Cdk phosphorylation of RUNX1 increases stimulation of proliferation. (A) Ba/F3 cells expressing CBFβ-SMMHC (INV) were transduced with empty pBabePuro (Puro) or pBabePuro encoding RUNX1-ER (WT) or its tripleA or tripleD mutants. Total cell extracts were subjected to Western blotting using ER antiserum (top panel) or CBFβ antiserum (bottom panel) to detect INV. (B) Ba/F3 cells expressing INV and RUNX1-ER were cultured in the absence (−) or presence (+) or 4HT for 24 hours. Total cell extracts were then subjected to Western blotting with anti-S48, anti-S303, or anti-S424 phospho-specific antisera. (C) The 4 indicated Ba/F3 cells lines were seeded at 5 × 103 cells/mL and cultured with 4HT and with or without zinc chloride for 4 days. Viable cell counts were then enumerated, and the ratios (+Zn)/(−Zn) are shown (mean and SE from 3 determinations). P value is from paired Student t test.
