In vivo bipartite interaction between the Hsp40 Sis1 and Hsp70 in Saccharomyces cerevisiae

Genetics. 2005 Apr;169(4):1873-82. doi: 10.1534/genetics.104.037242. Epub 2005 Jan 31.


The essential Hsp40, Sis1, is a J-protein cochaperone for the Ssa class of Hsp70's of Saccharomyces cerevisiae. Sis1 is required for the maintenance of the prion [RNQ(+)], as Sis1 lacking its 55-amino-acid glycine-rich region (G/F) does not maintain [RNQ(+)]. We report that overexpression of Sis1DeltaG/F in an otherwise wild-type strain had a negative effect on both cell growth and [RNQ(+)] maintenance, while overexpression of wild-type Sis1 did not. Overexpression of the related Hsp40 Ydj1 lacking its G/F region did not cause inhibition of growth, indicating that this dominant effect of Sis1DeltaG/F is not a characteristic shared by all Hsp40's. Analysis of small deletions within the SIS1 G/F region indicated that the observed dominant effects were caused by the absence of sequences known to be important for Sis1's unique cellular functions. These inhibitory effects of Sis1DeltaG/F were obviated by alterations in the N-terminal J-domain of Sis1 that affect interaction with Ssa's ATPase domain. In addition, a genetic screen designed to isolate additional mutations that relieved these inhibitory effects identified two residues in Sis1's carboxy-terminal domain. These alterations disrupted the interaction of Sis1 with the 10-kD carboxy-terminal regulatory domain of Ssa1, indicating that Sis1 has a bipartite interaction with Ssa in vivo.

Publication types

  • 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

  • Adenosine Triphosphatases / physiology
  • Amino Acid Sequence
  • Binding, Competitive
  • Cell Proliferation
  • Dose-Response Relationship, Drug
  • Enzyme-Linked Immunosorbent Assay
  • Fungal Proteins / chemistry
  • Gene Deletion
  • Gene Expression Regulation, Fungal*
  • Gene Library
  • Genes, Fungal
  • Genetic Techniques
  • Green Fluorescent Proteins / metabolism
  • HSP40 Heat-Shock Proteins
  • HSP70 Heat-Shock Proteins / physiology*
  • Heat-Shock Proteins / physiology*
  • Immunoblotting
  • Luciferases / metabolism
  • Molecular Sequence Data
  • Mutation
  • Plasmids / metabolism
  • Prions / metabolism
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / physiology*
  • Substrate Specificity
  • Temperature
  • Time Factors


  • Fungal Proteins
  • HSP40 Heat-Shock Proteins
  • HSP70 Heat-Shock Proteins
  • Heat-Shock Proteins
  • Prions
  • SIS1 protein, S cerevisiae
  • SSA3 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Green Fluorescent Proteins
  • Luciferases
  • Adenosine Triphosphatases
  • SSA1 protein, S cerevisiae