9604208 Berger Chromosomal DNA is packed into higher ordered structures by spaced assembly of nucleosomes composed of histone proteins. Gene activity is repressed by nucleosome binding and gene activation has been correlated with chemical modification of histones. In particular histone acetylation and deacetylation may be associated with modulation of gene activity. The recent discovery that the yeast transcription factor GCN5 has enzymatic histone acetyltransferase activity potentially links transcriptional activation and chromatin modification. GCN5 is one component of an ADA complex that physically interacts with both DNA-associated transcriptional activator proteins and basal transcription factors. The activity of the ADA complex suggests both a possible mechanism to target the HAT activity to chromatil through activator interaction, and a possible outcome of acetylation in the promotion of basal transcription factor binding to nucleosomal DNA. This research will investigate the relationship between the HAT activity of GCN5 and transcriptional activation. The HAT domain of yeast GCN5 will be mutagenized; growth deficient mutants will be selected and tested for coordinate reduction of enzymatic acetylation and transcription. Genetic suppression of GCN5 substitution mutants that exhibit profound growth defects but maintain HAT activity in vitro will be used to identify novel yeast genes whose products may interact with and/or modulate the HAT activity of GCN5. Exploration of the relationship between HAT activity and trascriptional activation will fill in a key gap in current understanding of eukaryotic gene regulation. Chromosomal DNA is packed into higher ordered structures by spaced assembly of nucleosomes composed of histone proteins. Gene activity is repressed by nucleosome binding and gene activation has been correlated with chemical modification of histones. In particular histone acetylation and deacetylation may be associated with modulation of gene activity. The recent discovery that the yeast transcription factor GCN5 has enzymatic histone acetyltransferase activity potentially links transcriptional activation and chromatin modification. GCN5 is one component of an ADA complex that physically interacts with both DNA-associated transcriptional activator proteins and basal transcription factors. This research will investigate the relationship between the HAT activity of GCN5 and transcriptional activation, and will fill in a key gap in current understanding of eukaryotic gene regulation.
