The rad2 mutation affects the molecular nature of UV and acridine-mustard-induced mutations in the ADE2 gene of Saccharomyces cerevisiae |
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Authors: | E. L. Ivanov S. V. Kovaltzova G. V. Kassinova L. M. Gracheva V. G. Korolev I. A. Zakharov |
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Affiliation: | B.P. Konstantinov Leningrad Institute of Nuclear Physics, Academy of Sciences of the U.S.S.R., Gatchina, 188350, U.S.S.R. |
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Abstract: | We have studied the molecular nature of ade2 mutations induced by UV light and bifunctional acridine-mustard (BAM) in wild-type (RAD) and in excision-deficient (rad2) strains of the yeast, Saccharomyces cerevisiae. In the RAD strain, UV causes 45% GC → AT transitions among all mutations; in the rad2 strain this value is 77%. BAM was shown to be highly specific for frameshift mutagenesis: 60% frameshifts in the RAD strain, and as many as 84% frameshifts in the rad2 strain were induced. Therefore, the rad2 mutation affects the specificity of UV- and BAM-induced mutagenesis in yeast. Experimental data agree with the view that the majority of mutations in the RAD strain are induced by a prereplicative mechanism, whereas mutations in the RAD strain are induced by a prereplicative mechanism, whereas mutations in the rad2 strain are predominantly postreplicative events. Our results also suggest that: (1) cytosine-containing photoproducts are the substances responsible for major premutational damage to DNA; (2) a fraction of the mutations may arise in the course of excision repair of UV photoproducts. |
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