Technical note: comparison of yields and repair kinetics of interphase chromosome breaks visualized by Sendai-virus or PEG-mediated cell fusion in irradiated CHO cells.

Abstract

We examined the initial yields and the kinetics of rejoining of interphase chromosome breaks in irradiated plateau-phase Chinese hamster ovary cells by means of premature chromosome condensation (PCC) using either Sendai virus or polyethylene glycol (PEG) as fusogens. We found a yield of 2.2 chromosome breaks/cell/Gy independently of the method used to induce PCC. Rejoining of interphase chromosome breaks also proceeded with identical kinetics in cells fused using either Sendai virus or PEG. In an additional set of experiments, we compared the kinetics of rejoining of interphase chromosome breaks in cells synchronized in G1 phase by elutriation to that measured in plateau-phase cells, using either Sendai virus or PEG as fusogens. Here again, the rejoining kinetics were not affected by the fusogen used, and were similar in synchronized G1 and plateau-phase cells. These observations suggest that both methods of fusion give equivalent results in terms of yields and rejoining kinetics of interphase chromosome breaks. They also suggest that differences in the fusogens or the metabolic state of the cells cannot explain differences in the yields, and probably also the kinetics of the rejoining of interphase chromosome breaks that have been reported elsewhere. Cell line characteristics and other as of yet unidentified technical parameters may underlie these differences.