FIG. 6.

Deletion of N-terminal sequences stabilizes c-Myc. (A) COS-7 cells were transiently transfected with 2 μg of an expression plasmid encoding wild-type (WT) murine c-Myc or the indicated c-Myc deletion mutant. Forty-eight hours after transfection, the cells were subjected to pulse-chase analysis as described in the legend to Fig. 1A, followed by immunoprecipitation of exogenous c-Myc proteins with anti-av-Myc12C. The arrow indicates a nonspecific background band. The data obtained from densitometric analysis of the experiment shown above were expressed as the relative percentage of the amount of c-Myc protein at the zero time point and plotted as a function of time. (B) COS-7 cells were transiently transfected with 2 μg of an expression plasmid encoding wild-type murine c-MycS or the indicated c-MycS deletion mutant. Pulse-chase analysis, immunoprecipitation of c-MycS, and densitometric plotting were carried out as described for panel A.