The association of dBrm with its target genes studied by ChIP.

(A) Chromatin was extracted from S2 cells after fixation with formaldehyde, and immunoprecipitation reactions were carried out with Ab1 to precipitate chromatin fragments bound to dBrm (lanes 2, 6, 10 and 14). A positive control immunoprecipitation was carried out using an antibody against the C-terminal domain of the largest subunit of RNA pol-II (lanes 3, 7, 11 and 15). A negative control immunoprecipitation was carried out in parallel with an unrelated rabbit antibody against mouse immunoglobulins (lanes 4, 8, 12 and 16). For each gene analyzed, PCR reactions were carried out with primers specific for the proximal promoter, the internal region involved in the alternative processing and the 3′-end of the gene, as indicated in the figure. (B) The actin 5C gene and an intergenic region were analyzed in parallel to assess the specificity of the ChIP (lanes 13–16).