Genome-wide
screen for genes controlling sensitivity to mutagenic base analogs in yeast.
Elena Stepchenkova (1), Vladimir Alenin (1), Youri Pavlov (2)
(1) Department of Genetics, St-Petersburg State University, Universitetskaja
7/9, St-Petersburg, 199034, Russia (stepchenkova@yahoo.com); (2) Laboratory of
Molecular Genetics, NIEHS, NIH, P.O. Box 12233, Research Triangle Park NC,
27709, USA
The purine base analogs 6-hydroxylaminopurine (HAP) and 2-amino-6-hydroxylaminopurine (AHA) are mutagenic in a variety of organisms. It is proposed that the bases are converted to corresponding nucleoside triphosphates, incorporated into DNA and provoke replication errors in the subsequent replication. We have shown earlier that a defect in the Ham1 triphosphatase specific for modified purine nucleotides leads to HAP-hypersensitivity. Defects in the earlier steps of purine salvage either increase HAP and AHA mutagenicity (adenine aminohydrolase encoded by the AAH1 gene) or decrease it (adenine phosphoribosyl transferase encoded by the APT1 gene). To identify new genes that control base analogs effects in yeast, we carried out a genome-wide screen for HAP and AHA sensitivity using a set of 4803 haploid strains with deletions of all nonessential ORFs. We have found 20 mutants that fall into several groups. One large group includes mutants that are hypermutable and exhibit poor growth on medium with either HAP or AHA (ham1 and aah1 mutants). Another class includes hypermutable strains that grow normally on media with the analogs (mutants with defects in de novo purine synthesis). Other groups consist of strains that display growth defects on either HAP or AHA but are not hypermutable. Results reveal complex control of base analog mutagenesis by genes encoding components of metabolic pathways, or cytoskeleton, or by other genes whose function has yet to be determined.