HepG2 cells were passaged to a new dish and cultured 2 days
Growth protocol
HepG2 cell were obtained from the Type Culture Collection of the Chinese Academy of Sciences (Shanghai, China). Which were cultured in Dulbecco’s modified Eagle’s medium (DMEM, Gibco) supplemented with 10% fetal bovine serum (FBS, Hyclone) and 1% penicillin–streptomycin.
Extracted molecule
genomic DNA
Extraction protocol
5x10E6 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 protein A sepharose beads (pre-absorbed with salmon sperm DNA and 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 sepharose 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
1 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).
HepG2 cells were passaged to a new dish and cultured 2 days
Growth protocol
HepG2 cell were obtained from the Type Culture Collection of the Chinese Academy of Sciences (Shanghai, China). Which were cultured in Dulbecco’s modified Eagle’s medium (DMEM, Gibco) supplemented with 10% fetal bovine serum (FBS, Hyclone) and 1% penicillin–streptomycin.
Extracted molecule
genomic DNA
Extraction protocol
5x10E6 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 protein A sepharose beads (pre-absorbed with salmon sperm DNA and 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 sepharose 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
1 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)