title: Caffeine abolishes the ultraviolet-induced REV3 translesion replication pathway in mouse cells.
abstract: When a replicative DNA polymerase stalls upon encountering a photoproduct on the template strand, it is relieved by other low-processivity polymerase(s), which insert nucleotide(s) opposite the lesion. Using an alkaline sucrose density gradient sedimentation technique, we previously classified this process termed UV-induced translesion replication (UV-TLS) into two types. In human cancer cells or xeroderma pigmentosum variant (XP-V) cells, UV-TLS was inhibited by caffeine or proteasome inhibitors. However, in normal human cells, the process was insensitive to these reagents. Reportedly, in yeast or mammalian cells, REV3 protein (a catalytic subunit of DNA polymerase ζ) is predominantly involved in the former type of TLS. Here, we studied UV-TLS in fibroblasts derived from the Rev3-knockout mouse embryo (Rev3KO-MEF). In the wild-type MEF, UV-TLS was slow (similar to that of human cancer cells or XP-V cells), and was abolished by caffeine or MG-262. In 2 cell lines of Rev3KO-MEF (Rev3(-/-)p53(-/-)), UV-TLS was not observed. In p53KO-MEF, which is a strict control for Rev3KO-MEF, the UV-TLS response was similar to that of the wild-type. Introduction of the Rev3 expression plasmid into Rev3KO-MEF restored the UV-TLS response in selected stable transformants. In some transformants, viability to UV was the same as that in the wild-type, and the death rate was increased by caffeine. Our findings indicate that REV3 is predominantly involved in UV-TLS in mouse cells, and that the REV3 translesion pathway is suppressed by caffeine or proteasome inhibitors.
authors.affiliation: Division of Genetic Biochemistry, National Institute of Health and Nutrition, Shinjuku-ku, Tokyo 162-8636, Japan. junt@nih.go.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Takezawa
authors.forename: Naomi
authors.initials: N
authors.lastname: Aiba
authors.forename: Kagemasa
authors.initials: K
authors.lastname: Kajiwara
authors.forename: Kouichi
authors.initials: K
authors.lastname: Yamada
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002460:Cell Line; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D051379:Mice; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D002110:Caffeine; D004259:DNA-Directed DNA Polymerase; D016159:Tumor Suppressor Protein p53; C486862:REV3L protein, mouse