FIG. 6.

p27 deficiency leads to impaired inhibition of Cdc2 in irradiated G₂/M cells. (A) FACS analysis demonstrates efficient synchronization of both p27^+/+ and p27^−/− primary MEFs used for panels B and C. (B) Whole-cell lysates were prepared from synchronized primary MEFs irradiated in late S/G₂, harvested at various times following 5 Gy gamma irradiation, and immunoblotted for the indicated proteins. (C) p27^+/+ and p27^−/− immortalized MEFs were synchronized and then irradiated with 5 Gy in late S/G₂ phase of the cell cycle. At the indicated times, cyclin B1 complexes were immunoprecipitated from cell lysates, and kinase activity toward histone H1 was measured. WT, wild type.