The deltex family of proteins is involved in the regulation of Notch signaling, and therefore may play roles in cell-to-cell communications that regulate mechanisms determining cell fate. They have a central RING-type zinc finger domain and contain a C-terminal domain, described here, that is also found in other domain architectures. Deltex-1 (DTX1) contains a RING finger and two WWE domains, indicating that it may be an E3 ubiquitin ligase. Human deltex 3-like, which contains an additional N-terminal domain (presumably with ubiquitin ligase activity) is also described as E3 ubiquitin-protein ligase DTX3L, B-lymphoma- and BAL-associated protein (BBAP), or rhysin-2. DTX3L mediates monoubiquitination of K91 of histone H4 in response to DNA damage.