Genetic analysis of ionizing radiation-induced mutagenesis in Saccharomyces cerevisiae reveals TransLesion Synthesis (TLS) independent of PCNA K164 SUMOylation and ubiquitination.
Ionizing radiation-induced mutagenesis (IR-IM) underlies a basis for radiation associated carcinogenesis as well as resistance to radiation therapy. This process was examined in Saccharomyces cerevisiae using an array of isogenic DNA repair deficient mutants. Mutations inactivating homologous recombination (rad51, 52, 54) or nucleotide excision repair (rad1, rad10, rad4) caused elevated IR-IM whereas inactivation of TransLesion Synthesis (TLS: rad6) caused severely defective IR-IM. Of the mutations inactivating TLS polymerases, rev3 and rev1 caused equally severe defects in IR-IM whereas rad30 did not significantly affect the process. The effects of the rev3, rev1, and rad6 mutations on IR-IM were epistatic, suggesting the requirement of both polymerase zeta and Rev1p in IR-IM related TLS. Although PCNA K164 SUMOylation/ubiquitination is a proposed prerequisite for TLS, the IR-IM defect of a rev3 or a rad6 mutant was worse than and epistatic to the pol30K164R mutant, a mutant in which the PCNA had been mutated to abolish such modifications. These results suggested that IR-IM related TLS occurs in the absence of PCNA K164 modification. Further analysis of a mutant simultaneously defective in SUMOylation and mono-ubiquitination (rad18 siz1) revealed that these modifications redundantly affected TLS as well as NHEJ. A genetic model based on these observations is proposed.
Chen
Clark C
CC
Department of Neurosurgery, Massachusetts General Hospital, 55 Fruit St., Boston, MA 02114, USA.
Motegi
Akira
A
Hasegawa
Yuko
Y
Myung
Kyungjae
K
Kolodner
Richard
R
D'Andrea
Alan
A
D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D009154:Mutation; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011839:Radiation, Ionizing; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics
D004268:DNA-Binding Proteins; D018809:Proliferating Cell Nuclear Antigen; C063607:RAD18 protein, S cerevisiae; C092219:REV7 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; D004259:DNA-Directed DNA Polymerase; C092602:REV3 protein, S cerevisiae; C436837:Siz1 protein, S cerevisiae