Molecular characterization of a novel fission yeast gene spUAP2 that interacts with the splicing factor spU2AF59.

A protein essential for pre-mRNA splicing, the U2 auxiliary factor (U2AF), is composed of a large and small subunit. Previously we cloned and characterized both subunits, spU2AF59 and spU2AF23, from fission yeast. We now report a novel U2AF-associated-protein, spUAP2, which interacts with both subunits. SpUAP2 contains a classical and a degenerate RNA recognition motif (RRM), both of which are required for interaction with spU2AF59. Interaction also requires the arginine/serine-rich region and the first RRM of spU2AF59. A null allele of the gene for spUAP2 is lethal.