H2BC21 and neoplasm: An exciting really interesting new gene (RING) family of E3 ubiquitin ligases, known as RNF20 and RNF40, monoubiquitinates histone H2A at K119 or H2B at K120, is known to function in transcriptional elongation, DNA double-strand break (DSB) repair processes, maintenance of chromatin differentiation, and exerting tumor suppressor activity.