May negatively regulate cell cycle progression. May act at least in part via inhibition of the cyclin-D1/CDK4 complex, thereby preventing phosphorylation of RB1 and blocking E2F-dependent transcription (By similarity). Interacts with CCND1 and GRAP2. May also interact with COPS5, RPLP0, SIRT6, SYF2 and TCF3. Phosphorylated. Belongs to the CCNDBP1 family.