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