VRK1

VRK1 is a nuclear Ser/Thr chromatin kinase that phosphorylates p53, histones, and DNA-damage-response proteins, linking cell proliferation with chromatin stability^[1][2][3]. Mechanistically, VRK1 supports cell-cycle entry, G2/M chromatin condensation, and non-homologous end joining through γH2AX, NBS1, and 53BP1 foci formation after ionizing radiation or chemotherapy^[1][2]. In p53 signaling, VRK1 phosphorylates p53 at Thr18, stabilizes transcriptionally active p53, and participates in a regulatory loop that modulates DNA-damage responses^[3]. In disease models, VRK1 overexpression associates with tumor progression and resistance to genotoxic treatments, and VRK1 loss reduces 53BP1 repair foci after ionizing radiation or doxorubicin in breast cancer cells^[1][4]. Compared with related isoforms, VRK1 is mostly nuclear, whereas VRK2A anchors to endoplasmic-reticulum and mitochondrial membranes and VRK2B distributes in cytosol and nucleus, suggesting localization-dependent substrate access^[5]. For experimental applications, kinase-inhibitor profiling shows VRK1 and VRK2 have different sensitivity patterns, providing a framework for designing VRK1-selective inhibitors with reduced VRK2 cross-inhibition^[6].