Data from: Mlh3 mutations in baker's yeast alter meiotic recombination outcomes by increasing noncrossover events genome-wide

Mlh1-Mlh3 is an endonuclease hypothesized to act in meiosis to resolve
double Holliday junctions into crossovers. It also plays a minor role in
eukaryotic DNA mismatch repair (MMR). To understand how Mlh1-Mlh3
functions in both meiosis and MMR, we analyzed in baker's yeast 60
new mlh3 alleles. Five alleles specifically disrupted MMR, whereas one
(mlh3-32) specifically disrupted meiotic crossing over. Mlh1-mlh3
representatives for each class were purified and characterized. Both
Mlh1-mlh3-32 (MMR+, crossover-) and Mlh1-mlh3-45 (MMR-, crossover+)
displayed wild-type endonuclease activities in vitro. Msh2-Msh3, an MSH
complex that acts with Mlh1-Mlh3 in MMR, stimulated the endonuclease
activity of Mlh1-mlh3-32 but not Mlh1-mlh3-45, suggesting that
Mlh1-mlh3-45 is defective in MSH interactions. Whole genome recombination
maps were constructed for wild-type and MMR+ crossover-, MMR- crossover+,
endonuclease defective and null mlh3 mutants in an S288c/YJM789 hybrid
background. Compared to wild-type, all of the mlh3 mutants showed
increases in the number of noncrossover events, consistent with
recombination intermediates being resolved through alternative
recombination pathways. Our observations provide a structure-function map
for Mlh3 that reveals the importance of protein-protein interactions in
regulating Mlh1-Mlh3's enzymatic activity. They also illustrate how
defective meiotic components can alter the fate of meiotic recombination
intermediates, providing new insights for how meiotic recombination
pathways are regulated.