The synergistic effect of aphidicolin on the yield of X-ray-induced chromosome aberrations throughout the cell cycle in JU56 cells.

The effect of a 2-h post-treatment with aphidicolin at a dose sufficient to inhibit DNA synthesis on the yield of X-ray-induced chromosomal aberrations throughout the cell cycle was measured. Exposure to aphidicolin during and after irradiation brought about an increase in exchanges in cells irradiated in G2, in sister unions only in cells irradiated in S, and in all chromosome aberration types (fragments, sister unions, and dicentrics) in cells irradiated in G1. It is suggested that, during G1 and G2 but not during S inhibiting the repair enzyme alpha-polymerase brings about the conversion of some X-ray-induced DNA lesions to double-strand which can then take part in aberrations.