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Contents lists available at ScienceDirect

Biochimie journal homepage: www.elsevier.com/locate/biochi

Editorial

Mitochondria: An organelle for life Mitochondria are essential intracellular organelles of eukaryotic cells discovered more than a century ago by Richard Altmann [1]. They obtained their name “mitochondria” from Carl Benda in 1896 [2], a term derived from the Greek language for the words thread (míso2) and granule (cóndro2). Mitochondria are responsible for a large number of processes, i.e. respiration, ATP-generation, synthesis of some amino acids, oxidation of fatty acids, regulation of reactive oxygen species, apoptosis, etc. They are also implicated in the aging process, in many severe and mostly incurable neuromuscular and neurodegenerative syndromes, as well as in illnesses such as Alzheimer’s disease or some cases of cancer and diabetes. All this made this organelle an extremely attractive target for studies, which have reached a real explosion nowadays (>50,000 publications in the last two years are somehow related to mitochondrial organization, functioning or pathology). So far, many crucial issues still await comprehension. The peculiarity of these organelles, protected by a double membrane, is the presence of their own mitochondrial genome (mt-DNA) in their inner compartment. The mt-DNA codes only for a few mitochondrial proteins and translation-related RNAs. It differs in organization and size among species, from several thousands of base pairs in plants to 16 kbp in humans, where the gene organization is so compact that there are almost no noncoding sequences and even some overlapping genes (this compactness was many times outlined and the genome was termed as “small is beautiful”; [3]). Since most of the macromolecules are nucleusencoded, mitochondrial biogenesis and activities, in health as well as in disease, depend on a continuous cross-talk with the nucleocytosolic compartment of the cell. In depth understanding of these interaction and coordination mechanisms and characterization of the involved mitochondrial molecular machines are therefore of primary importance from both fundamental and medico-social points of view. The current issue was set up under the supervision and contribution of a consortium “MitoCross”, gathering together six teams from Strasbourg (France) working on mitochondria and whose aim is to decipher these cross-talk mechanisms. It is obvious, however, that the field of research on mitochondria is broader and includes an extremely wide range of unsolved questions, which are at least partially covered by contributions presented here. The here-included 26 articles are reviews or original research contributions. This special issue is divided into 5 parts, each dealing with several aspects of “Mitochondria: an organelle for life”. Evolution and biogenesis of mitochondria is tackled through a review from Novaki’s group, which gives an insight into the environmental constraints that drive the evolution of eukaryotes and their organelles. Sissler’s group proposes a functional relaxation of a key enzyme from the mitochondrial translation in non-viriplantae organisms, when compared to bacterial and plant ones and despite common ancestry. Then, Bonnefoy’s group reviews the genetic

network of three genes and their relevance to the understanding of mitochondrial biogenesis. The Respiratory chain and metabolic pathways are addressed through the deciphering of the role of Lon protease in HeLa cells and the identification of the variety of cellular roles and molecular targets (Friguet’s group); reviews on model-dependent biogenesis of FeeS cluster (Puccio’s and Lill’s groups), on the mechanisms responsible for CoE-Q biosynthesis (Puccio’s group) and on the impact of pathology-related mutations; and the description of the role of ceramides as signaling and regulatory elements, modulating mitochondrial functions (Saada’s group). The Expression and regulation of mitochondrial genomes is then considered. The contribution by Maréchal-Drouard and coworkers deciphers the peculiarities in codon usage in mitochondrial genomes, and recalls some structural and functional peculiarities and the adaptive RNAeprotein partnership of some molecules from mitochondrial translation. A review of mechanisms, potentially involving recombination processes, and responsible for mt-DNA replication in plants is given by Dietrich’s group. Additional contributions review the role of two proteins in mitochondrial single strand break repair (Meagher’s group), the mechanisms of RNA editing and its functional coupling with pre- and post-editing 30 mRNA modification and guide RNA maturation pathways (Afasizhev’s group), the diversity of mechanistic features of translation initiation in eukaryotes and its divergence from bacterial ancestor (Kamenski’s group), and the features, distribution, functions and mode of action of novel protein families including pentatricopeptide repeat proteins (Giegé’s group). Also, the first biological evidence for the existence of the smallest tRNAs in mitochondria from enopleas is provided by Mörl’s group. Mitochondrial targeting by various macromolecules is addressed through the setting up of an in vitro mRNA binding assay with isolated plant mitochondria and identification of protein partners required for mRNA docking to mitochondria (Duchêne’s group), and the deciphering of the role of pre-sequences and the understanding of the physiological impact of a single destination of a protein naturally dual targeted (Glaser’s group). Mitochondrial dysfunctions, diseases and prospective therapy of “mitochondrial diseases” are also considered. Lombès’s group provides a comprehensive analysis of unsolved issues related to human mitochondrial diseases. Dupuis’s group gives a review on the mitochondrial quality control and its impairment during neurodegenerative diseases. Saada’s group investigates the impact of mutations in nucleus-encoded components of translation machinery on six mitochondrial parameters. Entelis’s group optimizes RNA-based vectors by using chemical modification in the scope of developing an anti-replicative strategy. Di Rago’s group analyzes the molecular impact of two mutations on yeast ATP synthase. And Remacle’s group

0300-9084/$ e see front matter Ó 2014 Published by Elsevier Masson SAS. http://dx.doi.org/10.1016/j.biochi.2014.02.003

Please cite this article in press as: L. Maréchal-Drouard, et al., Mitochondria: An organelle for life, Biochimie (2014), http://dx.doi.org/10.1016/ j.biochi.2014.02.003

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reviews the impact of respiratory-deficient mutants in the green algae and proposes this unicellular organism as a model system. Finally, several Technical aspects of structural and functional analysis of these organelles are presented. Spelbrink’s group discusses methods available to identify proteins associated with mt-DNA nucleoids. Meyer’s contribution is an improved protocol for the conservation of skeletal muscle biopsies, suitable for subsequent functional investigations. And Small’s group considers nuclear mutations as substitutes for phenotypically mimic mutations in the organelle genome. Acknowledgments We would like to thank all of our colleagues who agreed to participate in this task, either as authors or as reviewers. We are particularly grateful to the “Rédaction de Biochimie” (Richard Buckingham and Malika Hassini) for having accepted our proposition to set up a special issue on Mitochondria, which, we believe will adequately reflect the current state of this rapidly evolving and challenging field of research and will stimulate its further development. We are grateful to José Gualberto and Magali Daujat for the creation of the cover image. This special issue was also made possible due to the LABEX [ANR-11-LABX-0057_MITOCROSS] and benefits from funding from the state managed by the French National Research Agency as part of the Investments for the future program.

References [1] R. Altmann, Die Elementarorganismen und ihre Beziehungen zu den Zellen, German Publisher, 1890. [2] C. Benda, Die Mitochondria, 1903. [3] P. Borst, L.A. Grivell, Small is beautifuleportrait of a mitochondrial genome, Nature 290 (1981) 443e444.

L. Maréchal-Drouard Q1 Institut de Biologie Moléculaire des Plantes (IBMP e CNRS), 12 rue du Général Zimmer, 67084 Strasbourg, France E-mail address: [email protected]. M. Sissler* Institut de Biologie Moléculaire et Cellulaire (IBMC e CNRS), 15 rue René Descartes, 67084 Strasbourg, France I. Tarassov Génétique Moléculaire, Génomique, Microbiologie (GMGM e Université de Strasbourg e CNRS), 21 rue René Descartes, 67084 Strasbourg, France E-mail address: [email protected]. * Corresponding author. E-mail address: [email protected] (M. Sissler).

Available online xxx

Please cite this article in press as: L. Maréchal-Drouard, et al., Mitochondria: An organelle for life, Biochimie (2014), http://dx.doi.org/10.1016/ j.biochi.2014.02.003

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Mitochondria: an organelle for life.

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