Mutagenic specificity of the base analog 6-N-hydroxylaminopurine in the LYS2 gene of yeast Saccharomyces cerevisiae

We used the LYS2 gene mutational system to study mutation specificity of th e base analog 6-N-hydroxylaminopurine (HAP) in yeast. We characterized phen otypes of mutations using codon-specific nonsense suppressors and the test employing inactivation of the release factor Sup35 due to overexpression an d formation of prion-like derivative [PSI]. We have shown that HAP induces predominantly nonsense mutations. While the tests using codon-specific nons ense-suppressors allowed to identify only about 50% of nonsense-mutations, all the nonsense-mutations were identified in the test with defective Sup35 . We determined and analyzed the spectrum of MAP-induced nucleotide changes in two regions of the gene. HAP induces predominantly GC --> AT transition s in a hotspots of a central position of trinucleotide GGA or AGG. Directio nality of these transitions is consistent with the idea that initial dHAPMP incorporation in the leading strand is more genetically dangerous than in lagging DNA strand. We revealed a specific context inhibitory for HAP mutag enesis, a "T" in -1 position to mutation site. (C) 2001 Elsevier Science B. V. All rights reserved.