Functions as a transcriptional repressor (PubMed:17014843). May inhibit the activity of CTNNB1 in a TP53-dependent manner and thus regulate cell growth (PubMed:17873903). May function in adipocyte differentiation, negatively regulating mitotic clonal expansion (By similarity). Plays a role in cell-cell adhesion and epithelium development through its interaction with proteins of the beta-catenin family (By similarity). (Microbial infection) Plays a role in hepatitis delta virus (HDV) genomic replication. Interacts with CEBPB (By similarity). Interacts with EURL (By similarity). May interact with CEBPD (By similarity). Interacts with MCRS1 (PubMed:17014843). Interacts with TCF7L2; competes with CTNNB1 (PubMed:17873903). Interacts with ANKRD26 (PubMed:22666460). Interacts with the beta-catenin family proteins ARVCF, CTNND1, CTNND2 AND PKP4 (PubMed:25009281). (Microbial infection) Interacts with the viral phosphoprotein hepatitis delta antigen (HDAG); this interaction affects hepatitis delta virus (HDV) genomic replication in intact cells. Widely expressed including liver. Up-regulated by doxorubicin. May be the cellular homolog of HDAG. Overexpression inhibited HDV replication, whereas overexpression of HDAG reversed the inhibition, suggesting that HDAG may assist HDV replication by forming a complex with DIPA. Belongs to the CCDC85 family.