It has been shown that the acetylation of the amino-terminal lysine residues of histones is associated with transcriptional activity in chromatin. The studies described in this proposal will (1) resolve whether histone deacetylase (HDAC) proteins use a nonspecific, a targeting, or combination mechanism to affect transcriptional regulation and (2) identify associated factors which mediate the transcriptional response. The first series of experiments described in this proposal will determine what portion of genes are affected by the inhibition of HDAC proteins using differential display or gene transcript array. Quantitative analysis of the results will suggest a mechanism of transcriptional regulation by HDAC proteins. In the second part of the proposal the promoter regions of genes influenced by HDAC inhibitors will be analyzed to yield DNA binding proteins which associate with HDAC. The result will be the identification of new HDAC associated factors starting from the end result of transcription in vivo (mRNA production). These studies are necessary to understand at a basic level the effect of histone deacetylases on transcriptional regulation. The results will allow for a more thorough understanding of transcriptional regulation by detailing the mechanism of chromatin remodeling.