GSM1357919: Input sequencing in endoderm cells; Mus musculus; ChIP-Seq
Cells were fixed with 1% formaldehyde for 15 minutes at room temperature. Pellets containing ~40 x10^6 cells were flash frozen and stored at -80 oC. Cells were thawed on ice, resuspended in 5ml of Lysis Buffer A and incubated for 10 minutes at 4 oC in a rotating platform. Samples were spun down for 5 minutes at 1,350g, resuspended in 5ml Lysis Buffer B and incubated for 10 minutes at 4 oC in a rotating platform. Samples were spun down for 5 minutes at 1,350g, resuspended in 3ml of Sonication Buffer (SB). Nuclear extracts were sonicated using a Misonix 3000 model sonicator to sheer cross-linked DNA to an average fragment size of approximately 500bp. Sonicated chromatin was incubated for 16 hours at 4C with Protein-G beads (Invitrogen) conjugated with either rabbit anti-V5 (Abcam) or anti-FLAG (Sigma). After incubation and with the aid of a magnetic device, beads were washed once with SB+500nM NaCl, once with LiCl Wash Buffer and 1ml of TE. Then, beads were centrifugated at 950g for 3 min and remove residual TE with a pipette. 210ul of Elution Buffer was added to the beads followed by incubation at 65 oC for 45 minutes with a brief pulse of vortex every 10 minutes. 200ul of supernatant was removed after a 1 minute centrifugation at 16,000g. The crosslink was reversed by 16 hours incubation at 65 oC. RNA was digested by the addition of 200ul of TE and RNAseA (Sigma) at a final concentration of 0.2mg/ml and incubated for 2 hours at 37C. Protein was digested by the addition of Proteinase K (0.2 mg/ml final, Invitrogen) supplemented with CaCl2 followed by a 30 minutes incubation at 55 oC. DNA was extracted with phenol:chloroform:isoamyl alcohol (25:24:1) and then recovered with an ethanol precipitation with glycogens as carrier. The pellets were suspended in 70ul of water. Purified DNA fragments were processed according to the Illumina/Solexa library protocol and sequenced using a Genome Analyzer II (Illumina, http://www.illumina.com/pages.ilmn?ID=252).