Anti-RNF40 antibodies are used in the immunodetection of the protein ring finger protein 40. In humans, the canonical protein has a reported length of 1001 amino acid residues and a mass of 113.7 kDa. Its subcellular localization is in the nucleus. Alternative splicing is reported to yield 3 different isoforms for this protein. It is ubiquitously expressed across many tissue types. A member of a the BRE1 protein family, RNF40 is a known component of the RNF20/40 E3 ubiquitin-protein ligase complex that mediates monoubiquitination of 'Lys-120' of histone H2B (H2BK120ub1). Synonyms for this target antigen include RBP95, STARING, E3 ubiquitin-protein ligase BRE1B, 95 kDa retinoblastoma protein binding protein, 95 kDa retinoblastoma-associated protein, and BRE1B.