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The 2nd international fission yeast meeting@(2002N3Ass@sۉc)
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A PUTATIVE S. POMBE HOMOLOGUE FOR RNPS1 IS INVOLVED IN PRE-mRNA SPLICING AND mRNA EXPORT FROM THE NUCLEUS
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Sin Hwang1, Akila Mayeda2, Yasuaki Habara1, David Frendewey3, Yasumi Ohshima1 and Tokio Tani4
1Dept. Biol., Kyushu Univ., Fukuoka 812-8581, Japan, 2Dept. Biol. Sci., Kumamoto Univ., Kumamoto, 860-8555, Japan.
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@Human RNPS1 is a novel general activator of pre-mRNA splicing identified by biochemical purification of a protein with the SF7 activity, which promotes the selection of a distal alternative 3' splice site (Mayeda et al., EMBO J., 1999). To elucidate the detailed function of RNPS1, we characterized the S. pombe gene for a putative homologue of RNPS1 (spRNPS1), which shows a 34.8% identity in amino acid sequence with human RNPS1. spRNPS1 is localized in the nucleus as did human RNPS1 and is not essential for growth in S. pombe. spRNPS1 tagged with HA was cosediment with spliceosomal snRNAs and the double mutants with spRNPS1 and prp3-2, prp4-2 or prp11-1 showed synthetic effects on the temperature sensitivity for growth. Northern blot analysis revealed that the double mutant with spRNPS1 and prp4-2 exacerbated the defect of pre-mRNA splicing at 26. Interestingly, we found that prp3-2 is defective in mRNA export as well as pre-mRNA splicing at the restrictive temperature of 37. The double mutant with spRNPS1 and prp3-2 exacerbated the defect of mRNA export and accumulate mRNA at the periphery of the nucleus even at 26. The prp3+ encodes a protein with a single RRM, which is identical with Cwf2p in S. pombe. Cwf2p was identified as a component of Cdc5p complex associated with spliceosome (McDonald et al., Mol. Cell. Biol., 1999). These results suggest that spRNPS1 and Prp3p are functionally related and play a role in mRNA export in addition to pre-mRNA splicing.