| NIMA‑related kinase 6 (NEK6) is a serine/threonine protein kinase of the NIMA family that functions in mitotic cell cycle control, where it is required for progression through metaphase, proper chromosome segregation, robust mitotic spindle formation, and completion of cytokinesis. The kinase has a mostly globular catalytic domain with a short, conformationally flexible N‑terminal extension and lacks large accessory regulatory domains, and it behaves as a monomeric enzyme that depends on upstream activating kinases rather than stable multiprotein complexes for its core activity. Activation of NEK6 occurs downstream of NEK9, which is itself activated by CDK1‑ and PLK1‑dependent phosphorylation and then phosphorylates NEK6 on defined serine residues, establishing a NEK9–NEK6 kinase cascade that operates during G2/M to promote mitotic entry and progression. NEK6 phosphorylates a range of substrates involved in spindle dynamics and chromosome movement, including the kinesin KIF11/EG5 and β‑tubulin, and these phosphorylation events support assembly and maintenance of a bipolar mitotic spindle and efficient chromosome congression. The kinase also targets regulatory and chromatin‑associated proteins such as histones H1 and H3, transcriptional regulators, and factors linked to translational control, integrating its activity with broader control of gene expression and cell cycle–related transcriptional programs. NEK6 participates in the DNA damage response by contributing to G2/M phase arrest after genotoxic stress, and inhibition or loss of NEK6 activity under these conditions is associated with mitotic failure and apoptosis, indicating that NEK6 activity is necessary for the survival of dividing cells under checkpoint control. Expression of NEK6 is elevated in several human cancers, and NEK6 activity associates with suppression of p53‑dependent senescence, linking this kinase to oncogenic pathways that favor continued proliferation and resistance to growth arrest. Across tumor contexts, NEK6 expression correlates with pathways such as PI3K–Akt, cell cycle progression, and actin cytoskeleton regulation, and NEK6‑high tumors show transcriptional signatures consistent with enhanced mitotic activity and altered cell adhesion and migration. |
