RING finger, HC subclass, found in really interesting new gene 2 protein (RING2) and similar proteins
RING2, also known as huntingtin-interacting protein 2-interacting protein 3, HIP2-interacting protein 3, protein DinG, RING finger protein 1B (RING1B), RING finger protein 2 (RNF2), or RING finger protein BAP-1, is an E3 ubiquitin-protein ligase that interacts with both nucleosomal DNA and an acidic patch on histone H4 to achieve the specific monoubiquitination of K119 on histone H2A (H2AK119ub), thereby playing a central role in histone code and gene regulation. RING2 is a core component of polycomb repressive complex 1 (PRC1) that functions as an E3-ubuiquitin ligase transferring the mono-ubuiquitin mark to the C-terminal tail of Histone H2A at K118/K119. PRC1 is also capable of chromatin compaction, a function not requiring histone tails, and this activity appears important in gene silencing. The enzymatic activity of RING2 is enhanced by the interaction with BMI1/PCGF4, and it is dispensable for early embryonic development and much of the gene repression activity of PRC1. Moreover, RING2 plays a key role in terminating neural precursor cell (NPC)-mediated production of subcerebral projection neurons (SCPNs) during neocortical development. It also plays a critical role in nonhomologous end-joining (NHEJ)-mediated end-to-end chromosome fusions. Furthermore, RING2 is essential for expansion of hepatic stem/progenitor cells. It promotes hepatic stem/progenitor cell expansion through simultaneous suppression of cyclin-dependent kinase inhibitors (CDKIs) Cdkn1a and Cdkn2a, known negative regulators of cell proliferation. RING2 also negatively regulates p53 expression through directly binding with both p53 and MDM2 and promoting MDM2-mediated p53 ubiquitination in selective cancer cell types to stimulate tumor development. RING2 contains a C3HC4-type RING-HC finger.