ISOLATION OF AN EXTRAGENIC SUPPRESSOR OF THE RNA1-1 MUTATION IN SACCHAROMYCES-CEREVISIAE

The small GTPase Ran is essential for nucleocytoplasmic transport of m acromolecules. In the yeast Saccharomyces cerevisiae, Rna1p functions as a Ran-GTPase activating protein (RanGAP1). Strains carrying the rna 1-1 mutation exhibit defects in nuclear transport and, as a consequenc e, accumulate precursor tRNAs. We have isolated two recessive suppress ors of the rna1-1 mutation. Further characterization of one of the sup pressor mutations, srn10-1, reveals that the mutation (i) can not bypa ss the need for Rna1p function and (ii) suppresses the accumulation of unspliced pretRNA caused by ma1-1. The SRN10 gene is not essential fo r cell viability and encodes an acidic protein (pI = 5.27) of 24.8 kDa . Srn10p is located in the cytoplasm, as determined by indirect immuno fluorescence microscopy. Two-hybrid analysis reveals that there is a p hysical interaction between Srn10p and Rna1p in vive. Our results iden tify a protein that interacts with the yeast RanGAP1.