VRK1

Abstract

VRK1 is a nuclear chromatin Ser-Thr kinase functionally associated with different processes that require chromatin remodeling. The VRK1 activity is regulated by entry in cell cycle, and this kinase is also required for nuclear envelope dynamics, chromatin condensation, and Golgi fragmentation. Among its substrates, there are several transcription factors: p53, c-Jun, ATF2, CREB1, and SOX2. VRK1 probably acts cooperating with other signaling pathways that also phosphorylate these transcription factors. VRK1 stabilizes p53 by a specific phosphorylation in Thr18 and after induction of p53 responses, there is a VRK1 downregulation in the lysosome, in which the autophagic pathway participates in a p53-dependent manner. VRK1 also contributes to chromatin condensation, nuclear envelop kinetics by phosphorylation of histone H3 and BAF, and the regulation of Cajal bodies by phosphorylation of coilin. In DNA-damage responses, VRK1 actively participates in chromatin remodeling and regulates H2AX, NBS1, and 53BP1. VRK1 is downstream of MEK1 and Plk3 in the induction of Golgi fragmentation during mitosis. Furthermore, VRK1 is expressed in most tissues, is necessary in the early G1 phase for entry in cell cycle, and is associated with proliferation markers.