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Friedman Y, Hizi A, Avni D, Bakhanashvili M. Mitochondrial matrix-localized p53 participates in degradation of mitochondrial RNAs. Mitochondrion 2021; 58:200-212. [PMID: 33775872 DOI: 10.1016/j.mito.2021.03.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 03/11/2021] [Accepted: 03/22/2021] [Indexed: 11/18/2022]
Abstract
Mitochondrial RNA degradation plays an important role in maintenance of the mitochondria genetic integrity. Mitochondrial localization of p53 was observed in non-stressed and stressed cells. p53, as an RNA-binding protein, exerts 3'→5' exoribonuclease activity. The data suggest that in non-stressed cells, mitochondrial matrix-localized p53, with exoribonuclease activity, may play a housekeeping positive role. p53, through restriction the formation of new RNA/DNA hybrid and processing R-loop, might serve as mitochondrial R-loop suppressor. Conversely, stress-induced matrix-p53 decreases the amount of mitochondrial single-stranded RNA transcripts (including polyA- and non-polyA RNAs), thereby leading to the decline in the amount of mitochondria-encoded oxidative phosphorylation components.
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Affiliation(s)
- Yael Friedman
- Infectious Diseases Unit, Sheba Medical Center, Tel-Hashomer 5265601, Israel
| | - Amnon Hizi
- Department of Cellular and Developmental Biology, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Dror Avni
- Lab. Mol. Cell Biology, Center for Cancer Research & Dep. of Medicine C, Sheba Medical Center, Tel Hashomer, Israel
| | - Mary Bakhanashvili
- Infectious Diseases Unit, Sheba Medical Center, Tel-Hashomer 5265601, Israel; The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
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2
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IFN-γ restores the impaired function of RNase L and induces mitochondria-mediated apoptosis in lung cancer. Cell Death Dis 2019; 10:642. [PMID: 31501431 PMCID: PMC6733796 DOI: 10.1038/s41419-019-1902-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 07/17/2019] [Accepted: 08/11/2019] [Indexed: 11/24/2022]
Abstract
RNase L is an essential component in interferon (IFN)-mediated antiviral signaling that showed antitumor effects in cancer. Cancer immunotherapy based on interferon has achieved encouraging results that indicate an applicable potential for cancer therapy. Here we showed that function of RNase L, though highly upregulated, was functionally impaired both in nuclear and cytoplasm in lung cancer cells. In normal lung epithelial cells, RNase L activation induced by 2–5A promoted nuclear condensation, DNA cleavage, and cell apoptosis, while in lung cancer cells, these processes were inhibited and RNase L-mediated downregulation of fibrillarin, Topo I and hnRNP A1 was also impaired in lung cancer cells. Moreover, the impairment of RNase L in lung cancer cells was due to the elevated expression of RLI. Application of IFN-γ to lung cancer cells led to enhanced expression of RNase L that compensated the RLI inhibition and restored the cytoplasmic and nuclear function of RNase L, leading to apoptosis of lung cancer cells. Thus, the present study discovered the impaired function and mechanism of RNase L in lung cancer cells and proved the efficacy of IFN-γ in restoring RNase L function and inducing apoptosis in the lung cancer cell. These results indicated the RNase L as a therapeutic target in lung cancer cells and immunotherapy of IFN-γ may serve as an adjuvant to enhance the efficacy.
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3
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Rath S, Prangley E, Donovan J, Demarest K, Wingreen NS, Meir Y, Korennykh A. Concerted 2-5A-Mediated mRNA Decay and Transcription Reprogram Protein Synthesis in the dsRNA Response. Mol Cell 2019; 75:1218-1228.e6. [PMID: 31494033 DOI: 10.1016/j.molcel.2019.07.027] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 06/13/2019] [Accepted: 07/16/2019] [Indexed: 01/09/2023]
Abstract
Viral and endogenous double-stranded RNA (dsRNA) is a potent trigger for programmed RNA degradation by the 2-5A/RNase L complex in cells of all mammals. This 2-5A-mediated decay (2-5AMD) is a conserved stress response switching global protein synthesis from homeostasis to production of interferons (IFNs). To understand this mechanism, we examined 2-5AMD in human cells and found that it triggers polysome collapse characteristic of inhibited translation initiation. We determined that translation initiation complexes and ribosomes purified from translation-arrested cells remain functional. However, spike-in RNA sequencing (RNA-seq) revealed cell-wide decay of basal mRNAs accompanied by rapid accumulation of mRNAs encoding innate immune proteins. Our data attribute this 2-5AMD evasion to better stability of defense mRNAs and positive feedback in the IFN response amplified by RNase L-resistant molecules. We conclude that 2-5AMD and transcription act in concert to refill mammalian cells with defense mRNAs, thereby "prioritizing" the synthesis of innate immune proteins.
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Affiliation(s)
- Sneha Rath
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Eliza Prangley
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Jesse Donovan
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Kaitlin Demarest
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Ned S Wingreen
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Yigal Meir
- Department of Physics, Ben Gurion University, Beer-Sheva 84105, Israel
| | - Alexei Korennykh
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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4
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Wiatrek DM, Candela ME, Sedmík J, Oppelt J, Keegan LP, O'Connell MA. Activation of innate immunity by mitochondrial dsRNA in mouse cells lacking p53 protein. RNA (NEW YORK, N.Y.) 2019; 25:713-726. [PMID: 30894411 PMCID: PMC6521600 DOI: 10.1261/rna.069625.118] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 03/16/2019] [Indexed: 05/27/2023]
Abstract
Viral and cellular double-stranded RNA (dsRNA) is recognized by cytosolic innate immune sensors, including RIG-I-like receptors. Some cytoplasmic dsRNA is commonly present in cells, and one source is mitochondrial dsRNA, which results from bidirectional transcription of mitochondrial DNA (mtDNA). Here we demonstrate that Trp53 mutant mouse embryonic fibroblasts contain immune-stimulating endogenous dsRNA of mitochondrial origin. We show that the immune response induced by this dsRNA is mediated via RIG-I-like receptors and leads to the expression of type I interferon and proinflammatory cytokine genes. The mitochondrial dsRNA is cleaved by RNase L, which cleaves all cellular RNA including mitochondrial mRNAs, increasing activation of RIG-I-like receptors. When mitochondrial transcription is interrupted there is a subsequent decrease in this immune-stimulatory dsRNA. Our results reveal that the role of p53 in innate immunity is even more versatile and complex than previously anticipated. Our study, therefore, sheds new light on the role of endogenous RNA in diseases featuring aberrant immune responses.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Adenosine Deaminase/deficiency
- Adenosine Deaminase/genetics
- Adenosine Deaminase/immunology
- Animals
- Carrier Proteins/genetics
- Carrier Proteins/immunology
- DEAD Box Protein 58/genetics
- DEAD Box Protein 58/immunology
- Embryo, Mammalian
- Endoribonucleases/genetics
- Endoribonucleases/immunology
- Fibroblasts/cytology
- Fibroblasts/immunology
- Immunity, Innate/genetics
- Interferon Regulatory Factor-7/genetics
- Interferon Regulatory Factor-7/immunology
- Interferon-Induced Helicase, IFIH1/genetics
- Interferon-Induced Helicase, IFIH1/immunology
- Intracellular Signaling Peptides and Proteins
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Proteins/genetics
- Proteins/immunology
- RNA, Double-Stranded/genetics
- RNA, Double-Stranded/immunology
- RNA, Mitochondrial/genetics
- RNA, Mitochondrial/immunology
- RNA-Binding Proteins
- Transcription, Genetic
- Transfection
- Tumor Suppressor Protein p53/deficiency
- Tumor Suppressor Protein p53/genetics
- Tumor Suppressor Protein p53/immunology
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Affiliation(s)
| | | | - Jiří Sedmík
- CEITEC Masaryk University, 625 00 Brno, Czech Republic
| | - Jan Oppelt
- CEITEC Masaryk University, 625 00 Brno, Czech Republic
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, 625 00 Brno, Czech Republic
| | - Liam P Keegan
- CEITEC Masaryk University, 625 00 Brno, Czech Republic
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5
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Abstract
The main characteristic of alcohol use disorder is the consumption of large quantities of alcohol despite the negative consequences. The transition from the moderate use of alcohol to excessive, uncontrolled alcohol consumption results from neuroadaptations that cause aberrant motivational learning and memory processes. Here, we examine studies that have combined molecular and behavioural approaches in rodents to elucidate the molecular mechanisms that keep the social intake of alcohol in check, which we term 'stop pathways', and the neuroadaptations that underlie the transition from moderate to uncontrolled, excessive alcohol intake, which we term 'go pathways'. We also discuss post-transcriptional, genetic and epigenetic alterations that underlie both types of pathways.
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Affiliation(s)
- Dorit Ron
- Corresponding author: Dorit Ron, 675 Nelson Rising Lane, BOX 0663, San Francisco, CA 94143-0663,
| | - Segev Barak
- Department of Neurology, University of California, San Francisco, San Francisco, CA 94143, USA
- School of Psychological Sciences and Sagol School of Neuroscience, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
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6
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Hypoxic regulation of the expression of cell proliferation related genes in U87 glioma cells upon inhibition of IRE1 signaling enzyme. UKRAINIAN BIOCHEMICAL JOURNAL 2016; 88:11-21. [DOI: 10.15407/ubj88.01.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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7
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The Roles of RNase-L in Antimicrobial Immunity and the Cytoskeleton-Associated Innate Response. Int J Mol Sci 2016; 17:ijms17010074. [PMID: 26760998 PMCID: PMC4730318 DOI: 10.3390/ijms17010074] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 12/21/2015] [Accepted: 01/04/2016] [Indexed: 12/26/2022] Open
Abstract
The interferon (IFN)-regulated endoribonuclease RNase-L is involved in multiple aspects of the antimicrobial innate immune response. It is the terminal component of an RNA cleavage pathway in which dsRNA induces the production of RNase-L-activating 2-5A by the 2′-5′-oligoadenylate synthetase. The active nuclease then cleaves ssRNAs, both cellular and viral, leading to downregulation of their expression and the generation of small RNAs capable of activating retinoic acid-inducible gene-I (RIG-I)-like receptors or the nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome. This leads to IFNβ expression and IL-1β activation respectively, in addition to broader effects on immune cell function. RNase-L is also one of a growing number of innate immune components that interact with the cell cytoskeleton. It can bind to several cytoskeletal proteins, including filamin A, an actin-binding protein that collaborates with RNase-L to maintain the cellular barrier to viral entry. This antiviral activity is independent of catalytic function, a unique mechanism for RNase-L. We also describe here the interaction of RNase-L with the E3 ubiquitin ligase and scaffolding protein, ligand of nump protein X (LNX), a regulator of tight junction proteins. In order to better understand the significance and context of these novel binding partners in the antimicrobial response, other innate immune protein interactions with the cytoskeleton are also discussed.
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8
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Wood ER, Bledsoe R, Chai J, Daka P, Deng H, Ding Y, Harris-Gurley S, Kryn LH, Nartey E, Nichols J, Nolte RT, Prabhu N, Rise C, Sheahan T, Shotwell JB, Smith D, Tai V, Taylor JD, Tomberlin G, Wang L, Wisely B, You S, Xia B, Dickson H. The Role of Phosphodiesterase 12 (PDE12) as a Negative Regulator of the Innate Immune Response and the Discovery of Antiviral Inhibitors. J Biol Chem 2015; 290:19681-96. [PMID: 26055709 PMCID: PMC4528132 DOI: 10.1074/jbc.m115.653113] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 05/20/2015] [Indexed: 11/06/2022] Open
Abstract
2',5'-Oligoadenylate synthetase (OAS) enzymes and RNase-L constitute a major effector arm of interferon (IFN)-mediated antiviral defense. OAS produces a unique oligonucleotide second messenger, 2',5'-oligoadenylate (2-5A), that binds and activates RNase-L. This pathway is down-regulated by virus- and host-encoded enzymes that degrade 2-5A. Phosphodiesterase 12 (PDE12) was the first cellular 2-5A- degrading enzyme to be purified and described at a molecular level. Inhibition of PDE12 may up-regulate the OAS/RNase-L pathway in response to viral infection resulting in increased resistance to a variety of viral pathogens. We generated a PDE12-null cell line, HeLaΔPDE12, using transcription activator-like effector nuclease-mediated gene inactivation. This cell line has increased 2-5A levels in response to IFN and poly(I-C), a double-stranded RNA mimic compared with the parental cell line. Moreover, HeLaΔPDE12 cells were resistant to viral pathogens, including encephalomyocarditis virus, human rhinovirus, and respiratory syncytial virus. Based on these results, we used DNA-encoded chemical library screening to identify starting points for inhibitor lead optimization. Compounds derived from this effort raise 2-5A levels and exhibit antiviral activity comparable with the effects observed with PDE12 gene inactivation. The crystal structure of PDE12 complexed with an inhibitor was solved providing insights into the structure-activity relationships of inhibitor potency and selectivity.
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Affiliation(s)
| | | | - Jing Chai
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Philias Daka
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - Hongfeng Deng
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Yun Ding
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | | | | | | | | | | | - Ninad Prabhu
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Cecil Rise
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Timothy Sheahan
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - J Brad Shotwell
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | | | - Vince Tai
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | | | | | | | | | - Shihyun You
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - Bing Xia
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Hamilton Dickson
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
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9
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Mitochondrial localization of the OAS1 p46 isoform associated with a common single nucleotide polymorphism. BMC Cell Biol 2014; 15:33. [PMID: 25205466 PMCID: PMC4165621 DOI: 10.1186/1471-2121-15-33] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 08/29/2014] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND The expression of 2'-5'-Oligoadenylate synthetases (OASs) is induced by type 1 Interferons (IFNs) in response to viral infection. The OAS proteins have a unique ability to produce 2'-5' Oligoadenylates, which bind and activate the ribonuclease RNase L. The RNase L degrades cellular RNAs which in turn inhibits protein translation and induces apoptosis. Several single nucleotide polymorphisms (SNPs) in the OAS1 gene have been associated with disease. We have investigated the functional effect of two common SNPs in the OAS1 gene. The SNP rs10774671 affects splicing to one of the exons in the OAS1 gene giving rise to differential expression of the OAS1 isoforms, and the SNP rs1131454 (former rs3741981) resides in exon 3 giving rise to OAS1 isoforms with either a Glycine or a Serine at position 162 in the core OAS unit. RESULTS We have used three human cell lines with different genotypes in the OAS1 SNP rs10774671, HeLa cells with the AA genotype, HT1080 cells with AG, and Daudi cells with GG. The main OAS1 isoform expressed in Daudi and HT1080 cells was p46, and the main OAS1 isoform expressed in HeLa cells was p42. In addition, low levels of the OAS1 p52 mRNA was detected in HeLa cells and p48 mRNA in Daudi cells, and trace amounts of p44a mRNA were detected in the three cell lines treated with type 1 interferon. We show that the OAS1 p46 isoform was localized in the mitochondria in Daudi cells, whereas the OAS1 isoforms in HeLa cells were primarily localized in cytoplasmic vacuoles/lysosomes. By using recombinantly expressed OAS1 mutant proteins, we found that the OAS1 SNP rs1131454 (former rs3741981) did not affect the enzymatic OAS1 activity. CONCLUSIONS The SNP rs10774671 determines differential expression of the OAS1 isoforms. In Daudi and HT1080 cells the p46 isoform is the most abundantly expressed isoform associated with the G allele, whereas in HeLa cells the most abundantly expressed isoform is p42 associated with the A allele. The SNP rs1131454 (former rs3741981) does not interfere with OAS1 enzyme activity. The OAS1 p46 isoform localizes to the mitochondria, therefore a full 2-5A system can now be found in the mitochondria.
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10
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Gupta A, Rath PC. Expression of mRNA and protein-protein interaction of the antiviral endoribonuclease RNase L in mouse spleen. Int J Biol Macromol 2014; 69:307-18. [PMID: 24780566 DOI: 10.1016/j.ijbiomac.2014.04.042] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 04/18/2014] [Accepted: 04/21/2014] [Indexed: 10/25/2022]
Abstract
The interferon-inducible, 2',5'-oligoadenylate (2-5A)-dependent endoribonuclease, RNase L is a unique antiviral RNA-degrading enzyme involved in RNA-metabolism, translational regulation, stress-response besides its anticancer/tumor-suppressor and antibacterial functions. RNase L represents complex cellular RNA-regulations in mammalian cells but diverse functions of RNase L are not completely explained by its 2-5A-regulated endoribonuclease activity. We hypothesized that RNase L has housekeeping function(s) through interaction with cellular proteins. We investigated RNase L mRNA expression in mouse tissues by RT-PCR and its protein-protein interaction in spleen by GST-pulldown and immunoprecipitation assays followed by proteomic analysis. RNase L mRNA is constitutively and differentially expressed in nine different mouse tissues, its level is maximum in immunological tissues (spleen, thymus and lungs), moderate in reproductive tissues (testis and prostate) and low in metabolic tissues (kidney, brain, liver and heart). Cellular proteins from mouse spleen [fibronectin precursor, β-actin, troponin I, myosin heavy chain 9 (non-muscle), growth-arrest specific protein 11, clathrin light chain B, a putative uncharacterized protein (Ricken cDNA 8030451F13) isoform (CRA_d) and alanyl tRNA synthetase] were identified as cellular RNase L-interacting proteins. Thus our results suggest for more general cellular functions of RNase L through protein-protein interactions in the spleen for immune response in mammals.
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Affiliation(s)
- Ankush Gupta
- Molecular Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Pramod C Rath
- Molecular Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
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11
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Schild C, Hahn D, Schaller A, Jackson CB, Rothen-Rutishauser B, Mirkovitch J, Nuoffer JM. Mitochondrial leucine tRNA level and PTCD1 are regulated in response to leucine starvation. Amino Acids 2014; 46:1775-83. [DOI: 10.1007/s00726-014-1730-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 03/17/2014] [Indexed: 10/25/2022]
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12
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Szczesny RJ, Hejnowicz MS, Steczkiewicz K, Muszewska A, Borowski LS, Ginalski K, Dziembowski A. Identification of a novel human mitochondrial endo-/exonuclease Ddk1/c20orf72 necessary for maintenance of proper 7S DNA levels. Nucleic Acids Res 2013; 41:3144-61. [PMID: 23358826 PMCID: PMC3597694 DOI: 10.1093/nar/gkt029] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Although the human mitochondrial genome has been investigated for several decades, the proteins responsible for its replication and expression, especially nucleolytic enzymes, are poorly described. Here, we characterized a novel putative PD-(D/E)XK nuclease encoded by the human C20orf72 gene named Ddk1 for its predicted catalytic residues. We show that Ddk1 is a mitochondrially localized metal-dependent DNase lacking detectable ribonuclease activity. Ddk1 degrades DNA mainly in a 3'-5' direction with a strong preference for single-stranded DNA. Interestingly, Ddk1 requires free ends for its activity and does not degrade circular substrates. In addition, when a chimeric RNA-DNA substrate is provided, Ddk1 can slide over the RNA fragment and digest DNA endonucleolytically. Although the levels of the mitochondrial DNA are unchanged on RNAi-mediated depletion of Ddk1, the mitochondrial single-stranded DNA molecule (7S DNA) accumulates. On the other hand, overexperssion of Ddk1 decreases the levels of 7S DNA, suggesting an important role of the protein in 7S DNA regulation. We propose a structural model of Ddk1 and discuss its similarity to other PD-(D/E)XK superfamily members.
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Affiliation(s)
- Roman J Szczesny
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
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13
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Koning M, Werker PM, van Luyn MJ, Krenning G, Harmsen MC. A global downregulation of microRNAs occurs in human quiescent satellite cells during myogenesis. Differentiation 2012; 84:314-21. [DOI: 10.1016/j.diff.2012.08.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Revised: 08/12/2012] [Accepted: 08/15/2012] [Indexed: 12/11/2022]
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Abstract
Mammalian mitochondria contain their own genome that encodes mRNAs for thirteen essential subunits of the complexes performing oxidative phosphorylation as well as the RNA components (two rRNAs and 22 tRNAs) needed for their translation in mitochondria. All RNA species are produced from single polycistronic precursor RNAs, yet the relative concentrations of various RNAs differ significantly. This underscores the essential role of post-transcriptional mechanisms that control the maturation, stability and translation of mitochondrial RNAs. The present review provides a detailed summary on the role of RNA maturation in the regulation of mitochondrial gene expression, focusing mainly on messenger RNA polyadenylation and stability control. Furthermore, the role of mitochondrial ribosomal RNA stability, processing and modifications in the biogenesis of the mitochondrial ribosome is discussed.
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15
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Rackham O, Mercer TR, Filipovska A. The human mitochondrial transcriptome and the RNA-binding proteins that regulate its expression. WILEY INTERDISCIPLINARY REVIEWS-RNA 2012; 3:675-95. [DOI: 10.1002/wrna.1128] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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16
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Gupta A, Rath PC. Expression, purification and characterization of the interferon-inducible, antiviral and tumour-suppressor protein, human RNase L. J Biosci 2012; 37:103-13. [PMID: 22357208 DOI: 10.1007/s12038-011-9180-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The interferon (IFN)-inducible, 2',5'-oligoadenylate (2-5A)-dependent ribonuclease L (RNase L) plays key role in antiviral defense of mammalian cells. Induction by IFN and activation by double-stranded RNA lead to 2-5A cofactor synthesis, which activates RNase L by causing its dimerization. Active RNase L degrades single-stranded viral as well as cellular RNAs causing apoptosis of virus-infected cells. Earlier, we had reported that expression of recombinant human RNase L caused RNA-degradation and cell-growth inhibition in E. coli without the need for exogenous 2-5A. Expression of human RNase L in E. coli usually leads to problems of leaky expression, low yield and degradation of the recombinant protein, which demands number of chromatographic steps for its subsequent purification thereby, compromising its biochemical activity. Here, we report a convenient protocol for expression of full-length, soluble and biochemically active recombinant human RNase L as GST-RNase L fusion protein from E. coli utilizing a single-step affinity purification with an appreciable yield of the highly purified protein. Recombinant RNase L was characterized by SDS-PAGE, immunoblotting and MALDI-TOF analysis. A semi-quantitative agarose-gel-based ribonuclease assay was developed for measuring its 2-5A-dependent RNase L activity against cellular large rRNAs as substrates. The optimized expression conditions minimized degradation of the protein, making it a convenient method for purification of RNase L, which can be utilized to study effects of various agents on the RNase L activity and its protein-protein interactions.
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Affiliation(s)
- Ankush Gupta
- Molecular Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India
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17
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RNase L controls terminal adipocyte differentiation, lipids storage and insulin sensitivity via CHOP10 mRNA regulation. Cell Death Differ 2012; 19:1470-81. [PMID: 22441668 DOI: 10.1038/cdd.2012.23] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Adipose tissue structure is altered during obesity, leading to deregulation of whole-body metabolism. Its function depends on its structure, in particular adipocytes number and differentiation stage. To better understand the mechanisms regulating adipogenesis, we have investigated the role of an endoribonuclease, endoribonuclease L (RNase L), using wild-type and RNase L-knockout mouse embryonic fibroblasts (RNase L(-/-)-MEFs). Here, we identify C/EBP homologous protein 10 (CHOP10), a dominant negative member of the CCAAT/enhancer-binding protein family, as a specific RNase L target. We show that RNase L is associated with CHOP10 mRNA and regulates its stability. CHOP10 expression is conserved in RNase L(-/-)-MEFs, maintaining preadipocyte state while impairing their terminal differentiation. RNase L(-/-)-MEFs have decreased lipids storage capacity, insulin sensitivity and glucose uptake. Expression of ectopic RNase L in RNase L(-/-)-MEFs triggers CHOP10 mRNA instability, allowing increased lipids storage, insulin response and glucose uptake. Similarly, downregulation of CHOP10 mRNA with CHOP10 siRNA in RNase L(-/-)-MEFs improves their differentiation in adipocyte. In vivo, aged RNase L(-)/(-) mice present an expanded adipose tissue, which, however, is unable to correctly store lipids, illustrated by ectopic lipids storage in the liver and in the kidney. These findings highlight RNase L as an essential regulator of adipogenesis via the regulation of CHOP10 mRNA.
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18
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Orloff MS, Zhang L, Bebek G, Eng C. Integrative genomic analysis reveals extended germline homozygosity with lung cancer risk in the PLCO cohort. PLoS One 2012; 7:e31975. [PMID: 22384118 PMCID: PMC3288062 DOI: 10.1371/journal.pone.0031975] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Accepted: 01/16/2012] [Indexed: 11/25/2022] Open
Abstract
Susceptibility to common cancers is multigenic resulting from low-to-high penetrance predisposition-factors and environmental exposure. Genomic studies suggest germline homozygosity as a novel low-penetrance factor contributing to common cancers. We hypothesized that long homozygous regions (tracts-of-homozygosity [TOH]) harbor tobacco-dependent and independent lung-cancer predisposition (or protection) genes. We performed in silico genome-wide SNP-array-based analysis of lung-cancer patients of European-ancestry from the PLCO screening-trial cohort to identify TOH regions amongst 788 cancer-cases and 830 ancestry-matched controls. Association analyses was then performed between presence of lung cancer and common(c)TOHs (operationally defined as 10 or more subjects sharing ≥100 identical homozygous calls), aTOHs (allelically-matched groups within a cTOH), demographics and tobacco-exposure. Finally, integration of significant c/aTOH with transcriptome was performed to functionally-map lung-cancer risk-genes. After controlling for demographics and smoking, we identified 7 cTOHs and 5 aTOHs associated with lung cancer (adjusted p<0.01). Three cTOHs were over-represented in cases over controls (OR = 1.75–2.06, p = 0.007–0.001), whereas 4 were under-represented (OR = 0.28–0.69, p = 0.006–0.001). Interaction between smoking status and cTOH3/aTOH2 (2p16.3–2p16.1) was observed (adjusted p<0.03). The remaining significant aTOHs have ORs 0.23–0.50 (p = 0.004–0.006) and 2.95–3.97 (p = 0.008–0.001). After integrating significant cTOH/aTOHs with publicly-available lung-cancer transcriptome datasets followed by filtering based on lung cancer and its relevant pathways revealed 9 putative predisposing genes (p<0.0001). In conclusion, differentially-distributed cTOH/aTOH genomic variants between cases and controls harbor sets of plausible differentially-expressed genes accounting for the complexity of lung-cancer predisposition.
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Affiliation(s)
- Mohammed S Orloff
- Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
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Ezelle HJ, Hassel BA. Pathologic effects of RNase-L dysregulation in immunity and proliferative control. Front Biosci (Schol Ed) 2012; 4:767-86. [PMID: 22202089 DOI: 10.2741/s298] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The endoribonuclease RNase-L is the terminal component of an RNA cleavage pathway that mediates antiviral, antiproliferative and immunomodulatory activities. Inactivation or dysregulation of RNase-L is associated with a compromised immune response and increased risk of cancer, accordingly its activity is tightly controlled and requires an allosteric activator, 2',5'-linked oligoadenylates, for enzymatic activity. The biological activities of RNase-L are a result of direct and indirect effects of RNA cleavage and microarray analyses have revealed that RNase-L impacts the gene expression program at multiple levels. The identification of RNase-L-regulated RNAs has provided insights into potential mechanisms by which it exerts antiproliferative, proapoptotic, senescence-inducing and innate immune activities. RNase-L protein interactors have been identified that serve regulatory functions and are implicated as alternate mechanisms of its biologic functions. Thus, while the molecular details are understood for only a subset of RNase-L activities, its regulation by small molecules and critical roles in host defense and as a candidate tumor suppressor make it a promising therapeutic target.
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Affiliation(s)
- Heather J Ezelle
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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Szczesny RJ, Borowski LS, Malecki M, Wojcik MA, Stepien PP, Golik P. RNA degradation in yeast and human mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:1027-34. [PMID: 22178375 DOI: 10.1016/j.bbagrm.2011.11.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 11/29/2011] [Accepted: 11/30/2011] [Indexed: 01/23/2023]
Abstract
Expression of mitochondrially encoded genes must be finely tuned according to the cell's requirements. Since yeast and human mitochondria have limited possibilities to regulate gene expression by altering the transcription initiation rate, posttranscriptional processes, including RNA degradation, are of great importance. In both organisms mitochondrial RNA degradation seems to be mostly depending on the RNA helicase Suv3. Yeast Suv3 functions in cooperation with Dss1 ribonuclease by forming a two-subunit complex called the mitochondrial degradosome. The human ortholog of Suv3 (hSuv3, hSuv3p, SUPV3L1) is also indispensable for mitochondrial RNA decay but its ribonucleolytic partner has so far escaped identification. In this review we summarize the current knowledge about RNA degradation in human and yeast mitochondria. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.
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Affiliation(s)
- Roman J Szczesny
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
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21
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Choumar A, Tarhuni A, Lettéron P, Reyl-Desmars F, Dauhoo N, Damasse J, Vadrot N, Nahon P, Moreau R, Pessayre D, Mansouri A. Lipopolysaccharide-induced mitochondrial DNA depletion. Antioxid Redox Signal 2011; 15:2837-54. [PMID: 21767162 DOI: 10.1089/ars.2010.3713] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Hepatic energy depletion has been described in severe sepsis, and lipopolysaccharide (LPS) has been shown to cause mitochondrial DNA (mtDNA) damage. To clarify the mechanisms of LPS-induced mtDNA damage and mitochondrial alterations, we treated wild-type (WT) or transgenic manganese superoxide dismutase-overerexpressing (MnSOD(+++)) mice with a single dose of LPS (5 mg/kg). In WT mice, LPS increased mitochondrial reactive oxygen species formation, hepatic inducible nitric oxide synthase (NOS) mRNA and protein, tumor necrosis factor-alpha, interleukin-1 beta, and high-mobility group protein B1 concentrations. Six to 48 h after LPS administration (5 mg/kg), liver mtDNA levels, respiratory complex I activity, and adenosine triphosphate (ATP) contents were decreased. In addition, LPS increased interferon-β concentration and decreased mitochondrial transcription factor A (Tfam) mRNA, Tfam protein, and mtDNA-encoded mRNAs. Morphological studies showed mild hepatic inflammation. The LPS (5 mg/kg)-induced mtDNA depletion, complex I inactivation, ATP depletion, and alanine aminotransferase increase were prevented in MnSOD(+++) mice or in WT mice cotreated with 1400W (a NOS inhibitor), (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl)triphenylphosphonium chloride, monohydrate (a superoxide scavenger) or uric acid (a peroxynitrite scavenger). The MnSOD overexpression delayed death in mice challenged by a higher, lethal dose of LPS (25 mg/kg). In conclusion, LPS administration damages mtDNA and alters mitochondrial function. The protective effects of MnSOD, NOS inhibitors, and superoxide or peroxynitrite scavengers point out a role of the superoxide anion reacting with NO to form mtDNA- and protein-damaging peroxynitrite. In addition to the acute damage caused by reactive species, decreased levels of mitochondrial transcripts contribute to mitochondrial dysfunction.
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Affiliation(s)
- Amal Choumar
- INSERM, U773, Centre de Recherche Biomédicale Bichat Beaujon CRB3, Paris, France
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Pessayre D, Fromenty B, Berson A, Robin MA, Lettéron P, Moreau R, Mansouri A. Central role of mitochondria in drug-induced liver injury. Drug Metab Rev 2011; 44:34-87. [PMID: 21892896 DOI: 10.3109/03602532.2011.604086] [Citation(s) in RCA: 182] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A frequent mechanism for drug-induced liver injury (DILI) is the formation of reactive metabolites that trigger hepatitis through direct toxicity or immune reactions. Both events cause mitochondrial membrane disruption. Genetic or acquired factors predispose to metabolite-mediated hepatitis by increasing the formation of the reactive metabolite, decreasing its detoxification, or by the presence of critical human leukocyte antigen molecule(s). In other instances, the parent drug itself triggers mitochondrial membrane disruption or inhibits mitochondrial function through different mechanisms. Drugs can sequester coenzyme A or can inhibit mitochondrial β-oxidation enzymes, the transfer of electrons along the respiratory chain, or adenosine triphosphate (ATP) synthase. Drugs can also destroy mitochondrial DNA, inhibit its replication, decrease mitochondrial transcripts, or hamper mitochondrial protein synthesis. Quite often, a single drug has many different effects on mitochondrial function. A severe impairment of oxidative phosphorylation decreases hepatic ATP, leading to cell dysfunction or necrosis; it can also secondarily inhibit ß-oxidation, thus causing steatosis, and can also inhibit pyruvate catabolism, leading to lactic acidosis. A severe impairment of β-oxidation can cause a fatty liver; further, decreased gluconeogenesis and increased utilization of glucose to compensate for the inability to oxidize fatty acids, together with the mitochondrial toxicity of accumulated free fatty acids and lipid peroxidation products, may impair energy production, possibly leading to coma and death. Susceptibility to parent drug-mediated mitochondrial dysfunction can be increased by factors impairing the removal of the toxic parent compound or by the presence of other medical condition(s) impairing mitochondrial function. New drug molecules should be screened for possible mitochondrial effects.
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Affiliation(s)
- Dominique Pessayre
- INSERM, U, Centre de Recherche Bichat Beaujon CRB, Faculté de Médecine Xavier-Bichat, Paris, France.
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23
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Li XL, Ezelle HJ, Hsi TY, Hassel BA. A central role for RNA in the induction and biological activities of type 1 interferons. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 2:58-78. [PMID: 21956969 DOI: 10.1002/wrna.32] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In mammals the type 1 interferon (IFN) system functions as the primary innate antiviral defense and more broadly as a stress response and regulator of diverse homeostatic mechanisms. RNA plays a central role in the induction of IFN and in its biologic activities. Cellular toll-like receptors (TLR), RIG-I-like receptors (RLR), and nucleotide organization domain-like receptors (NLR) sense pathogen- and danger-associated RNAs as nonself based on structural features and subcellular location that distinguish them from ubiquitous host RNAs. Detection of nonself RNAs activates signaling pathways to induce IFN transcription and secretion. In turn, IFN binds cell surface receptors to initiate signaling that results in the induction of IFN-stimulated genes (ISGs) that mediate its biologic activities. RNA also plays a critical role in this effector phase of the IFN system, serving as an activator of enzyme activity for protein kinase RNA-dependent (PKR) and oligoadenylate synthetase (OAS), and as a substrate for 2('), 5(') -linked oligoadenylate dependant-endoribonuclease (RNase-L). In contrast to the transcriptional response induced by RNA receptors, these key ISGs mediate their activities primarily through post transcriptional mechanisms to regulate the translation and stability of host and microbial RNAs. Together RNA-sensing and RNA-effector molecules comprise a network of coordinately regulated proteins with integrated feedback and feed-forward loops that tightly regulate the cellular response to RNA. This stringent regulation is essential to prevent deleterious effects of uncontrolled IFN expression and effector activation. In light of this extensive crosstalk, targeting key mediators of the cellular response to RNA represents a viable strategy for therapeutic modulation of immune function and treatment of diseases in which this response is dysregulated (e.g., cancer).
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Affiliation(s)
- Xiao-Ling Li
- Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA
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Domingo-Gil E, González JM, Esteban M. Identification of cellular genes induced in human cells after activation of the OAS/RNaseL pathway by vaccinia virus recombinants expressing these antiviral enzymes. J Interferon Cytokine Res 2010; 30:171-88. [PMID: 20038200 DOI: 10.1089/jir.2009.0037] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Interferon (IFN) type I induces the expression of antiviral proteins such as 2',5'-oligoadenylate synthetases (OAS). The enzyme OAS is activated by dsRNA to produce 5'-phosphorylated, 2-5-linked oligoadenylates (2-5A) that activate RNaseL which, in turn, triggers RNA breakdown, leading to multiple biological functions. Although RNaseL is required for IFN antiviral function, there are many aspects of the molecular mechanisms that remain obscure. Here, we have used microarray analyses from human HeLa cells infected with vaccinia virus (VACV) recombinants expressing OAS-RNaseL enzymes (referred as 2-5A system) with the aim to identify host genes that are up- or down-regulated in the course of infection by the activation of this antiviral pathway. We found that activation of the 2-5A system from VACV recombinants produces a remarkable stimulation of transcription for genes that regulate many cellular processes, like those that promote cell growth arrest, GADD45B and KCTD11, apoptosis as CUL2, PDCD6, and TNFAIP8L2, IFN-stimulated genes as IFI6, and related to tumor suppression as PLA2G2A. The 2-5A system activation produces down-regulation of transcription of some genes that promote cell growth as RUNX2 and ESR2 and of genes in charge to maintain mitochondria homeostasis as MIPEP and COX5A. These results reveal new genes induced in response to the activation of the 2-5A system with roles in apoptosis, translational control, cell growth arrest, and tumor suppression.
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Affiliation(s)
- Elena Domingo-Gil
- Department of Cellular and Molecular Biology, Centro Nacional de Biotecnología, CSIC, Ciudad Universitaria Cantoblanco, Madrid, Spain
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25
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Burnicka-Turek O, Kata A, Buyandelger B, Ebermann L, Kramann N, Burfeind P, Hoyer-Fender S, Engel W, Adham IM. Pelota interacts with HAX1, EIF3G and SRPX and the resulting protein complexes are associated with the actin cytoskeleton. BMC Cell Biol 2010; 11:28. [PMID: 20406461 PMCID: PMC2867792 DOI: 10.1186/1471-2121-11-28] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Accepted: 04/20/2010] [Indexed: 02/05/2023] Open
Abstract
Background Pelota (PELO) is an evolutionary conserved protein, which has been reported to be involved in the regulation of cell proliferation and stem cell self-renewal. Recent studies revealed the essential role of PELO in the No-Go mRNA decay, by which mRNA with translational stall are endonucleotically cleaved and degraded. Further, PELO-deficient mice die early during gastrulation due to defects in cell proliferation and/or differentiation. Results We show here that PELO is associated with actin microfilaments of mammalian cells. Overexpression of human PELO in Hep2G cells had prominent effect on cell growth, cytoskeleton organization and cell spreading. To find proteins interacting with PELO, full-length human PELO cDNA was used as a bait in a yeast two-hybrid screening assay. Partial sequences of HAX1, EIF3G and SRPX protein were identified as PELO-interacting partners from the screening. The interactions between PELO and HAX1, EIF3G and SRPX were confirmed in vitro by GST pull-down assays and in vivo by co-immunoprecipitation. Furthermore, the PELO interaction domain was mapped to residues 268-385 containing the c-terminal and acidic tail domain. By bimolecular fluorescence complementation assay (BiFC), we found that protein complexes resulting from the interactions between PELO and either HAX1, EIF3G or SRPX were mainly localized to cytoskeletal filaments. Conclusion We could show that PELO is subcellularly localized at the actin cytoskeleton, interacts with HAX1, EIF3G and SRPX proteins and that this interaction occurs at the cytoskeleton. Binding of PELO to cytoskeleton-associated proteins may facilitate PELO to detect and degrade aberrant mRNAs, at which the ribosome is stalled during translation.
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Mitochondrial translation and beyond: processes implicated in combined oxidative phosphorylation deficiencies. J Biomed Biotechnol 2010; 2010:737385. [PMID: 20396601 PMCID: PMC2854570 DOI: 10.1155/2010/737385] [Citation(s) in RCA: 144] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Accepted: 01/29/2010] [Indexed: 12/22/2022] Open
Abstract
Mitochondrial disorders are a heterogeneous group of often multisystemic and early fatal diseases, which are amongst the most common inherited human diseases. These disorders are caused by defects in the oxidative phosphorylation (OXPHOS) system, which comprises five multisubunit enzyme complexes encoded by both the nuclear and the mitochondrial genomes. Due to the multitude of proteins and intricacy of the processes required for a properly functioning OXPHOS system, identifying the genetic defect that underlies an OXPHOS deficiency is not an easy task, especially in the case of combined OXPHOS defects. In the present communication we give an extensive overview of the proteins and processes (in)directly involved in mitochondrial translation and the biogenesis of the OXPHOS system and their roles in combined OXPHOS deficiencies. This knowledge is important for further research into the genetic causes, with the ultimate goal to effectively prevent and cure these complex and often devastating disorders.
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Abstract
Mitochondrial dysfunction is a major mechanism of liver injury. A parent drug or its reactive metabolite can trigger outer mitochondrial membrane permeabilization or rupture due to mitochondrial permeability transition. The latter can severely deplete ATP and cause liver cell necrosis, or it can instead lead to apoptosis by releasing cytochrome c, which activates caspases in the cytosol. Necrosis and apoptosis can trigger cytolytic hepatitis resulting in lethal fulminant hepatitis in some patients. Other drugs severely inhibit mitochondrial function and trigger extensive microvesicular steatosis, hypoglycaemia, coma, and death. Milder and more prolonged forms of drug-induced mitochondrial dysfunction can also cause macrovacuolar steatosis. Although this is a benign liver lesion in the short-term, it can progress to steatohepatitis and then to cirrhosis. Patient susceptibility to drug-induced mitochondrial dysfunction and liver injury can sometimes be explained by genetic or acquired variations in drug metabolism and/or elimination that increase the concentration of the toxic species (parent drug or metabolite). Susceptibility may also be increased by the presence of another condition, which also impairs mitochondrial function, such as an inborn mitochondrial cytopathy, beta-oxidation defect, certain viral infections, pregnancy, or the obesity-associated metabolic syndrome. Liver injury due to mitochondrial dysfunction can have important consequences for pharmaceutical companies. It has led to the interruption of clinical trials, the recall of several drugs after marketing, or the introduction of severe black box warnings by drug agencies. Pharmaceutical companies should systematically investigate mitochondrial effects during lead selection or preclinical safety studies.
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Abstract
The efficient turnover of messenger RNA represents an important mechanism that allows the cell to control gene expression. Until recently, the mechanism of mRNA decay was mainly attributed to exonucleases, comprising enzymes that degrade RNAs from the ends of the molecules. This article summarizes the endoribonucleases, comprising enzymes that cleave RNA molecules internally, which were identified in more recent years in eukaryotic mRNA metabolism. Endoribonucleases have received little attention in the past, based on the difficulty in their identification and a lack of understanding of their physiological significance. This review aims to compare the similarities and differences among this group of enzymes, as well as their known cellular functions. Despite the many differences in protein structure, and thus difficulties in identifying them based on amino acid sequence, most endoribonucleases possess essential cellular functions and have been shown to play an important role in mRNA turnover.
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Affiliation(s)
- Wai Ming Li
- Chemistry Program, University of Northern British Columbia, Prince George, BC, Canada
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Endoribonuclease L (RNase L) regulates the myogenic and adipogenic potential of myogenic cells. PLoS One 2009; 4:e7563. [PMID: 19851509 PMCID: PMC2762314 DOI: 10.1371/journal.pone.0007563] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2009] [Accepted: 09/29/2009] [Indexed: 12/22/2022] Open
Abstract
Skeletal muscle maintenance and repair involve several finely coordinated steps in which pluripotent stem cells are activated, proliferate, exit the cell cycle and differentiate. This process is accompanied by activation of hundreds of muscle-specific genes and repression of genes associated with cell proliferation or pluripotency. Mechanisms controlling myogenesis are precisely coordinated and regulated in time to allow the sequence of activation/inactivation of genes expression. Muscular differentiation is the result of the interplay between several processes such as transcriptional induction, transcriptional repression and mRNA stability. mRNA stability is now recognized as an essential mechanism of control of gene expression. For instance, we previously showed that the endoribonuclease L (RNase L) and its inhibitor (RLI) regulates MyoD mRNA stability and consequently muscle differentiation. We now performed global gene expression analysis by SAGE to identify genes that were down-regulated upon activation of RNase L in C2C12 myogenic cells, a model of satellite cells. We found that RNase L regulates mRNA stability of factors implicated in the control of pluripotency and cell differentiation. Moreover, inappropriate RNase L expression in C2C12 cells led to inhibition of myogenesis and differentiation into adipocytes even when cells were grown in conditions permissive for muscle differentiation. Conversely, over-expression of RLI allowed muscle differentiation of myogenic C2C12 cells even in non permissive conditions. These findings reveal the central role of RNase L and RLI in controlling gene expression and cell fate during myogenesis. Our data should provide valuable insights into the mechanisms that control muscle stem cell differentiation and into the mechanism of metaplasia observed in aging or muscular dystrophy where adipose infiltration of muscle occurs.
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Kim WC, Lee CH. The role of mammalian ribonucleases (RNases) in cancer. Biochim Biophys Acta Rev Cancer 2009; 1796:99-113. [PMID: 19463900 DOI: 10.1016/j.bbcan.2009.05.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Revised: 05/08/2009] [Accepted: 05/13/2009] [Indexed: 01/01/2023]
Abstract
Ribonucleases (RNases) are a group of enzymes that cleave RNAs at phosphodiester bonds resulting in remarkably diverse biological consequences. This review focuses on mammalian RNases that are capable of, or potentially capable of, cleaving messenger RNA (mRNA) as well as other RNAs in cells and play roles in the development of human cancers. The aims of this review are to provide an overview of the roles of currently known mammalian RNases, and the evidence that associate them as regulators of tumor development. The roles of these RNases as oncoproteins and/or tumor suppressors in influencing cell growth, apoptosis, angiogenesis, and other cellular hallmarks of cancer will be presented and discussed. The RNases under discussion include RNases from the conventional mRNA decay pathways, RNases that are activated under cellular stress, RNases from the miRNA pathway, and RNases with multifunctional activity.
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Affiliation(s)
- Wan-Cheol Kim
- Chemistry Program, University of Northern British Columbia, 3333 University Way, Prince George, BC, Canada V2N 4Z9
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31
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Bisbal C, Salehzada T. [RNase L, a crucial mediator of innate immunity and other cell functions]. Med Sci (Paris) 2009; 24:859-64. [PMID: 18950583 DOI: 10.1051/medsci/20082410859] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The 2-5A/RNase L pathway is one of the first cellular defences against viruses. RNase L is an unusual endoribonuclease which activity is strictly regulated by its binding to a small oligonucleotide, 2-5A. 2-5A itself is very unusual, consisting of a series of 5'- triphosphorylated oligoadenylates with 2'-5' bonds. But RNase L activity is not limited to viral RNA cleavage. RNase L plays a central role in innate immunity, apoptosis, cell growth and differentiation by regulating cellular RNA stability and expression. Default in its activity leads to increased susceptibility to virus infections and to tumor development. RNase L gene has been identified as HPC1 (Hereditary Prostate Cancer 1) gene. Study of RNase L variant R462Q in etiology of prostate cancer has led to the identification of the novel human retrovirus closely related to xenotropic murine leukemia viruses (MuLVs) and named XMRV.
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Affiliation(s)
- Catherine Bisbal
- Inserm ERI25-EA 4202, Muscle et Pathologies, Bâtiment Crastes de Paulet, CHU Arnaud de Villeneuve, 371, avenue du Doyen Gaston Giraud, 34295 Montpellier Cedex 5, France.
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Enhanced expression of RNase L as a novel intracellular signal generated by NMDA receptors in mouse cortical neurons. Neurochem Int 2008; 53:71-8. [PMID: 18585418 DOI: 10.1016/j.neuint.2008.06.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 05/10/2008] [Accepted: 06/03/2008] [Indexed: 11/23/2022]
Abstract
Recently we showed that the level of mitochondrial mRNA was decreased prior to neuronal death induced by glutamate. As the level of mRNA is regulated by ribonuclease (RNase), we examined RNase activity and its expression in the primary cultures of cortical neurons after glutamate treatment in order to evaluate the involvement of RNase in glutamate-induced neuronal death. A 15-min exposure of the cultures to glutamate at the concentration of 100 microM produced marked neuronal damage (more than 70% of total cells) at 24-h post-exposure. Under the experimental conditions used, RNA degradation was definitely observed at a period of 4-12-h post-exposure, a time when no damage was seen in the neurons. Glutamate-induced RNA degradation was completely prevented by the N-methyl-d-aspartic acid (NMDA) receptor channel blocker MK-801 or the NR2B-containing NMDA receptor antagonist ifenprodil. Glutamate exposure produced enhanced expression of RNase L at least 2-12h later, which was absolutely abolished by MK-801. However, no significant change was seen in the level of RNase H1 mRNA at any time point post-glutamate treatment. Immunocytochemical studies revealed that RNase L expressed in response to glutamate was localized within the nucleus, mitochondria, and cytoplasm in the neurons. Taken together, our data suggest that expression of RNase L is a signal generated by NMDA receptor in cortical neurons. RNase L expression and RNA degradation may be events that cause neuronal damage induced by NMDA receptor activation.
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Silverman RH. Viral encounters with 2',5'-oligoadenylate synthetase and RNase L during the interferon antiviral response. J Virol 2007; 81:12720-9. [PMID: 17804500 PMCID: PMC2169107 DOI: 10.1128/jvi.01471-07] [Citation(s) in RCA: 460] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Robert H Silverman
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue NB40, Cleveland, OH 44195, USA.
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