A role of Sep1 (= Kem1, Xrn1) as a microtubule‐associated protein in Saccharomyces cerevisiae

• Published in: The EMBO journal 1995-03, Vol.14 (6), p.1057-1066
• Main Authors: Interthal, H., Bellocq, C., Bähler, J., Bashkirov, V.I., Edelstein, S., Heyer, W.D.
• Format: Article
• Language: English
• Subjects: Animals; Benomyl - pharmacology; Brain Chemistry; Cell Division - drug effects; Cell Division - physiology; Cell Nucleus - physiology; Deoxyribonucleases - genetics; Deoxyribonucleases - isolation & purification; Deoxyribonucleases - physiology; DNA Mutational Analysis; Epistasis, Genetic; Exoribonucleases; Fungal Proteins - genetics; Fungal Proteins - isolation & purification; Fungal Proteins - physiology; Genes, Fungal - genetics; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - isolation & purification; Microtubule-Associated Proteins - physiology; Microtubules - drug effects; Microtubules - physiology; Microtubules - ultrastructure; Nocodazole - pharmacology; Saccharomyces cerevisiae; Saccharomyces cerevisiae - cytology; Saccharomyces cerevisiae Proteins; Spindle Apparatus; Swine; Tubulin - biosynthesis; Tubulin - genetics
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1995.tb07088.x

Saccharomyces cerevisiae cells lacking the SEP1 (also known as XRN1, KEM1, DST2, RAR5) gene function exhibit a number of phenotypes in cellular processes related to microtubule function. Mutant cells show increased sensitivity to the microtubule‐destabilizing drug benomyl, increased chromosome loss, a karyogamy defect, impaired spindle pole body separation, and defective nuclear migration towards the bud neck. Analysis of the arrest morphology and of the survival during arrest strongly suggests a structural defect accounting for the benomyl hypersensitivity, rather than a regulatory defect in a checkpoint. Biochemical analysis of the purified Sep1 protein demonstrates its ability to promote the polymerization of procine brain and authentic S.cerevisiae tubulin into flexible microtubules in vitro. Furthermore, Sep1 co‐sediments with these microtubules in sucrose cushion centrifugation. Genetic analysis of double mutant strains containing a mutation in SEP1 and in one of the genes coding for alpha‐ or beta‐tubulin further suggests interaction between Sep1 and microtubules. Taken together these three lines of evidence constitute compelling evidence for a role of Sep1 as an accessory protein in microtubule function in the yeast S.cerevisiae.