Mitotic recombination in Saccharomyces cerevisiae.

Mitotic homologous recombination (HR) is an important mechanism for the repair of double-strand breakS and errors occurring during DNA replication. It is likely that the recombinational repair of DNA lesions occurs preferentially by sister chromatid exchanges that have no genetic consequences. However, most genetically detectable HR events occur between homologous DNA sequences located at allelic positions in homologous chromosomes, or between DNA repeats located at ectopic positions in either the same, homologous or heterologous chromosomes. Mitotic recombination may occur by multiple mechanisms, including double-strand break repair, synthesis-dependent strand annealing, break-induced replication and single-strand annealing. The occurrence of one recombination mechanism versus another depends on different elements, including the position of the homologous partner, the initiation event, the length of homology of the recombinant molecules and the genotype. The genetics and molecular biology of the yeast Saccharomyces cerevisiae have proved essential for the understanding of mitotic recombination mechanisms in eukaryotes. Here, we review recent genetic yeast data that contribute to our understanding of the different mechanisms of mitotic recombination and the in vivo role of the recombination proteins.