R3H domain of mainly fungal proteins which are associated with a RNA recognition motif (RRM) domain. Present in this group is the RNA-binding post-transcriptional regulator Cip2 (Csx1-interacting protein 2) involved in counteracting Csx1 function. Csx1 plays a central role in controlling gene expression during oxidative stress. 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.