The covalent conjugation of ubiquitin to proteins regulates diverse cellular pathways and proteins. Ubiquitin is transferred to a target protein through a concerted action of a ubiquitin-activating enzyme (E1), a ubiquitin-conjugating enzyme (E2), such as UBE2T, and a ubiquitin ligase (E3) (Machida et al., 2006 [PubMed 16916645]).[supplied by OMIM, Mar 2008]