KU80 - PRODUCT OF THE XRCC5 GENE AND ITS ROLE IN DNA-REPAIR AND V(D)JRECOMBINATION

The radiosensitive mutant xrs-6, derived from Chinese hamster ovary ce lls, is defective in DNA double-strand break repair and in ability to undergo V(D)J recombination. The human XRCC5 DNA repair gene, which co mplements this mutant, is shown here through genetic and biochemical e vidence to be the 80-kilodalton subunit of the Ku protein. Ku binds to free double-stranded DNA ends and is the DNA-binding component of the DNA-dependent protein kinase. Thus, the Ku protein is involved in DNA repair and in V(D)J recombination, and these results may also indicat e a role for the Ku-DNA-dependent protein kinase complex in those same processes.