Plays a role in the regulation of the cell cycle by phosphorylating the nuclear envelope protein barrier-to-autointegration factor/BAF that is required for disassembly and reassembly, respectively, of the nuclear envelope during mitosis (PubMed:25899223). Under normal physiological conditions, negatively regulates ERK activity along with VHR/DUSP3 phosphatase in the nucleus, causing timely and transient action of ERK. Stress conditions activate CDK5 which phosphorylates VRK3 to increase VHR phosphatase activity and suppress prolonged ERK activation that causes cell death (PubMed:27346674). For example, upon glutamate induction, promotes nuclear localization of HSP70/HSPA1A to inhibit ERK activation via VHR/DUSP3 phosphatase (PubMed:27941812). {ECO:0000250|UniProtKB:Q8K3G5, ECO:0000269|PubMed:14645249, ECO:0000269|PubMed:19141289, ECO:0000269|PubMed:25899223, ECO:0000269|PubMed:27346674, ECO:0000269|PubMed:27941812}. This is the function of ENSG00000105053 (VRK3, VRK serine/threonine kinase 3).