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Li Z, Fan EK, Liu J, Scott MJ, Li Y, Li S, Xie W, Billiar TR, Wilson MA, Jiang Y, Wang P, Fan J. Cold-inducible RNA-binding protein through TLR4 signaling induces mitochondrial DNA fragmentation and regulates macrophage cell death after trauma. Cell Death Dis 2017; 8:e2775. [PMID: 28492546 PMCID: PMC5584526 DOI: 10.1038/cddis.2017.187] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 03/24/2017] [Accepted: 03/27/2017] [Indexed: 02/06/2023]
Abstract
Trauma is a major cause of systemic inflammatory response syndrome and multiple organ dysfunction syndrome. Macrophages (Mϕ) direct trauma-induced inflammation, and Mϕ death critically influences the progression of the inflammatory response. In the current study, we explored an important role of trauma in inducing mitochondrial DNA (mtDNA) damage in Mϕ and the subsequent regulation of Mϕ death. Using an animal pseudo-fracture trauma model, we demonstrated that tissue damage induced NADPH oxidase activation and increased the release of reactive oxygen species via cold-inducible RNA-binding protein (CIRP)–TLR4–MyD88 signaling. This in turn, activates endonuclease G, which serves as an executor for the fragmentation of mtDNA in Mϕ. We further showed that fragmented mtDNA triggered both p62-related autophagy and necroptosis in Mϕ. However, autophagy activation also suppressed Mϕ necroptosis and pro-inflammatory responses. This study demonstrates a previously unidentified intracellular regulation of Mϕ homeostasis in response to trauma.
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Affiliation(s)
- Zhigang Li
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.,Research and Development, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA 15240, USA
| | - Erica K Fan
- University of Pittsburgh School of Arts and Science, Pittsburgh, PA 15213, USA
| | - Jinghua Liu
- Guangdong Provincial Key Laboratory of Proteomics, State Key Laboratory of Organ Failure Research, Southern Medical University, Guangzhou 510515, China
| | - Melanie J Scott
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Yuehua Li
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.,Research and Development, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA 15240, USA
| | - Song Li
- Department of Pharmaceutical Sciences, Center for Pharmacogenetics, University of Pittsburgh School of Pharmacy, Pittsburgh, PA 15261, USA
| | - Wen Xie
- Department of Pharmaceutical Sciences, Center for Pharmacogenetics, University of Pittsburgh School of Pharmacy, Pittsburgh, PA 15261, USA
| | - Timothy R Billiar
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.,McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Mark A Wilson
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.,Research and Development, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA 15240, USA
| | - Yong Jiang
- Guangdong Provincial Key Laboratory of Proteomics, State Key Laboratory of Organ Failure Research, Southern Medical University, Guangzhou 510515, China
| | - Ping Wang
- The Feinstein Institute for Medical Research, Manhasset, NY 11030, USA
| | - Jie Fan
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.,Research and Development, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA 15240, USA.,McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA
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2
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Radhakrishnan J, Bazarek S, Chandran B, Gazmuri RJ. Cyclophilin-D: a resident regulator of mitochondrial gene expression. FASEB J 2015; 29:2734-48. [PMID: 25837584 DOI: 10.1096/fj.14-263855] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 02/25/2015] [Indexed: 12/11/2022]
Abstract
Cyclophilin-D (Cyp-D) is a mitochondrial matrix peptidyl-prolyl isomerase. Because cyclophilins can regulate nuclear gene expression, we examined whether Cyp-D could regulate mitochondrial gene expression. We demonstrated in HEK 293T cells that transfected Cyp-D interacts with mitochondrial transcription factors B1 and B2 (TFB2M) but not with mitochondrial transcription factor A. We also demonstrated that Cyp-D interacts in vivo with TFB2M. Genetic silencing of Cyp-D and pharmacologic inhibition of Cyp-D markedly reduced mitochondrial transcription to 18 ± 5% (P < 0.05) and 24 ± 3% (P < 0.05) of respective controls. The level of interaction between Cyp-D and TFB2M correlated with the level of nascent mitochondrial RNA intensity (r = 0.896; P = 0.0156). Cyp-D silencing down-regulated mitochondrial transcripts initiated from the heavy strand promoter 2 [i.e., NADH dehydrogenase 1 (ND1) by 11-fold, P < 0.005; cytochrome oxidase 1 (COX1) by 4-fold, P < 0.001; and ATP synthase subunit 6 (ATP6) by 6.5-fold, P < 0.005); but not NADH dehydrogenase 6 (ND6)], which is initiated from the light strand promoter. Cyp-D silencing reduced mitochondrial membrane potential and cellular oxygen consumption (from 59 ± 5 to 34 ± 1 µmol oxygen/min/10(6) cells, P < 0.001); the latter without a statistically significant reversal after uncoupling electron transport from ATP synthesis, consistent with down-regulation of electron transport complexes. Accordingly, these studies provide novel evidence that Cyp-D could play a key role in regulating mitochondrial gene expression.
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Affiliation(s)
- Jeejabai Radhakrishnan
- *Department of Medicine and Resuscitation Institute, Center for Stem Cell and Regenerative Medicine, Department of Neuroscience, and H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA; and Captain James A. Lovell Federal Health Care Center, North Chicago, Illinois, USA
| | - Stanley Bazarek
- *Department of Medicine and Resuscitation Institute, Center for Stem Cell and Regenerative Medicine, Department of Neuroscience, and H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA; and Captain James A. Lovell Federal Health Care Center, North Chicago, Illinois, USA
| | - Bala Chandran
- *Department of Medicine and Resuscitation Institute, Center for Stem Cell and Regenerative Medicine, Department of Neuroscience, and H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA; and Captain James A. Lovell Federal Health Care Center, North Chicago, Illinois, USA
| | - Raúl J Gazmuri
- *Department of Medicine and Resuscitation Institute, Center for Stem Cell and Regenerative Medicine, Department of Neuroscience, and H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA; and Captain James A. Lovell Federal Health Care Center, North Chicago, Illinois, USA
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3
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Anand SK, Tikoo SK. Viruses as modulators of mitochondrial functions. Adv Virol 2013; 2013:738794. [PMID: 24260034 PMCID: PMC3821892 DOI: 10.1155/2013/738794] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 08/30/2013] [Indexed: 02/07/2023] Open
Abstract
Mitochondria are multifunctional organelles with diverse roles including energy production and distribution, apoptosis, eliciting host immune response, and causing diseases and aging. Mitochondria-mediated immune responses might be an evolutionary adaptation by which mitochondria might have prevented the entry of invading microorganisms thus establishing them as an integral part of the cell. This makes them a target for all the invading pathogens including viruses. Viruses either induce or inhibit various mitochondrial processes in a highly specific manner so that they can replicate and produce progeny. Some viruses encode the Bcl2 homologues to counter the proapoptotic functions of the cellular and mitochondrial proteins. Others modulate the permeability transition pore and either prevent or induce the release of the apoptotic proteins from the mitochondria. Viruses like Herpes simplex virus 1 deplete the host mitochondrial DNA and some, like human immunodeficiency virus, hijack the host mitochondrial proteins to function fully inside the host cell. All these processes involve the participation of cellular proteins, mitochondrial proteins, and virus specific proteins. This review will summarize the strategies employed by viruses to utilize cellular mitochondria for successful multiplication and production of progeny virus.
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Affiliation(s)
- Sanjeev K. Anand
- Vaccine & Infection Disease Organization-International Vaccine Center (VIDO-InterVac), University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, Canada S7E 5E3
- Veterinary Microbiology, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, Canada S7E 5E3
| | - Suresh K. Tikoo
- Vaccine & Infection Disease Organization-International Vaccine Center (VIDO-InterVac), University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, Canada S7E 5E3
- Veterinary Microbiology, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, Canada S7E 5E3
- School of Public Health, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, Canada S7E 5E3
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4
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Chueh FY, Leong KF, Cronk RJ, Venkitachalam S, Pabich S, Yu CL. Nuclear localization of pyruvate dehydrogenase complex-E2 (PDC-E2), a mitochondrial enzyme, and its role in signal transducer and activator of transcription 5 (STAT5)-dependent gene transcription. Cell Signal 2011; 23:1170-8. [PMID: 21397011 DOI: 10.1016/j.cellsig.2011.03.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Revised: 02/28/2011] [Accepted: 03/03/2011] [Indexed: 10/18/2022]
Abstract
STAT (signal transducer and activator of transcription) proteins play a critical role in cellular response to a wide variety of cytokines and growth factors by regulating specific nuclear genes. STAT-dependent gene transcription can be finely tuned through the association with co-factors in the nucleus. We showed previously that STAT5 (including 5a and 5b) specifically interacts with a mitochondrial enzyme PDC-E2 (E2 subunit of pyruvate dehydrogenase complex) in both leukemic T cells and cytokine-stimulated cells. However, the functional significance of this novel association remains largely unknown. Here we report that PDC-E2 may function as a co-activator in STAT5-dependent nuclear gene expression. Subcellular fractionation analysis revealed that a substantial amount of PDC-E2 was constitutively present in the nucleus of BaF3, an interleukin-3 (IL-3)-dependent cell line. IL-3-induced tyrosine-phosphorylated STAT5 associated with nuclear PDC-E2 in co-immunoprecipitation analysis. These findings were confirmed by confocal immunofluorescence microscopy showing constant nuclear localization of PDC-E2 and its co-localization with STAT5 after IL-3 stimulation. Similar to mitochondrial PDC-E2, nuclear PDC-E2 was lipoylated and associated with PDC-E1. Overexpression of PDC-E2 in BaF3 cells augmented IL-3-induced STAT5 activity as measured by reporter assay with consensus STAT5-binding sites. Consistent with the reporter data, PDC-E2 overexpression in BaF3 cells led to elevated mRNA levels of endogenous SOCS3 (suppressor of cytokine signaling 3) gene, a known STAT5 target. We further identified two functional STAT5-binding sites in the SOCS3 gene promoter important for its IL-3-inducibility. The observation that both cis-acting elements were essential to detect the stimulatory effect by PDC-E2 strongly supports the role of PDC-E2 in up-regulating the transactivating ability of STAT5. All together, our results reveal a novel function of PDC-E2 in the nucleus. It also raises the possibility of nuclear-mitochondrial crosstalk through the interaction between STAT5 and PDC-E2.
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Affiliation(s)
- Fu-Yu Chueh
- Department of Microbiology and Immunology, H. M. Bligh Cancer Research Laboratories, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA
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5
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Watanabe A, Arai M, Koitabashi N, Niwano K, Ohyama Y, Yamada Y, Kato N, Kurabayashi M. Mitochondrial transcription factors TFAM and TFB2M regulate Serca2 gene transcription. Cardiovasc Res 2010; 90:57-67. [PMID: 21113058 DOI: 10.1093/cvr/cvq374] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
AIMS Sarco(endo)plasmic reticulum Ca²(+)-ATPase 2a (SERCA2a) transports Ca²(+) by consuming ATP produced by mitochondrial respiratory chain enzymes. Messenger RNA (mRNA) for these enzymes is transcribed by mitochondrial transcription factors A (TFAM) and B2 (TFB2M). This study examined whether TFAM and TFB2M coordinately regulate the transcription of the Serca2 gene and mitochondrial genes. METHODS AND RESULTS Nuclear localization of TFAM and TFB2M was demonstrated by immunostaining in rat neonatal cardiac myocytes. Chromatin immunoprecipitation assay and fluorescence correlation spectroscopy revealed that TFAM and TFB2M bind to the -122 to -114 nt and -122 to -117 nt regions of the rat Serca2 gene promoter, respectively. Mutation of these sites resulted in decreased Serca2 gene transcription. In a rat myocardial infarction model, Serca2a mRNA levels significantly correlated with those of Tfam (r = 0.54, P < 0.001) and Tfb2m (r = 0.73, P < 0.001). Overexpression of TFAM and TFB2M blocked hydrogen peroxide- and norepinephrine-induced decreases in Serca2a mRNA levels. In addition, overexpression of TFAM and TFB2M increased the mitochondrial DNA (mtDNA) copy number and mRNA levels of mitochondrial enzymes. CONCLUSION Although TFAM and TFB2M are recognized as mtDNA-specific transcription factors, they also regulate transcription of nuclear DNA, i.e. the Serca2 gene. Our findings suggest a novel paradigm in which the transcription of genes for mitochondrial enzymes that produce ATP and the gene for SERCA2a that consumes ATP is coordinately regulated by the same transcription factors. This mechanism may contribute to maintaining proper cardiac function.
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Affiliation(s)
- Atai Watanabe
- Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
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Gangelhoff TA, Mungalachetty PS, Nix JC, Churchill MEA. Structural analysis and DNA binding of the HMG domains of the human mitochondrial transcription factor A. Nucleic Acids Res 2009; 37:3153-64. [PMID: 19304746 PMCID: PMC2691818 DOI: 10.1093/nar/gkp157] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mitochondrial transcription factor A (mtTFA) is central to assembly and initiation of the mitochondrial transcription complex. Human mtTFA (h-mtTFA) is a dual high mobility group box (HMGB) protein that binds site-specifically to the mitochondrial genome and demarcates the promoters for recruitment of h-mtTFB1, h-mtTFB2 and the mitochondrial RNA polymerase. The stoichiometry of h-mtTFA was found to be a monomer in the absence of DNA, whereas it formed a dimer in the complex with the light strand promoter (LSP) DNA. Each of the HMG boxes and the C-terminal tail were evaluated for their ability to bind to the LSP DNA. Removal of the C-terminal tail only slightly decreased nonsequence specific DNA binding, and box A, but not box B, was capable of binding to the LSP DNA. The X-ray crystal structure of h-mtTFA box B, at 1.35 Å resolution, revealed the features of a noncanonical HMG box. Interactions of box B with other regions of h-mtTFA were observed. Together, these results provide an explanation for the unusual DNA-binding properties of box B and suggest possible roles for this domain in transcription complex assembly.
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Affiliation(s)
- Todd A Gangelhoff
- Department of Pharmacology, University of Colorado Denver, School of Medicine, 12801 East 17th Avenue, Aurora, CO 80045-0511, USA
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Ricci C, Pastukh V, Leonard J, Turrens J, Wilson G, Schaffer D, Schaffer SW. Mitochondrial DNA damage triggers mitochondrial-superoxide generation and apoptosis. Am J Physiol Cell Physiol 2007; 294:C413-22. [PMID: 18077603 DOI: 10.1152/ajpcell.00362.2007] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Recently, it has become apparent that mitochondrial DNA (mtDNA) damage can rapidly initiate apoptosis independent of mutations, although the mechanism involved remains unclear. To elucidate this mechanism, angiotensin II-mediated apoptosis was studied in cells that were transduced with a lentiviral vector to overexpress the DNA repair enzyme 8-oxoguanine glycosylase or were treated with inhibitors known to block angiotensin II-induced mtDNA damage. Cells exhibiting angiotensin II-induced mtDNA damage showed two phases of superoxide generation, the first derived from NAD(P)H oxidase and the second of mitochondrial origin, whereas cells prevented from experiencing mtDNA damage importantly exhibited only the first phase. Furthermore, cells with mtDNA damage demonstrated impairments in mitochondrial protein expression, cellular respiration, and complex 1 activity before the onset of the second phase of oxidation. After the second phase, the mitochondrial membrane potential collapsed, cytochrome c was released, and the cells underwent apoptosis, all of which were prevented by disrupting mtDNA damage. Collectively, these data reveal a novel mechanism of apoptosis that is initiated when mtDNA damage triggers mitochondrial superoxide generation and ultimately the activation of the mitochondrial permeability transition. This novel mechanism may play an important pathological role.
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Affiliation(s)
- Craig Ricci
- Department of Pharmacolgy, College of Medicine, University of South Alabama, Mobile, AL 36688, USA
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8
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Ricci C, Pastukh V, Mozaffari M, Schaffer SW. Insulin withdrawal induces apoptosis via a free radical-mediated mechanism. Can J Physiol Pharmacol 2007; 85:455-64. [PMID: 17612655 DOI: 10.1139/y07-029] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Diabetes is characterized by chronic hyperglycemia as well as insulin deficiency or resistance. However, the majority of research has focused on the consequences of hyperglycemia in development of diabetic complications, whereas the effects of insulin deficiency or resistance, independent of hyperglycemia, have received little attention. Since insulin is a well known cytoprotective factor, we hypothesized that its removal could significantly impact cell survival. To examine this possibility, cultured neonatal cardiomyocytes were subjected to insulin withdrawal and examined for apoptosis. Insulin deficient cells succumbed to apoptosis, an effect associated with impaired PI3-kinase/Akt signaling and reduction in the Bcl-2 to Bax ratio. Perhaps more importantly, superoxide generation was altered in cells subjected to insulin withdrawal. Removal of insulin caused a significant increase in reactive oxygen species production and resulted in oxidative mitochondrial DNA damage the latter effect is associated with impaired expression of mitochondrially encoded proteins that make up the electron transport chain. Significantly, the effects of insulin withdrawal could be mitigated by treatment with the antioxidant, Tiron. Collectively, these data demonstrate that insulin deficiency leads to apoptosis and suggest a role for oxidative mitochondrial DNA damage in this cascade.
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Affiliation(s)
- Craig Ricci
- University of South Alabama, College of Medicine, Department of Pharmacology, Mobile, AL 36688, USA
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Bhattacharya P. 3D model of RNA polymerase and bidirectional transcription. Biochem Biophys Res Commun 2007; 355:103-10. [PMID: 17288994 PMCID: PMC1995083 DOI: 10.1016/j.bbrc.2007.01.130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Accepted: 01/22/2007] [Indexed: 10/23/2022]
Abstract
In the in vitro mitochondrial (mt) transcription initiation system with mt RNA polymerase fraction and mt lysate, the transcription initiation products were shown to be synthesized bidirectionally from the only H-strand-promoter (HSP)/L-strand-promoter region (LSP) of the mitochondrial D-loop genome segment. These transcription products ranged between >100 and >800 bp with the purified mitochondrial RNA polymerase fraction, but were larger (>2030-4000 bp) in size with the mitochondrial lysate in both human and mouse. In this brief report, an in vitro reconstituted mitochondrial transcription system purified by affinity chromatography (heparin-Sepharose) from mouse hypotetraploid letter Ehrlich ascites tumor cell mitochondria was shown to initiate transcription bidirectionally from the mitochondrial D-loop region (HSP/LSP), as evidenced by in vitro generated transcription products. The in vitro generated transcription products were separated by sequencing gel. But this in vitro reconstituted transcription system was not studied beyond the D-loop region. A 3D model of the enzyme RNA polymerase was docked with both ATP and CTP.
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Affiliation(s)
- Pradip Bhattacharya
- Department of Biochemistry, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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10
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Abstract
Mitochondria are ubiquitous organelles that are intimately involved in many cellular processes, but whose principal task is to provide the energy necessary for normal cell functioning and maintenance. Disruption of this energy supply can have devastating consequences for the cell, organ, and individual. Over the last two decades, mutations in both mitochondrial DNA (mtDNA) and nuclear DNA have been identified as causative in a number of well-characterized clinical syndromes, although for mtDNA mutations in particular, this relationship between genotype and phenotype is often not straightforward. Despite this, a number of epidemiological studies have been undertaken to assess the prevalence of mtDNA mutations and these have highlighted the impact that mtDNA disease has on both the community and individual families. Although there has been considerable improvement in the diagnosis of mitochondrial disorders, disappointingly this has not been matched by developments toward effective treatment. Nevertheless, our understanding of mitochondrial biology is gathering pace and progress in this area will be crucial to devising future treatment strategies. In addition to mitochondrial disease, evidence for a central role of mitochondria in other processes, such as aging and neurodegeneration, is slowly accumulating, although their role in cancer remains controversial. In this chapter, we discuss these issues and offer our own views based on our cumulative experience of investigating and managing these diseases over the last 20 years.
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Affiliation(s)
- R McFarland
- Mitochondrial Research Group, School of Neurology, Neurobiology, and Psychiatry, The Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, United Kingdom
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Marubuchi S, Wada YI, Okuda T, Hara Y, Qi ML, Hoshino M, Nakagawa M, Kanazawa I, Okazawa H. Polyglutamine tract-binding protein-1 dysfunction induces cell death of neurons through mitochondrial stress. J Neurochem 2005; 95:858-70. [PMID: 16104847 DOI: 10.1111/j.1471-4159.2005.03405.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Polyglutamine tract-binding protein-1 (PQBP-1) is a nuclear protein that interacts and colocalizes with mutant polyglutamine proteins. We previously reported that PQBP-1 transgenic mice show a late-onset motor neuron disease-like phenotype and cell death of motor neurons analogous to human neurodegeneration. To investigate the molecular mechanisms underlying the motor neuron death, we performed microarray analyses using the anterior horn tissues of the spinal cord and compared gene expression profiles between pre-symptomatic transgenic and age-matched control mice. Surprisingly, half of the spots changed more than 1.5-fold turned out to be genes transcribed from the mitochondrial genome. Northern and western analyses confirmed up-regulation of representative mitochondrial genes, cytochrome c oxidase (COX) subunit 1 and 2. Immunohistochemistry revealed that COX1 and COX2 proteins are increased in spinal motor neurons. Electron microscopic analyses revealed morphological abnormalities of mitochondria in the motor neurons. PQBP-1 overexpression in primary neurons by adenovirus vector induced abnormalities of mitochondrial membrane potential from day 5, while cytochrome c release and caspase 3 activation were observed on day 9. An increase of cell death by PQBP-1 was also confirmed on day 9. Collectively, these results indicate that dysfunction of PQBP-1 induces mitochondrial stress, a key molecular pathomechanism that is shared among human neurodegenerative disorders.
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Affiliation(s)
- Shigeki Marubuchi
- Department of Neuropathology, Medical Research Institute and Center of Excellence Program (COE) for Brain Integration and Its Disorders, Tokyo Medical and Dental University, Tokyo, Japan
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Rodríguez-Santiago B, Nunes V. Expression of mitochondrial genes and transcription estimation in different brain areas in Alzheimer's disease patients. Neurobiol Dis 2005; 18:296-304. [PMID: 15686958 DOI: 10.1016/j.nbd.2004.10.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2004] [Revised: 09/16/2004] [Accepted: 10/13/2004] [Indexed: 10/26/2022] Open
Abstract
Accumulation of mitochondrial defects is hypothesised to play a role in the complex pathophysiology of the sporadic form of Alzheimer's disease (SAD). Changes in expression of mtDNA encoded genes have been reported in SAD. However no conclusive results were obtained by using different methodologies and analysing distinct transcripts in a variety of brain areas. Here, we measured the expression of five mitochondrial-encoded genes in three brain areas and in lymphocytes from patients and controls by performing reverse transcription followed by quantitative real-time PCR. The analysis of gene expression was also performed by carrying out classic dot-blot experiments to evaluate the two techniques. SAD and control samples showed similar gene expression levels. Estimation of the transcription rate was also measured. No differences were observed when comparing patients and controls. Selective differences in transcription rates were observed only when samples were pooled by tissue, lymphocytes being the tissue with the highest rates.
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Affiliation(s)
- Benjamín Rodríguez-Santiago
- Medical and Molecular Genetics Center-Institut de Recerca Oncologica, IDIBELL, Hospital Duran i Reynals, Gran Via s/n, L'Hospitalet del Llobregat 08907, Barcelona, Spain
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13
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The functional organization of mitochondrial genomes in human cells. BMC Biol 2004; 2:9. [PMID: 15157274 PMCID: PMC425603 DOI: 10.1186/1741-7007-2-9] [Citation(s) in RCA: 232] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2003] [Accepted: 05/24/2004] [Indexed: 12/24/2022] Open
Abstract
Background We analyzed the organization and function of mitochondrial DNA in a stable human cell line (ECV304, which is also known as T-24) containing mitochondria tagged with the yellow fluorescent protein. Results Mitochondrial DNA is organized in ~475 discrete foci containing 6–10 genomes. These foci (nucleoids) are tethered directly or indirectly through mitochondrial membranes to kinesin, marked by KIF5B, and microtubules in the surrounding cytoplasm. In living cells, foci have an apparent diffusion constant of 1.1 × 10-3 μm2/s, and mitochondria always split next to a focus to distribute all DNA to one daughter. The kinetics of replication and transcription (monitored by immunolabelling after incorporating bromodeoxyuridine or bromouridine) reveal that each genome replicates independently of others in a focus, and that newly-made RNA remains in a focus (residence half-time ~43 min) long after it has been made. This mitochondrial RNA colocalizes with components of the cytoplasmic machinery that makes and imports nuclear-encoded proteins – that is, a ribosomal protein (S6), a nascent peptide associated protein (NAC), and the translocase in the outer membrane (Tom22). Conclusions The results suggest that clusters of mitochondrial genomes organize the translation machineries on both sides of the mitochondrial membranes. Then, proteins encoded by the nuclear genome and destined for the mitochondria will be made close to mitochondrial-encoded proteins so that they can be assembled efficiently into mitochondrial complexes.
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Camasamudram V, Fang JK, Avadhani NG. Transcription termination at the mouse mitochondrial H-strand promoter distal site requires an A/T rich sequence motif and sequence specific DNA binding proteins. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:1128-40. [PMID: 12631272 DOI: 10.1046/j.1432-1033.2003.03461.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Termination of mitochondrial (mt) H-strand transcription in mammalian cells occurs at two distinct sites on the genome. The first site of termination, referred to as mt-TERM occurs beyond the 16 S rRNA gene. However, the second and final site of termination beyond the tRNAThr gene remains unclear. In this study we have characterized the site of termination of the polycistronic distal gene transcript beyond the D-loop region, immediately upstream of the tRNAPhe gene. This region, termed D-TERM, maps to nucleotides 16274-16295 of the mouse genome and includes a conserved A/T rich sequence motif AATAAA as a part of the terminator. Gel-shift analysis showed that the 22 bp D-TERM DNA forms two major complexes with mouse liver mt extract in a sequence-specific manner. Protein purification by DNA-affinity chromatography yielded two major proteins of 45 kDa and 70 kDa. Finally, the D-TERM DNA can mediate transcription termination in a unidirectional manner in a HeLa mt transcription system, only in the presence of purified mouse liver mt D-TERM DNA binding proteins. We have therefore characterized a novel mt transcription termination system, similar in some properties to that of sea urchin, as well as the nuclear RNA Pol I and Pol II transcription termination systems.
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Affiliation(s)
- Vijayasarathy Camasamudram
- Laboratories of Biochemistry, Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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