A novel gene, spp91-1, suppresses the splicing defect and the pre-mRNA nuclear export in the prp9-1 mutant.
Processing and export of nuclear pre-mRNA are believed to be competing processes in the nucleus. In order to identify factors which are involved in these processes, we isolated suppressors that relieve the growth defect of a prp9-1 temperature-sensitive mutant strain of Saccharomyces cerevisiae. The prp9-1 mutation was previously shown to abolish splicing and to target pre-mRNA to the cytoplasm. One of the suppressors, spp91-1, corrects the prp9-1 growth defect through partial restoration of splicing and by a complete reversion of the pre-mRNA escape phenotype. This suppressor is specific for two prp9 alleles and cannot substitute for PRP9 function. The mutant and wild-type alleles of SPP91 were cloned and sequenced. SPP91 encodes a novel protein essential for mitotic growth whose sequence contains motifs indicative of a nuclear localization. In vivo depletion of SPP91 in a prp9-1 genetic background is lethal and is associated with reduced amounts of spliced mRNA and accumulation of pre-mRNA. This observation strongly supports the hypothesis that SPP91 encodes a PRP factor. We suggest that spp91-1 increases pre-mRNA retention in the nucleus by improving the formation of the spliceosome and thereby allowing a larger proportion of the pre-mRNA molecules to be spliced.
Chapon
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Département de Biologie Moléculaire, Institut Pasteur, Paris, France.
Legrain
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D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D004271:DNA, Fungal; D005800:Genes, Fungal / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010641:Phenotype; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism*; D012326:RNA Splicing; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D013489:Suppression, Genetic
D004271:DNA, Fungal; D012322:RNA Precursors; D012331:RNA, Fungal