Positive regulatory subunit of the cyclin-dependent kinases CDK14/PFTK1 and CDK16. 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. Recruits CDK16 to the plasma membrane. Isoform 3 might play a role in the activation of MYC-mediated transcription. 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 (PubMed:27821587). Interacts with CDK14 (PubMed:19524571, PubMed:20059949). Interacts with CDK16 (PubMed:22184064). Interacts with LRP6 (PubMed:20059949). Widely expressed. Enriched at G2/M. 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.