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Functional interaction between Ssu72 and the Rpb2 subunit of RNA polymerase II in Saccharomyces cerevisiae.

SSU72 is an essential gene encoding a phylogenetically conserved protein of unknown function that interacts with the general transcription factor TFIIB. A recessive ssu72-1 allele was identified as a synthetic enhancer of a TFIIB (sua7-1) defect, resulting in a heat-sensitive (Ts(-)) phenotype and a dramatic downstream shift in transcription start site selection. Here we describe a new allele, ssu72-2, that confers a Ts(-) phenotype in a SUA7 wild-type background. In an effort to further define Ssu72, we isolated suppressors of the ssu72-2 mutation. One suppressor is allelic to RPB2, the gene encoding the second-largest subunit of RNA polymerase II (RNAP II). Sequence analysis of the rpb2-100 suppressor defined a cysteine replacement of the phylogenetically invariant arginine residue at position 512 (R512C), located within homology block D of Rpb2. The ssu72-2 and rpb2-100 mutations adversely affected noninduced gene expression, with no apparent effects on activated transcription in vivo. Although isolated as a suppressor of the ssu72-2 Ts(-) defect, rpb2-100 enhanced the transcriptional defects associated with ssu72-2. The Ssu72 protein interacts directly with purified RNAP II in a coimmunoprecipitation assay, suggesting that the genetic interactions between ssu72-2 and rpb2-100 are a consequence of physical interactions. These results define Ssu72 as a highly conserved factor that physically and functionally interacts with the RNAP II core machinery during transcription initiation.

Pubmed ID: 11046131


  • Pappas DL
  • Hampsey M


Molecular and cellular biology

Publication Data

November 19, 2000

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM39484

Mesh Terms

  • Amino Acid Sequence
  • Carrier Proteins
  • Conserved Sequence
  • Fungal Proteins
  • Molecular Sequence Data
  • Mutation
  • Phosphoprotein Phosphatases
  • Phylogeny
  • Protein Subunits
  • RNA Polymerase II
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Suppression, Genetic
  • Transcription Factor TFIIB
  • Transcription Factors
  • Transcription, Genetic
  • mRNA Cleavage and Polyadenylation Factors