Figure 3.

Effects of progrowth signals and rapamycin on nucleophosmin mRNA levels. A, WT MEFs were serum starved and subsequently incubated with 10% serum for the durations indicated. Proteins were resolved by SDS-PAGE and antibodies recognizing γ-tubulin and cyclin D1 were used. Total RNA was isolated at the indicated times and nucleophosmin mRNAs were visualized by Northern blot analysis (NB) with murine nucleophosmin probes. Ribosomal 28S and 18S rRNAs were visualized by methylene blue staining as a loading control. B, WT MEFs were infected with retroviruses encoding β-galactosidase (EV) and Ras^V12. Rapamycin (100 nmol/L) was added as indicated 24 h postinfection. All samples were collected 120 h postinfection and analyzed by Northern blot with probes specific for murine nucleophosmin. Ribosomal 28S and 18S rRNAs were detected by methylene blue staining.