Cti6, a PHD domain protein, bridges the Cyc8-Tup1 corepressor and the SAGA coactivator to overcome repression at GAL1

Mol Cell. 2002 Jun;9(6):1297-305. doi: 10.1016/s1097-2765(02)00545-2.


The yeast Cyc8 and Tup1 proteins form a corepressor complex that, when tethered to DNA, turns off transcription. Release of the Cyc8-Tup1 corepressor from a promoter has been considered as a prerequisite for subsequent transcriptional activation. Contrasting this, we demonstrate that Cyc8-Tup1 is continuously associated with target promoters under both repressive and inducing conditions. At the GAL1 promoter, Cyc8-Tup1 facilitates recruitment of SAGA (Spt-Ada-Gcn5-acetyltranferase) via Cti6, a PHD domain protein that physically links the Cyc8-Tup1 and SAGA complexes. Lack of functional corepressor renders GAL1 transcription largely independent of specific SAGA subunits. Thus, corepressor's release is not the mechanism of derepression; instead, it is the coactivator complex that alleviates Cyc8-Tup1-mediated repression under induction conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA-Binding Proteins*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Expression Regulation, Fungal
  • Macromolecular Substances
  • Nuclear Proteins*
  • Promoter Regions, Genetic*
  • Protein Structure, Tertiary
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription, Genetic


  • CYC8 protein, S cerevisiae
  • DNA-Binding Proteins
  • Fungal Proteins
  • GAL4 protein, S cerevisiae
  • Macromolecular Substances
  • Nuclear Proteins
  • Repressor Proteins
  • Saccharomyces cerevisiae Proteins
  • TUP1 protein, S cerevisiae
  • Transcription Factors