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Vol. 17, Issue 9, 3745-3755, September 2006
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,
*Institut für Zellbiologie,
Abteilung für Elektronenmikroskopie, and
Bayreuther Zentrum für Molekulare Biowissenschaften, Universität Bayreuth, 95440 Bayreuth, Germany; and
Institut für Genetik, Universität zu Köln, 50674 Köln, Germany
Submitted January 18, 2006;
Revised June 7, 2006;
Accepted June 8, 2006
Monitoring Editor: Sandra Schmid
Mitochondria constantly fuse and divide to adapt organellar morphology to the cells ever-changing physiological conditions. Little is known about the molecular mechanisms regulating mitochondrial dynamics. F-box proteins are subunits of both Skp1-Cullin-F-box (SCF) ubiquitin ligases and non-SCF complexes that regulate a large number of cellular processes. Here, we analyzed the roles of two yeast F-box proteins, Mfb1 and Mdm30, in mitochondrial dynamics. Mfb1 is a novel mitochondria-associated F-box protein. Mitochondria in mutants lacking Mfb1 are fusion competent, but they form aberrant aggregates of interconnected tubules. In contrast, mitochondria in mutants lacking Mdm30 are highly fragmented due to a defect in mitochondrial fusion. Fragmented mitochondria are docked but nonfused in
mdm30 cells. Mitochondrial fusion is also blocked during sporulation of homozygous diploid mutants lacking Mdm30, leading to a mitochondrial inheritance defect in ascospores. Mfb1 and Mdm30 exert nonredundant functions and likely have different target proteins. Because defects in F-box protein mutants could not be mimicked by depletion of SCF complex and proteasome core subunits, additional yet unknown factors are likely involved in regulating mitochondrial dynamics. We propose that mitochondria-associated F-box proteins Mfb1 and Mdm30 are key components of a complex machinery that regulates mitochondrial dynamics throughout yeasts entire life cycle.
This article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E06-01-0053) on June 21, 2006.
Address correspondence to: Benedikt Westermann (benedikt. westermann{at}uni-bayreuth.de)
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