Plays a role in the cellular response to UV irradiation. Mediates G2/M cell cycle arrest, MEK autoactivation and ERK1/2-signaling pathway activation in response to UV irradiation. In ciliated cells, it is involved in the regulation of mucociliary transport. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with RAF1 and MAP2K1; the interaction is direct with RAF1 and required for ERK1/2-signaling pathway activation in response to UV irradiation. Expressed in the mammary gland, lung, spleen, and kidney. Belongs to the protein kinase superfamily. NEK Ser/Thr protein kinase family. NIMA subfamily.