Serine/threonine kinase involved in the regulation of key cellular processes including the cell cycle, nuclear condensation, transcription regulation, and DNA damage response (PubMed:14645249, PubMed:18617507, PubMed:19103756, PubMed:33076429). Controls chromatin organization and remodeling by mediating phosphorylation of histone H3 on 'Thr-4' and histone H2AX (H2aXT4ph) (PubMed:31527692, PubMed:37179361). It also phosphorylates KAT5 in response to DNA damage, promoting KAT5 association with chromatin and histone acetyltransferase activity (PubMed:33076429). Is involved in the regulation of cell cycle progression of neural progenitors, and is required for proper cortical neuronal migration (By similarity). Is involved in neurite elongation and branching in motor neurons, and has an essential role in Cajal bodies assembly, acting through COIL phosphorylation and the control of coilin degradation (PubMed:21920476, PubMed:31090908, PubMed:31527692). Involved in Golgi disassembly during the cell cycle: following phosphorylation by PLK3 during mitosis, it is required to induce Golgi fragmentation (PubMed:19103756). Phosphorylates BANF1: disrupts its ability to bind DNA, reduces its binding to LEM domain-containing proteins and causes its relocalization from the nucleus to the cytoplasm (PubMed:16495336). Phosphorylates TP53BP1 and p53/TP53 on 'Thr-18', preventing the interaction between p53/TP53 and MDM2 (PubMed:10951572, PubMed:31527692). Phosphorylates ATF2 which activates its transcriptional activity (PubMed:15105425). Phosphorylates JUN (PubMed:31527692). {ECO:0000250|UniProtKB:Q80X41, ECO:0000269|PubMed:10951572, ECO:0000269|PubMed:14645249, ECO:0000269|PubMed:15105425, ECO:0000269|PubMed:16495336, ECO:0000269|PubMed:18617507, ECO:0000269|PubMed:19103756, ECO:0000269|PubMed:21920476, ECO:0000269|PubMed:31090908, ECO:0000269|PubMed:31527692, ECO:0000269|PubMed:33076429, ECO:0000269|PubMed:37179361}. This is the function of Ensembl gene identifier ENSG00000100749 (VRK1, VRK serine/threonine kinase 1).