Inhibitory role of DDX3, DEAD box RNA helicase DDX3X, in VRK1 activity

Abstract

VRK1-mediated phosphorylation of some proteins, like as histone H3, BAF and CREB etc. should be dependent on cell cycle. Defects in the regulations induce cellular malfunctions, resulting in cancer or cell death. While the regulator of VRK1 in inter phase and M phase is well known as macroH2A1, the regulator of VRK1 in resting cell or during G0 phase has not been studied so far. Here, we show that the ATP-dependent RNA helicase DDX3X is a suppressor against VRK1 during G0 phase. The localization of DDX3 was changed only G0 phase from cytoplasm to nucleus, and the VRK1-mediated phosphorylation in G0 phase was inhibited by DDX3. We also found direct binding between VRK1 and DDX3, and VRK1 specific inhibition of DDX3. Thus, our findings showed that DDX3 is a novel suppressor against VRK1 during G0 phase.