InterPro domain: IPR041966

This predicted RNA-binding domain found in insect Oskar and vertebrate TDRD5/TDRD7 proteins that nucleate or organise structurally related ribonucleoprotein (RNP) complexes, the polar granule and nuage, is poorly understood [ 1 , 2 ]. The domain adopts the winged helix-turn-helix fold and binds RNA with a potential specificity for dsRNA [ 3 ]. In eukaryotes, this domain is often combined in the same polypeptide with protein-protein- or lipid- interaction domains that might play a role in anchoring these proteins to specific cytoskeletal structures. Thus, proteins with this domain might have a key role in the recognition and localisation of dsRNA, including miRNAs, rasiRNAs and piRNAs hybridized to their targets. In other cases, this domain is fused to ubiquitin-binding, E3 ligase and ubiquitin-like domains, indicating a previously under-appreciated role for ubiquitination in regulating the assembly and stability of nuage-like RNP complexes. Both bacteria and eukaryotes encode a conserved family of proteins that combines this predicted RNA-binding domain with a previously uncharacterised RNAse domain belonging to the superfamily that includes the 5'->3' nucleases, PIN and NYN domains [ 3 ].

This superfamily represents a RNA-binding domain identified when studying Tudor domain containing proteins and was designed LOTUS after Limkain, Oskar and TUdor-containing proteins 5 and 7.

1. OST-HTH: a novel predicted RNA-binding domain. Biol. Direct 5, 13
2. LOTUS, a new domain associated with small RNA pathways in the germline. Bioinformatics 26, 1140-4