Essential for the regulation of ciliary length and required for the long-term survival of photoreceptors (By similarity). Could play an important function in spermatogenesis. Phosphorylates FZR1 in a cell cycle-dependent manner (By similarity). Plays a role in the transcriptional coactivation of AR (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with RP1. Interacts with AR and CDK20. Found in a complex containing MAK, AR and NCOA3. Interacts with FZR1 (via WD repeats) (By similarity). Localized in both the connecting cilia and the outer segment axonemes. Expressed mainly in testicular cells at and after meiosis. Expression in testis is detected 16 days after birth and increases gradually to reach a plateau about 4 weeks after birth (at protein level). Autophosphorylated (By similarity). Phosphorylated on serine and threonine residues. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.