Use of a chromosomal inverted repeat to demonstrate that the RAD51 and RAD52 genes of Saccharomyces cerevisiae have different roles in mitotic recombination.
An intrachromosomal recombination assay that monitors events between alleles of the ade2 gene oriented as inverted repeats was developed. Recombination to adenine prototrophy occurred at a rate of 9.3 x 10(-5)/cell/generation. Of the total recombinants, 50% occurred by gene conversion without crossing over, 35% by crossover and 15% by crossover associated with conversion. The rate of recombination was reduced 3,000-fold in a rad52 mutant, but the distribution of residual recombination events remained similar to that seen in the wild type strain. In rad51 mutants the rate of recombination was reduced only 4-fold. In this case, gene conversion events unassociated with a crossover were reduced 18-fold, whereas crossover events were reduced only 2.5-fold. A rad51 rad52 double mutant strain showed the same reduction in the rate of recombination as the rad52 mutant, but the distribution of events resembled that seen in rad51. From these observations it is concluded that (i) RAD52 is required for high levels of both gene conversions and reciprocal crossovers, (ii) that RAD51 is not required for intrachromosomal crossovers, and (iii) that RAD51 and RAD52 have different functions, or that RAD52 has functions in addition to those of the Rad51/Rad52 protein complex.
Department of Microbiology, Columbia University College of Physicians and Surgeons, New York, New York 10032.
A J
AJ
Rattray
L S
LS
Symington
D015825:Chromosomes, Fungal; D003434:Crossing Over, Genetic; D004271:DNA, Fungal; D004268:DNA-Binding Proteins / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics*; D005785:Gene Conversion; D008938:Mitosis / Q000235:genetics*; D051135:Rad51 Recombinase; D051721:Rad52 DNA Repair and Recombination Protein; D011995:Recombination, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C497197:RAD52 protein, S cerevisiae; D051721:Rad52 DNA Repair and Recombination Protein; D029701:Saccharomyces cerevisiae Proteins; C495151:RAD51 protein, S cerevisiae; D051135:Rad51 Recombinase