 15 sec&#160;pulse, 0.9 sec on and 0.1 sec off setting. Keep the tubes on ice after every round of sonication to avoid heating of the samples.
	<ol>
		<li>Check the shearing on a DNA gel as the shearing efficiency will vary between different sonicators. To check sonication, reverse crosslink by adding NaCl to a concentration of 0.16 M and perform steps 1.17.1. - 1.22. Run eluted 10 &#181;l DNA on a 1.5% agarose gel to check whether the shearing is between 300 - 700 bp with an average intensity at 500 bp.</li>
	</ol>
	</li>
	<li>Following sonication, centrifuge samples for 10 min at 17,949 x g at 4 &#176;C and transfer the supernatant to a new tube.
	<ol>
		<li>Perform protein estimation using the commercial protein assay kit according to manufacturer&#39;s protocol. Use equal amount of lysate for ChIP of control and experimental samples. Generally, use 1 mg of total lysate per ChIP reaction.</li>
	</ol>
	</li>
	<li>Prepare 50% slurry of protein A-agarose using FA140 buffer containing protease inhibitor cocktail. Add 1/10 volume of the protease inhibitor cocktail. Calculate the volume of beads needed based on the number of samples in total.
	<ol>
		<li>Wash Protein A-agarose beads with FA140 buffer twice to remove the storage buffer and add an equal volume to FA140 buffer to the beads to make 50% slurry.</li>
		<li>To remove proteins that non-specifically bind to the beads, add 50 &#181;l of 50% slurry of Protein A-agarose and incubate the samples at 4 &#176;C with constant end-over-end rotation in a rotisserie mixer for 30 min.</li>
	</ol>
	</li>
	<li>Spin the samples at 956 x g at 4 &#176;C for a minute. Collect the supernatant and perform immunoprecipitation by adding either 8 &#956;l H4K16ac antibody or 5 &#956;l (5 &#956;g) of 1 mg/ml SMARCA5 antibody to the supernatant. Incubate at 4 &#176;C O/N&#160;with constant end-over-end rotation in a rotisserie mixer.</li>
	<li>Save 1/10th of the extract for &#39;input&#39; control and set it as aside at -20 &#176;C. The input needs to be reverse cross-linked along with the IP samples.</li>
	<li>Use equal amount of rabbit IgG (5&#160;&#956;l of 1 mg/ml) as the negative control immunoprecipitation sample.</li>
	<li>The following day, add 50 &#956;l of 50% protein A-agarose slurry to the extract and incubate for 1 hr at 4 &#176;C with rotation.</li>
	<li>Pellet agarose beads by centrifugation at 956 x g for 2 min at 4 &#176;C, carefully remove the supernatant and wash the beads with the following buffers sequentially. In buffer preparations, add protease inhibitors right before use.
	<ol>
		<li>Wash with Low Salt Immune Complex Wash Buffer (FA140; final concentration of 50 mM of HEPES KOH pH 7.5, 140 mM of NaCl, 1 mM of EDTA (pH 8.0), 1% Triton-X-100 and 0.1% Sodium deoxycholate) for 5 min at 4 &#176;C with end-over-end rotation.</li>
		<li>Wash with High Salt Immune Complex Wash Buffer (FA500; final concentration of 50 mM of HEPES KOH pH 7.5, 500 mM of NaCl, 1 mM of EDTA (pH 8.0), 1% Triton-X-100 and 0.1% Sodium deoxycholate) for 5 min at 4 &#176;C with end-over-end rotation.</li>
		<li>Wash with LiCl Immune Complex Wash Buffer (final concentration of 10 mM of Tris-Cl pH 8.0, 250 mM of LiCl, 0.5% NP40 and 0.5% Sodium deoxycholate) for 5 min at 4 &#176;C with end-over-end rotation.</li>
	</ol>
	</li>
	<li>Following washes as described above, add 200 &#181;l elution solution (final concentration of 1% SDS and 100 mM Sodium bicarbonate) and incubate at RT for 15 min with end-over-end rotation at RT.</li>
	<li>Spin the samples at 956 x g at RT and transfer the eluate to a new 1.5 ml tube. Repeat step 1.15 with additional 200 &#181;l elution solution.</li>
	<li>To 400 &#181;l of the eluate, add NaCl to a concentration of 0.16 M and mix well.
	<ol>
		<li>In addition, add 400 &#181;l elution solution to 10 &#181;l input that was set aside (step 1.11) and add NaCl to a concentration of 0.16 M to reverse crosslink input samples as well. Reverse crosslink the samples by incubating in 65 &#176;C water bath for 5 hr.</li>
	</ol>
	</li>
	<li>Add 1 ml&#160;of 100% EtOH to the reverse-crosslinked eluate. Mix well and incubate at -80 &#176;C for 2 - 3 hr or at -20 &#176;C O/N. Spin the samples at 17,949 x g for 15 min and discard ethanol.</li>
	<li>Add 800 &#181;l 70% ethanol to wash the pellet. Spin at 17,949 x g for 15 min at 4 &#176;C and discard ethanol. Spin briefly to remove any residual ethanol. Air-dry the samples at 37 &#176;C for 10 min to remove residual ethanol.</li>
	<li>Dissolve DNA in 90 &#181;l RNase and DNase free water and add 2 &#181;l 10 mg/ml RNase at a 0.2 mg/ml final concentration. Incubate at 37 &#176;C in water bath for 30 min.</li>
	<li>Add 10 &#181;l 10x&#160;Proteinase K Buffer (100 mM Tris-Cl pH 8.0, 50 mM EDTA pH 8.0, 5% SDS). Mix well and add 1 &#181;l Proteinase K. Incubate at 42 &#176;C for 1 hr.</li>
	<li>Purify input and ChIP DNA using commercial PCR purification kit according to manufacturer&#39;s protocol and elute DNA in 50 &#181;l water. Store DNA at -20 &#176;C until further use.</li>
</ol>
2. Slot Blot Analysis of ChIP DNA
<ol>
	<li>Measure the yield of input and ChIP DNA eluted in 50 &#181;l water as described in step 1.22 using a spectrophotometer at 280 nm according to manufacturer&#39;s protocol.</li>
	<li>Take equal volumes (50 &#181;l) of input or immunoprecipitated DNA that are within the linear range of detection.
	<ol>
		<li>For instance, if input DNA yield is 1.5 ng/&#181;l, then take 30 &#181;l (or 45 ng total DNA) and make volume to 50 &#181;l with water. For factor ChIP, take the entire 50 &#181;l eluate from Step 2.1 and proceed to step 2.3.</li>
	</ol>
	</li>
	<li>Denature 50 &#181;l input or immunoprecipitated DNA by adding 2.5 volumes of 0.4 N NaOH, briefly vortex and centrifuge for 956 x g for 10 sec, and incubate at RT for 30 min.</li>
	<li>Neutralize the denatured DNA by adding 175 &#181;l of 1 M Tris-HCl, pH 6.8, vortex, centrifuge for 956 x g for 10 sec and place the samples on ice.</li>
	<li>Prepare a serial dilution of input and immunoprecipitated DNA for the Slot Blot assay as described below.
	<ol>
		<li>Follow steps 2.3 - 2.4 to get a total sample volume of 350 &#181;l (i.e., 50 &#181;l Input/ChIP DNA, 125 &#181;l 0.4 N NaOH, 175 &#181;l 1 M Tris-HCl, pH 6.8). 
		Note: For the instance stated above, 45 ng of input DNA will end up being 0.129 ng/ &#181;l.</li>
		<li>For input DNA, label three tubes as 100, 50 and 25 and add 100 &#181;l, 50 &#181;l and 25 &#181;l of the denatured and neutralized DNA sample. Make the final volume to 100 &#181;l with nuclease-free water. For ChIP DNA, label three tubes as 200, 100 and 50 and add 200 &#181;l, 100 &#181;l and 50 &#181;l of the denatured and neutralized DNA sample. Make final volume to 200 &#181;l&#160;with nuclease free water.</li>
	</ol>
	</li>
	<li>Cut the membrane to the size of the Slot Blot apparatus. Pre-wet the membrane and blotting papers in 20x SSC before and prior to adding DNA. Assemble them into the Slot Blot apparatus according to the manufacturer&#39;s protocol.</li>
	<li>Pipet DNA from step 2.5.2 into appropriate slots. Apply vacuum slowly to pull the DNA onto the zeta-probe membrane. Stop vacuum after all samples have passed through the apparatus.
	<ol>
		<li>Disassemble the apparatus and immediately immobilize the DNA onto the membrane using a UV crosslinker. Have the DNA side up in the UV crosslinker and use the autocrosslink setting in the crosslinker. Follow manufacturer&#39;s protocol.</li>
	</ol>
	</li>
	<li>Detect BrdU on the slot blot by performing western blotting.
	<ol>
		<li>Block the membrane with 5% non-fat dry milk in PBS containing 0.1% Tween-20 (PBST) for 1 hr&#160;at RT to prevent the non-specific binding of antibodies to the membrane.</li>
		<li>Add primary anti-BrdU antibody (1:500 dilution) diluted in 1% non-fat dry milk in PBST and incubate the blot with the primary antibody for 3 hr at RT on a shaker. Wash the membrane with PBST three times after the primary antibody incubation.</li>
		<li>Add HRP-conjugated anti-mouse secondary antibody to the blot (1:5,000 dilution) and incubate at RT for 1 hr. Wash the membrane with PBST three times after the secondary antibody incubation. 
		NOTE: Use enough volume of the antibodies to completely cover the membrane during primary and secondary antibody incubations.</li>
	</ol>
	</li>
	<li>Prepare the ECL mix and add it to the blot according to the manufacturer&#39;s protocol. Incubate the membrane with ECL mix for 5 min at RT.
	<ol>
		<li>Place the membrane in an X-ray cassette, expose the membrane to the X-ray film and develop the blot using the manufacturer&#39;s protocol.</li>
		<li>Quantify the signal obtained for input and ChIPed DNA after scanning the blots using the Image J software according to manufacturer&#39;s protocol. For quantitation, use the signal that is within the linear range of detection in order to ensure accuracy of measurement.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Podhorecka, M., Skladanowski, A., Bozko, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=H2AX+Phosphorylation:+Its+Role+in+DNA+Damage+Response+and+Cancer+Therapy.">H2AX Phosphorylation: Its Role in DNA Damage Response and Cancer Therapy.</a> J nucleic acids. , (2010).</li><li>Groth, A., Rocha, W., Verreault, A., Almouzni, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatin+challenges+during+DNA+replication+and+repair.">Chromatin challenges during DNA replication and repair.</a> 128, 721-733 (2007).</li><li>Demeret, C., Vassetzky, Y., Mechali, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatin+remodelling+and+DNA+replication:+from+nucleosomes+to+loop+domains.">Chromatin remodelling and DNA replication: from nucleosomes to loop domains.</a> Oncogene. 20, 3086-3093 (2001).</li><li>Bhaskara, S., 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=Deletion+of+histone+deacetylase+3+reveals+critical+roles+in+S+phase+progression+and+DNA+damage+control.">Deletion of histone deacetylase 3 reveals critical roles in S phase progression and DNA damage control.</a> Mol Cell. 30, 61-72 (2008).</li><li>Bhaskara, S., Hiebert, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+for+histone+deacetylase+3+in+maintenance+of+genome+stability.">Role for histone deacetylase 3 in maintenance of genome stability.</a> Cell Cycle. 10, 727-728 (2011).</li><li>Bhaskara, S., 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=Histone+deacetylases+1+and+2+maintain+S-phase+chromatin+and+DNA+replication+fork+progression.">Histone deacetylases 1 and 2 maintain S-phase chromatin and DNA replication fork progression.</a> Epigenetics Chromatin. 6, 27 (2013).</li><li>Bhaskara, S., 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=Hdac3+is+essential+for+the+maintenance+of+chromatin+structure+and+genome+stability.">Hdac3 is essential for the maintenance of chromatin structure and genome stability.</a> Cancer Cell. 18, 436-447 (2010).</li><li>Johnson, D. P., 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=HDAC1,2+inhibition+impairs+EZH2-+and+BBAP-mediated+DNA+repair+to+overcome+chemoresistance+in+EZH2+gain-of-function+mutant+diffuse+large+B-cell+lymphoma.">HDAC1,2 inhibition impairs EZH2- and BBAP-mediated DNA repair to overcome chemoresistance in EZH2 gain-of-function mutant diffuse large B-cell lymphoma.</a> Oncotarget. 6, 4863-4887 (2015).</li><li>Bhaskara, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Histone+deacetylases+1+and+2+regulate+DNA+replication+and+DNA+repair:+potential+targets+for+genome+stability-mechanism-based+therapeutics+for+a+subset+of+cancers.">Histone deacetylases 1 and 2 regulate DNA replication and DNA repair: potential targets for genome stability-mechanism-based therapeutics for a subset of cancers.</a> Cell Cycle. 14, 1779-1785 (2015).</li><li>Taddei, A., Roche, D., Sibarita, J. B., Turner, B. M., Almouzni, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Duplication+and+maintenance+of+heterochromatin+domains.">Duplication and maintenance of heterochromatin domains.</a> J Cell Biol. 147, 1153-1166 (1999).</li><li>Alabert, C., Groth, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatin+replication+and+epigenome+maintenance.">Chromatin replication and epigenome maintenance.</a> Nat Rev Mol Cell Biol. 13, 153-167 (2012).</li><li>Clapier, C. R., Cairns, B. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+ISWI+involves+inhibitory+modules+antagonized+by+nucleosomal+epitopes.">Regulation of ISWI involves inhibitory modules antagonized by nucleosomal epitopes.</a> Nature. 492, 280-284 (2012).</li><li>Sirbu, B. 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=Analysis+of+protein+dynamics+at+active,+stalled,+and+collapsed+replication+forks.">Analysis of protein dynamics at active, stalled, and collapsed replication forks.</a> Genes Dev. 25, 1320-1327 (2011).</li></ol>

I have no competing financial interests.

The protocol described in this manuscript is a relatively quick method to demonstrate the presence of proteins or their post-translationally modified forms on newly replicated or nascent DNA. Additionally, this technique permits one to measure the association-dissociation kinetics of a protein or its modified form with nascent DNA. This technique is complementary to the elegant iPOND technology13. In the iPOND technology, newly synthesized DNA is labeled with ethyl deoxyuridine (EdU). A biotin conjugate is the...

Defective DNA repair and/or DNA replication are a major cause of genome instability, which can trigger cell death. A single unrepaired double strand break is sufficient to cause cell death1. Chromatin organization is transiently altered during both replication and repair2,3, and failure to maintain epigenetic information during these processes will result in a threat to genome integrity. Loss of HDAC3 or HDAC1,2 function impedes S-phase progression,&#160;DNA replication and repair leading to genotoxic stress (DNA damage) and cell&#160;death4-9. It is therefore a practical strategy to use selective HDAC inhibitors to disrupt replication, repair and chromatin in cancer cells and cause DNA damage, which in turn can stop growth and induce cell death selectively in rapidly growing cancer cells.
During DNA replication, chromatin is rapidly disassembled and then reassembled following DNA duplication. Newly synthesized histone H4 is acetylated at K5 and K12 residues (H4K5K12ac) and following deposition onto chromatin, they are rapidly deacetylated by histone deacetylases (HDACs)10,11. Failure of cells to maintain nascent chromatin integrity by histone deacetylation can lead to fork collapse, which in turn can result in DNA damage and cell death. We recently showed that selective inhibition of HDAC1,2 increases histone acetylation (H4K5ac, H4K12ac and H4K16ac) and inhibits SMARCA5 chromatin remodeler activity on nascent chromatin, which correlates with reduced replication fork progression, increased fork collapse and increased replication stress-induced DNA damage6. Thus, HDAC inhibitor treatment can alter nascent chromatin structure to trigger DNA damage and death very quickly in cancer cells, as these cells cycle rapidly and pass many times through the S-phase. It is therefore important to understand how HDACs function to regulate histone acetylation and protein binding to maintain DNA replication in mammalian cells.
To quantitatively measure the amount of histone acetylation and SMARCA5 chromatin remodeler associated with nascent DNA during DNA replication, we devised a modified ChIP assay called the BrdU-ChIP-Slot-Western technique. Following chromatin immunoprecipitation (ChIP) of a desired protein or histone modification, the amount of nascent DNA (labeled using thymidine analog, BrdU) in the ChIP sample can be detected using western analysis of BrdU-labeled ChIP DNA transferred onto a membrane using a Slot Blot apparatus. Using this technique, we showed that H4K16ac (a mark involved in chromatin packaging) and the ISWI family member SMARCA5 (SWI/SNF-related matrix-associated actin-dependent regulator of chromatin) chromatin remodeler are associated with nascent DNA in S-phase cells6. We also found that the nascent H4K16ac mark is deacetylated by HDAC1,2 during DNA replication6. H4K16ac inhibits chromatin remodeler activity of the ISWI family member SMARCA512. Hence, using the BrdU-CHIP-Slot-Western technique, we could connect the functions for HDAC1,2 in regulating chromatin remodeling during DNA replication. Hence, the BrdU-ChIP-Slot-Western Blot technique is a powerful approach to quantitatively measure the association and dissociation dynamics of proteins or their post-translational modifications that are bound to nascent DNA.

<table border="0" cellpadding="0" cellspacing="0" width="608">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Anti-BrdU (westerns)</td>
			<td style="width:107px;">BD Biosciences</td>
			<td style="width:119px;">B555627</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti-SMARCA5</td>
			<td>Abcam</td>
			<td style="width:119px;">ab3749</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Anti-H4K16ac</td>
			<td style="width:107px;">Active Motif</td>
			<td>39167</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Zeta-Probe GT Membrane</td>
			<td style="width:107px;">Bio-Rad</td>
			<td style="width:119px;">162-0197</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Formaldehyde</td>
			<td style="width:107px;">Fisher</td>
			<td style="width:119px;">BP531-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Protein A agarose</td>
			<td style="width:107px;">Millipore</td>
			<td style="width:119px;">16-156</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Rnase A</td>
			<td style="width:107px;">Qiagen</td>
			<td style="width:119px;">19101</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Proteinase K</td>
			<td style="width:107px;">Sigma</td>
			<td style="width:119px;">P4850</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">PCR Purification Kit</td>
			<td style="width:107px;">Qiagen</td>
			<td style="width:119px;">28106</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Glycine</td>
			<td style="width:107px;">Sigma</td>
			<td style="width:119px;">G7403</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Protease inhibitor cocktail</td>
			<td style="width:107px;">Roche</td>
			<td style="width:119px;">11836170001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">BrdU</td>
			<td style="width:107px;">Sigma</td>
			<td style="width:119px;">B9285</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Rabbit IgG&#160;</td>
			<td style="width:107px;">Millipore</td>
			<td style="width:119px;">12-370</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">HEPES</td>
			<td style="width:107px;">Sigma</td>
			<td style="width:119px;">H3375</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">NaCl</td>
			<td style="width:107px;">Sigma</td>
			<td style="width:119px;">S-3014</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Triton-X-100</td>
			<td style="width:107px;">Sigma</td>
			<td style="width:119px;">93443</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">NP40</td>
			<td style="width:107px;">USB Corporation</td>
			<td style="width:119px;">19628</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium deoxycholate</td>
			<td style="width:107px;">Sigma</td>
			<td style="width:119px;">D6750</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium bicarbonate</td>
			<td style="width:107px;">Sigma</td>
			<td style="width:119px;">S-4019</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ethanol</td>
			<td style="width:107px;">Decon Laboratories</td>
			<td style="width:119px;">04-355-222</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">DEPC-treated water</td>
			<td style="width:107px;">Sigma</td>
			<td style="width:119px;">95284</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tris</td>
			<td style="width:107px;">Fisher</td>
			<td style="width:119px;">BP-152-5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">EDTA</td>
			<td style="width:107px;">Invitrogen</td>
			<td style="width:119px;">15575-020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">SDS</td>
			<td style="width:107px;">Ambion</td>
			<td style="width:119px;">AM9820</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sodium hydroxide</td>
			<td style="width:107px;">Mallinckrodt GenAR&#160;</td>
			<td style="width:119px;">MAL7772-06</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">20X SSC</td>
			<td style="width:107px;">Life Technologies</td>
			<td style="width:119px;">15557-036</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Non-fat dry milk</td>
			<td style="width:107px;">Lab Scientific Inc</td>
			<td style="width:119px;">M0841</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">ECL</td>
			<td style="width:107px;">Thermo Fisher</td>
			<td style="width:119px;">80196</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">X-ray film</td>
			<td style="width:107px;">Genesee Sci</td>
			<td style="width:119px;">30-101</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Developer</td>
			<td style="width:107px;">Konica Minolta</td>
			<td style="width:119px;">SRX-101A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">UV Crosslinker</td>
			<td style="width:107px;">Stratagene</td>
			<td style="width:119px;">XLE-1000</td>
			<td></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Sonicator</td>
			<td style="width:107px;">Branson Sonifier&#160; Digital Ultrasonic Cell Disruptor</td>
			<td style="width:119px;">Model: 450</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Centrifuge</td>
			<td style="width:107px;">Eppendorf</td>
			<td style="width:119px;">Model: 5810R</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Water bath</td>
			<td style="width:107px;">Fisher Scientific Isotemp</td>
			<td style="width:119px;">Model: 2322</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">NanoDrop 1000 spectrophotometer</td>
			<td style="width:107px;">ThermoScientific</td>
			<td style="width:119px;">Model: 1000</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Slot Blot apparatus&#160;</td>
			<td style="width:107px;">Schleicher and Schuell Minifold II</td>
			<td style="width:119px;">44-27570</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Tissue Culture Incubator</td>
			<td style="width:107px;">Thermo Scientific</td>
			<td style="width:119px;">Series II 3110 Water-Jacketed CO2 Incubators</td>
			<td></td>
		</tr>
	</tbody>
</table>

examination of proteins bound to nascent dna in mammalian cells using  brdu-chip-slot-western technique

Histone deacetylases 1 and 2 (HDAC1,2) localize to the sites of DNA replication. In the previous study, using a selective inhibitor and a genetic knockdown system, we showed novel functions for HDAC1,2 in replication fork progression and nascent chromatin maintenance in mammalian cells. Additionally, we used a BrdU-ChIP-Slot-Western technique that combines chromatin immunoprecipitation (ChIP) of bromo-deoxyuridine (BrdU)-labeled DNA with slot blot and Western analyses to quantitatively measure proteins or histone modification associated with nascent DNA.
Actively dividing cells were treated with HDAC1,2 selective inhibitor or transfected with siRNAs against Hdac1 and Hdac2 and then newly synthesized DNA was labeled with the thymidine analog bromodeoxyuridine (BrdU). The BrdU labeling was done at a time point when there was no significant cell cycle arrest or apoptosis due to the loss of HDAC1,2 functions. Following labeling of cells with BrdU, chromatin immunoprecipitation (ChIP) of histone acetylation marks or the chromatin-remodeler was performed with specific antibodies. BrdU-labeled input DNA and the immunoprecipitated (or ChIPed) DNA was then spotted onto a membrane using the slot blot technique and immobilized using UV. The amount of nascent DNA in each slot was then quantitatively assessed using Western analysis with an anti-BrdU antibody. The effect of loss of HDAC1,2 functions on the levels of newly synthesized DNA-associated histone acetylation marks and chromatin remodeler was then determined by normalizing the BrdU-ChIP signal obtained from the treated samples to the control samples.

To determine the specificity of HDAC1,2-selective inhibitors, Hdac1,2FL/FL and Hdac3FL/FL fibrosarcoma cells were used. Adenovirus-containing Cre recombinase (Ad-Cre) was used to delete Hdac1,2 and Hdac3 in these cells. Following Ad-Cre infection of Hdac1,2FL/FL cells, a robust increase in H4K5ac was observed. Treatment of Hdac1,2&#160;knockout cells with 233 or 898 did not result in...

Watch this Scientific Journal Video about Examination of Proteins Bound to Nascent DNA in Mammalian Cells Using  BrdU-ChIP-Slot-Western Technique at JoVE.com

Examination of Proteins Bound to Nascent DNA in Mammalian Cells Using  BrdU-ChIP-Slot-Western Technique

In this protocol, we describe a novel BrdU-ChIP-Slot-Western technique to examine proteins and histone modifications associated with newly synthesized or nascent DNA.

Histone deacetylases 1 and 2 (HDAC1,2) localize to the sites of DNA replication. In the previous study, using a selective inhibitor and a genetic ...

examination-proteins-bound-to-nascent-dna-mammalian-cells-using-brdu

Research

JoVE Journal

Biology

9.1K Views.  University of Utah School of Medicine. In this protocol, we describe a novel BrdU-ChIP-Slot-Western technique to examine proteins and histone modifications associated with newly synthesized or nascent DNA. 

Video: Examination of Proteins Bound to Nascent DNA in Mammalian Cells Using  BrdU-ChIP-Slot-Western Technique

Long-term Imaging Mammalian Cells using Wide-Field Microscopy

Actually what I'm gonna do, mount it in here first and then swap out You. So now I'm gonna aspirate try and be as gentle as possible.Okay. A few seconds just holding.Okay.Alright.So the important features of our lifestyle imaging grid are that, so it's an inverted scope, which means the objective, the samples here in the objective is underneath. So the objective is pointing up and the whole scope, or practically the whole, practically the whole scope, including the objectives and the sample are at 37 degrees. So everything in this plastic box is at 37 degrees.And right on top of the stage we have an air and CO2 mix. That is 5%CO2. So the idea is that the sample is actually in a cell, it's like a cell incubator.And so we have, this is our mixer for the air and the CO2 and, and it gets humidified and heated and then piped onto the, the sample on the stage.Okay. And today we're just gonna be doing fluorescence one channel GFP fluorescence. This is the hose that the CO2 and 5%CO2 goes in and it just fits into the stage holder.That's important. And then we can close these, take these down, and then we go to our first position. And what I'm gonna do is go to the first field, which is my control sample, and I'll pick positions based on what I see on the screen.So I just make sure I actually look into the microscope in each new, well, because the focal plane for each of the wells is different, the, the dish is not perfectly flat on the bottom. So you will need to make fine adjustments when you move from well to the well. So right now I'm on the first, well, what I'll do is I'll focus, so I just hit, I just told, I just turned on the light, the transmitted light for the microscope.And I have make sure all the light is going to the eye pieces. And so I just look in, make sure I get a nice clean field. And then what I'll do is turn that light off, turn the fluorescence light on, make sure the cells that I'm looking at look healthy and they're not apoptotic.And, and I turn that off. And what I do next is send, so now I'm gonna start picking positions, which means I have to te send the light path to the camera. This is the camera right here.So I tell the microscope to send all the camera, they don't see anything in the eye pieces. What I'll do is in the software controlling the microscope, I'll choose the right filter set, which for our purposes is psy. And then set an exposure time.And I know these cells very well and I know that they take a 0.2 second exposure time. So I tell, that's what I tell the software to do. And what I'll do is hit focus.This is, and it's basically just alive. The, A light will turn on and you can, oh, I don't know if you can see cells, but the reason this is a good field is because there's, all the cells are, even in terms of their fluorescence, There are no apoptotic cells. Apoptotic cells tend to be very bright and there's no dirt or schmutz in the field.And you can see that they're actually, this is a metaphase cell and that's a metaphase cell, that's a cell that's probably just exited mitosis. And I can just tell that because it looks like those are, those two sets of chromatin are very nicely oriented to each other. Like they just exited an face.So that's a good field. So, and now that I know that the exposure time and the filter set is correct, and this is gonna be software specific, I'll go and I'll take positions and now the software has memorized the X, Y, Z position of that field. And then when I do pick another field, it's, and I'll, so when I'm picking, when I'm picking new fields, but in the same, well, I'll use the, I'll move the i'll, I'll turn the shutter, I'll open the shutter and I'll look to see what I see on the screen and I'll pick fields based on that versus looking in the field.So I don't see any of my tonics in there. But again, even nicely centered, these cells will go through my PS I continue, here's a good example. Here's a good example of what I would avoid that, see how bright that is?That's very bright. That's probably remnants of an apoptotic cell. And the reason I would avoid that is because since it's so bright, when the software auto focuses, it will autofocus just on that and it won't be in the same plane as all these other cells.And so I won't get any information from that field. That looks nice. There's a, this is a pro metaphase right here, That's A metaphase.So, and I'm gonna take three positions per well. So that was three positions and now I'm going to go to my next Well, so you can, so what I will probably do is take images every 10 minutes. So it's a compromise.Lifestyle imaging is always a compromise, right? You have to image, you have to keep the cells healthy, especially if you're interested in mitosis. So you have to minimize their exposure to the fluorescent line.And, but you wanna get information. So you have to take images, you have to, so you have to compromise, you have to make a choice about what you want to capture, what kind of information you wanna capture. For our purposes, mitosis tends to take about an hour.So if we're taking 10 minute intervals, that's pretty good. We see prophase, we see metaphase, we see anaphase, and we can, we can see when there are, there are treatments or drugs or siRNAs that affect those specific cell cycle stages. So for our purposes, that's enough, but we always want more.We always want more positions or finer time and interval or something like that. So it's a compromise. So, and then I'll hit start.And so our software, it does an autofocusing pass on the first pass. So once I hit start, it should start auto autofocusing and you'll see the shutter open, open and close between auto focusing. So I'll hit start.So that's the shutter opening and closing. The Z motor is engaging and it's actually trying to find the plane with the most contrast, which will be the most in focus. You can actually see on the screen going in and out of finding the best plane of focus that might be worrisome.So what it does is it, it drives the Z motor to find the best, the most in focus plane focus, well the most in image. And then it acquires picture there and then it learns that Z position. And then we'll use that Z position for the next 12 passes.And then we'll do the auto focusing pass again. What Kind of experiments do they do? Okay, so our lab is mostly interested in understanding what regulates mitic progression, or at least I'm most interested in understanding that.So with live cell imaging and especially our multi position, long-term imaging scope, you can take, you can film cells for two or three days entering anding mitosis, and you can image multiple rounds of mitosis so you can understand. And then you can put drugs or RNAs or any kind of perturbations on the cells that you would like to study. So you can understand how, how those drugs or, or genes are, are important in regulating mitotic progression.Because it's not fixed cell work and live cell work, you can understand what, when you need to have a perturbation to affect mitosis or what stage of mitosis is affected. So it's really powerful in that respect. What, what are the main technical elements of this experiments?What are the possible problems? Well, the biggest problem besides getting the rig set up, getting the rig set up is not trivial. A lot of people have the rig, but just making sure it works well for your application.The financial element is not, you know, is not small. So there's the setting up of the apparatus and then, and then once you gather the data, there's a real data analysis issue. It takes these movie, if, so, if you're gathering 40 movies each with 30 cells, so you have 40 in 40 fields that you just filmed and each of those fields has 30 cells, then you have to sit down with each one of those movies and look at each one of those cells in that movie.So it takes a really long time to do data analysis. And that's, so it takes a week to analyze data that it took you two days to collect. So there's a, that's a very big obstacle in terms of gathering lots of data.So it's not, while it's high throughput data collection, it's not high throughput analysis. So what would you make to make this experiment really high throughput? So our lab is in the process of developing a program that does the data analysis automatically.And it's a pretty decent program. It's not perfect. The human eye is always better, but it's getting there.So What are the interesting application of this experiment? Maybe other fields you can mention? Besides cell division?You mean for the, oh, for the live cell imaging? Yes.Well, you can do cell motility assays. You can, depending on the, the microscopy that's involved, you can, you know, look at how cells, you could look at tumor development if you really wanted to.But there, you, you're, if as long as you have the right imaging set up, you can, you're pretty much not limited in terms of anything. Our scope happens to be just a wide field and we use 20 by 20 x objective. So it's a pretty low resolution set up, but that's sufficient for what we need to see.So there are, but there definitely aren't, you wouldn't be limited. Anything that has any dynamic kind of experiment, which is biology, it would be, would really benefit from lifestyle imaging. So calcium imaging, although you couldn't do it on our apparatus, that's a live cell.You definitely need live cell imaging for that. Like I said, patient assays, motility assays, those kinds of things would really benefit from live cell imaging. Would you like to tell a few words about your previous experience?How long do you work on these techniques? What do you you work on before? Wow.So in my PhD I didn't work.I did a lot of confocal microscopy, but no lifestyle imaging. And so during my postdoc I was, I helped Dr.King get this apparatus that, that we just used to set up these fragment, get that up and running. And, and so during my postdoc, I had a lot of experience with both widefield with TimeLapse imaging on our scope, which is the widefield and also TimeLapse imaging with confocal microscopy.And I would say that it's really powerful. You get a lot of information, but it's not easy to get working perfectly. So it really requires a lot of attention and a lot of attention to details at every little step of the process.And, and then you still have problems. So it's a tough application, but you can really get, if, if it's what you need to have to, to study your problem, your scientific problem, then it, it's invaluable in that respect, but it's tough. So find someone who knows what they're doing and use them.That's my advice. So good.

Długoterminowe Imaging komórkach ssaków przy dużym polu Mikroskopia

DNA Transfection of Mammalian Skeletal Muscles using In Vivo Electroporation

A growing interest in cell biology is to express transgenically modified forms of essential proteins (e.g. fluorescently tagged constructs and/or mutant variants) in order to investigate their endogenous distribution and functional relevance. An interesting approach that has been implemented to fulfill this objective in fully differentiated cells is the in vivo transfection of plasmids by various methods into specific tissues such as liver1, skeletal muscle2,3, and even the brain4. We present here a detailed description of the steps that must be followed in order to efficiently transfect genetic material into fibers of the flexor digitorum brevis (FDB) and interosseus (IO) muscles of adult mice using an in vivo electroporation approach. The experimental parameters have been optimized so as to maximize the number of muscle fibers transfected while minimizing tissue damages that may impair the quality and quantity of the proteins expressed in individual fibers. We have verified that the implementation of the methodology described in this paper results in a high yield of soluble proteins, i.e. EGFP and ECFP3, calpain, FKBP12, &beta;2a-DHPR, etc. ; structural proteins, i.e. minidystrophin and &alpha;-actinin; and membrane proteins, i.e. &alpha;1s-DHPR, RyR1, cardiac Na/Ca2+ exchanger , NaV1.4 Na channel, SERCA1, etc., when applied to FDB, IO and other muscles of mice and rats. The efficient expression of some of these proteins has been verified with biochemical3 and functional evidence5. However, by far the most common confirmatory approach used by us are standard fluorescent microscopy and 2-photon laser scanning microscopy (TPLSM), which permit to identify not only the overall expression, but also the detailed intracellular localization, of fluorescently tagged protein constructs. The method could be equally used to transfect plasmids encoding for the expression of proteins of physiological relevance (as shown here), or for interference RNA (siRNA) aiming to suppress the expression of normally expressed proteins (not tested by us yet). It should be noted that the transfection of FDB and IO muscle fibers is particularly relevant for the investigation of mammalian muscle physiology since fibers enzymatically dissociated from these muscles are currently one of the most suitable models to investigate basic mechanisms of excitability and excitation-contraction coupling under current or voltage clamp conditions2,6-8.

DNA Transfection of Mammalian Skeletal Muscles using In Vivo Electroporation

We describe detailed procedures for the efficient transfection of plasmid DNA into the fibers of foot muscles of live mice using electroporation and the subsequent visualization of protein expression using fluorescence microscopy.

 A growing interest in cell biology is to express transgenically modified forms of essential proteins (e.g. fluorescently tagged constructs and/or mutant ...

Intranuclear Microinjection of DNA into Dissociated Adult Mammalian Neurons

Primary neuronal cell cultures are valuable tools to study protein function since they represent a more biologically relevant system compared to immortalized cell lines. However, the post-mitotic nature of primary neurons prevents effective heterologous protein expression using common procedures such as electroporation or chemically-mediated transfection. Thus, other techniques must be employed in order to effectively express proteins in these non-dividing cells.
In this article, we describe the steps required to perform intranuclear injections of cDNA constructs into dissociated adult sympathetic neurons. This technique, which has been applied to different types of neurons, can successfully induce heterologous protein expression. The equipment essential for the microinjection procedure includes an inverted microscope to visualize cells, a glass injection pipet filled with cDNA solution that is connected to a N2(g) pressure delivery system, and a micromanipulator. The micromanipulator coordinates the injection motion of microinjection pipet with a brief pulse of pressurized N2 to eject cDNA solution from the pipet tip. 
This technique does not have the toxicity associated with many other transfection methods and enables multiple DNA constructs to be expressed at a consistent ratio. The low number of injected cells makes the microinjection procedure well suited for single cell studies such as electrophysiological recordings and optical imaging, but may not be ideal for biochemical assays that require a larger number of cells and higher transfection efficiencies. Although intranuclear microinjections require an investment of equipment and time, the ability to achieve high levels of heterologous protein expression in a physiologically relevant environment makes this technique a very useful tool to investigate protein function.

Direct intranuclear injection of cDNA is an effective transfection technique for post-mitotic cells. This method provides high levels of heterologous protein expression from single or multiple cDNA constructs and enables protein function to be studied in a physiologically relevant environment with a variety of single cell assays.

Primary neuronal cell cultures are valuable tools to study protein function since they represent a more biologically relevant system compared to ...

Analysis of DNA Double-strand Break (DSB) Repair in Mammalian Cells

DNA double-strand breaks are the most dangerous DNA lesions that may lead to massive loss of genetic information and cell death. Cells repair DSBs using two major pathways: nonhomologous end joining (NHEJ) and homologous recombination (HR). Perturbations of NHEJ and HR are often associated with premature aging and tumorigenesis, hence it is important to have a quantitative way of measuring each DSB repair pathway. Our laboratory has developed fluorescent reporter constructs that allow sensitive and quantitative measurement of NHEJ and HR. The constructs are based on an engineered GFP gene containing recognition sites for a rare-cutting I-SceI endonuclease for induction of DSBs. The starting constructs are GFP negative as the GFP gene is inactivated by an additional exon, or by mutations. Successful repair of the I-SceI-induced breaks by NHEJ or HR restores the functional GFP gene. The number of GFP positive cells counted by flow cytometry provides quantitative measure of NHEJ or HR efficiency.

Analysis of DNA Double-strand Break DSB Repair in Mammalian Cells

This article describes GFP-based fluorescence in vivo assays that separately quantify homologous recombination and nonhomologous end joining in mammalian cells.

DNA double-strand breaks are the most dangerous DNA lesions that may lead to massive loss of genetic information and cell death.  Cells repair DSBs using ...

Visualization of DNA Replication in the Vertebrate Model System DT40 using the DNA Fiber Technique

Maintenance of replication fork stability is of utmost importance for dividing cells to preserve viability and prevent disease. The processes involved not only ensure faithful genome duplication in the face of endogenous and exogenous DNA damage but also prevent genomic instability, a recognized causative factor in tumor development.
Here, we describe a simple and cost-effective fluorescence microscopy-based method to visualize DNA replication in the avian B-cell line DT40. This cell line provides a powerful tool to investigate protein function in vivo by reverse genetics in vertebrate cells1. DNA fiber fluorography in DT40 cells lacking a specific gene allows one to elucidate the function of this gene product in DNA replication and genome stability. Traditional methods to analyze replication fork dynamics in vertebrate cells rely on measuring the overall rate of DNA synthesis in a population of pulse-labeled cells. This is a quantitative approach and does not allow for qualitative analysis of parameters that influence DNA synthesis. In contrast, the rate of movement of active forks can be followed directly when using the DNA fiber technique2-4. In this approach, nascent DNA is labeled in vivo by incorporation of halogenated nucleotides (Fig 1A). Subsequently, individual fibers are stretched onto a microscope slide, and the labeled DNA replication tracts are stained with specific antibodies and visualized by fluorescence microscopy (Fig 1B). Initiation of replication as well as fork directionality is determined by the consecutive use of two differently modified analogues. Furthermore, the dual-labeling approach allows for quantitative analysis of parameters that influence DNA synthesis during the S-phase, i.e. replication structures such as ongoing and stalled forks, replication origin density as well as fork terminations. Finally, the experimental procedure can be accomplished within a day, and requires only general laboratory equipment and a fluorescence microscope.

DT40, a model vertebrate genetic system, provides a powerful tool to analyze protein function. Here we describe a simple method that allows qualitative analysis of parameters that influence DNA synthesis during the S-phase in DT40 cells at the single molecule level.

Maintenance of replication fork stability is of utmost importance for dividing cells to preserve viability and prevent disease. The processes involved not ...

Analysis of Cell Cycle Position in Mammalian Cells

The regulation of cell proliferation is central to tissue morphogenesis during the development of multicellular organisms. Furthermore, loss of control of cell proliferation underlies the pathology of diseases like cancer. As such there is great need to be able to investigate cell proliferation and quantitate the proportion of cells in each phase of the cell cycle. It is also of vital importance to indistinguishably identify cells that are replicating their DNA within a larger population. Since a cell&prime;s decision to proliferate is made in the G1 phase immediately before initiating DNA synthesis and progressing through the rest of the cell cycle, detection of DNA synthesis at this stage allows for an unambiguous determination of the status of growth regulation in cell culture experiments.
DNA content in cells can be readily quantitated by flow cytometry of cells stained with propidium iodide, a fluorescent DNA intercalating dye. Similarly, active DNA synthesis can be quantitated by culturing cells in the presence of radioactive thymidine, harvesting the cells, and measuring the incorporation of radioactivity into an acid insoluble fraction. We have considerable expertise with cell cycle analysis and recommend a different approach. We Investigate cell proliferation using bromodeoxyuridine/fluorodeoxyuridine (abbreviated simply as BrdU) staining that detects the incorporation of these thymine analogs into recently synthesized DNA. Labeling and staining cells with BrdU, combined with total DNA staining by propidium iodide and analysis by flow cytometry1 offers the most accurate measure of cells in the various stages of the cell cycle. It is our preferred method because it combines the detection of active DNA synthesis, through antibody based staining of BrdU, with total DNA content from propidium iodide. This allows for the clear separation of cells in G1 from early S phase, or late S phase from G2/M. Furthermore, this approach can be utilized to investigate the effects of many different cell stimuli and pharmacologic agents on the regulation of progression through these different cell cycle phases.
In this report we describe methods for labeling and staining cultured cells, as well as their analysis by flow cytometry. We also include experimental examples of how this method can be used to measure the effects of growth inhibiting signals from cytokines such as TGF-&beta;1, and proliferative inhibitors such as the cyclin dependent kinase inhibitor, p27KIP1. We also include an alternate protocol that allows for the analysis of cell cycle position in a sub-population of cells within a larger culture5. In this case, we demonstrate how to detect a cell cycle arrest in cells transfected with the retinoblastoma gene even when greatly outnumbered by untransfected cells in the same culture. These examples illustrate the many ways that DNA staining and flow cytometry can be utilized and adapted to investigate fundamental questions of mammalian cell cycle control.

Determining the cell cycle position of a population of cells, or understanding how signals affect proliferation, can be readily measured by flow cytometry using this protocol. We report a simple experimental approach to staining cells and quantifying their position in the cell cycle.

The regulation of cell proliferation is central to tissue morphogenesis during the development of multicellular organisms. Furthermore, loss of control of ...

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the messagefor review see 1. However, it's now widely accepted that synonymous codon usage is the primary cause of non-uniform translational elongation rates1. Synonymous codons are not used with identical frequency. A bias exists in the use of synonymous codons with some codons used more frequently than others2. Codon bias is organism as well as tissue specific2,3. Moreover, frequency of codon usage is directly proportional to the concentrations of cognate tRNAs4. Thus, a frequently used codon will have higher multitude of corresponding tRNAs, which further implies that a frequent codon will be translated faster than an infrequent one. Thus, regions on mRNA enriched in rare codons (potential pause sites) will as a rule slow down ribosome movement on the message and cause accumulation of nascent peptides of the respective sizes5-8. These pause sites can have functional impact on the protein expression, mRNA stability and protein foldingfor review see 9. Indeed, it was shown that alleviation of such pause sites can alter ribosome movement on mRNA and subsequently may affect the efficiency of co-translational (in vivo) protein folding1,7,10,11. To understand the process of protein folding in vivo, in the cell, that is ultimately coupled to the process of protein synthesis it is essential to gain comprehensive insights into the impact of codon usage/tRNA content on the movement of ribosomes along mRNA during translational elongation.
Here we describe a simple technique that can be used to locate major translation pause sites for a given mRNA translated in various cell-free systems6-8. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA. The rationale is that at low-frequency codons, the increase in the residence time of the ribosomes results in increased amounts of nascent peptides of the corresponding sizes. In vitro transcribed mRNA is used for in vitro translational reactions in the presence of radioactively labeled amino acids to allow the detection of the nascent chains. In order to isolate ribosome bound nascent polypeptide complexes the translation reaction is layered on top of 30% glycerol solution followed by centrifugation. Nascent polypeptides in polysomal pellet are further treated with ribonuclease A and resolved by SDS PAGE. This technique can be potentially used for any protein and allows analysis of ribosome movement along mRNA and the detection of the major pause sites. Additionally, this protocol can be adapted to study factors and conditions that can alter ribosome movement and thus potentially can also alter the function/conformation of the protein.

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

A technique to identify translational pause sites on mRNA is described. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA, followed by the size analysis of the nascent chains using a denaturing gel electrophoresis.

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the ...

Using SecM Arrest Sequence as a Tool to Isolate Ribosome Bound Polypeptides

Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway that polypeptide chain follows during co-translational folding to achieve its functional form is still an enigma. In order to understand this process and to determine the exact conformation of the co-translational folding intermediates, it is essential to develop techniques that allow the isolation of RNCs carrying nascent chains of predetermined sizes to allow their further structural analysis.
SecM (secretion monitor) is a 170 amino acid E. coli protein that regulates expression of the downstream SecA (secretion driving) ATPase in the secM-secA operon6. Nakatogawa and Ito originally found that a 17 amino acid long sequence (150-FSTPVWISQAQGIRAGP-166) in the C-terminal region of the SecM protein is sufficient and necessary to cause stalling of SecM elongation at Gly165, thereby producing peptidyl-glycyl-tRNA stably bound to the ribosomal P-site7-9. More importantly, it was found that this 17 amino acid long sequence can be fused to the C-terminus of virtually any full-length and/or truncated protein thus allowing the production of RNCs carrying nascent chains of predetermined sizes7. Thus, when fused or inserted into the target protein, SecM stalling sequence produces arrest of the polypeptide chain elongation and generates stable RNCs both in vivo in E. coli cells and in vitro in a cell-free system. Sucrose gradient centrifugation is further utilized to isolate RNCs.
The isolated RNCs can be used to analyze structural and functional features of the co-translational folding intermediates. Recently, this technique has been successfully used to gain insights into the structure of several ribosome bound nascent chains10,11. Here we describe the isolation of bovine Gamma-B Crystallin RNCs fused to SecM and generated in an in vitro translation system.

We describe here a technique that is now routinely used to isolate stably bound ribosome nascent chain complexes (RNCs). This technique takes advantage of the discovery that a 17 amino acid long SecM "arrest sequence" can halt translation elongation in a prokaryotic (E. coli) system, when inserted into (or fused to the C-terminus) of virtually any protein.

Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway ...

Real-time Imaging of Single Engineered RNA Transcripts in Living Cells Using Ratiometric Bimolecular Beacons

The growing realization that both the temporal and spatial regulation of gene expression can have important consequences on cell function has led to the development of diverse techniques to visualize individual RNA transcripts in single living cells. One promising technique that has recently been described utilizes an oligonucleotide-based optical probe, ratiometric bimolecular beacon (RBMB), to detect RNA transcripts that were engineered to contain at least four tandem repeats of the RBMB target sequence in the 3&#8217;-untranslated region. RBMBs are specifically designed to emit a bright fluorescent signal upon hybridization to complementary RNA, but otherwise remain quenched. The use of a synthetic probe in this approach allows photostable, red-shifted, and highly emissive organic dyes to be used for imaging. Binding of multiple RBMBs to the engineered RNA transcripts results in discrete fluorescence spots when viewed under a wide-field fluorescent microscope. Consequently, the movement of individual RNA transcripts can be readily visualized in real-time by taking a time series of fluorescent images. Here we describe the preparation and purification of RBMBs, delivery into cells by microporation and live-cell imaging of single RNA transcripts.

Ratiometric bimolecular beacons (RBMBs) can be used to image single engineered RNA transcripts in living cells. Here, we describe the preparation and purification of RBMBs, delivery of RBMBs into cells by microporation and fluorescent imaging of single RNA transcripts in real-time.

The growing realization that both the temporal and spatial regulation of gene expression can have important consequences on cell function has led to the ...

Identification of Protein Interaction Partners in Mammalian Cells Using SILAC-immunoprecipitation Quantitative Proteomics

Quantitative proteomics combined with immuno-affinity purification, SILAC immunoprecipitation, represent a powerful means for the discovery of novel protein:protein interactions. By allowing the accurate relative quantification of protein abundance in both control and test samples, true interactions may be easily distinguished from experimental contaminants. Low affinity interactions can be preserved through the use of less-stringent buffer conditions and remain readily identifiable. This protocol discusses the labeling of tissue culture cells with stable isotope labeled amino acids, transfection and immunoprecipitation of an affinity tagged protein of interest, followed by the preparation for submission to a mass spectrometry facility. This protocol then discusses how to analyze and interpret the data returned from the mass spectrometer in order to identify cellular partners interacting with a protein of interest. As an example this technique is applied to identify proteins binding to the eukaryotic translation initiation factors: eIF4AI and eIF4AII.

SILAC immunoprecipitation experiments represent a powerful means for discovering novel protein:protein interactions. By allowing the accurate relative quantification of protein abundance in both control and test samples, true interactions may be easily distinguished from experimental contaminants, and low affinity interactions preserved through use of less-stringent buffer conditions.

Quantitative proteomics combined with immuno-affinity purification, SILAC immunoprecipitation, represent a powerful means for the discovery of novel ...

Examination of Proteins Bound to Nascent DNA in Mammalian Cells Using BrdU-ChIP-Slot-Western Technique

Podsumowanie

Przeglądaj więcej filmów

Rozdziały w tym wideo

Długoterminowe Imaging komórkach ssaków przy dużym polu Mikroskopia

DNA Transfection of Mammalian Skeletal Muscles using In Vivo Electroporation

Intranuclear Microinjection of DNA into Dissociated Adult Mammalian Neurons

Analysis of DNA Double-strand Break (DSB) Repair in Mammalian Cells

Visualization of DNA Replication in the Vertebrate Model System DT40 using the DNA Fiber Technique

Analysis of Cell Cycle Position in Mammalian Cells

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

Using SecM Arrest Sequence as a Tool to Isolate Ribosome Bound Polypeptides

Real-time Imaging of Single Engineered RNA Transcripts in Living Cells Using Ratiometric Bimolecular Beacons

Identification of Protein Interaction Partners in Mammalian Cells Using SILAC-immunoprecipitation Quantitative Proteomics