Allele specific suppression of a Saccharomyces cerevisiae prp20 mutation by overexpression of a nuclear serine/threonine protein kinase
1996
Fleischmann, M. | Stagljar, I. | Aebi, M. (Eidgenoessische Technische Hochschule, Zuerich (Switzerland). Mikrobiologisches Inst.)
The yeast PRP20 protein is homologous to the RCC1 protein of higher eukaryotes and is required for mRNA export and maintenance of nuclear structure. RCC1/PRP20 act as guanine nucleotide exchange factors for the nuclear Ras-like Ran/GSP1 proteins. In a search for prp20-10 allele-specific high-copy-number suppressors, the KSP1 locus, encoding a serine/threonine protein kinase was isolated. Ksp1p is a nuclear protein that is not essential for vegetative growth of yeast. Inactivation of the kinase activity by a mutation affecting the catalytic center of the Ksp1p eliminated the suppressing activity. Based on the isolation of a protein kinase as a high-copy-number suppressor, the phosphorylation of Prp20p was examined. In vivo labeling experiments showed that Prp20p is a phosphoprotein; however, deletion of the KSP1 kinase did not affect Prp20p phosphorylation.
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