Protein chibby homolog 1 is a protein that in humans is encoded by the CBY1 gene.

Beta-catenin is a transcriptional activator and oncoprotein involved in the development of several cancers. The protein encoded by this gene interacts directly with the C-terminal region of beta-catenin, inhibiting oncogenic beta-catenin-mediated transcriptional activation by competing with transcription factors for binding to beta-catenin. Two transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq].
Function: Inhibits the Wnt/Wingless pathway by binding to beta-catenin and inhibiting beta-catenin-mediated transcriptional activation through competition with TCF/LEF transcription factors. Has also been shown to play a role in regulating the intracellular trafficking of polycystin-2/PKD2 and possibly of other intracellular proteins. Promotes adipocyte and cardiomyocyte differentiation.