E3 ubiquitin-protein ligase RING1 (RING1)

Constitutes among the E3 ubiquitin-protein ligases that mediate monoubiquitination of'Lys-119' of histone H2A, thereby playing a central role in histone code and gene regulation. H2A 'Lys-119' ubiquitination gives a specific tag for epigenetic transcriptional repression and participates in X chromosome inactivation of female mammals.

Essential component of a Polycomb group (PcG) multiprotein PRC1-like complex, a complex class required to keep the transcriptionally repressive state of many genes, including Hox genes, throughout development. PcG PRC1 complex acts through chromatin remodeling and modification of histones, rendering chromatin heritably changed in its expressibility.