RPD3 encodes a histone deacetylase (7). Covalent modifications of histones, including acetylation and deacetylation, are implicated in transcriptional regulation in yeast and other eukaryotes (reviewed in 16 and 17). Rpd3p, Sin3p and Ume1p form the core of the Sin3 complex, a class I histone deacetylase complex (HDAC) that is conserved, in some form, from yeast to mammals (for review see 18 and 19). In fungi, two functionally distinct Sin3 complexes, Rpd3L and Rpd3S, have been characterized, both of which may contribute to transcriptional regulation (20, 21, 8, 12 and references therein).The larger, Rpd3L (1.2 MDA), is required for the heat stress response (13) and has been demonstrated to be involved in Sir2-mediated silencing (10) and replication origin firing (11). The smaller, Rpd3S (0.9 MDa), interacts with Set2p-methylated histones and may contribute to transcription elongation (20, 8). Other Rpd3p- or Sin3p-containing complexes have also been isolated (22) and it is hypothesized that some core HDAC components are shared between complexes with different functions (for review see 18 and 19). A second histone deactylase, Hda1p, shows sequence similarity to Rpd3p but is found in a complex distinct from the complexes containing Rpd3p (7); the Hda1p-containing and Rpd3p-containing complexes affect transcription of distinct, partially overlapping sets of genes (7, 17). Deletion of RPD3 increases histone acetylation in vivo, increases telomeric repression of transcription (7), and extends life span (23). In diploids, mutations in RPD3 cause defects in mitotic recombination and sporulation (2), and the recombination mutant rec3-1 (24) has been shown to be allelic to RPD3 (2). Three more histone deactylases, Hos1p, Hos2p, and Hos3p, have been identified in yeast; they share sequence similarity with Rpd3p and Hda1p but are less well characterized (7).

Last updated: 2010-07-20