Functional dissection of the yeast Cyc8-Tup1 transcriptional co-repressor complex

Nature. 1994 Jun 30;369(6483):758-61. doi: 10.1038/369758a0.


DNA-binding repressor proteins mediate regulation of yeast genes by cell type (Mcm1/alpha 2 and a1/alpha 2), glucose (Mig1) and oxygen (Rox1) (refs 1-4 respectively). An unusual feature of all these regulatory pathways is that transcriptional repression requires two physically associated proteins that do not bind DNA Cyc8(Ssn6) and Tup1. The Cyc8-Tup1 complex has been proposed to be a co-repressor that is recruited to target promoters by pathway-specific DNA-binding proteins, but the specific functions of the individual proteins are unknown. Here we show that when it is bound upstream of a functional promoter through the LexA DNA-binding domain, Tup1 represses transcription in the absence of Cyc8. Deletion analysis indicates that Tup1 contains at least two non-overlapping transcriptional repression regions with minimal primary sequence similarity, and a separable Cyc8-interaction domain. These Tup1 domains, which do not include the beta-transducin motifs, are necessary and partially sufficient for Tup1 function. We suggest that Tup1 performs the repression function of the Cyc8-Tup1 co-repressor complex, and that Cyc8 serves as a link with the pathway-specific DNA-binding proteins.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / metabolism
  • Base Sequence
  • Cloning, Molecular
  • DNA, Fungal / metabolism
  • DNA-Binding Proteins / metabolism*
  • Fungal Proteins / metabolism*
  • Molecular Sequence Data
  • Nuclear Proteins*
  • Promoter Regions, Genetic
  • Repressor Proteins / metabolism*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins*
  • Sequence Deletion
  • Serine Endopeptidases*
  • Transcription, Genetic
  • beta-Galactosidase / metabolism


  • Bacterial Proteins
  • CYC8 protein, S cerevisiae
  • DNA, Fungal
  • DNA-Binding Proteins
  • Fungal Proteins
  • LexA protein, Bacteria
  • Nuclear Proteins
  • Repressor Proteins
  • Saccharomyces cerevisiae Proteins
  • TUP1 protein, S cerevisiae
  • beta-Galactosidase
  • Serine Endopeptidases