Cells were fixed for 15 min in culture media containing 1% formaldehyde and were processed for ChIP as in Dietrich et al. (2007) EMBO J 26: 1637–1648. DNA from three parallel ChIPs were pooled and 10 ng was used for making ChIP-seq libraries. Libraries were generated according to Illumina recommendations and sequencing was done on a Genome Analyzer II (Illumina).