title: The regulation of mitochondrial transcription factor A (Tfam) expression during skeletal muscle cell differentiation.
abstract: The ATP demand required for muscle development is accommodated by elevations in mitochondrial biogenesis, through the co-ordinated activities of the nuclear and mitochondrial genomes. The most important transcriptional activator of the mitochondrial genome is mitochondrial transcription factor A (Tfam); however, the regulation of Tfam expression during muscle differentiation is not known. Thus, we measured Tfam mRNA levels, mRNA stability, protein expression and localization and Tfam transcription during the progression of muscle differentiation. Parallel 2-fold increases in Tfam protein and mRNA were observed, corresponding with 2-3-fold increases in mitochondrial content. Transcriptional activity of a 2051 bp promoter increased during this differentiation period and this was accompanied by a 3-fold greater Tfam mRNA stabilization. Interestingly, truncations of the promoter at 1706 bp, 978 bp and 393 bp promoter all exhibited 2-3-fold higher transcriptional activity than the 2051 bp construct, indicating the presence of negative regulatory elements within the distal 350 bp of the promoter. Activation of AMP kinase augmented Tfam transcription within the proximal promoter, suggesting the presence of binding sites for transcription factors that are responsive to cellular energy state. During differentiation, the accumulating Tfam protein was progressively distributed to the mitochondrial matrix where it augmented the expression of mtDNA and COX (cytochrome c oxidase) subunit I, an mtDNA gene product. Our data suggest that, during muscle differentiation, Tfam protein levels are regulated by the availability of Tfam mRNA, which is controlled by both transcription and mRNA stability. Changes in energy state and Tfam localization also affect Tfam expression and action in differentiating myotubes.
authors.affiliation: School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, Ontario, Canada M3J 1P3.
authors.forename: Melania
authors.initials: M
authors.lastname: Collu-Marchese
authors.affiliation: School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, Ontario, Canada M3J 1P3.
authors.forename: Michael
authors.initials: M
authors.lastname: Shuen
authors.affiliation: School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, Ontario, Canada M3J 1P3.
authors.forename: Marion
authors.initials: M
authors.lastname: Pauly
authors.affiliation: School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, Ontario, Canada M3J 1P3.
authors.forename: Ayesha
authors.initials: A
authors.lastname: Saleem
authors.affiliation: School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, Ontario, Canada M3J 1P3 dhood@yorku.ca.
authors.forename: David A
authors.initials: DA
authors.lastname: Hood
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D002454:Cell Differentiation; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006609:High Mobility Group Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology*; D011401:Promoter Regions, Genetic; D020871:RNA Stability; D012265:Ribonucleotides / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D012265:Ribonucleotides; C081930:Tfam protein, mouse; D000620:Aminoimidazole Carboxamide; D003576:Electron Transport Complex IV; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide
keywords: adenosine 5′-phosphate (AMP) kinase; messenger ribonucleic acid (mRNA) stability; mitochondrial biogenesis; myogenesis; transcription