Description
XRCC5 (X-ray Repair, Complementing Defective, In Chinese Hamster, 5), also known as Ku80 or Ku86, is a protein that in humans, is encoded by the XRCC5 gene. The XRCC5 gene encodes the 80-kD subunit of the Ku autoantigen, a heterodimer which contributes to genomic integrity through its ability to bind DNA double-strand breaks and facilitate repair by the nonhomologous end joining(NHEJ) pathway. Human colon cancer cells heterozygous for Ku80 are haploinsufficient with an increase in polyploid cells, a reduction in cell proliferation, elevated p53 levels, and a slight hypersensitivity to ionizing radiation. Functional inactivation of the second Ku80 allele results in cells with a drastically reduced doubling time. The locus is essential in human somatic tissue culture cells by experiments demonstration. A rare microsatellite polymorphism in the protein is associated with cancer in patients of varying radiosensitivity