Role of the error-free damage bypass postreplication repair pathway in the maintenance of genomic stability.

The postreplication repair pathway (PRR) is composed of error-free and error-prone sub-pathways that allow bypass of DNA damage-induced replication-blocking lesions. The error-free sub-pathway is also used for bypass of spontaneous DNA damage and functions in cooperation with recombination pathways. In diploid yeast cells, error-free PRR is needed to prevent genomic instability, which is manifest as loss of heterozygosity (LOH) events of increased chromosome loss and recombination. Homologous recombination acts synergistically with the error-free damage avoidance branch of PRR to prevent chromosome loss. The DNA damage checkpoint gene MEC1 acts synergistically with the PRR pathway in maintaining genomic stability. Integration of the PRR pathway with other cellular pathways for preventing genomic instability is discussed. In diploid strains, the most dramatic increase is in the abnormality of chromosome loss when a repair or damage detection pathway is defective.