Effect of the Major Repeat Sequence on Mitotic Recombination in Candida albicans

The major repeat sequence (MRS) is known to play a role in karyotypic variation in Candida albicans. The MRS affects karyotypic variation by expanding and contracting internal repeats, by altering the frequency of chromosome loss, and by serving as a hotspot for chromosome translocation. We proposed that the effects of the MRS on translocation could be better understood by examination of the effect of the MRS on a similar event, mitotic recombination between two chromosome homologs. We examined the frequency of mitotic recombination across an MRS of average size (approximately 50 kb) as well as the rate of recombination in a 325-kb stretch of DNA adjacent to the MRS. Our results indicate that mitotic recombination frequencies across the MRS were not enhanced compared to the frequencies measured across the 325-kb region adjacent to the MRS. Mitotic recombination events were found to occur throughout the 325-kb region analyzed as well as within the MRS itself. This analysis of mitotic recombination frequencies across a large portion of chromosome 5 is the first large-scale analysis of mitotic recombination done in C. albicans and indicates that mitotic recombination frequencies are similar to the rates found in Saccharomyces cerevisiae.