title: Why mitochondria need a genome revisited.
abstract: In this paper, we experimentally address the debate about why functional transfer of mitochondrial genes to the nucleus has been halted in some organismal groups and why cytosolic expression of mitochondrial proteins has proven remarkably difficult. By expressing all 13 human mitochondrial-encoded genes with strong mitochondrial-targeting sequences in the cytosol of human cells, we show that all proteins, except ATP8, are transported to the endoplasmic reticulum (ER). These results confirm and extend previous findings based on three mitochondrial genes lacking mitochondrial-targeting sequences that also were relocated to the ER during cytosolic expression. We conclude that subcellular protein targeting constitutes a major barrier to functional transfer of mitochondrial genes to the nuclear genome.
authors.affiliation: Department of Molecular Evolution, Cell and Molecular Biology, Uppsala University, Sweden.
authors.forename: Patrik
authors.initials: P
authors.lastname: Björkholm
authors.affiliation: Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Ernst
authors.affiliation: Department of Molecular Evolution, Cell and Molecular Biology, Uppsala University, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Hagström
authors.affiliation: Department of Molecular Evolution, Cell and Molecular Biology, Uppsala University, Sweden.
authors.forename: Siv G E
authors.initials: SG
authors.lastname: Andersson
mesh_terms: D004721:Endoplasmic Reticulum / Q000378:metabolism; D050259:Genes, Mitochondrial; D005818:Genetic Engineering; D054629:Genome, Mitochondrial; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000235:genetics*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
chemical_list: D024101:Mitochondrial Proteins; D011994:Recombinant Proteins
keywords: endoplasmic reticulum; hydrophobicity; mitochondria; signal recognition particle; transmembrane domain