Polycomb Group Proteins in Drosophila melanogaster.

The development of multicellular organisms relies on the precise establishment and stable inheritance of cell type-specific transcriptional programs without changes to the underlying DNA sequence. Polycomb group (PcG) proteins are evolutionarily conserved epigenetic repressors that govern developmental gene expression by assembling into multiprotein complexes to establish robust and spatiotemporally restricted transcriptional silencing. Since their discovery through the classic Polycomb mutant phenotype in Drosophila melanogaster, PcG proteins have become a central paradigm for understanding epigenetic regulation during animal development. Here, we synthesize current knowledge of the molecular composition and functional organization of the core Polycomb repressive complexes (PRC1 and PRC2) and the accessory complexes PhoRC, PR-DUB, and dRAF, with particular emphasis on canonical hierarchical recruitment and emerging noncanonical regulatory mechanisms of Polycomb-mediated gene repression. We further summarize the dynamic roles of PcG proteins across the Drosophila life cycle, from embryonic patterning and larval organogenesis to metamorphic transition and adult tissue homeostasis. By integrating recent advances from Drosophila studies, this review provides a comprehensive overview of the molecular mechanisms and developmental functions of PcG proteins while highlighting future directions for investigating the conserved epigenetic mechanisms governing metazoan development.