Noncanonical Contributions of MutLγ to VDE-Initiated Crossovers During Meiosis.

In Saccharomyces cerevisiae, the meiosis-specific axis proteins and are present nonuniformly across the genome. In a previous study, the meiosis-specific -derived endonuclease () was used to examine -independent recombination in a recombination reporter inserted in a /-enriched region () and in a /-poor region (). -initiated crossovers at HIS4 were mostly dependent on , a component of the MutL gamma meiotic recombination intermediate resolvase, while -initiated crossovers at were mostly -independent. These differences were abolished in the absence of the chromosome axis remodeler , and crossovers at both loci became partly -dependent. To test the generality of these observations, we examined inserts at six additional loci that differed in terms of / enrichment, chromosome size, and distance from centromeres and telomeres. All six loci behaved similarly to : the vast majority of -initiated crossovers were -independent. This indicates that, counter to previous suggestions, levels of meiotic chromosome axis protein enrichment alone do not determine which recombination pathway gives rise to crossovers during -initiated meiotic recombination. In increment mutants, the fraction of -induced crossovers that were -dependent increased to levels previously observed for -initiated crossovers in increment , indicating that -dependent processes play an important role in controlling the balance between MutL gamma-dependent and MutL gamma-independent crossovers.