The role of the global co-activator CREB-binding protein in transcription : a study of competitive interactions of diverse nuclear proteins with CBP
The recruitment of the histone acetyltransferases CREB binding protein (CBP) and its homologue p300, is necessary for chromatin modification and assembly of the Pre Initiation Complex (PIC) at many gene promoters. CBP has multiple protein binding domains and we have focused our studies on the Steroid Receptor Coactivator-1 (SRC1) Interaction Domain (SID) of CBP. A novel conserved sequence motif is described which facilitates the binding of these nuclear proteins such as p160 proteins, Ets2, E1A and p53 to the CBP SID. We have confirmed the interaction of Ets2 by GST pull down with CBP SID and we show that SRC1, Ets2 and E1A full length proteins compete with each other to bind to the SID in vitro. We also show that the short peptide encompassing the SRC1 AD1 sequence is indeed sufficient to compete with SRC1, Ets2, E1A12S and p53 full length proteins on SID. Furthermore, we demonstrate that the transcriptional activity of Ets2 is inhibited by E1A 12S, but not by E1A Delta2-36 (CBP binding site) mutant in vivo. This inhibition by E1A was rescued with overexpression of CBP but not CBPDeltaSID.;In AML, the MOZ-TIF2 fusion protein transforms bone marrow cells in vitro and causes leukaemia in animal model. I have conducted the ChIP analysis of the effects of MOZ-TIF2 on chromatin modification and co-activator recruitment at the RAR beta2 promoter. I have successfully established the ChIP analysis of the RARbeta2 promoter in U20s, and demonstrated that ATRA treatment induces recruitment of RARbeta, CBP, p300 and to the RARbeta2 promoter with concomitant of acetylation of histone H3 K9 and K14 residues. I also have shown that MOZ-TIF2 is recruited to the RARbeta2 promoter and this correlates with the loss of CBP and p300.