Fig. 3. The role of the RB family in the repression of plk1. MEFs were exposed to adriamycin (ADR, 345 nM) and total RNA was analyzed by northern blot. (A) plk1 mRNA expression in wild-type and p130/p107-null MEFs. To indicate loading, the gel is shown stained with ethidium bromide before transfer. (B) plk1 mRNA expression in cells lacking all three RB-family proteins (triple-knockout, TKO cells). The transfer was stripped and probed for the expression of gapdh to assess loading.