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Takai M, Yamamoto M, Yashiro N, Nagano S, Kusumoto Y, Tamura M, Taniguchi A, Tsujiuchi T. Impact of cellular ATP levels on cell viability in response to fluorouracil through lysophosphatidic acid (LPA) receptor-4 (LPA 4) and LPA 6 in colon cancer cells. Adv Biol Regul 2024; 93:101042. [PMID: 39024813 DOI: 10.1016/j.jbior.2024.101042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2024] [Revised: 07/11/2024] [Accepted: 07/15/2024] [Indexed: 07/20/2024]
Abstract
Lysophosphatidic acid (LPA) signaling via LPA receptors (LPA1 to LPA6) mediates various aspects of cancer cell behaviors. This study aimed to investigate the variation in intracellular ATP levels and its impact on cell viability in response to fluorouracil (5-FU) through LPA4 and LPA6 in colon cancer DLD-1 cells. LPA4 and LPA6 are linked to Gs and Gi proteins. Gs protein stimulates the activity of adenylyl cyclase, which catalyzes the conversion of ATP to cAMP, whereas Gi protein inhibits this activity. In cell survival assay, cells were treated with 5-FU every 24 h for 3 days. The viability in response to 5-FU in DLD-1 cells was enhanced by LPA4 and LPA6 knockdowns. Furthermore, LPA4 and LPA6 knockdowns reduced the expression of cleaved-PARP1 protein when cells were treated with 5-FU. Since ethidium bromide (EtBr) reduces mitochondrial DNA level in cultured cells, EtBr-treated (DLD-EtBr) cells were generated from DLD-1 cells. The viability to 5-FU in DLD-EtBr cells was higher than that of DLD-1 cells. Additionally, culturing DLD-1 cells in a low glucose-containing medium led to increased viability to 5-FU. LPAR4 and LPAR6 expressions were reduced in both DLD-EtBr and low glucose-treated cells. The cellular ATP levels were significantly decreased in DLD-1 cells following EtBr treatment and exposure to low glucose conditions. Conversely, in the presence of LPA, LPA4 and LPA6 knockdowns resulted in a marked elevation of ATP levels. These results suggest that cell viability to 5-FU is negatively regulated via the activation of LPA4-and LPA6-Gs protein pathways in DLD-1 cells rather than Gi protein.
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Affiliation(s)
- Miwa Takai
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
| | - Mao Yamamoto
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
| | - Narumi Yashiro
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
| | - Shion Nagano
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
| | - Yuka Kusumoto
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
| | - Moemi Tamura
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
| | - Anri Taniguchi
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
| | - Toshifumi Tsujiuchi
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan.
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Takai M, Takauchi M, Kuribayashi M, Tsujiuchi T. LPA receptor-mediated signaling regulates cell motility and survival to anticancer drug of pancreatic cancer cells under glucose-deprived and hypoxic conditions. Biochem Biophys Res Commun 2023; 661:21-27. [PMID: 37084489 DOI: 10.1016/j.bbrc.2023.04.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 04/05/2023] [Accepted: 04/14/2023] [Indexed: 04/23/2023]
Abstract
In tumor microenvironment, cancer cells can adapt to low conditions of nutrients and oxygen. Lysophosphatidic acid (LPA) receptor-mediated signaling is involved in the promotion of malignant properties in cancer cells. In the present study, to examine the roles of LPA receptors in the regulation of cell motility and survival to cisplatin (CDDP) of pancreatic cancer PANC-1 cells under glucose-deprived and hypoxic conditions, cells were cultured in 4500 mg/L high glucose (HG)-DMEM, 500 mg/L middle glucose (MG)-DMEM and 100 mg/L low glucose (LG)-DMEM at 21% and 1% O2. The expression levels of LPAR1 and LPAR2 genes in cells cultured in MG-DMEM and LG-DMEM were significantly elevated, compared with HG-DMEM cells. The cell motility and survival rate to CDDP of cells cultured in MG-DMEM and LG-DMEM were significantly lower than those of cells cultured in HG-DMEM. The cell survival to CDDP was enhanced by LPA1 knockdown and suppressed by LPA2 knockdown. Under hypoxic conditions (1% O2), LPAR1, LPAR2 and LPAR3 expressions were markedly higher in cells cultured in MG-DMEM and LG-DMEM than in cells cultured in HG-DMEM. The cell survival rates to CDDP of cells cultured in MG-DMEM and LG-DMEM were elevated in comparison with HG-DMEM. The cell survival to CDDP was reduced by LPA3 knockdown. These results suggest that LPA receptor-mediated signaling is involved in the regulation of malignant properties of PANC-1 cells under glucose-deprived and hypoxic conditions.
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Affiliation(s)
- Miwa Takai
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
| | - Minori Takauchi
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
| | - Mako Kuribayashi
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
| | - Toshifumi Tsujiuchi
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan.
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Kurisu R, Takamoto M, Minami K, Ueda N, Yamada M, Shima N, Otani T, Sakai Y, Kondo D, Tsujiuchi T. Effects of lysophosphatidic acid (LPA) signaling via LPA receptors on cellular functions associated with ATP reduction in osteosarcoma cells treated with ethidium bromide. J Bioenerg Biomembr 2022; 54:109-117. [PMID: 35260987 DOI: 10.1007/s10863-022-09933-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Accepted: 02/07/2022] [Indexed: 11/29/2022]
Abstract
Lysophosphatidic acid (LPA) signaling via LPA receptors (LPA1 to LPA6) exhibits a variety of malignant properties in cancer cells. Intracellular ATP depletion leads to the development of necrosis and apoptosis. The present study aimed to evaluate the effects of LPA receptor-mediated signaling on the regulation of cancer cell functions associated with ATP reduction. Long-term ethidium bromide (EtBr) treated (MG63-EtBr) cells were established from osteosarcoma MG-63 cells. The intracellular ATP levels of MG63-EtBr cells were significantly lower than that of MG-63 cells. LPAR2, LPAR3, LPAR4 and LPAR6 gene expressions were elevated in MG63-EtBr cells. The cell motile and invasive activities of MG63-EtBr cells were markedly higher than those of MG-63 cells. The cell motile activity of MG-63 cells was increased by LPA4 and LPA6 knockdowns. In cell survival assay, cells were treated with cisplatin (CDDP) every 24 h for 3 days. The cell survival to CDDP of MG63-EtBr cells was lower than that of MG-63 cells. LPA2 knockdown decreased the cell survival to CDDP of MG-63 cells. The cell survival to CDDP of MG-63 cells was inhibited by (2 S)-OMPT (LPA3 agonist). Moreover, the cell survival to CDDP of MG-63 cells was enhanced by LPA4 and LPA6 knockdowns. These results indicate that LPA signaling via LPA receptors is involved in the regulation of cellular functions associated with ATP reduction in MG-63 cells treated with EtBr.
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Affiliation(s)
- Rio Kurisu
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, 577-8502, Higashiosaka, Osaka, Japan
| | - Miyu Takamoto
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, 577-8502, Higashiosaka, Osaka, Japan
| | - Kanako Minami
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, 577-8502, Higashiosaka, Osaka, Japan
| | - Nanami Ueda
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, 577-8502, Higashiosaka, Osaka, Japan
| | - Marina Yamada
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, 577-8502, Higashiosaka, Osaka, Japan
| | - Nanami Shima
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, 577-8502, Higashiosaka, Osaka, Japan
| | - Tomoka Otani
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, 577-8502, Higashiosaka, Osaka, Japan
| | - Yuma Sakai
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, 577-8502, Higashiosaka, Osaka, Japan
| | - Daisuke Kondo
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, 577-8502, Higashiosaka, Osaka, Japan
| | - Toshifumi Tsujiuchi
- Division of Molecular Oncology, Department of Life Science, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, 577-8502, Higashiosaka, Osaka, Japan.
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Mazunin IO, Levitskii SA, Patrushev MV, Kamenski PA. Mitochondrial Matrix Processes. BIOCHEMISTRY (MOSCOW) 2016; 80:1418-28. [PMID: 26615433 DOI: 10.1134/s0006297915110036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Mitochondria possess their own genome that, despite its small size, is critically important for their functioning, as it encodes several dozens of RNAs and proteins. All biochemical processes typical for bacterial and nuclear DNA are described in mitochondrial matrix: replication, repair, recombination, and transcription. Commonly, their mechanisms are similar to those found in bacteria, but they are characterized by several unique features. In this review, we provide an overall description of mitochondrial matrix processes paying special attention to the typical features of such mechanisms.
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Affiliation(s)
- I O Mazunin
- Immanuil Kant Baltic Federal University, Institute of Chemistry and Biology, Kaliningrad, 236038, Russia.
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Campbell CT, Kolesar JE, Kaufman BA. Mitochondrial transcription factor A regulates mitochondrial transcription initiation, DNA packaging, and genome copy number. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1819:921-9. [DOI: 10.1016/j.bbagrm.2012.03.002] [Citation(s) in RCA: 236] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 03/08/2012] [Accepted: 03/15/2012] [Indexed: 10/28/2022]
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Guja KE, Garcia-Diaz M. Hitting the brakes: termination of mitochondrial transcription. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:939-47. [PMID: 22137970 DOI: 10.1016/j.bbagrm.2011.11.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 11/07/2011] [Accepted: 11/15/2011] [Indexed: 10/15/2022]
Abstract
Deficiencies in mitochondrial protein production are associated with human disease and aging. Given the central role of transcription in gene expression, recent years have seen a renewed interest in understanding the molecular mechanisms controlling this process. In this review, we have focused on the mostly uncharacterized process of transcriptional termination. We review how several recent breakthroughs have provided insight into our understanding of the termination mechanism, the protein factors that mediate termination, and the functional relevance of different termination events. Furthermore, the identification of termination defects resulting from a number of mtDNA mutations has led to the suggestion that this could be a common mechanism influencing pathogenesis in a number of mitochondrial diseases, highlighting the importance of understanding the processes that regulate transcription in human mitochondria. We discuss how these recent findings set the stage for future studies on this important regulatory mechanism. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.
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Affiliation(s)
- Kip E Guja
- Medical Scientist Training Program, Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, NY 11794, USA.
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Mitochondrial transcription: lessons from mouse models. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:961-9. [PMID: 22120174 DOI: 10.1016/j.bbagrm.2011.11.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 11/09/2011] [Accepted: 11/10/2011] [Indexed: 11/22/2022]
Abstract
Mammalian mitochondrial DNA (mtDNA) is a circular double-stranded DNA genome of ~16.5 kilobase pairs (kb) that encodes 13 catalytic proteins of the ATP-producing oxidative phosphorylation system (OXPHOS), and the rRNAs and tRNAs required for the translation of the mtDNA transcripts. All the components needed for transcription and replication of the mtDNA are, therefore, encoded in the nuclear genome, as are the remaining components of the OXPHOS system and the mitochondrial translation machinery. Regulation of mtDNA gene expression is very important for modulating the OXPHOS capacity in response to metabolic requirements and in pathological processes. The combination of in vitro and in vivo studies has allowed the identification of the core machinery required for basal mtDNA transcription in mammals and a few proteins that regulate mtDNA transcription. Specifically, the generation of knockout mouse strains in the last several years, has been key to understanding the basis of mtDNA transcription in vivo. However, it is well accepted that many components of the transcription machinery are still unknown and little is known about mtDNA gene expression regulation under different metabolic requirements or disease processes. In this review we will focus on how the creation of knockout mouse models and the study of their phenotypes have contributed to the understanding of mitochondrial transcription in mammals. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.
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Hyvärinen AK, Kumanto MK, Marjavaara SK, Jacobs HT. Effects on mitochondrial transcription of manipulating mTERF protein levels in cultured human HEK293 cells. BMC Mol Biol 2010; 11:72. [PMID: 20846394 PMCID: PMC2955023 DOI: 10.1186/1471-2199-11-72] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Accepted: 09/16/2010] [Indexed: 11/22/2022] Open
Abstract
Background Based on its activities in vitro, the mammalian mitochondrial transcription termination factor mTERF has been proposed to regulate mitochondrial transcription by favouring termination at its high-affinity binding immediately downstream of the rDNA segment of mitochondrial DNA, and initiation selectively at the PH1 site of the heavy-strand promoter. This defines an rDNA transcription unit distinct from the 'global' heavy-strand transcription unit initiating at PH2. However, evidence that the relative activities of the two heavy-strand transcription units are modulated by mTERF in vivo is thus far lacking. Results To test this hypothesis, we engineered human HEK293-derived cells for over-expression or knockdown of mTERF, and measured the steady-state levels of transcripts belonging to different transcription units, namely tRNALeu(UUR) and ND1 mRNA for the PH2 transcription unit, and tRNAPhe plus 12S and 16S rRNA for the PH1 transcription unit. The relative levels of 16S rRNA and ND1 mRNA were the same under all conditions tested, although mTERF knockdown resulted in increased levels of transcripts of 12S rRNA. The amount of tRNAPhe relative to tRNALeu(UUR) was unaffected by mTERF over-expression, altered only slightly by mTERF knockdown, and was unchanged during recovery from ethidium bromide-induced depletion of mitochondrial RNA. mTERF overexpression or knockdown produced a substantial shift (3-5-fold) in the relative abundance of antisense transcripts either side of its high-affinity binding site. Conclusions mTERF protein levels materially affect the amount of readthrough transcription on the antisense strand of mtDNA, whilst the effects on sense-strand transcripts are complex, and suggest the influence of compensatory mechanisms.
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Affiliation(s)
- Anne K Hyvärinen
- Institute of Medical Technology and Tampere University Hospital, FI-33014 University of Tampere, Finland
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Isolation of mitochondria for biogenetical studies: An update. Mitochondrion 2009; 10:253-62. [PMID: 20034597 DOI: 10.1016/j.mito.2009.12.148] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Revised: 11/11/2009] [Accepted: 12/11/2009] [Indexed: 10/20/2022]
Abstract
The use of good quality preparations of isolated mitochondria is necessary when studying the mitochondrial biogenetical activities. This article explains a fast and simple method for the purification of mammalian mitochondria from different tissues and cultured cells, that is suitable for the analysis of many aspects of the organelle's biogenesis. The mitochondria isolated following the protocol described here, are highly active and capable of DNA, RNA and protein synthesis. Mitochondrial tRNA aminoacylation, mtDNA-protein interactions and specific import of added proteins into the organelles, can also be studied using this kind of preparations.
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Markov DA, Savkina M, Anikin M, Del Campo M, Ecker K, Lambowitz AM, De Gnore JP, McAllister WT. Identification of proteins associated with the yeast mitochondrial RNA polymerase by tandem affinity purification. Yeast 2009; 26:423-40. [PMID: 19536766 PMCID: PMC2896726 DOI: 10.1002/yea.1672] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The abundance of mitochondrial (mt) transcripts varies under different conditions, and is thought to depend upon rates of transcription initiation, transcription termination/attenuation and RNA processing/degradation. The requirement to maintain the balance between RNA synthesis and processing may involve coordination between these processes; however, little is known about factors that regulate the activity of mtRNA polymerase (mtRNAP). Recent attempts to identify mtRNAP–protein interactions in yeast by means of a generalized tandem affinity purification (TAP) protocol were not successful, most likely because they involved a C-terminal mtRNAP–TAP fusion (which is incompatible with mtRNAP function) and because of the use of whole-cell solubilization protocols that did not preserve the integrity of mt protein complexes. Based upon the structure of T7 RNAP (to which mtRNAPs show high sequence similarity), we identified positions in yeast mtRNAP that allow insertion of a small affinity tag, confirmed the mature N-terminus, constructed a functional N-terminal TAP–mtRNAP fusion, pulled down associated proteins, and identified them by LC–MS–MS. Among the proteins found in the pull-down were a DEAD-box protein (Mss116p) and an RNA-binding protein (Pet127p). Previous genetic experiments suggested a role for these proteins in linking transcription and RNA degradation, in that a defect in the mt degradadosome could be suppressed by overexpression of either of these proteins or, independently, by mutations in either mtRNAP or its initiation factor Mtf1p. Further, we found that Mss116p inhibits transcription by mtRNAP in vitro in a steady-state reaction. Our results support the hypothesis that Mss116p and Pet127p are involved in modulation of mtRNAP activity. Copyright © 2009 John Wiley & Sons, Ltd.
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Affiliation(s)
- Dmitriy A Markov
- Departments of Cell Biology, University of Medicine and Dentistry of New Jersey, Stratford, USA.
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11
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Sologub MY, Kochetkov SN, Temiakov DE. Transcription and its regulation in mammalian and human mitochondria. Mol Biol 2009. [DOI: 10.1134/s0026893309020034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Pohjoismäki JLO, Wanrooij S, Hyvärinen AK, Goffart S, Holt IJ, Spelbrink JN, Jacobs HT. Alterations to the expression level of mitochondrial transcription factor A, TFAM, modify the mode of mitochondrial DNA replication in cultured human cells. Nucleic Acids Res 2006; 34:5815-28. [PMID: 17062618 PMCID: PMC1635303 DOI: 10.1093/nar/gkl703] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Mitochondrial transcription factor A (TFAM) is an abundant mitochondrial protein of the HMG superfamily, with various putative roles in mitochondrial DNA (mtDNA) metabolism. In this study we have investigated the effects on mtDNA replication of manipulating TFAM expression in cultured human cells. Mammalian mtDNA replication intermediates (RIs) fall into two classes, whose mechanistic relationship is not properly understood. One class is characterized by extensive RNA incorporation on the lagging strand, whereas the other has the structure of products of conventional, strand-coupled replication. TFAM overexpression increased the overall abundance of RIs and shifted them substantially towards those of the conventional, strand-coupled type. The shift was most pronounced in the rDNA region and at various replication pause sites and was accompanied by a drop in the relative amount of replication-termination intermediates, a substantial reduction in mitochondrial transcripts, mtDNA decatenation and progressive copy number depletion. TFAM overexpression could be partially phenocopied by treatment of cells with dideoxycytidine, suggesting that its effects are partially attributable to a decreased rate of fork progression. TFAM knockdown also resulted in mtDNA depletion, but RIs remained mainly of the ribosubstituted type, although termination intermediates were enhanced. We propose that TFAM influences the mode of mtDNA replication via its combined effects on different aspects of mtDNA metabolism.
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Affiliation(s)
- Jaakko L. O. Pohjoismäki
- Institute of Medical Technology and Tampere University HospitalFI-33014 University of Tampere, Finland
| | - Sjoerd Wanrooij
- Institute of Medical Technology and Tampere University HospitalFI-33014 University of Tampere, Finland
| | - Anne K. Hyvärinen
- Institute of Medical Technology and Tampere University HospitalFI-33014 University of Tampere, Finland
| | - Steffi Goffart
- Institute of Medical Technology and Tampere University HospitalFI-33014 University of Tampere, Finland
| | - Ian J. Holt
- MRC-Dunn Human Nutrition Unit, Hill RoadCambridge CB2 2XY, England, UK
| | - Johannes N. Spelbrink
- Institute of Medical Technology and Tampere University HospitalFI-33014 University of Tampere, Finland
| | - Howard T. Jacobs
- Institute of Medical Technology and Tampere University HospitalFI-33014 University of Tampere, Finland
- IBLS Division of Molecular Genetics, University of GlasgowGlasgow G12 8QQ, Scotland, UK
- To whom correspondence should be addressed. Tel: +358 33 55 17 731; Fax: +358 32 15 77 10;
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von Wurmb-Schwark N, Cavelier L, Cortopassi GA. A low dose of ethidium bromide leads to an increase of total mitochondrial DNA while higher concentrations induce the mtDNA 4997 deletion in a human neuronal cell line. Mutat Res 2006; 596:57-63. [PMID: 16488450 DOI: 10.1016/j.mrfmmm.2005.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Accepted: 12/15/2005] [Indexed: 05/06/2023]
Abstract
Ethidium bromide (EtBr) is widely used to deplete mitochondrial DNA (mtDNA) and produce mitochondrial DNA-less cell lines. However, it frequently fails to deplete mtDNA in mouse cells. In this study we show by using a highly sensitive real-time PCR, that low doses of EtBr (10 microM) did lead to a three-fold increase of the total amount of mitochondrial DNA in a human neuronal cell line (Ntera 2). A higher dose of EtBr (25 microM) led to the expected decrease of mtDNA until day 22 when the cells almost died. Cell growth and mtDNA content could be restored after additional 22 days of non-EtBr treatment. The highest concentration of 50 microM also led to a significant increase of mtDNA. The cells died when they had only about 10% of mtDNA left, indicating a mtDNA threshold for cell survival. Additionally, the so-called common 4977 bp deletion could be induced by prolonged exposure to ethidium bromide. Whereas the higher doses led to significant higher amounts of deleted mtDNA.
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Affiliation(s)
- N von Wurmb-Schwark
- Institute of Legal Medicine, Christian-Albrechts-University of Kiel, Arnold-Heller-Str. 12, 24105 Kiel, Germany.
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Koulintchenko M, Temperley RJ, Mason PA, Dietrich A, Lightowlers RN. Natural competence of mammalian mitochondria allows the molecular investigation of mitochondrial gene expression. Hum Mol Genet 2005; 15:143-54. [PMID: 16321989 DOI: 10.1093/hmg/ddi435] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Respiration, a fundamental process in mammalian cells, requires two genomes, those of the nucleus and the mitochondrion (mtDNA). Mutations of mtDNA are being increasingly recognized in disease and may play an important role in the ageing process. Accepting the vital role of mtDNA gene products, our limited knowledge concerning the details of mitochondrial gene expression is surprising. This is, in part, due to our inability to transfect mitochondria and to manipulate their genome. There have been claims of successful DNA import into isolated organelles, but most reports lacked evidence of expression and no method has furthered our understanding of gene expression. Here, we report that mammalian mitochondria possess a natural competence for DNA import. Using five functional assays, we show imported DNA can act as templates for DNA synthesis or promoter-driven transcription, with the resultant polycistronic RNA being processed (5' and 3') and excised mt-tRNA matured. Exploiting this natural competence will allow us to explore mitochondrial gene expression in organello and provides the potential for mitochondrial transfection in vivo.
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Affiliation(s)
- Milana Koulintchenko
- Mitochondrial Research Group, Institutes of Neuroscience, University of Newcastle upon Tyne, UK
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Abstract
The mitochondrial ribomotor model has been proposed to explain how the balance between rRNA and mRNA in mammalian mitochondria is regulated. In this model, the interaction of the mitochondrial transcription termination factor (mTERF) with some unknown component(s), causes a loop to form in the mtDNA chain that brings the initiation and termination regions together at its base. By bringing these sites into closer proximity, the mtRNA polymerase molecules can be directly transferred from the termination site to the IH1 initiation site of the H-strand once transcription terminates. This process occurs when mTERF is phosphorylated. When unphosphorylated, transcription is initiated from the IH2 site and the polymerase reads through the mTERF-dependent termination site, resulting in the transcription of almost the entire H-strand.
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16
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Taanman JW, Llewelyn Williams S. The Human Mitochondrial Genome. OXIDATIVE STRESS AND DISEASE 2005. [DOI: 10.1201/9781420028843.ch3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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17
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Maniura-Weber K, Goffart S, Garstka HL, Montoya J, Wiesner RJ. Transient overexpression of mitochondrial transcription factor A (TFAM) is sufficient to stimulate mitochondrial DNA transcription, but not sufficient to increase mtDNA copy number in cultured cells. Nucleic Acids Res 2004; 32:6015-27. [PMID: 15547250 PMCID: PMC534614 DOI: 10.1093/nar/gkh921] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mitochondrial transcription factor A (TFAM) stimulates transcription from mitochondrial DNA (mtDNA) promoters in vitro and in organello. To investigate whether changes of TFAM levels also modulate transcription and replication in situ, the protein was transiently overexpressed in cultured cells. Mitochondrial mRNAs were significantly elevated at early time points, when no expansion of the TFAM pool was yet observed, but were decreased when TFAM levels had doubled, resemb-ling in vitro results. HEK cells contain about 35 molecules of TFAM per mtDNA. High levels of TFAM were not associated with increases of full-length mtDNA, but nucleic acid species sensitive to RNAse H increased. Stimulation of transcription was more evident when TFAM was transiently overexpressed in cells pre-treated with ethidium bromide (EBr) having lowered mtDNA, TFAM and mitochondrial transcript levels. EBr rapidly inhibited mtDNA transcription, while decay of mtDNA was delayed and preferentially slowly migrating, relaxed mtDNA species were depleted. In conclusion, we show that transcription of mtDNA is submaximal in cultured cells and that a subtle increase of TFAM within the matrix is sufficient to stimulate mitochondrial transcription. Thus, this protein meets all criteria for being a key factor regulating mitochondrial transcription in vivo, but other factors are necessary for increasing mtDNA copy number, at least in cultured cells.
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Affiliation(s)
- Katharina Maniura-Weber
- Institute of Vegetative Physiology, Medical Faculty, University of Köln, Robert-Koch-Strasse 39, D-50931 Köln, FRG
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Garstka HL, Schmitt WE, Schultz J, Sogl B, Silakowski B, Pérez-Martos A, Montoya J, Wiesner RJ. Import of mitochondrial transcription factor A (TFAM) into rat liver mitochondria stimulates transcription of mitochondrial DNA. Nucleic Acids Res 2003; 31:5039-47. [PMID: 12930954 PMCID: PMC212813 DOI: 10.1093/nar/gkg717] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mitochondrial transcription factor A (TFAM) has been shown to stimulate transcription from mitochondrial DNA promoters in vitro. In order to determine whether changes in TFAM levels also regulate RNA synthesis in situ, recombinant human precursor proteins were imported into the matrix of rat liver mitochondria. After uptake of wt-TFAM, incorporation of [alpha-32P]UTP into mitochondrial mRNAs as well as rRNAs was increased 2-fold (P < 0.05), whereas import of truncated TFAM lacking 25 amino acids at the C-terminus had no effect. Import of wt-TFAM into liver mitochondria from hypothyroid rats stimulated RNA synthesis up to 4-fold. We conclude that the rate of transcription is submaximal in freshly isolated rat liver mitochondria and that increasing intra-mitochondrial TFAM levels is sufficient for stimulation. The low transcription rate associated with the hypothyroid state observed in vivo as well as in organello seems to be a result of low TFAM levels, which can be recovered by treating animals with T3 in vivo or by importing TFAM in organello. Thus, this protein meets the criteria for being a key factor in regulating mitochondrial gene expression in vivo.
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Affiliation(s)
- Heike L Garstka
- Department of Physiology II, University of Heidelberg, Im Neuenheimer Feld, D-69120 Heidelberg, Germany
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19
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Eads BD, Hand SC. Transcriptional initiation under conditions of anoxia-induced quiescence in mitochondria from Artemia franciscana embryos. J Exp Biol 2003; 206:577-89. [PMID: 12502778 DOI: 10.1242/jeb.00110] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In response to anoxia, embryos of the brine shrimp Artemia franciscana are able coordinately to downregulate metabolism to levels low enough to permit survival for several years at room temperature. In addition to dramatic decreases in free ATP levels and heat production, intracellular pH drops from 7.8 to 6.3 overnight. Use of isolated mitochondria to study transcriptional responses to anoxia offers several advantages: (1). the localized nature of transcript initiation, processing and degradation, all of which may be followed in organello; (2). the relatively simple cis- and trans-machinery involved and (3). the ability to provide relevant physiological treatments in vitro. In response to anoxic incubation of embryos in vivo for 4 h followed by anoxic mitochondrial isolation and anoxic transcription assay at pH 6.4, a significant decrease in overall UTP incorporation (77%) was seen after 30 min relative to normoxic, pH 7.9 controls. A less severe inhibition of transcription under anoxia (52%) was observed compared with controls when pH was raised to 7.9. Similarly, under normoxia, the incubation at low pH (6.4) reduced transcription by 59%. Ribonuclease protection assays showed that the contribution of in vitro initiation during the assay fell from 78% at pH 7.9 to approximately 32% at pH 6.4 under either normoxic or anoxic conditions. DNA footprinting of putative transcriptional promoters revealed proteins at regular intervals upstream of the 12S rRNA in the control region, which previously had been indirectly inferred to contain promoters for H-strand transcription. The area between 1230 and 12065 contains a sequence in the tRNA(leu) gene believed to bind the transcription termination factor mTERF or TERM, and we provide the first evidence that this sequence is protein-bound in A. franciscana. However, our hypothesis that initiation is reduced at low pH because of a change in DNA binding by mitochondrial transcription factors was not confirmed. We propose that regulation of initiation may be mediated by covalent modification or by protein-protein interactions not detected by footprinting.
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Affiliation(s)
- Brian D Eads
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
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20
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Rapoport SI. Coupled reductions in brain oxidative phosphorylation and synaptic function can be quantified and staged in the course of Alzheimer disease. Neurotox Res 2003; 5:385-98. [PMID: 14715441 DOI: 10.1007/bf03033167] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In vivo, post-mortem and biopsy data suggest that coupled declines occur in brain synaptic activity and brain energy consumption during the evolution of Alzheimer disease. In the first stage of these declines, changes in synaptic structure and function reduce neuronal energy demand and lead to potentially reversible downregulation of oxidative phosphorylation (OXPHOS) within neuronal mitochondria. At this stage, measuring brain glucose metabolism or brain blood flow in patients, using positron emission tomography (PET), shows that the brain can be almost normally activated in response to stimulation. Thus, therapy at this stage should be designed to re-establish synaptic integrity or prevent its further deterioration. As disease progresses, neurofibrillary tangles with abnormally phosphorylated tau protein accumulate within neuronal cytoplasm, to the point that they co-opt the nonphosphorylated tau necessary for axonal transport of mitochondria between the cell nucleus and the synapse. In this second stage, severe energy depletion and other pathological processes associated with irreversibly downregulated OXPHOS lead to cell death, and the brain cannot normally respond to functional stimulation.
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Affiliation(s)
- Stanley I Rapoport
- Brain Physiology and Metabolism Sections, Bldg. 10, Rm. 6N202, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
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21
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DasGupta SF, Rapoport SI, Gerschenson M, Murphy E, Fiskum G, Russell SJ, Chandrasekaran K. ATP synthesis is coupled to rat liver mitochondrial RNA synthesis. Mol Cell Biochem 2001; 221:3-10. [PMID: 11506183 DOI: 10.1023/a:1010812128765] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Rat liver mitochondria respond to changes in energy demand by modulating the amount of RNA synthesized. Coupled rat liver mitochondria were used to determine the relationship between mitochondrial respiration, ATP levels, and mitochondrial transcription. This system included oxidizable substrates (malate and glutamate) and constituents that could support both mitochondrial respiration and transcription. The respiratory inhibitor rotenone, phosphorylation inhibitor oligomycin, and the uncoupler of oxidative phosphorylation carbonyl-cyanide p-triflouromethoxyphehylhydrazone inhibited RNA synthesis. Addition of ADP stimulated mitochondrial transcription and peak RNA synthesis was observed at 1-2 mM ADP. At ADP concentrations above 2 mM, RNA synthesis decreased. These results demonstrate that mitochondrial transcription is tightly coupled to ATP levels.
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Affiliation(s)
- S F DasGupta
- Section on Brain Physiology and Metabolism, NIA, NIH, Bethesda, MD, USA
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22
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Chomyn A, Enriquez JA, Micol V, Fernandez-Silva P, Attardi G. The mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode syndrome-associated human mitochondrial tRNALeu(UUR) mutation causes aminoacylation deficiency and concomitant reduced association of mRNA with ribosomes. J Biol Chem 2000; 275:19198-209. [PMID: 10858457 DOI: 10.1074/jbc.m908734199] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The pathogenetic mechanism of the mitochondrial tRNA(Leu(UUR)) A3243G transition associated with the mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome has been investigated in transmitochondrial cell lines constructed by transfer of mutant mitochondrial DNA (mtDNA)-carrying mitochondria from three genetically unrelated MELAS patients or of isogenic wild-type mtDNA-carrying organelles into human mtDNA-less cells. An in vivo footprinting analysis of the mtDNA segment within the tRNA(Leu(UUR)) gene that binds the transcription termination factor failed to reveal any difference in occupancy of sites or qualitative interaction with the protein between mutant and wild-type mtDNAs. Cell lines nearly homoplasmic for the mutation exhibited a strong (70-75%) reduction in the level of aminoacylated tRNA(Leu(UUR)) and a decrease in mitochondrial protein synthesis rate. The latter, however, did not show any significant correlation between synthesis defect of the individual polypeptides and number or proportion of UUR codons in their mRNAs, suggesting that another step, other than elongation, may be affected. Sedimentation analysis in sucrose gradient showed a reduction in size of the mitochondrial polysomes, while the distribution of the two rRNA components and of the mRNAs revealed decreased association of mRNA with ribosomes and, in the most affected cell line, pronounced degradation of the mRNA associated with slowly sedimenting structures. Therefore, several lines of evidence indicate that the protein synthesis defect in A3243G MELAS mutation-carrying cells is mainly due to a reduced association of mRNA with ribosomes, possibly as a consequence of the tRNA(Leu(UUR)) aminoacylation defect.
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Affiliation(s)
- A Chomyn
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
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Enríquez JA, Fernández-Sílva P, Montoya J. Autonomous regulation in mammalian mitochondrial DNA transcription. Biol Chem 1999; 380:737-47. [PMID: 10494823 DOI: 10.1515/bc.1999.094] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The regulation of the oxidative phosphorylation system (OXPHOS) biogenesis in eukaryotic cells is unique since it involves the expression of two genomes, the mitochondrial DNA (mtDNA) and the nuclear DNA (nDNA). The considerable effort done in collecting information on the factors that influence the expression of the genes encoded in mtDNA and nDNA has revealed that a multiplicity of regulatory options are available in mammalian cells to perform this task. Thus, at least three archetypal situations can be distinguished: mitochondrial proliferation, mitochondrial differentiation, and mitochondrial local tuning (MLT). Each of them seems to be predominantly under the control of specific strategies of regulation, although the description of the detailed molecular mechanisms involved is still in its beginnings. In the present review, we focus on the evidence supporting the existence of mechanisms for autonomous regulation of mtDNA transcription and its role in the integrated regulation of the OXPHOS system biogenesis.
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Affiliation(s)
- J A Enríquez
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragova, Spain
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Taanman JW. The mitochondrial genome: structure, transcription, translation and replication. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1410:103-23. [PMID: 10076021 DOI: 10.1016/s0005-2728(98)00161-3] [Citation(s) in RCA: 1004] [Impact Index Per Article: 40.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mitochondria play a central role in cellular energy provision. The organelles contain their own genome with a modified genetic code. The mammalian mitochondrial genome is transmitted exclusively through the female germ line. The human mitochondrial DNA (mtDNA) is a double-stranded, circular molecule of 16569 bp and contains 37 genes coding for two rRNAs, 22 tRNAs and 13 polypeptides. The mtDNA-encoded polypeptides are all subunits of enzyme complexes of the oxidative phosphorylation system. Mitochondria are not self-supporting entities but rely heavily for their functions on imported nuclear gene products. The basic mechanisms of mitochondrial gene expression have been solved. Cis-acting mtDNA sequences have been characterised by sequence comparisons, mapping studies and mutation analysis both in vitro and in patients harbouring mtDNA mutations. Characterisation of trans-acting factors has proven more difficult but several key enzymes involved in mtDNA replication, transcription and protein synthesis have now been biochemically identified and some have been cloned. These studies revealed that, although some factors may have an additional function elsewhere in the cell, most are unique to mitochondria. It is expected that cell cultures of patients with mitochondrial diseases will increasingly be used to address fundamental questions about mtDNA expression.
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Affiliation(s)
- J W Taanman
- Department of Clinical Neurosciences, Royal Free Hospital School of Medicine, University of London, Rowland Hill Street, London NW3 2PF,
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Enríquez JA, Fernández-Silva P, Garrido-Pérez N, López-Pérez MJ, Pérez-Martos A, Montoya J. Direct regulation of mitochondrial RNA synthesis by thyroid hormone. Mol Cell Biol 1999; 19:657-70. [PMID: 9858589 PMCID: PMC83923 DOI: 10.1128/mcb.19.1.657] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have analyzed the influence of in vivo treatment and in vitro addition of thyroid hormone on in organello mitochondrial DNA (mtDNA) transcription and, in parallel, on the in organello footprinting patterns at the mtDNA regions involved in the regulation of transcription. We found that thyroid hormone modulates mitochondrial RNA levels and the mRNA/rRNA ratio by influencing the transcriptional rate. In addition, we found conspicuous differences between the mtDNA dimethyl sulfate footprinting patterns of mitochondria derived from euthyroid and hypothyroid rats at the transcription initiation sites but not at the mitochondrial transcription termination factor (mTERF) binding region. Furthermore, direct addition of thyroid hormone to the incubation medium of mitochondria isolated from hypothyroid rats restored the mRNA/rRNA ratio found in euthyroid rats as well as the mtDNA footprinting patterns at the transcription initiation area. Therefore, we conclude that the regulatory effect of thyroid hormone on mitochondrial transcription is partially exerted by a direct influence of the hormone on the mitochondrial transcription machinery. Particularly, the influence on the mRNA/rRNA ratio is achieved by selective modulation of the alternative H-strand transcription initiation sites and does not require the previous activation of nuclear genes. These results provide the first functional demonstration that regulatory signals, such as thyroid hormone, that modify the expression of nuclear genes can also act as primary signals for the transcriptional apparatus of mitochondria.
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Affiliation(s)
- J A Enríquez
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, E-50013 Zaragoza, Spain
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