RING finger, HC subclass, found in RING finger protein 20 (RNF20)
RNF20, also known as BRE1A or BRE1, is an E3 ubiquitin-protein ligase that forms a heterodimeric complex together with BRE1B, also known as RNF40, to facilitate the K120 monoubiquitination of histone H2B (H2Bub1), a DNA damage-induced histone modification that is crucial for recruitment of the chromatin remodeler SNF2h to DNA double-strand break (DSB) damage sites. It regulates the cell cycle and differentiation of neural precursor cells (NPCs), and links histone H2B ubiquitylation with inflammation and inflammation-associated cancer. Moreover, RNF20 promotes the polyubiquitination and proteasome-dependent degradation of transcription factor activator protein 2alpha (AP-2alpha), a negative regulator of adipogenesis by repressing the transcription of CCAAT/enhancer binding protein (C/EBPalpha) gene. Furthermore, RNF20 functions as an additional chromatin regulator that is necessary for mixed-lineage leukemia (MLL)-fusion-mediated leukemogenesis. It also inhibits TFIIS-facilitated transcriptional elongation to suppress pro-oncogenic gene expression. TFIIS is a factor capable of relieving stalled RNA polymerase II. RNF20 contains a C3HC4-type RING-HC finger at its C-terminus.