The Saccharomyces cerevisiae ubiquitin-proteasome system

Mark Hochstrasser, Phoebe R. Johnson, Cassandra S. Arendt, Alexander Yu Amerik, Sowmya Swaminathan, Robert Swanson, Shyr Jiann Li, Jeffrey Laney, Robin Pals-Rylaarsdam, Jonathan Nowak, Pamela L. Connerly

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Our studies of the yeast ubiquitin-proteasome pathway have uncovered a number of general principles that govern substrate selectivity and proteolysis in this complex system. Much of the work has focused on the destruction of a yeast transcription factor, MATα2. The α2 protein is polyubiquitinated and rapidly degraded in α-haploid cells. One pathway of proteolytic targeting, which depends on two distinct endoplasmic reticulum-localized ubiquitin-conjugating enzymes, recognizes the hydrophobic face of an amphipathic helix in α2. Interestingly, degradation of α2 is blocked in a/α-diploid cells by heterodimer formation between the α2 and a1 homeodomain proteins. The data suggest that degradation signals may overlap protein-protein interaction surfaces, allowing a straightforward steric mechanism for regulated degradation. Analysis of α2 degradation led to the identification of both 20S and 26S proteasome subunits, and several key features of proteasome assembly and active-site formation were subsequently uncovered. Finally, it has become clear that protein (poly)ubiquitination is highly dynamic in vivo, and our studies of yeast de-ubiquitinating enzymes illustrate how such enzymes can facilitate the proteolysis of diverse substrates.

Original languageEnglish (US)
Pages (from-to)1513-1522
Number of pages10
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Issue number1389
StatePublished - Sep 29 1999


  • Mating type
  • Proteasome
  • Proteolysis
  • Ubiquitin
  • Yeast

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)


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