The E3 ubiquitin-protein ligase ARIH2 (TRIAD1) is an Ariadne subfamily ligase involved in the polyubiquitination of proteins designated for proteasomal degradation. The TRIAD1 nuclear protein contains an amino-terminal acidic region, a pair of RING fingers, two carboxyl terminal coiled coil domains and a novel C6HC DRIL/IBR domain located between the RING fingers. Together, the paired RING fingers and DRIL/IBR domain form a highly conserved TRIAD (two RING fingers and DRIL) domain. Research studies suggest that TRIAD1 mediates both Lys48 and Lys63 protein polyubiquitination and acts as a negative regulator of myelopoiesis. TRIAD1 ubiquitin ligase inhibits myeloid cell proliferation by mediating protein ubiquitination through the ubiquitin-conjugating enzymes UbcH7 and UbcH13. Experimental deletion of TRIAD1 in mice has a lethal effect, leading to death at the embryonic stage or later due to a severe, multi-organ inflammatory response. Results indicate that TRIAD1 binds IκBβ in dendritic cells and promotes the degradation of the NF-κB inhibitor.
