A UV-resistant mutant without an increased repair synthesis activity, established from a UV-sensitive human clonal cell line.
When cells of a human clonal cell line, RSa, with high sensitivity to UV lethality, were treated with the mutagen, ethyl methanesulfonate, a variant cell strain, UVr-1, was established as a mutant resistant to 254-nm far-ultraviolet radiation (UV). Cell proliferation studies showed that UVr-1 cells survived and actively proliferated at doses of UV-irradiation that greatly suppressed the proliferation of RSa cells. Colony-formation assays also confirmed the increased resistance of UVr-1 cells to UV. The recovery from a UV-induced inhibition in DNA synthesis, as [methyl-3H]thymidine uptake into cellular DNA, was more pronounced in UVr-1 cells than in RSa cells. Nevertheless, there was no significant difference in the activity of UV-induced DNA repair synthesis in either cell line, as estimated by the extent of unscheduled DNA synthesis and DNA repair replication. UVr-1 cells were also more refractory to 4-nitroquinoline 1-oxide (4NQO), but the activity of DNA repair synthesis induced by 4NQO in UVr-1 cells was much the same as in the RSa cells. Both N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) sensitivity and MNNG-induced DNA repair synthesis activity in UVr-1 cells were similar to that of RSa cells. These characteristics of UVr-1 cells are discussed in the light of a previously reported UV-resistant variant, UVr-10, which had an increased DNA repair synthesis activity.
D015112:4-Nitroquinoline-1-oxide / Q000633:toxicity; D002453:Cell Cycle / Q000528:radiation effects; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D002999:Clone Cells; D004260:DNA Repair; D004261:DNA Replication / Q000187:drug effects / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D007700:Kinetics; D008769:Methylnitronitrosoguanidine / Q000633:toxicity; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum
D008769:Methylnitronitrosoguanidine; D015112:4-Nitroquinoline-1-oxide