title: Molecular changes in UV-induced and gamma-ray-induced mutations in human lymphoblastoid cells.
abstract: We have characterized the structural changes in the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene of 14 UV-induced, 15 gamma-ray-induced and 17 spontaneous mutants of human lymphoblastoid cells selected for 6-thioguanine (6TG) resistance. Southern blot analysis using the full-length HPRT cDNA as a probe revealed that 29% (5/17) of the spontaneous mutants contained detectable alterations in their restriction fragment patterns. Among the 15 mutants induced by gamma rays, 7 (47%) had such alterations indicative of large deletions in the HPRT gene. In contrast, all 14 UV-induced mutants exhibited hybridization patterns indistinguishable from those of the wild-type cells. These results suggest that UV is likely to induce point mutations at the HPRT locus on the human chromosome and that the molecular mechanism of UV-induced mutation is quite different from that of ionizing radiation-induced mutation or spontaneous mutation in human cells.
authors.affiliation: Department of Molecular Oncology, Faculty of Medicine, Kyoto University, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Tachibana
authors.forename: T
authors.initials: T
authors.lastname: Ohbayashi
authors.forename: H
authors.initials: H
authors.lastname: Takebe
authors.forename: K
authors.initials: K
authors.lastname: Tatsumi
mesh_terms: D015139:Blotting, Southern; D002460:Cell Line; D004247:DNA / Q000528:radiation effects*; D004351:Drug Resistance / Q000235:genetics; D005720:Gamma Rays; D005796:Genes; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D008214:Lymphocytes; D009154:Mutation; D012150:Polymorphism, Restriction Fragment Length; D013866:Thioguanine / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D004247:DNA; D007041:Hypoxanthine Phosphoribosyltransferase; D013866:Thioguanine