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Vol. 19, Issue 3, 1022-1031, March 2008

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Dissection of the Carboxyl-Terminal Domain of the Proteasomal Subunit Rpn11 in Maintenance of Mitochondrial Structure and Function

Teresa Rinaldi^*,, Line Hofmann^,, Alessia Gambadoro^*, Raynald Cossard, Nurit Livnat-Levanon, Michael H. Glickman, Laura Frontali^*, and Agnès Delahodde

*Pasteur Institute-Cenci Bolognetti Foundation, Department of Cell and Developmental Biology, University of Rome La Sapienza, 00185 Rome, Italy; Université Paris-Sud, Centre National de la Recherche Scientifique 91405 Orsay Cedex, France; and Department of Biology, Technion, Israel Institute of Technology, 32000 Haifa, Israel

Submitted July 28, 2007; Revised December 6, 2007; Accepted December 20, 2007
Monitoring Editor: Janet Shaw

We have previously demonstrated that the C-terminal part of Rpn11, a deubiquitinating enzyme in the lid of the proteasome, is essential for maintaining a correct cell cycle and normal mitochondrial morphology and function. The two roles are apparently unlinked as the mitochondrial role is mapped to the Carboxy-terminus, whereas the catalytic deubiquitinating activity is found within the N-terminal region. The mitochondrial defects are observed in rpn11-m1 (originally termed mpr1-1), a mutation that generates Rpn11 lacking the last 31 amino acids. No mitochondrial phenotypes are recorded for mutations in the MPN+/JAMM motif. In the present study, we investigated the participation of the last 31 amino acids of the Rpn11 protein by analysis of intragenic revertants and site-specific mutants. We identified a putative -helix necessary for the maintenance of a correct cell cycle and determined that a very short region at the C-terminus of Rpn11 is essential for the maintenance of tubular mitochondrial morphology. Furthermore, we show that expression of the C-terminal part of Rpn11 is able to complement in trans all of the rpn11-m1 mitochondrial phenotypes. Finally, we investigate the mechanisms by which Rpn11 controls the mitochondrial shape and show that Rpn11 may regulate the mitochondrial fission and tubulation processes.

These authors contributed equally to this work.

Address correspondence to: Teresa Rinaldi (teresa.rinaldi{at}uniroma1.it)