title: Proteasomal regulation of the mutagenic translesion DNA polymerase, Saccharomyces cerevisiae Rev1.
abstract: Translesion DNA synthesis (TLS) functions as a tolerance mechanism for DNA damage at a potentially mutagenic cost. Three TLS polymerases (Pols) function to bypass DNA damage in Saccharomyces cerevisiae: Rev1, Pol ζ, a heterodimer of the Rev3 and Rev7 proteins, and Pol η (Rad30). Our lab has shown that S. cerevisiae Rev1 protein levels are under striking cell cycle regulation, being ∼50-fold higher during G2/M than during G1 and much of S phase (Waters and Walker, 2006). REV1 transcript levels only vary ∼3-fold in a similar cell cycle pattern, suggesting a posttranscriptional mechanism controls protein levels. Here, we show that the S. cerevisiae Rev1 protein is unstable during both the G1 and the G2/M phases of the cell cycle, however, the protein's half-life is shorter in G1 arrested cells than in G2/M arrested cells, indicating that the rate of proteolysis strongly contributes to Rev1's cell cycle regulation. In the presence of the proteasome inhibitor, MG132, the steady-state levels and half-life of Rev1 increase during G1 and G2/M. Through the use of a viable proteasome mutant, we confirm that the levels of Rev1 protein are dependent on proteasome-mediated degradation. The accumulation of higher migrating forms of Rev1 under certain conditions shows that the degradation of Rev1 is possibly directed through the addition of a polyubiquitination signal or another modification. These results support a model that proteasomal degradation acts as a regulatory system of mutagenic TLS mediated by Rev1.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 01239, USA.
authors.forename: Mary Ellen
authors.initials: ME
authors.lastname: Wiltrout
authors.forename: Graham C
authors.initials: GC
authors.lastname: Walker
mesh_terms: D002453:Cell Cycle; D002455:Cell Division; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000235:genetics; D016193:G1 Phase; D016195:G2 Phase; D016296:Mutagenesis; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D061988:Proteasome Inhibitors; D016196:S Phase; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D000099270:Y-Family DNA Polymerases
chemical_list: D004259:DNA-Directed DNA Polymerase; D009713:Nucleotidyltransferases; D046988:Proteasome Endopeptidase Complex; D061988:Proteasome Inhibitors; D029701:Saccharomyces cerevisiae Proteins; C092219:REV7 protein, S cerevisiae; C100951:REV1 protein, S cerevisiae; D000099270:Y-Family DNA Polymerases; C092602:REV3 protein, S cerevisiae