Figure 9.

Induction of p21 but not MyoD after activation of transfected Akt. (A) Akt does not induce MyoD. Pictured are representative fluorescence micrographs of C2AS12 cells transiently transfected with hydroxytamoxifen-inducible HA-tagged Akt (iAkt), as described in Materials and Methods. After a 24-h incubation with DM in the absence or presence of hydroxytamoxifen, cells were fixed and immunostained using antibodies to the HA tag (top) and MyoD (bottom). The graph shows that the fraction of transfected cells expressing MyoD was not significantly different in cells incubated without or with HT (mean ± SEM of three experiments, counting 100 cells per experiment). (B) Akt induces p21. Illustrated are representative fluorescence micrographs of C2AS12 cells transiently transfected with iAkt, as described in Materials and Methods. After a 24-h incubation in DM without or with HT, the cells were immunostained using antibodies to the HA tag (top) and to p21 (bottom). The graph shows that the percentage of transfected cells expressing p21 was significantly greater after incubation with HT (mean ± SEM of three experiments, counting 100 cells per experiment, *P < 0.01).