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). {ECO:0000250|UniProtKB:A2CEM9, ECO:0000250|UniProtKB:Q6PDY0, ECO:0000269|PubMed:17014843, ECO:0000269|PubMed:17873903}. (Microbial infection) Plays a role in hepatitis delta virus (HDV) genomic replication. . This is the function of CCDC85B (coiled-coil domain containing 85B, ENSG00000175602).