The family includes Drosophila melanogaster protein pygopus (dPYGO) and its two homologs, PYGO1 and PYGO2. dPYGO is a fundamental Wnt signaling transcriptional component in Drosophila. PYGO1 is essential for the association with Legless (Lgs)/Bcl9 that acts an adaptor between Pygopus (Pygo) and Arm/beta-catenin. dPYGO and PYGO2 function as context-dependent beta-catenin coactivators, and they bind di- and trimethylated lysine 4 of histone H3 (H3K4me2/3). Moreover, PYGO2 acts as a histone methylation reader, and a chromatin remodeler in a testis-specific and Wnt-unrelated manner. It also mediates chromatin regulation and links Wnt signaling and Notch signaling to suppress the luminal/alveolar differentiation competence of mammary stem and basal cells. PYGO2 also plays a new role in rRNA transcription during cancer cell growth. It regulates mammary tumor initiation and heterogeneity in MMTV-Wnt1 mice. All family members contain a plant homeodomain (PHD) finger.
Jiyao W et al.(2023). "The conserved domain database in 2023.",