Molecular analysis of a novelSchizosaccharomyces pombe gene containing two RNP consensus-sequence RNA-binding domains

Proteins containing RNP consensus-sequence RNA-binding domains (CS-RBDs) play diverse roles in many aspects of RNA metabolism. Using a PCR strategy, we cloned portions of six newSchizosaccharomyces pombe genes encoding RBD proteins, including a putative homolog of the mammalian splicing factor SAP49. The genomic locus corresponding to a second PCR product, designatedrnp24, was cloned and characterized in detail. Sequence analysis revealed that the Rnp24 protein is highly charged and contains a second RBD with an unusually long Loop-3 sequence. Strains containing a disrupted copy of thernp24 gene display neither loss of viability nor any discernible growth defects under a variety of conditions, suggesting that the function of Rnp24p overlaps with that of another fission yeast protein. Although database searches did not identify proteins that share extensive amino-acid identity with Rnp24p, phylogenetic analysis suggests that its closest relatives are metazoan hnRNP proteins. The lack of an observable phenotype inS. pombe cells lacking Rnp24p is consistent with this classification, since hnRNP proteins in higher cells include several distinct subfamilies with similar sequences and RNA-binding specifities.GenBank Accession Number U24430