SAP30, A COMPONENT OF THE MSIN3 COREPRESSOR COMPLEX INVOLVED IN N-COR-MEDIATED REPRESSION BY SPECIFIC TRANSCRIPTION FACTORS

The transcriptional corepressor mSin3 is found in a large multiprotein complex containing the histone deacetylases HDAC1 and HDAC2, in addit ion to at least five tightly associated polypeptides. We have cloned a nd characterized a novel component of the mSin3 complex, SAP30. SAP30 binds to mSin3 and is capable of mediating transcriptional repression via histone deacetylases. SAP30 also binds the N-CoR corepressor and i s required for N-CoR-mediated repression by antagonist-bound estrogen receptor and the homeodomain protein Rpx, as well as N-CoR suppression of transactivation by the POU domain protein Pit-1. However, SAP30 is not required for N-CoR-mediated repression by unliganded retinoic aci d receptor or thyroid hormone receptor, suggesting that SAP30 is invol ved in the functional recruitment of the mSin3-histone deacetylase com plex to a specific subset of N-CoR corepressor complexes.