ASSIGNMENT OF THE XRCC2 HUMAN DNA-REPAIR GENE TO CHROMOSOME 7Q36 BY COMPLEMENTATION ANALYSIS

The V79 hamster cell line irs1 is a repair deficient mutant hypersensi tive to radiation and DNA-reactive chemical agents. Somatic cell hybri ds were formed by fusing irs1 cells with human lymphocytes and selecti ng for complementation in medium containing concentrations of mitomyci n C (MMC) that are toxic to irs1. Thirty-eight MMC-resistant hybrids s howed extensive segregation of human chromosomes, with 35 of them reta ining human chromosome 7, as indicated by molecular marker and cytogen etic analyses. Inter-Alu-PCR products from the DNA of hybrids, when us ed as fluorescence in situ hybridization probe onto normal human metap hases, indicated that one resistant hybrid was monochromosomal for chr omosome 7 and that the three resistant hybrids shown to be negative fo r chromosome 7 markers have retained portions of chromosome 7, with re gion 7q36 being the smallest common region, MMC-sensitive subclones of a resistant hybrid lost human chromosome 7. Therefore, the gene compl ementing the repair defect, XRCC2 (X-ray repair cross complementing), is assigned to human chromosome 7q36. (C) 1995 Academic Press, Inc.