Published data on mutagenesis by ionizing radiation of plasmids in solution probably reflect in part the specificity of adventitious transition metal ions complexed to the DNA.
A number of recent papers show that single base changes induced by mutagenesis with ionizing radiation of genes on plasmids in solution, followed by transfection into mammalian or bacterial cells for assay, are mostly at G:C base pairs, with mutagenic hot spots. Genes irradiated in mammalian or bacterial cells, on the other hand, have comparable numbers of base changes at all sites, with no evidence for hot spots. The differences are ascribed to induction of many base change mutations in vitro by reactions catalyzed by adventitious transition metal ions complexed to the DNA. Reasons are given why this process should play a much smaller role in vivo.
Radiobiology Laboratory, Yale University, New Haven, CT 06510.
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Hutchinson
D001482:Base Composition; D004247:DNA / Q000737:chemistry*; D008670:Metals / Q000737:chemistry*; D016296:Mutagenesis; D010957:Plasmids / Q000235:genetics / Q000528:radiation effects*; D012996:Solutions
D008670:Metals; D012996:Solutions; D004247:DNA