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Two different types of double-strand breaks in Saccharomyces cerevisiae are repaired by similar RAD52-independent, nonhomologous recombination events

Journal Article · · Molecular and Cellular Biology
; ;  [1]
  1. Brandeis Univ., Waltham, MA (United States); and others
In haploid rad52 Saccharomyces cerevisiae strains unable to undergo homologous recombination, a chromosomal double-strand break (DSB) can be repaired by imprecise rejoining of the broken chromosome ends. We have used two different strategies to generate broken chromosomes: (i) a site-specific DSB generated at the MAT locus by HO endonuclease cutting or (ii) a random DSB generated by mechanical rupture during mitotic segregation of a conditionally dicentric chromosome. Broken chromosomes were repaired by deletions that were highly variable in size, all of which removed more sequences than was required either to prevent subsequent HO cleavage or to eliminate a functional centromere, respectively. The junction of the deletions frequently occurred where complementary strands from the flanking DNA could anneal to form 1 to 5 bp, although 12% (4 of 34) of the events appear to have occurred by blunt-end ligation. These types of deletions are very similar to the junctions observed in the repair of DSBs by mammalian cells. When a high level of HO endonuclease, expressed in all phases of the cell cycle, was used to create DSBs, we also recovered a large class of very small (2- or 3-bp) insertions in the HO cleavage site. These insertions appear to represent still another mechanism of DSB repair, apparently by annealing and filling in the overhanging 3{prime} ends of the cleavage site. These types of events have also been well documented for vertebrate cells. 69 refs., 7 figs.
Sponsoring Organization:
USDOE
OSTI ID:
577138
Journal Information:
Molecular and Cellular Biology, Journal Name: Molecular and Cellular Biology Journal Issue: 2 Vol. 14; ISSN 0270-7306; ISSN MCEBD4
Country of Publication:
United States
Language:
English