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. Interacts with CCND1 and GRAP2. May also interact with COPS5, RPLP0, SIRT6, SYF2 and TCF3. Ubiquitously expressed. Expression is down-regulated in a variety of tumor types including breast, colon, prostate and rectal tumors, and is up-regulated in certain hepatic carcinomas. Expression may increase during differentiation. Expression is induced by sodium butyrate, an inhibitor of colon cancer cell proliferation. Phosphorylated. Belongs to the CCNDBP1 family.