Acts as component of the CYC8-TUP1 corepressor complex which is involved in the repression of many genes in a wide variety of physiological processes including heme-regulated and catabolite repressed genes. May also be involved in the derepression of at least some target genes. The complex is recruited to target genes by interaction with DNA-bound transcriptional repressors, like MATALPHA2, MIG1, RFX1 and SKO1. The complex recruits histone deacetylases to produce a repressive chromatin structure, interacts with hypoacetylated N-terminal tails of histones H3 and H4 that have been programmed for repression by the action of histone deacetylases and interferes directly with the transcriptional machinery by associating with the RNA polymerase II mediator complex. Associates with CYC8/SSN6 to form the CYC8-TUP1 (or TUP1-SSN6) corepressor complex that is composed of 4 copies of TUP1 and one copy of CYC8. Interacts with histone H3, histone H4, MATALPHA2, RFX1, SKO1, PGD1, HDA1, HDA2, HOS1, HOS2 AND RPD3. Present with 5840 molecules/cell in log phase SD medium. Belongs to the WD repeat TUP1 family.