Human islets were fixed and sonicated as described previously (Nammo et al, 2012). Briefly, frozen crosslinked cell pellets of ~4,000 islets were thawed on ice in 1 mL lysis buffer and disrupted with five 1-min cycles with 0.5 mm glass beads (BioSpec). Samples were sonicated for 10-20 cycles of 30 pulses each (1s on and 0.5 s off) using a Brandson Sonifier 450D at 15 % amplitude. The size for the bulk of chromatin obtained with this procedure was checked to be in the range from 200-1000 bp. For ChIPs, around 300-400 human islet equivalents (IEQs) were pre-cleared with A/G sepharose beads (Ge Healthcare) for 1 h, rotating at 4 degrees C, and then incubated with each antibody. Afterwards, samples were rotated for 2 hr at 4 degrees C with protein A/G sepharose beads and then sequentially washed with low salt, high salt, LiCl and TE buffers. Next, chromatin was eluted with SDS 1% buffer and sequentially treated with RNAse (greater than 5 hr at 65 degrees C) and Proteinase K (overnight at 45 degrees C). Finally, DNA was extracted with phenol-chloroform followed by ethanol precipitation. The immunoprecipitated DNA was modified for sequencing following the Illumina sequencing following the manufacturer protocol (Preparing Sample for ChIP Sequencing of DNA (11257047 Rev A)).