Molecular analysis of spontaneous and ethyl methanesulphonate-induced mutations of the hprt gene in hamster cells.
Independent spontaneous or ethyl methanesulphonate (EMS)-induced mutants lacking HPRT enzyme activity were analysed for changes in hprt gene structure. Of 21 spontaneous mutants, 6 had total gene deletions, 2 had partial gene deletions, and 13 were indistinguishable from wild-type by Southern analysis. In contrast a sample of 23 EMS-induced mutants, each of which showed potentially interesting characteristics (e.g. high reversion frequency, X-chromosome rearrangement), showed no detectable hprt gene changes. RNA isolated from 59 mutants with presumptive point mutations (13 spontaneous, 46 EMS-induced) was analysed on dot blots for changes in the amount of hprt mRNA. A wide range of mRNA levels was found, from mutants with undetectable amounts to those with more than wild-type amounts. However, Northern blots of all these mutant RNAs revealed only one (EMS-induced) mutation with a change in hprt mRNA size. Taken with our previously-published data on these mutants, it is argued that they represent a broad range of mutational types, and that the hprt gene mutation system provides a sensitive means of distinguishing mutational spectra of different DNA-damaging agents.
Thacker
J
J
MRC Radiobiology Unit, Chilton, Didcot, Oxon, Great Britain.
Ganesh
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AN
D000818:Animals; D015152:Blotting, Northern; D015139:Blotting, Southern; D002872:Chromosome Deletion; D006224:Cricetinae; D003412:Cricetulus; D005020:Ethyl Methanesulfonate / Q000633:toxicity*; D005796:Genes; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D009154:Mutation / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics
D012333:RNA, Messenger; D005020:Ethyl Methanesulfonate; D007041:Hypoxanthine Phosphoribosyltransferase