The Saccharomyces cerevisiae DNA damage checkpoint is required for efficient repair of double strand breaks by non‐homologous end joining

In this work we report that the Saccharomyces cerevisiae RAD9, RAD24, RAD17, MEC1, MEC3 and RAD53 checkpoint genes are required for efficient non-homologous end joining (NHEJ). RAD9 and RAD24 function additionally in this process. Defective NHEJ in rad9Delta-rad24Delta, but not yku80Delta cells, is only partially rescued by imposing G1 or G2/M delays. Thus, checkpoint functions other than transient cell cycle delays may be required for normal levels of NHEJ. Epistasis analysis also indicated that YKU80 and RAD9/RAD24 function in the same pathway for repair of lesions caused by MMS and gamma-irradiation. Unlike NHEJ, the checkpoint pathway is not required for efficient site-specific integration of plasmid DNA into the yeast genome, which is RAD52-dependent, but RAD51-independent.