The COP9 signalosome-like complex in S. cerevisiae and links to other PCI complexes

Vered Maytal-Kivity, Elah Pick, Ron Piran, Kay Hofmann, Michael H. Glickman

Research output: Contribution to journalArticlepeer-review


The COP9 signalosome (CSN), the lid subcomplex of the proteasome and translational intitation factor 3 (eIF3) share structural similarities and are often referred to as the PCI family of complexes. In multicellular eukaryotes, the CSN is highly conserved as an 8-subunit complex but in Saccharomyces cerevisiae the complex is rather divergent. We further characterize the composition and properties of the CSN in budding yeast and its interactions with these related complexes. Using the generalized profile method we identified CSN candidates, four with PCI domains: Csn9, Csn10, Pci8/Csn11, and Csn12, and one with an MPN domain, Csn5/Rri1. These proteins and an additional interactor, Csi1, were tested for pairwise interactions by yeast two-hybrid and were found to form a cluster surrounding Csn12. Csn5 and Csn12 cofractionate in a complexed form with an apparent molecular weight of roughly 250kDa. However, Csn5 migrates as a monomer in Δcsn12 supporting the pivotal role of Csn12 in stabilizing the complex. Confocal fluorescence microscopy detects GFP-tagged Csn5 preferentially in the nucleus, whereas in absence of Csn12, Csn10, Pci8/Csn11, or Csi1, Csn5 is delocalized throughout the cell, indicating that multiple subunits are required for nuclear localization of Csn5. Two CSN subunits, Csn9 and Csi1, interact with the proteasome lid subunit Rpn5. Pci8/Csn11 has previously been shown to interact with eIF3. Together, these results point to a network of interactions between these three structurally similar, yet functionally diverse, complexes.

Original languageEnglish
Pages (from-to)706-715
Number of pages10
JournalInternational Journal of Biochemistry and Cell Biology
Issue number5
StatePublished - 1 May 2003
Externally publishedYes

Bibliographical note

Funding Information:
Hongyong Fu generously shared Y2H plasmids with Rpn subunits. We thank Noa Reis for technical assistance and suggestions. This work was supported by the German Israel foundation for scientific research (GIF) with additional funding from the Israel Science Foundation (ISF), The Israel Cancer Research foundation (ICRF), a Technion Vice president grant for research at the Technion, and the Wolfson foundation for research on ubiquitin.


  • COP9 signalosome
  • CSN
  • MPN
  • PCI
  • Proteasome
  • Ubiquitin
  • eIF3

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology


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