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Description

E3 ubiquitin-protein ligase BRE1B (UniProt O75150, also known as 95 kDa retinoblastoma-associated protein, BRE1-B, RBP95, RING finger protein 40, Syntaxin-1-interacting RING finger protein, Protein staring) is encoded by the RNF40 (also known as BRE1B, KIAA0661) gene (Gene ID 9810) in human. Proteini ubiquitination is mediated by ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), and ubiquitin ligases (E3s). There exist RING finger-type (really interesting new gene), HECT-type (homologous to E6-AP C-terminus), and U-box type of E3 ligases. RING finger ubiquitin ligase members can function as monomers, dimers, or multi-subunit complexes. The RNF20-RNF40 heterodimer mediates the ubiquitination of histone H2B at Lysine 120, an event that plays an important role in decompacting chromatin fiber to allow transcription elongation, in stem cell differentiation, as well as in DNA double-strand breaks (DSBs) repair via the homologous recombination (HR) and nonhomologous end-joining (NHEJ) pathways. Human RNF40 is a 1001-amino acid protein containing a RING-type zinc finger in its C-terminal region (a.a. 948-987) that mediates its interaction with RNF20.