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 RIS Download
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