Gene regulation by phosphomimetic Myc (MycD), cytosine arabinoside (AraC) and retinoic acid (RA)

We aimed to investigate whether the previously observed synergistic effects of AraC and RA in stimulating leukemia differentiation could be at least partially dependent on Pak2-mediated phosphorylation of Myc. Genome-wide analysis of NB4 cells treated with RA, AraC with RA, or MycD with RA revealed a significant 60% overlap between RA-target genes superactivated by AraC with RA, or MycD with RA, with respect to RA alone. NB4 cells infected with ER-tagged inducible empty vector (CTL), MycD or MycA were treated with 4-OHT (200 nM, 16 h) to induce MycD-ER and MycA-ER expression. CTL cells were either vehicle or AraC (25 μM) treated for 16 h. Short treatment of RA (10 nM, 4 h) was performed in CTL, AraC and MycD-expressing cells. Four biologically independent experiments were performed at each time.