Acts as component of the trfA-tupA corepressor complex which is involved in the repression of many genes in a wide variety of physiological processes. 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. 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 (By similarity). Associates with trfA to form the trfA-tupA corepressor complex. Belongs to the WD repeat TUP1 family.