Smt3, a SUMO-1 homolog, is conjugated to Cdc3, a component of septin rings at the mother-bud neck in budding yeast

Biochem Biophys Res Commun. 1999 Jun 16;259(3):582-7. doi: 10.1006/bbrc.1999.0821.


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.

MeSH terms

  • Cell Cycle Proteins / metabolism*
  • Cell Division
  • Enzyme Inhibitors / metabolism
  • Genetic Complementation Test
  • Humans
  • Hydroxyurea / metabolism
  • Mutation
  • Nocodazole / metabolism
  • Profilins
  • Repressor Proteins / metabolism*
  • SUMO-1 Protein
  • Saccharomyces cerevisiae / chemistry*
  • Saccharomyces cerevisiae Proteins*
  • Small Ubiquitin-Related Modifier Proteins
  • Ubiquitins / chemistry*


  • CDC3 protein, S cerevisiae
  • Cell Cycle Proteins
  • Enzyme Inhibitors
  • Profilins
  • Repressor Proteins
  • SMT3 protein, S cerevisiae
  • SUMO-1 Protein
  • SUMO2 protein, human
  • Saccharomyces cerevisiae Proteins
  • Small Ubiquitin-Related Modifier Proteins
  • Ubiquitins
  • Nocodazole
  • Hydroxyurea