Integration of the catalytic subunit activates deneddylase activity in vivo as final step in fungal COP9 signalosome assembly

Mol Microbiol. 2015 Jul;97(1):110-24. doi: 10.1111/mmi.13017. Epub 2015 Apr 23.


The eight-subunit COP9 signalosome (CSN) is conserved from filamentous fungi to humans and functions at the interface between cellular signalling and protein half-life control. CSN consists of six PCI and two MPN domain proteins and forms a scaffold for additional interacting proteins. CSN controls protein stability in the ubiquitin-proteasome system where the MPN domain CSN5/CsnE subunit inactivates cullin-RING ligases. The CSN5/CsnE isopeptidase functions as deneddylase and removes the ubiquitin-like protein Nedd8. The six PCI domain proteins of human CSN form a horseshoe-like ring and all eight subunits are connected by a bundle of C-terminal α-helices. We show that single deletions of any csn subunit of Aspergillus nidulans resulted in the lack of deneddylase activity and identical defects in the coordination of development and secondary metabolism. The CSN1/CsnA N-terminus is dispensable for deneddylase activity but required for asexual spore formation. Complex analyses in mutant strains revealed the presence of a seven-subunit pre-CSN without catalytic activity. Reconstitution experiments with crude extracts of deletion strains and recombinant proteins allowed the integration of CSN5/CsnE into pre-CSN resulting in an active deneddylase. This supports a stable seven subunit pre-CSN intermediate where deneddylase activation in vivo can be controlled by CSN5/CsnE integration as final assembly step.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspergillus nidulans / enzymology*
  • Aspergillus nidulans / genetics
  • Aspergillus nidulans / metabolism
  • COP9 Signalosome Complex
  • Catalytic Domain*
  • Fungal Proteins / chemistry*
  • Fungal Proteins / metabolism*
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Molecular Sequence Data
  • Multiprotein Complexes / chemistry*
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism*
  • Peptide Hydrolases / chemistry*
  • Peptide Hydrolases / genetics
  • Peptide Hydrolases / metabolism*
  • Protein Binding
  • Protein Structure, Tertiary
  • Protein Subunits / metabolism
  • Spores, Fungal / metabolism


  • Fungal Proteins
  • Intracellular Signaling Peptides and Proteins
  • Multiprotein Complexes
  • Protein Subunits
  • Peptide Hydrolases
  • COP9 Signalosome Complex

Associated data

  • GENBANK/G21234