Peak calling for ChIP-chip experiments was performed using MAT (Johnson et al. 2006. Proc. Natl. Acad. Sci. U.S.A. 103(33): 12457-12462). Peak calls from ChiP-Seq data were performed using MACS (Zhang et al. 2008. Genome Biol. 9(9): R137) or Peakseq (Rozowsky et al. 2009. Nat. Biotechnol. 27(1): 66-75). Peaks from CBP ChIP-chip and ChIP-seq experiments were filtered to exclude peaks falling between -500bp and +500bp of annotated promoters. CBP binding sites occuring at only one of the 12 developmental stages analyzed were also removed. Peaks were merged and a final list of sites occuring only during embryogenesis was generated.