Vector-mediated DNA double-strand break repair analysis in normal, and radiation-sensitive, Chinese hamster V79 cells

Abstract DNA double-strand break repair was assessed in 2 new radiation-sensitive V79 hamster cell lines ( irsl and irs2 ) by their ability to rejoin restriction endonuclease cuts in a transferred selectable SV40- E. coli gpt recombinant gene. The studied gene was carried in the vector pPMH16 which also contained a second selectable HSV tk-neo recombinant gene which acted as a control for DNA transformation. The parental V79 cells showed correct rejoining of Kpn I and Eco RV double-strand breaks in ∼ 18% and 36% of transformants respectively (correcting for the expression of undamaged gpt in neo + transformants). irs1 shows a significantly reduced (∼ 3-fold) ability to rejoin correctly such double-strand scissions. However, irs2 rejoined such lesions as correctly as the V79 cells. The data are discussed in the context of the assay and the possible repair deficiencies of these radiosensitive mutant cells.