The fission yeast COP9/signalosome is involved in cullin modification by ubiquitin-related Ned8p.
BACKGROUND
The function of the fission yeast cullins Pcu1p and Pcu4p requires modification by the ubiquitin-related peptide Ned8p. A recent report by Lyapina et al. shows that the COP9/signalosome (CSN), a multifunctional eight subunit complex, regulates Ned8p modification of Pcu1p. Disruption of caa1/csn1, which encodes subunit 1 of the putative S. pombe CSN, results in accumulation of Pcu1p exclusively in the modified form. However, it remained unclear whether this reflects global control of all cullins by the entire CSN complex.


RESULTS
We demonstrate that multiple CSN subunits control Ned8p modification of Pcu3p, another fission yeast cullin, which, in complex with the RING domain protein Pip1p, forms a ubiquitin ligase that functions in cellular stress response. Pcu3p is modified by Ned8p on Lys 729 and accumulates exclusively in the neddylated form in cells lacking the CSN subunits 1, 3, 4, and 5. These CSN subunits co-elute with Pcu3p in gel filtration fractions corresponding to approximately 550 kDa and specifically bind both native and Ned8p-modified Pcu3p in vivo. While CSN does not influence the subcellular localization of Pcu3p, Pcu3p-associated in vitro ubiquitin ligase activity is stimulated in the absence of CSN.


CONCLUSIONS
Taken together, our data suggest that CSN is a global regulator of Ned8p modification of multiple cullins and potentially other proteins involved in cellular regulation.
Zhou
C
C
Department of Cancer Cell Biology, Harvard School of Public Health, Boston, MA, USA. czhou@hsph.harvard.edu
Seibert
V
V
Geyer
R
R
Rhee
E
E
Lyapina
S
S
Cope
G
G
Deshaies
R J
RJ
Wolf
D A
DA
D000075686:COP9 Signalosome Complex; D017124:Conserved Sequence; D003545:Cysteine / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics; D005816:Genetic Complementation Test; D008025:Ligases / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism; D046911:Macromolecular Substances; D046912:Multiprotein Complexes; D009154:Mutation; D010447:Peptide Hydrolases; D011506:Proteins / Q000502:physiology*; D012568:Schizosaccharomyces / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics; D014452:Ubiquitins / Q000378:metabolism*
D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D046912:Multiprotein Complexes; C499610:Ned8 protein, S pombe; D011506:Proteins; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors; D014452:Ubiquitins; D010447:Peptide Hydrolases; D000075686:COP9 Signalosome Complex; D008025:Ligases; D008239:Lysine; D003545:Cysteine