R3H domain of the NF-kappaB-repression factor (NRF). NRF is a nuclear inhibitor of NF-kappaB proteins that can silence the IFNbeta promoter via binding to a negative regulatory element (NRE). Beside R3H NRF also contains a G-patch domain. The name of the R3H domain comes from the characteristic spacing of the most conserved arginine and histidine residues. The function of the domain is predicted to bind ssDNA or ssRNA in a sequence-specific manner.