Acetylation of histones and transcription-related factors

The state of chromatin (the packaging of DNA in eukaryotes) has long been r ecognized to have major effects on levels of gene expression, and numerous chromatin-altering strategies-including ATP-dependent remodeling and histon e modification-are employed in the cell to bring about transcriptional regu lation. Of these, histone acetylation is one of the best characterized, as recent years have seen the identification and further study of many histone acetyltransferase (HAT) proteins and their associated complexes. Interesti ngly, most of these proteins were previously shown to have coactivator or o ther transcription-related functions. Confirmed and putative HAT proteins h ave been identified from various organisms from yeast to humans, and they i nclude Gcn5-related N-acetyltransferase (GNAT) superfamily members Gcn5, PC AF, Elp3, Hpa2 and Hat1: MYSTproteins Sas2, Sas3, Esa1, MOF, Tip60, MOZ, MO RF, and HBO1; global coactivators p300 and CREB-binding protein; nuclear re ceptor coactivators SRC-1, ACTR, and TIF2; TATA-binding protein-associated factor TAF(II)250 and its homologs; and subunits of RNA polymerase III gene ral factor TFIIIC. The acetylation and transcriptional functions of these H ATs and the native complexes containing them (such as yeast SAGA, NuA4, and possibly analogous human complexes) are discussed. In addition some of the se HA Ts are also known to modify certain nonhistone transcription-related proteins, including high-mobility-group chromatin proteins activators such as p53, coactivators, and general factors. Thus, we also detail these known factor acetyltransferase (FAT) substrates and the demonstrated or potentia l roles of their acetylation in transcriptional processes.