Repair of Genotoxic Damage in Chromatin

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DESCRIPTION: Formidable effects of the restricted accessibility of nucleosomal DNA to components of gene transcription and DNA repair machinery cannot be overstated. CREB Binding Protein (CBP)/p300, a coactivator for a number of transcription factors including p53, has recently been shown to potentiate transcriptional activation of many genes transcribed by the RNA polymerase II. The intrinsic histone acetyltransferase activity of CBP/p300 is suggested to play a key role in unfolding the repressive chromatin and facilitates the events associated with gene transcription. This proposal is based on the premise that the well-established DNA transcription-associated observations provide a useful and timely paradigm for unraveling the intrinsic mechanism of nucleosome rearrangements associated with nucleotide excision repair. The proposed studies, on the regulation of DNA repair in chromatin, are based upon our recent data that support the linkage of p53 pathway to DNA repair. The overall experiments are designed to address the specific hypothesis that p53 transcription activation machinery, which includes p53 tumor suppressor protein, CBP/p300 and transcription factor IIH, is targeted to scattered lesion sites of the genome via a recruitment process involving complex multiprotein interactions during early stage of DNA repair. The proposed work will utilize relevant biochemical, cellular and molecular technologies, established in the applicant?s laboratory, to address the following specific aims. (1) To establish the formation of p53 transcription activation/DNA damage recognition complex through interaction of various component factors, e.g., p53, p300, XPC-hHR23B and TFIIH. (2) To determine the critical role of XPC-hHR23B in the recruiting of p53 transcription activation machinery to DNA damage. (3) To identify the physically interacting regions of XPC and TFIIH component proteins, XPB and p62, required to function in the formation of p53 transcription activation/DNA recognition complex. (4) To delineate the relationship of CBP/p300 mediated histone hyperacetylation and nucleotide excision repair. (5) To demonstrate the influence of chromatin structure on the site-specific repair within the target gene. The long-term goal of these studies is to reveal the nature of several important interconnected gene functions and their role in the maintenance of genomic sequence integrity. Understanding the mechanistic basis of the prompt reversal of deleterious genomic alterations, occurring in human cells from exposures to diverse exogenous and endogenous mutagenic carcinogens, has clear implications in the pathogenesis of cancer.