COP9 signalosome subunit 7 from Arabidopsis interacts with and regulates the small subunit of ribonucleotide reductase (RNR2)

Yair Halimi, Moshe Dessau, Shaul Pollak, Tslil Ast, Tamir Erez, Nurit Livnat-Levanon, Baruch Karniol, Joel A. Hirsch, Daniel A. Chamovitz

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


The COP9 Signalosome protein complex (CSN) is a pleiotropic regulator of plant development and contains eight-subunits. Six of these subunits contain the PCI motif which mediates specific protein interactions necessary for the integrity of the complex. COP9 complex subunit 7 (CSN7) contains an N-terminal PCI motif followed by a C-terminal extension which is also necessary for CSN function. A yeast-interaction trap assay identified the small subunit of ribonucelotide reductase (RNR2) from Arabidopsis as interacting with the C-terminal section of CSN7. This interaction was confirmed in planta by both bimolecular fluorescence complementation and immuoprecipitation assays with endogenous proteins. The subcellular localization of RNR2 was primarily nuclear in meristematic regions, and cytoplasmic in adult cells. RNR2 was constitutively nuclear in csn7 mutant seedlings, and was also primarily nuclear in wild type seedlings following exposure to UV-C. These two results correlate with constitutive expression of several DNA-damage response genes in csn7 mutants, and to increased tolerance of csn7 seedlings to UV-C treatment. We propose that the CSN is a negative regulator of RNR activity in Arabidopsis.

Original languageEnglish
Pages (from-to)77-89
Number of pages13
JournalPlant Molecular Biology
Issue number1
StatePublished - Sep 2011
Externally publishedYes

Bibliographical note

Funding Information:
Acknowledgments We thank Professor Nir Ohad with assistance and use of the confocal microscope, and Professor Amram Eshel for assistance with PAM. YH is the recipient of an Eshkol Foundation predoctoral fellowship. MD was supported in part by a matching Tel Aviv University Rector doctoral fellowship. This work was supported by a grant from Israel Science Foundation (783/05) to DAC and JAH, and from the Israel—US Binational Agricultural Research and Development Fund (IS-2775-96R) to DAC.


  • Arabidopsis
  • Cop9 signalosome
  • DNA damage
  • PCI
  • Ribonucleotide reductase


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