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RNA polymerase III defects suppress a conditional-lethal poly(A) polymerase mutation in Saccharomyces cerevisiae.

We isolated spontaneous extragenic suppressors of a temperature-sensitive, lethal poly(A) polymerase mutation (pap1-1) in Saccharomyces cerevisiae that restore growth at the restrictive temperature of 30 degrees. Three of five suppressors represent alleles of the PDS2 complementation group. The recessive pds2-1 mutation exerts dominant allele-specific suppression over pap1-1, suggesting a direct functional interaction. The suppressor restores to near normal the steady-state concentrations of various mRNAs and total poly(A) reduced by pap1-1 at 30 degrees. Transcriptional chase experiments detect no reduction in the decay rates of mRNAs in the suppressor strain, suggesting that the restoration of steady-state message levels results from increased stable mRNA synthesis. Molecular cloning shows PDS2 to be allelic to RET1, which encodes the second-largest subunit of RNA polymerase III. We observe alterations in both the length and the steady-state amounts of RNA polymerase III transcripts in pds2-1 strains. Previously identified ret1 alleles do not suppress pap1-1, indicating that the pds2 alleles we isolated represent a specific class of RET1 mutations that suppress pap1-1. Suppression of pap1-1 by mutations in an RNA polymerase III subunit suggests a number of potentially novel interactions between these enzymes.

Pubmed ID: 8807289


  • Briggs MW
  • Butler JS



Publication Data

July 6, 1996

Associated Grants

  • Agency: NIGMS NIH HHS, Id: T32-GM07102

Mesh Terms

  • Cloning, Molecular
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Fungal
  • Mutation
  • Poly A
  • Polynucleotide Adenylyltransferase
  • RNA Polymerase III
  • RNA, Messenger
  • Saccharomyces cerevisiae
  • Suppression, Genetic
  • Temperature
  • Transcription, Genetic