MLF1 induces G1 arrest in a p53-dependent manner. Growth curves of wild-type (A), p53−/− (B) and p27−/− (C) MEFs infected with retroviruses that expressed GFP alone, GFP-P-MLF1 and GFP-T-MLF1. (D) Cell lysates from MEFs were analyzed by immunoblotting using antibodies against MLF1, p21, p53, p27 and γ-tubulin.