Involvement of the essential yeast DNA polymerases in induced gene conversion

In the yeast Saccharomyces cerevisiae three different DNA polymerases α, δ and ε are involved in DNA replication. DNA polymerase α is responsible for initiation of DNA synthesis and polymerases δ and ε are required for elongation of DNA strand during replication. DNA polymerases δ and ε are also involved in DNA repair. In this work we studied the role of these three DNA polymerases in the process of recombinational synthesis. Using thermo-sensitive heteroallelic mutants in genes encoding DNA polymerases we studied their role in the process of induced gene conversion. Mutant strains were treated with mutagens, incubated under permissive or restrictive conditions and the numbers of convertants obtained were compared. A very high difference in the number of convertants between restrictive and permissive conditions was observed for polymerases α and δ, which suggests that these two polymerases play an important role in DNA synthesis during mitotic gene conversion. Marginal dependence of gene conversion on the activity of polymerase ε indicates that this DNA polymerase may be involved in this process but rather as an auxiliary enzyme.