Fig. 4. Actin integrity is not required for G1-phase progression in the ongoing cell cycle of N2A cells. (A) Cyclin D and cyclin E expression levels were monitored by western blotting in lysates of mitotic cells and post-mitotic cells treated for up to 3 hours with either CCD or LB (p42 MAPK=loading control). Each experiment was conducted at least three times with similar results and representative blots are shown. (B) Effect of cytoskeletal disorganization on expression levels of G1/S cyclins in mid- to late G1 phase. Depicted are representative blots out of at least three experiments with identical results (p42 MAPK, loading control). (C) Expression levels of cyclins D, E and A were quantified by densitometry. Values shown are means ±s.e.m. from three independent experiments normalized to expression of p42 MAPK. Statistically significant differences are marked by asterisks (triangles, untreated; open squares, CCD; closed squares, LB). AU, arbitrary units. (D) DNA synthesis was examined in synchronized N2A cells incubated overnight with actin inhibitors and 10 µM BrdU. Values shown represent the average percentages ± s.e.m. obtained from three independent experiments.