Journal of Microbiology

Journal Article

Effects of the loss of mismatch repair genes on single-strand annealing between divergent sequences in Saccharomyces cerevisiae: Ye-Seul Lim , Ju-Hee Choi , Kyu-Jin Ahn , Min-Ku Kim , Sung-Ho Bae; J. Microbiol. 2021;59(4):401-409. Published online March 29, 2021; DOI: https://doi.org/10.1007/s12275-021-1076-x

Abstract: Eukaryotic genomes contain many duplicated genes closely located with each other, such as the hexose transporter (HXT) genes in Saccharomyces cerevisiae. They can potentially recombine via single-strand annealing (SSA) pathway. SSA between highly divergent sequences generates heteroduplex DNA intermediates with many mismatches, which can be corrected by mismatch repair (MMR), resulting in recombinant sequences with a single junction point. In this report, we demonstrate that SSA between HXT1 and HXT4 genes in MMR-deficient yeast cells produces recombinant genes with multiple-junctions resulting from alternating HXT1 and HXT4 tracts. The mutations in MMR genes had differential effects on SSA frequencies; msh6Δ mutation significantly stimulated SSA events, whereas msh2Δ and msh3Δ slightly suppressed it. We set up an assay that can identify a pair of recombinant genes derived from a single heteroduplex DNA. As a result, the recombinant genes with multiple-junctions were found to accompany genes with single-junctions. Based on the results presented here, a model was proposed to generate multiple-junctions in SSA pathway involving an alternative short-patch repair system.

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