Cyclin B1 accumulates in a cell-cycle independent manner following γ-irradiation.

(A) Flow cytometry histograms of human Ramos cells 4 hours following treatment with 200 cGy radiation. (B) Effect of γ-radiation on cyclin B1 protein levels at different phases of the cell cycle. Ramos cells were irradiated and 4 hours later separated into G1, S, and G2 cell-cycle fractions by centrifugal elutriation. Total protein lysates of each fraction were probed with cyclin B1 antibodies (5 μg total protein per lane). Untreated cells were mock irradiated and maintained under identical culture conditions to the irradiated Ramos cells. (C) Cell cycle histograms from control and γ-irradiated cell fractions.