Smt3, a SUMO-1 homolog, is conjugated to Cdc3, a component of septin rings at the mother-bud neck in budding yeast. |
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Authors: | Y Takahashi M Iwase M Konishi M Tanaka A Toh-e Y Kikuchi |
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Affiliation: | Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113, Japan. |
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Abstract: | SMT3 of Saccharomyces cerevisiae is an essential gene encoding a ubiquitin-like protein similar to mammalian SUMO-1. When a tagged Smt3 or human SUMO-1 was expressed from GAL1 promoter, either gene rescued the lethality of the smt3 disruptant. By indirect-immunofluorescent microscopy, the HA-tagged Smt3 was detected mostly in nuclei and also at the mother-bud neck just like septin fibers. Indeed immunoprecipitation experiments revealed that Cdc3, one of septin components, was modified with Smt3. Furthermore, the protein level of the Cdc3-Smt3 conjugate was reduced and the septin rings disappeared in a ubc9-1 mutant at a restrictive temperature, where the Smt3 conjugation system should be defective. Thus, we conclude that Smt3 was conjugated to Cdc3 in septin rings localized at the mother-bud neck. Around the time of cytokinesis the Cdc3-Smt3 conjugate disappeared. We discuss the biological significance of this Smt3 conjugation to a septin component. |
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