Rapamycin inhibits yeast nucleotide excision repair independently of tor kinases

Toxicol Sci. 2010 Jan;113(1):77-84. doi: 10.1093/toxsci/kfp238. Epub 2009 Oct 5.

Abstract

The yeast target of rapamycin (Tor) kinases, Tor1 and Tor2, belong to the phosphatidylinositol 3-kinase-related family of proteins, which are involved in the cellular response to DNA damage and changes in nutrient conditions. In contrast to yeast, many eukaryotes possess a single Tor kinase. Regardless of the number of Tor kinases in an organism, two distinct complexes involving Tor proteins exist in eukaryotes, TORC1 and TORC2. The yeast TORC1, containing Tor1 or Tor2, is sensitive to the antibiotic rapamycin. The yeast TORC2 is insensitive to rapamycin. We examined the influence of rapamycin treatment upon yeast transcription-coupled nucleotide excision repair in a gene transcribed by RNA polymerase II. We also examined tor mutants for their ability to perform transcription-coupled repair in the absence or presence of rapamycin. Ostensibly lacking TORC1 and TORC2 function, a tor1tor2(ts) mutant grown at the nonpermissive temperature exhibited similar rates of repair as the wild-type strain. However, repair of both strands in genes decreases in the wild-type strain and the tor1tor2(ts) mutant exposed to rapamycin. Rapamycin may be inhibiting DNA repair independently of the Tor kinases. In yeast, FPR1 encodes the rapamycin-binding protein Fpr1 that inhibits the TORC1 kinase in the presence of rapamycin. Fap1 competes with rapamycin for Fpr1 binding. Deletion of the FPR1 or FAP1 gene abolishes the inhibitory effect of rapamycin on repair. Thus, the decreased repair observed following rapamycin treatment is independent of TORC1/2 function and likely due to a function of Fap1. We suggest that Fap1 and peptidyl-prolyl isomerases, particularly Fpr1, function in the cellular response to genotoxic stress. Our findings have clinical implications for genetic toxicities associated with genotoxic agents when coadministered with rapamycin.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cell Cycle Proteins / antagonists & inhibitors
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • DNA Damage
  • DNA Repair / drug effects*
  • DNA Repair / radiation effects
  • DNA, Fungal / metabolism*
  • Mutagens / toxicity*
  • Mutation
  • Peptidylprolyl Isomerase / metabolism
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors / toxicity
  • RNA Polymerase II / metabolism
  • Repressor Proteins / metabolism
  • Saccharomyces cerevisiae / drug effects*
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / radiation effects
  • Saccharomyces cerevisiae Proteins / antagonists & inhibitors
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Signal Transduction / drug effects*
  • Sirolimus / toxicity*
  • Temperature
  • Time Factors
  • Transcription, Genetic / drug effects
  • Ultraviolet Rays

Substances

  • Cell Cycle Proteins
  • DNA, Fungal
  • FAP1 protein, S cerevisiae
  • Mutagens
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors
  • Repressor Proteins
  • Saccharomyces cerevisiae Proteins
  • TOR1 protein, S cerevisiae
  • TOR2 protein, S cerevisiae
  • RNA Polymerase II
  • Peptidylprolyl Isomerase
  • Sirolimus