The protein encoded by ring finger protein 8 contains a RING finger motif and a FHA domain. This protein has been shown to interact with several class II ubiquitin-conjugating enzymes (E2), including UBE2E1/UBCH6, UBE2E2, and UBE2E3, and may act as an ubiquitin ligase (E3) in the ubiquitination of certain nuclear proteins. Alternatively spliced transcript variants encoding distinct isoforms have been reported. [provided by RefSeq].
E3 ubiquitin-protein ligase required for assembly of repair proteins to sites of DNA damage. Catalyzes the \'Lys-63\'-linked ubiquitination of histone H2A and H2AX. Following DNA double-strand breaks (DSBs), it is recruited to the sites of damage by ATM-phosphorylated MDC1, mediates the ubiquitination of histones H2A and H2AX, thereby promoting the formation of TP53BP1 and BRCA1 ionizing radiation-induced foci (IRIF). Promotes the formation of  \'Lys-63\'-linked polyubiquitin chains and functions with the specific ubiquitin-conjugating UBE2N/UBC13. Substrates that are polyubiquitinated at \'Lys-63\' are usually not targeted for degradation. Enforces the G2/M DNA damage checkpoint. Controls the recruitment of UIMC1-BRCC3 (RAP80-BRCC36) and PAXIP1/PTIP to DNA damage sites following DNA double-strand breaks (DSBs). Ubiquitination of histone H2A requires UBE2N but not MMS2 (UBE2V2). May also ubiquitinate histone H2B. Catalyzes the \'Lys-63\'-linked ubiquitination of PCNA. May be required for proper exit from mitosis after spindle checkpoint activation and may regulate cytokinesis. May play a role in the regulation of RXRA-mediated transcriptional activity. Not involved in RXRA ubiquitination by UBE2E2