Essential for the regulation of ciliary length and required for the long-term survival of photoreceptors (By similarity). Phosphorylates FZR1 in a cell cycle-dependent manner. Plays a role in the transcriptional coactivation of AR. Could play an important function in spermatogenesis. May play a role in chromosomal stability in prostate cancer cells. 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 (By similarity). Interacts with AR and CDK20. Found in a complex containing MAK, AR and NCOA3. Interacts with FZR1 (via WD repeats). Localized in both the connecting cilia and the outer segment axonemes (By similarity). Localized uniformly in nuclei during interphase, to the mitotic spindle and centrosomes during metaphase and anaphase, and also to midbody at anaphase until telophase. Expressed in prostate cancer cell lines at generally higher levels than in normal prostate epithelial cell lines. Isoform 1 is expressed in kidney, testis, lung, trachea, and retina. Isoform 2 is retina-specific where it is expressed in rod and cone photoreceptors. Up-regulated by dihydrotestosterone (DHT) in androgen-sensitive LNCaP prostate cancer cells in a dose-dependent manner. Up-regulation by DHT is transient, reaching maximum levels after 24 hours and decreases slightly after 48 hours. Autophosphorylated. Phosphorylated on serine and threonine residues. The disease is caused by variants affecting the gene represented in this entry. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.