Meiotic recombination in Saccharomyces cerevisiae is initiated by double- strand breaks (DSBs). We have developed a system to compare the properties of meiotic DSBs with those created by the site-specific HO endonuclease. HO endonuclease was expressed under the control of the meiotic-specific SPO13 promoter, creating a DSB at a single site on one of yeast's 16 chromosomes. In Rad+ strains the times of appearance of the HO-induced DSBs and of subsequent recombinants are coincident with those induced by normal meiotic DSBs. Physical monitoring of DNA showed that SPO13: : HO induced gene conversions both in Rad+ and in rad50 delta cells that cannot initiate normal meiotic DSBs. We find that the RAD50 gene is important, but not essential, for recombination even after a DSB has been created in a meiotic cell. In rad50 delta cells, some DSBs are not repaired until a broken chromosome has been packaged into a spore and is subsequently germinated. This suggests that a broken chromosome does not signal an arrest of progression through meiosis. The recombination defect in rad50 delta diploids is not, however, meiotic specific, as mitotic rad50 diploids, experiencing an HO-induced DSB, exhibit similar departures from wild-type recombination.

• PMID: 8725223
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Journal Article | Research Support, Non-U.S. Gov't | Research Support, U.S. Gov't, Non-P.H.S. | Research Support, U.S. Gov't, P.H.S.

Authors

Malkova A, Ross L, Dawson D, Hoekstra MF, Haber JE

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