Jurkat 1x10E6 cells were fixed with 1% formaldehyde in culture medium for 10 min at room temperature followed by quenching with 0.125 M glycine for 5 min. The cells were washed twice with ice-cold PBS and lysed in 1 ml of lysis buffer (1% SDS, 10 mM EDTA, 50 mM Tris pH8.0) for at least 30 min on ice. The crosslinked chromatin was sheared to an average size of 500 bp by ten 30-second pulses using a BiorupterTM sonicator (Diagenode). The lysate was then centrifuged to remove cell debris, and the chromatin was quantified in a UV spectrophotometer. The chromatin (400 µg) was diluted 10-fold in dilution buffer (0.01% SDS, 1.1% Triton X-100, 1.2 mM EDTA 16.7 mM Tris pH8.10, 167 mM NaCl) and pre-cleared with 25 µl magnetic beads (in BSA) for 2 h at 4C. The chromatin supernatant was then incubated overnight with 5 µg of purified antibody at 4C. After incubation with protein A magnetic beads (50 µl) for 2h at 4C, the immune complexes were collected by centrifugation and washed with the following buffers each for 10 min at 4C; RIPA buffer (150 mM NaCl, 50 mM Tris pH8.0, 0.1% SDS), high-salt buffer (500 mM NaCl, 50 mM Tris pH8.0, 0.1% SDS, 1% NP40) LiCl buffer (250 mM LiCl, 50 mM Tris pH8.0, 0.5% Na deoxycholate, 1% NP40) and 2x TE (20 mM Tris pH8.0, 2 mM EDTA). The protein-DNA complexes were eluted from the beads in 450 µl elution buffer (1% SDS, 100 mM NaHCO3) at 55C for 2 h followed by the addition of proteinaseK to 500 µg/ml and overnight incubaton at 65C. Genomic DNA was isolated from the precipitated material as well as from the sheared chromatin input (1/100 of the material used for ChIP) by phenol extraction and ethanol precipitation.
Label
Cy3
Label protocol
4 µg ChIP DNA was directly labeled by Klenow (New England Biolabs) random priming with Cy3 nonamers (ChIP DNA isolated from normal rabbit IgG-immunoprecipitated cells) per manufacturer's protocol (http://www.nimblegen.com/products/lit/lit.html).
Jurkat 1x10E6 cells were fixed with 1% formaldehyde in culture medium for 10 min at room temperature followed by quenching with 0.125 M glycine for 5 min. The cells were washed twice with ice-cold PBS and lysed in 1 ml of lysis buffer (1% SDS, 10 mM EDTA, 50 mM Tris pH8.0) for at least 30 min on ice. The crosslinked chromatin was sheared to an average size of 500 bp by ten 30-second pulses using a BiorupterTM sonicator (Diagenode). The lysate was then centrifuged to remove cell debris, and the chromatin was quantified in a UV spectrophotometer. The chromatin (400 µg) was diluted 10-fold in dilution buffer (0.01% SDS, 1.1% Triton X-100, 1.2 mM EDTA 16.7 mM Tris pH8.10, 167 mM NaCl) and pre-cleared with 25 µl magnetic beads (in BSA) for 2 h at 4C. The chromatin supernatant was then incubated overnight with 5 µg of purified antibody at 4C. After incubation with protein A magnetic beads (50 µl) for 2h at 4C, the immune complexes were collected by centrifugation and washed with the following buffers each for 10 min at 4C; RIPA buffer (150 mM NaCl, 50 mM Tris pH8.0, 0.1% SDS), high-salt buffer (500 mM NaCl, 50 mM Tris pH8.0, 0.1% SDS, 1% NP40) LiCl buffer (250 mM LiCl, 50 mM Tris pH8.0, 0.5% Na deoxycholate, 1% NP40) and 2x TE (20 mM Tris pH8.0, 2 mM EDTA). The protein-DNA complexes were eluted from the beads in 450 µl elution buffer (1% SDS, 100 mM NaHCO3) at 55C for 2 h followed by the addition of proteinaseK to 500 µg/ml and overnight incubaton at 65C. Genomic DNA was isolated from the precipitated material as well as from the sheared chromatin input (1/100 of the material used for ChIP) by phenol extraction and ethanol precipitation.
Label
Cy5
Label protocol
4 µg ChIP DNA was directly labeled by Klenow (New England Biolabs) random priming with Cy3 nonamers (ChIP DNA isolated from normal rabbit IgG-immunoprecipitated cells) per manufacturer's protocol (http://www.nimblegen.com/products/lit/lit.html).
Hybridization protocol
The labeled ChIP DNA was precipitated with 0.1 volume 5M NaCl and 1 volume isopropanol, and hybridized in 45 ul of buffer containing 20% formamide, 1.2 M betaine, 0.1 ug/ul herring sperm DNA and 10 ug of human COT1 DNA (Invitrogen). Arrays were hybridized in Maui hybridization stations for 16-18 h at 42C, and then washed in 42C 0.2% SDS/0.2x SSC, room temperature 0.2x SSC, and 0.05x SSC. Hybridization buffers and washes were completed using manufacturer's protocols (http://www.nimblegen.com/products/lit/lit.html)
Arrays were processed using Nimblegen's standard protocol for Nimblescan 2.4 ChIP data extraction. Roche NimbleGen scales the GFF files by subtracting the bi-weight mean for the log-ratio values from each log-ratio value. Procedure for Lowess_ratios annalysis * take pair data from Nimblegen * normalize them with limma package (script available from Metzler hompage (http://watson.nci.nih.gov/twiki/bin/view/Main/MeltzerLabSoftware) * create file with required informations for ACME sofware/Analysis (like ratio (R/G) chromosomal position etc (same as for the first analysis already done) run program (parameters: window size 2000 bp, threshold 0,90) calculate p-values (FDR-analysis; false discovery rate) create list with: chromosome, chromosomal position, p-value, accession number
