Cell cycle responses of two X-ray sensitive mutants defective in DNA repair.

Both the xrs and V-3 lines of Chinese hamster ovary cells exhibit marked sensitivity to ionizing radiation. They are also sensitive to agents such as bleomycin and H2O2 but exhibit normal responses to ultraviolet light and mitomycin C. Both cell lines are defective in split-dose repair and repair of double-strand breaks in DNA. Analysis of response to radiation as a function of age in the cell cycle indicates that both cell lines exhibit a marked sensitivity in late G1 and early S phase with more limited sensitization throughout the remainder of the cell cycle.