A HUMAN RNA-POLYMERASE-II COMPLEX CONTAINING FACTORS THAT MODIFY CHROMATIN STRUCTURE

We have isolated a human RNA polymerase II complex that contains chrom atin structure remodeling activity and histone acetyltransferase activ ity. This complex contains the Srb proteins, the Swi-Snf complex, and the histone acetyltransferases CBP and PCAF in addition to RNA polymer ase II. Notably, the general transcription factors are absent from thi s complex. The complex was purified by two different methods: conventi onal chromatography and affinity chromatography using antibodies direc ted against CDK8, the human homolog of the yeast Srb10 protein. Protei n interaction studies demonstrate a direct interaction between RNA pol ymerase II and the histone acetyltransferases p300 and PCAF. Important ly, p300 interacts specifically with the nonphosphorylated, initiation -competent form of RNA polymerase II. In contrast, PCAF interacts with the elongation-competent, phosphorylated form of RNA polymerase II.