Catalytic component of the RPD3 histone deacetylase complexes RPD3C(L) and RPD3C(S) responsible for the deacetylation of lysine residues on the N-terminal part of the core histones (H2A, H2B, H3 and H4). Histone deacetylation gives a tag for epigenetic repression and plays an important role in transcriptional regulation, cell cycle progression and developmental events. Component of the RPD3C(L) complex composed of at least ASH1, CTI6, DEP1, PHO23, RPD3, RXT2, RXT3, SAP30, SDS3, SIN3, UME1 and UME6. Component of the RPD3C(S) complex composed of at least EAF3, RCO1, RPD3, SIN3, and UME1. Interacts with RPD3. By glucose. The NEE-box motif is required for the association to RPD3. Present with 3040 molecules/cell in log phase SD medium.