The study identifies a RING finger-containing protein (A07) that binds ubiquitin-conjugating enzymes (E2s) and undergoes E2-dependent ubiquitination. Mutations of cation-coordinating residues within A07's RING finger or chelation of zinc abolished ubiquitination. Several unrelated RING finger proteins, including BRCA1, Siah-1, TRC8, NF-X1, IκF, and Praja1, were also found to facilitate E2-dependent ubiquitination. The RING fingers were implicated directly in this activity through mutations of metal-coordinating residues or chelation of zinc. These findings suggest that a large number of RING finger-containing proteins, with diverse structures and functions, may play previously unappreciated roles in modulating protein levels via ubiquitination. The study provides strong evidence that the RING finger, in the appropriate molecular context, is a module that interacts with E2s and facilitates ubiquitination.The study identifies a RING finger-containing protein (A07) that binds ubiquitin-conjugating enzymes (E2s) and undergoes E2-dependent ubiquitination. Mutations of cation-coordinating residues within A07's RING finger or chelation of zinc abolished ubiquitination. Several unrelated RING finger proteins, including BRCA1, Siah-1, TRC8, NF-X1, IκF, and Praja1, were also found to facilitate E2-dependent ubiquitination. The RING fingers were implicated directly in this activity through mutations of metal-coordinating residues or chelation of zinc. These findings suggest that a large number of RING finger-containing proteins, with diverse structures and functions, may play previously unappreciated roles in modulating protein levels via ubiquitination. The study provides strong evidence that the RING finger, in the appropriate molecular context, is a module that interacts with E2s and facilitates ubiquitination.