Cancer, birth defects and aging are all thought to result from of an accumulation of genetic damage. Cells respond to the challenge of DNA damage by activating a protein kinase cascade that causes cell cycle arrest and the induction of repair genes. Alterations in either of these responses lead to human disease. Kinases in these pathways have been identified, however, their transcription factor targets have remained elusive. We have identified potential targets. Through our genetic study of the TATA-box binding protein associated factors (yTAFIIS) from the budding yeast Saccharomyces cerevisiae, we have discovered that yTAFIIS are required for the cellular response to DNA damage and damage- induced transcription. This is a significant discovery, because the in vivo functions of TAFIIS are largely unknown. Biochemical studies have implicated them as being important for the control of transcription from all promoters, and they are thought to do so by acting as coactivators and promoter selectivity factors. However, analysis of TAFII mutants in vivo in both yeast and mammalian systems have challenged this model. Mutation of multiple yeast TAFIIS, and mutation of the largest mammalian TAFII, do not lead to global defects in transcription, but lead to cell cycle defects and alterations in transcription of a select number of genes. Previous work identified two classes of genes that are dependent upon TAF145 for transcription. Most surprisingly, TAF145 determinants are not activator binding sites, but core promoter elements, leaving the issue of what signals are acting through TAFIIS an open question. We have found that the transcription of DNA damage response genes requires multiple TAFII subunits, which makes their regulation distinct from the previously identified gene classes. This proposal will extend these preliminary observations by characterizing the role of TAFIIS in the regulation of DNA damage responsive genes and explore the signaling pathways that mediate their activities. These studies will identify the determinants of TAFII-dependent genes, the cellular signals controlling TAFII function, and attempt to establish TAFIIS as the transcription factor targets of the DNA damage protein kinase cascade. This work will impact the fields of transcription, DNA damage and cell cycle control.
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