IDENTIFICATION AND CHARACTERIZATION OF SRP1, A GENE OF FISSION YEAST ENCODING A RNA-BINDING DOMAIN AND A RS DOMAIN TYPICAL OF SR SPLICING FACTORS

The SR protein family is involved in constitutive and regulated pre-mR NA splicing and has been found to be evolutionarily conserved in metaz oan organisms, In contrast, the genome of the unicellular yeast Saccha romyces cerevisiae does not contain genes encoding typical SR proteins , The mammalian SR proteins consist of one or two characteristic RNA b inding domains (RED), containing the signature sequences RDAEDA and SW QDLKD respectively, and a RS (arginine/serine-rich) domain which gave the family its name. We have now cloned from the fission yeast Schizos accharomyces pombe the gene srp1. This gene is the first yeast gene en coding a protein with typical features of mammalian SR protein family members, The gene is not essential for growth, We show that overexpres sion of the RNA binding domain inhibits pre-mRNA splicing and that the highly conserved sequence RDAEDA in the RED is involved, Overexpressi on of Srp1 containing mutations in the RS domain also inhibits pre-mRN A splicing activity, Furthermore, we show that overexpression of Srp1 and overexpression of the mammalian SR splicing factor ASF/SF2 suppres s the pre-mRNA splicing defect of the temperature-sensitive prp4-73 al lele, prp4 encodes a protein kinase involved in pre-mRNA splicing, The se findings are consistent with the notion that Srp1 plays a role in t he splicing process.