Roquin is an E3 ubiquitin ligase with a poorly understood but essential role in preventing T-cell-mediated autoimmune disease and in microRNA-mediated repression of inducible costimulator (Icos) mRNA. Roquin and its mammalian paralogue membrane-associated nucleic acid binding protein (MNAB) define a protein family distinguished by an 200 amino acid domain of unknown function, ROQ, that is highly conserved from mam-mals to invertebrates and is flanked by a RING-1 zinc finger and a CCCH zinc finger
