Sds3 (suppressor of defective silencing 3) is an integral component of theyeast Sin3 center dot Rpd3 histone deacetylase complex and is required forhistone deacetylase activity

SDS3 (suppressor of defective silencing 3) was originally identified in a s creen for mutations that cause increased silencing of a crippled HMR silenc er in a rap1 mutant background, In addition, sds3 mutants have phenotypes v ery similar to those seen in sind and rpd3 mutants, suggesting that it func tions in the same genetic pathway. In this manuscript we demonstrate that S ds3p is an integral subunit of a previously identified high molecular weigh t Rpd3p.Sin3p containing yeast histone deacetylase complex. By analyzing an sds3 Delta strain we show that, in the absence of Sds3p, Sin3p can be chro matographically separated from Rpd3p, indicating that Sds3p promotes the in tegrity of the complex. Moreover, the remaining Rpd3p complex in the sds3 D elta strain had little or no histone deacetylase activity. Thus, Sds3p play s important roles in the integrity and catalytic activity of the Rpd3p.Sin3 p complex.