Characterization of the role of COP9 signalosome in regulating cullin E3 ubiquitin ligase activity.
Cullin RING ligases (CRLs) are the largest family of cellular E3 ubiquitin ligases and mediate polyubiquitination of a number of cellular substrates. CRLs are activated via the covalent modification of the cullin protein with the ubiquitin-like protein Nedd8. This results in a conformational change in the cullin carboxy terminus that facilitates the ubiquitin transfer onto the substrate. COP9 signalosome (CSN)-mediated cullin deneddylation is essential for CRL activity in vivo. However, the mechanism through which CSN promotes CRL activity in vivo is currently unclear. In this paper, we provide evidence that cullin deneddylation is not intrinsically coupled to substrate polyubiquitination as part of the CRL activation cycle. Furthermore, inhibiting substrate-receptor autoubiquitination is unlikely to account for the major mechanism through which CSN regulates CRL activity. CSN also did not affect recruitment of the substrate-receptor SPOP to Cul3, suggesting it may not function to facilitate the exchange of Cul3 substrate receptors. Our results indicate that CSN binds preferentially to CRLs in the neddylation-induced, active conformation. Binding of the CSN complex to active CRLs may recruit CSN-associated proteins important for CRL regulation. The deneddylating activity of CSN would subsequently promote its own dissociation to allow progression through the CRL activation cycle.
Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 117597 Singapore.
Yin Yin
YY
Choo
Boon Kim
BK
Boh
Jessica Jie Wei
JJ
Lou
Jolane
J
Eng
Yee Chin
YC
Leck
Benjamin
B
Anders
Peter G
PG
Smith
Thilo
T
Hagen
D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D000075687:NEDD8 Protein; D009687:Nuclear Proteins / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D054875:Ubiquitination / Q000502:physiology*; D014452:Ubiquitins / Q000235:genetics / Q000378:metabolism*
C503645:CUL3 protein, human; D044842:Cullin Proteins; D046912:Multiprotein Complexes; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; D009687:Nuclear Proteins; D012097:Repressor Proteins; C509761:SPOP protein, human; D014452:Ubiquitins