Ubiquitination is an important mechanism through which three classes of enzymes act in concert to target short-lived or abnormal proteins for destruction. The three classes of enzymes involved in ubiquitination are the ubiquitin-activating enzymes (E1s), the ubiquitin-conjugating enzymes (E2s) and the ubiquitin-protein ligases (E3s). RNF25 (RING finger protein 25), also known as AO7, is a 459 amino acid protein that contains one RWD domain and one RING-type zinc finger. Via its RING-type zinc finger (a common domain that contains a conserved cysteine-rich region and is found in a number of viral and eukaryotic proteins), RNF25 is thought to exhibit E2-dependent E3 ubiquitin-protein ligase activity. Specifically, the RING finger of RNF25 interacts with an E2 ligase and, through this interaction, facilitates the ubiquitination of target proteins. RNF25 may also regulate the transcriptional activity of NF-kappa-B, a protein that plays important roles in cell survival, inflammation response, host defense and proliferation.