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). MARCH9 (membrane-associated ring finger (C3HC4) 9), also known as RNF179, is a 346 amino acid multi-pass membrane protein that localizes to the golgi apparatus and contains one RING-CH-type zinc finger. Expressed ubiquitously, MARCH9 exists as a homodimer and functions as an E3 ubiquitin-protein ligase that accepts a ubiquitin residue from an E2 ubiquitin-conjugating enzyme and is thought to promote the degradation of target proteins, such as CD4 and MHC-I. Multiple isoforms of MARCH9 exist due to alternative splicing events.