Effects of cell cycle position on ionizing radiation mutagenesis. I. Quantitative assays of two genetic loci in a human lymphoblastoid cell line.
Relatively little work has been done on the influence of the position of the cell in the cell cycle on ionizing radiation-induced mutagenesis. We synchronized WTK1 human lymphoblastoid cells with 200 microM lovastatin for 48 h; under these conditions more than 80% of the cells were arrested in G1 phase. Upon release, there was a 12-15-h lag followed by movement of a large fraction into S phase. We irradiated cells with either 1.5 Gy X rays at 1, 15, 18, 21 or 24 h or 1.5 Gy gamma rays at 1, 5, 10, 15 or 24 h after release from lovastatin. We showed that WTK1 cells were most sensitive to ionizing radiation-induced toxicity in G1 and into S phase, and more resistant in mid to late S and G2/M phase. Somewhat surprisingly, we found that the two different gene loci had different sensitivities to radiation-induced mutation through the cell cycle. Cells in late G1 through mid-S phase were most sensitive to radiation-induced mutations at the autosomal thymidine kinase (TK) locus, whereas G1 phase was the most sensitive phase at the X-linked hypoxanthine guanine phosphoribosyl transferase (HPRT) locus.
Chuang
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Department of Cancer Biology, Harvard School of Public Health, Boston, Massachusetts 02115, USA.
Liber
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D002453:Cell Cycle; D002460:Cell Line; D002874:Chromosome Mapping; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D016296:Mutagenesis / Q000528:radiation effects*; D017354:Point Mutation; D013937:Thymidine Kinase / Q000235:genetics*
D007041:Hypoxanthine Phosphoribosyltransferase; D013937:Thymidine Kinase