Histone modifications and Pol II loading at the MAD1 promoter. A. Summary of primer sets used for ChIP PCR relative to the major transcriptional start site within the MAD1 gene. B. and C. Proliferating U937 cells were treated with or without 2.5 ng/ml TGFβ1 for 1.5 h. ChIP experiments were performed with the indicated antibodies and primers. For control the immunoprecipitations were performed with Protein A Sepharose beads only. Signals obtained from input DNA, given as part of the immunoprecipitated material, are shown for comparison. D. U937 cells were treated with or without 2.5 ng/ml TGFβ1 for 20 and 40 min prior to cross-linking. For ChIP, total Pol II and Ser-2 and Ser-5 phosphorylated Pol II was immunoprecipitated. Loading and distribution of the different Pol II isoforms were examined on the MAD1 gene with the indicated primers.