title: The leucine-rich pentatricopeptide repeat-containing protein (LRPPRC) does not activate transcription in mammalian mitochondria.
abstract: Regulation of mtDNA expression is critical for controlling oxidative phosphorylation capacity and has been reported to occur at several different levels in mammalian mitochondria. LRPPRC (leucine-rich pentatricopeptide repeat-containing protein) has a key role in this regulation and acts at the post-transcriptional level to stabilize mitochondrial mRNAs, to promote mitochondrial mRNA polyadenylation, and to coordinate mitochondrial translation. However, recent studies have suggested that LRPPRC may have an additional intramitochondrial role by directly interacting with the mitochondrial RNA polymerase POLRMT to stimulate mtDNA transcription. In this study, we have further examined the intramitochondrial roles for LRPPRC by creating bacterial artificial chromosome transgenic mice with moderately increased LRPPRC expression and heterozygous Lrpprc knock-out mice with moderately decreased LRPPRC expression. Variation of LRPPRC levels in mice in vivo, occurring within a predicted normal physiological range, strongly affected the levels of an unprocessed mitochondrial precursor transcript (ND5-cytochrome b) but had no effect on steady-state levels of mitochondrial transcripts or de novo transcription of mtDNA. We further assessed the role of LRPPRC in mitochondrial transcription by performing size exclusion chromatography and immunoprecipitation experiments in human cell lines and mice, but we found no interaction between LRPPRC and POLRMT. Furthermore, addition of purified LRPPRC to a recombinant human in vitro transcription system did not activate mtDNA transcription. On the basis of these data, we conclude that LRPPRC does not directly regulate mtDNA transcription but rather acts as a post-transcriptional regulator of mammalian mtDNA expression.
authors.affiliation: Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, D-50931 Cologne, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Harmel
authors.forename: Benedetta
authors.initials: B
authors.lastname: Ruzzenente
authors.forename: Mügen
authors.initials: M
authors.lastname: Terzioglu
authors.forename: Henrik
authors.initials: H
authors.lastname: Spåhr
authors.forename: Maria
authors.initials: M
authors.lastname: Falkenberg
authors.forename: Nils-Göran
authors.initials: NG
authors.lastname: Larsson
mesh_terms: D000818:Animals; D045303:Cytochromes b / Q000235:genetics / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D042967:Electron Transport Complex I / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008929:Mitochondria, Heart / Q000235:genetics / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D004272:DNA, Mitochondrial; C087940:LRPPRC protein, human; C486222:Lrpprc protein, mouse; D024101:Mitochondrial Proteins; D009363:Neoplasm Proteins; D045303:Cytochromes b; C481838:MT-ND5 protein, human; D009245:NADH Dehydrogenase; C541921:ND5 protein, mouse; D012321:DNA-Directed RNA Polymerases; C519567:POLRMT protein, human; D042967:Electron Transport Complex I
keywords: LRPPRC; Mitochondria; Mitochondrial DNA; Mitochondrial Diseases; Mitochondrial RNA Polymerase; Mitochondrial Transcription; Mouse Genetics; Post-transcriptional Regulation; mRNA