Smt3, a SUMO-1 homolog, is conjugated to Cdc3, a component of septin rings at the mother-bud neck in budding yeast.
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.
Takahashi
Y
Y
Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113, Japan.
Iwase
M
M
Konishi
M
M
Tanaka
M
M
Toh-e
A
A
Kikuchi
Y
Y
D018797:Cell Cycle Proteins / Q000378:metabolism*; D002455:Cell Division; D004791:Enzyme Inhibitors / Q000378:metabolism; D005816:Genetic Complementation Test; D006801:Humans; D006918:Hydroxyurea / Q000378:metabolism; D009154:Mutation; D015739:Nocodazole / Q000378:metabolism; D051304:Profilins; D012097:Repressor Proteins / Q000378:metabolism*; D025842:SUMO-1 Protein; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; D014452:Ubiquitins / Q000737:chemistry*
C086662:CDC3 protein, S cerevisiae; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D051304:Profilins; D012097:Repressor Proteins; C099362:SMT3 protein, S cerevisiae; D025842:SUMO-1 Protein; C117909:SUMO2 protein, human; D029701:Saccharomyces cerevisiae Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; D014452:Ubiquitins; D015739:Nocodazole; D006918:Hydroxyurea