A unique pathway of double-strand break repair operates in tandemly repeated genes.
The RAD52 gene product of the yeast Saccharomyces cerevisiae is required for most spontaneous recombination and almost all double-strand break (DSB) repair. In contrast to recombination elsewhere in the genome, recombination in the ribosomal DNA (rDNA) array is RAD52 independent. To determine the fate of a DSB in the rDNA gene array, a cut site for the HO endonuclease was inserted into the rDNA in a strain containing an inducible HO gene. DSBs were efficiently repaired at this site, even in the absence of the RAD52 gene product. Efficient RAD52-independent DSB repair was also observed at another tandem gene array, CUP1, consisting of 18 repeat units. However, in a smaller CUP1 array, consisting of only three units, most DSBs (ca. 80%) were not repaired and resulted in cell death. All RAD52-independent DSB repair events examined resulted in the loss of one or more repeat units. We propose a model for DSB repair in repeated sequences involving the generation of single-stranded tails followed by reannealing.
Ozenberger
B A
BA
Department of Biology, Yale University, New Haven, CT 06511-8112.
Roeder
G S
GS
D015139:Blotting, Southern; D003001:Cloning, Molecular; D004260:DNA Repair; D004275:DNA, Ribosomal / Q000235:genetics; D005785:Gene Conversion; D005800:Genes, Fungal; D011995:Recombination, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000235:genetics*
D004275:DNA, Ribosomal