Abstract
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.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1475-1488 |
| Number of pages | 14 |
| Journal | DNA Repair |
| Volume | 5 |
| Issue number | 12 |
| DOIs | |
| State | Published - Dec 9 2006 |
Bibliographical note
Funding Information:PCNA modification at K164 is mediated by the Rad6p-Rad18p or the Ubc9p-Siz1p complex [28,29] . Previously, the mutagenic defect in a rad18 siz1 mutant was entirely attributed to defective TLS from the abolishment of PCNA modification. Our study, however, suggests that rad18 siz1 harbor sources of mutagenic defects in addition to TLS deficiency. This conclusion was supported by the different IR-IM spectrum of the rad18 siz1 and the rev3 mutant. Additionally, the IR-IM defect in a rad18 siz1 rev3 mutant was significantly worse than those of rev3 or rad18 siz1.
Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
Keywords
- DNA repair
- Deoxycytidyl transferase
- Homologous recombination
- Ionizing radiation
- Mutagenesis
- Non-homologous end joining
- Nuclotide excision repair
- PCNA
- Polymerase eta
- Polymerase zeta
- RAD30
- REV1
- REV3
- REV7
- SUMOylation
- Translesion synthesis
- Ubiquitination