Fig. 5. CDK7, XPB and XPD are positioned at active promoters at the onset of transcription in early Drosophila embryos. Chromatin of embryos at 30-180 minutes of development was precipitated using antisera against CDK7, XPD, XPB and RNA pol II. Two neutral, unrelated IgG (Mock 1) and IgM (Mock 2) antisera were used as controls. The immunoprecipitated regions were amplified by PCR using oligonucleotides that cover the zygotic hb promoter, hb second exon, the sgs5 promoter, the atrx second exon and the H3 promoter; each amplified region is indicated in the figure. Input amplification is also shown for each PCR. The fraction of the input for each ChIP is indicated below each band. The sequences of the different promoters analyzed in this work are derived form the Drosophila core promoter database (http://www-biology.ucsd.edu/labs/Kadonaga/DCPD.html).