Positive regulatory subunit of the cyclin-dependent kinase CDK14/PFTK1. Acts as a cell-cycle regulator of Wnt signaling pathway during G2/M phase by recruiting CDK14/PFTK1 to the plasma membrane and promoting phosphorylation of LRP6, leading to the activation of the Wnt signaling pathway (By similarity). Recruits CDK16 to the plasma membrane (By similarity). Positive regulatory subunit of the cyclin-dependent kinase CDK16. Found in a complex with CAPRIN2, LRP6 AND CDK14 during G2/M stage; CAPRIN2 functions as a scaffold for the complex by binding to CCNY via its N terminus and to CDK14 via its C terminus (By similarity). Interacts with CDK14 (By similarity). Interacts with CDK16 (PubMed:22184064). Interacts with LRP6 (By similarity). Detected in brain, heart, lung, skeletal muscle, ovary, thymus and testis (at protein level). Ubiquitinated; leading to its degradation. Heavily phosphorylated. Phosphorylation at Ser-71 and Ser-73 by CDK14 is enhanced during the G2 and M cell cycle phases, and creates a phosphodegron triggering SCF-dependent ubiquitination. Belongs to the cyclin family. Cyclin Y subfamily.