The structure of Sif2p, a WD repeat protein functioning in the SET3 corepressor complex

J Mol Biol. 2005 Aug 26;351(4):923-35. doi: 10.1016/j.jmb.2005.06.025.


In Saccharomyces cerevisiae, the SIF2 gene product is an integral component of the Set3 complex (SET3C), an assembly of proteins with some homology to the human SMRT and N-CoR corepressor complexes. SET3C has histone deacetylase activity that is responsible for repressing a set of meiotic genes. We have determined the X-ray crystal structure of a 46 kDa C-terminal domain of a SET3C core protein, Sif2p to 1.55 A resolution and a crystallographic R-factor of 19.0%. This domain contains an unusual eight-bladed beta-propeller structure, which differs from other transcriptional corepressor structures such as yeast Tup1p and human groucho (Gro)/TLE1, which have only seven. We have demonstrated intact Sif2p is a tetramer and the N-terminal LisH (Lis-homology)-containing domain mediates tetramerization and interaction with another component of SET3C, Snt1p. Multiple sequence alignments indicate that a surface on the "top" of the protein is conserved among species, suggesting that it may play a common role in binding partner proteins. Since Sif2p appears to be the yeast homolog of human TBL1 and TBLR1, which function in the N-CoR/SMRT complexes, its structural and oligomeric properties are likely to be very similar.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Binding Sites
  • Conserved Sequence
  • Crystallography, X-Ray
  • DNA, Fungal / genetics
  • Histone Deacetylases
  • Humans
  • Models, Molecular
  • Molecular Sequence Data
  • Multiprotein Complexes
  • Protein Binding
  • Protein Structure, Tertiary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Repetitive Sequences, Amino Acid
  • Repressor Proteins / chemistry*
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / chemistry*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism
  • Sequence Homology, Amino Acid


  • DNA, Fungal
  • Multiprotein Complexes
  • Recombinant Proteins
  • Repressor Proteins
  • SIF2 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Histone Deacetylases

Associated data

  • PDB/1R5M