Recombination initiated by double-strand breaks

摘要

TheHOendonuclease was used to introduce a site-specific double-strand break (DSB) in an interval designed to monitor mitotic recombination. The interval included thetrp1andhis3genes inserted into chromosome III ofS. cerevisiaebetween theCRY1andMATloci. Mitotic recombination was monitored in a diploid carrying heteroalleles oftrp1andhis3. The normal recognition sites for theHOendonuclease were mutated at theMATalleles and a synthetic recognition site forHOendonuclease was placed betweentrp1andhis3on one of the chromosomes.HO-induced cleavage resulted in efficient recombination in this interval. Most of the data can be explained by double-strand gap repair in which the cut chromosome acts as the recipient. However, analysis of some of the recombinants indicates that regions of heteroduplex were generated flanking the site of the cut, and that some recombinants were the result of the cut chromosome acting as the genetic donor.