A novel Rad18 function involved in protection of the vertebrate genome after exposure to camptothecin.
In Saccharomyces cerevisiae, Rad18 functions in post-replication repair pathways, such as error-free damage bypass involving Rad30 (Poleta) and error-prone damage bypass involving Rev3/7 (Polzeta). Chicken DT40 RAD18(-/-) cells were found to be hypersensitive to camptothecin (CPT), while RAD30(-/-) and REV3(-/-) cells, which are defective in translesion DNA synthesis, were not. RAD18(-/-) cells also showed higher levels of H2AX phosphorylation and chromosomal aberrations, particularly chromosomal gaps and breaks, upon exposure to CPT. Detailed analysis by alkaline sucrose density gradient centrifugation revealed that RAD18(-/-) and wild type cells exhibited similar rates of elongation of newly synthesized DNA in the presence or absence of low concentrations of CPT but that DNA breaks frequently occurred on both parental and nascent strands within 1h after a brief exposure to an elevated concentration of CPT, with more breaks induced in RAD18(-/-) cells than in wild type cells. These data suggest a previously unanticipated role for Rad18 in dealing with replication forks upon encountering DNA lesions induced by CPT.
Yoshimura
Akari
A
Molecular Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Aramaki, Sendai 980-8578, Japan.
Nishino
Katsuaki
K
Takezawa
Jun
J
Tada
Shusuke
S
Kobayashi
Takayuki
T
Sonoda
Eiichiro
E
Kawamoto
Takuo
T
Takeda
Shunichi
S
Ishii
Yutaka
Y
Yamada
Kouichi
K
Enomoto
Takemi
T
Seki
Masayuki
M
D000818:Animals; D002166:Camptothecin / Q000633:toxicity*; D002460:Cell Line; D002645:Chickens / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology*; D004259:DNA-Directed DNA Polymerase / Q000502:physiology; D016678:Genome
D004268:DNA-Binding Proteins; D004247:DNA; D004259:DNA-Directed DNA Polymerase; D002166:Camptothecin