SUBCHROMOSOMAL LOCALIZATION OF A GENE (XRCC5) INVOLVED IN DOUBLE-STRAND BREAK REPAIR TO THE REGION 2Q34-36

We have previously shown that human chromosome 2 can complement both t he radiation sensitivity and the defect in double strand break rejoini ng characteristic of ionizing radiation (IR) group 5 mutants. A number of human-hamster hybrids containing segments of human chromosome 2 we re obtained by microcell transfer. into two group 5 mutants. In most, but not all, of these hybrids, the repair defect was complemented by t he human chromosomal DNA. Two complementing microcell hybrids were irr adiated and fused to XR-V15B, an IR group 5 mutant, to generate furthe r hybrids bearing smaller regions of chromosome 2. All hybrids were ex amined for complementation of the repair defect. The region of chromos ome 2 present was determined using PCR with primers specific for vario us human genes located on chromosome 2. A complementing hybrid bearing only a small region of chromosome 2 was finally generated. From this analysis we deduced that the XRCC5 gene was tightly linked to the mark er, TNP1, which is located in the region 2q35.