Complementation of DNA repair defect in xeroderma pigmentosum cells of group C by the transfer of human chromosome 5

Complementation of DNA excision repair defect in xeroderma pigmentosum cells of group C (XP-C) has been achieved by the transfer of human chromosome 5. Individual human chromosomes tagged with a selectable marker were transferred to XP-C cells by microcell fusion from mouse-human hybrid cell lines each bearing a single different human chromosome. Analysis of the chromosome transfer clones revealed that introduction of chromosome 5 into XP-C cells corrected the DNA repair defect as well as UV-sensitive phenotypes, while chromosomes 2, 6, 7, 9, 13, 15, 17, and 21 failed to complement. The introduced chromosome 5 in complemented UVr clones was distinguished from the parental XP-C chromosomes by polymorphism for dinucleotide (CA)n repeats at two loci, D5S117 and D5S209. In addition, an intact marked chromosome 5 was rescued into mouse cells from a complemented UVr clone by microcell fusion. Five subclones of a complemented clone that had lost the marked chromosome 5 exhibited UV-sensitive and repair-deficient phenotypes identical to parental XP-C cells. Concordant loss of the transferred chromosome and reappearance of XP-C phenotype further confirmed the presence of a DNA repair gene on human chromosome 5.