The RAD27 gene of Saccharomyces cerevisiae encodes a 5'-3' flap exo/endonuclease, which plays role in Okazaki fragment maturation during DNA replication.
rad27 Delta mutants are viable in yeast, although temperature sensitive. They also exhibit increased sensitivity to alkylating agents, enhanced spontaneous recombination, and repetitive DNA instability. Biochemical and genetical analyses indicate that Okazaki fragment processing can be assured by other enzymatic activities or by alternative pathways such as homologous recombination. It has been demonstrated, making use of a synthetic lethality assay, that all the genes of the recombinational repair pathway are required for the survival of
rad27 Delta strains. Recombination as well as other pathways can therefore bypass the replication defects that arise in the absence of the Rad27 protein.