E3 ubiquitin-protein ligase that mediates monoubiquitination of 'Lys-118' of histone H2A, thereby playing a central role in histone code and gene regulation. H2A 'Lys-118' ubiquitination gives a specific tag for epigenetic transcriptional repression. Polycomb group (PcG) protein. PcG proteins act by forming multiprotein complexes, which are required to maintain the transcriptionally repressive state of homeotic genes throughout development. PcG proteins are not required to initiate repression, but to maintain it during later stages of development. PcG complexes act via modification of histones, such as methylation, deacetylation, ubiquitination rendering chromatin heritably changed in its expressibility. May play a role in meiotic sister chromatid cohesion.

(UniProt, Q9VB08)

A dominant enhancer of Mcp in the BXC. Sce/Sce zygotes from Sce/+ mothers die as first instar larvae with weak posteriorly directed transformations, i.e., A7 displays some A8 characteristics. Heterozygous offspring normal. Sce/Sce embryos from clones of homozygous oocytes produced by pole-cell transplantation display extreme posteriorly directed segmental transformation. Ventral setal belts of all abdominal and thoracic segments transformed toward A8; head involution blocked; abdominal type denticle belts also found anterior to T1 in the presumptive labial and maxillary segments; in addition an extensive belt of abdominal denticles of unknown derivation forms on the anterodorsal surface of the embryo. Keilin's organs and ventral pits suppressed in thoracic segments; wart-like sensilla normally found in A8 formed anteriorally as far as A2. Tracheal branches in A1-7 resemble those normally found more posteriorly. Sce/+ offspring from homozygous germ line clones in the mothers may survive to adulthood or die as pharate adults; they show patches of tissue transformed toward A8.