The RNF40 antibody targets the RNF40 protein, a member of the RING finger (Really Interesting New Gene) family of E3 ubiquitin ligases. RNF40. along with its homolog RNF20. forms a heterodimeric complex critical for catalyzing monoubiquitination of histone H2B at lysine 120 (H2Bub1), a post-translational modification implicated in transcriptional regulation, DNA repair, and chromatin dynamics. This modification facilitates RNA polymerase II-dependent transcription elongation and maintains genomic stability. RNF40’s E3 ligase activity is dependent on its RING domain, which mediates interactions with ubiquitin-conjugating enzymes (E2s). Beyond histone ubiquitination, RNF40 has been linked to diverse cellular processes, including NF-κB signaling, cell cycle progression, and apoptosis. Dysregulation of RNF40 is associated with cancers, such as breast and colorectal carcinomas, where altered H2Bub1 levels correlate with tumor progression or suppression. Antibodies against RNF40 are essential tools for studying its expression, localization, and molecular interactions via techniques like Western blotting, immunoprecipitation, and immunofluorescence. They also aid in exploring RNF40’s role in epigenetic regulation and its potential as a therapeutic target. Recent studies highlight its context-dependent functions, underscoring the need for high-specificity antibodies to dissect its complex regulatory networks in health and disease.