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Originally published as Genetics Published Articles Ahead of Print on June 18, 2008.

Genetics, Vol. 179, 1251-1262, July 2008, Copyright © 2008
doi:10.1534/genetics.108.090233

Sequence Divergence Impedes Crossover More Than Noncrossover Events During Mitotic Gap Repair in Yeast

Caroline Welz-Voegele and Sue Jinks-Robertson1

Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710

1 Corresponding author: Department of Molecular Genetics and Microbiology, Duke University Medical Center 3020, 228 Jones Bldg., Research Dr., Durham, NC 27710.
E-mail: sue.robertson{at}duke.edu

Homologous recombination between dispersed repeated sequences is important in shaping eukaryotic genome structure, and such ectopic interactions are affected by repeat size and sequence identity. A transformation-based, gap-repair assay was used to examine the effect of 2% sequence divergence on the efficiency of mitotic double-strand break repair templated by chromosomal sequences in yeast. Because the repaired plasmid could either remain autonomous or integrate into the genome, the effect of sequence divergence on the crossover–noncrossover (CO–NCO) outcome was also examined. Finally, proteins important for regulating the CO–NCO outcome and for enforcing identity requirements during recombination were examined by transforming appropriate mutant strains. Results demonstrate that the basic CO–NCO outcome is regulated by the Rad1-Rad10 endonuclease and the Sgs1 and Srs2 helicases, that sequence divergence impedes CO to a much greater extent than NCO events, that an intact mismatch repair system is required for the discriminating identical and nonidentical repair templates, and that the Sgs1 and Srs2 helicases play additional, antirecombination roles when the interacting sequences are not identical.


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Genetics 2008 179: NP. [Full Text]