Research article

The fission yeast COP9/signalosome is involved in cullin modification by ubiquitin-related Ned8p

Chunshui Zhou¹ , Volker Seibert¹ , Rory Geyer¹ , Edward Rhee¹ , Svetlana Lyapina² , Greg Cope² , Raymond J Deshaies^2,3 and Dieter A Wolf¹

¹  Department of Cancer Cell Biology, Harvard School of Public Health, Boston, MA, USA

²  Division of Biology, California Institute of Technology, CA, USA

³  Howard Hughes Medical Institute, California Institute of Technology, CA, USA

author email corresponding author email

BMC Biochemistry 2001, 2:7doi:10.1186/1471-2091-2-7

Published:	18 July 2001

Abstract

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 ∼ 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.