The yeast RNA1 protein, necessary for RNA processing, is homologous to the human ribonuclease/angiogenin inhibitor (RAI).

Mutations in the RNA1 gene of Saccharomyces cerevisiae, which encodes an essential cytosolic protein, affect the production and processing of all major classes of RNA. The mechanisms underlying these effects are not at all understood. Detailed comparative sequence analyses revealed that the RNA1 protein belongs to a superfamily, the members of which contain repetitive "leucine-rich motifs" (LRM). Within this superfamily RNA1 is most closely related to the ribonuclease/angiogenin inhibitor (RAI), which is a tightly binding inhibitor of ribonucleolytic activities in mammals. These results not only provide important clues to the structure, function and evolution of the RNA1 protein, but also have intriguing implications for possible novel functions of RAI.