Human chromosome 13 compensates a DNA repair defect in UV-sensitive mouse cells by mouse--human cell hybridization.

A human chromosome responsible for excision repair of UV-induced DNA damage has been identified by studying somatic cell hybrids between an UV-sensitive mutant of mouse lymphoma L5178Y cells and normal human lymphocytes. An autosomal recessive mutant, Q31, of complementation group I is deficient in excision repair of UV-induced DNA damage. Somatic cell hybrids between Q31 and human lymphocytes exhibited the same UV resistance as did parental L5178Y cells. In addition, both the levels of UV-induced unscheduled DNA synthesis and chromosomal sensitivity were recovered from the UV-resistant hybrid clones. Segregation of the hybrid cells gave rise to UV-sensitive clones. The segregation of UV sensitivity was not correlated with the loss of human X chromosome. Karyotype analysis of the segregants gave evidence that a gene on human chromosome 13 compensates for UV hypersensitivity of Q31 mutant.