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Regulation of ribosomal RNA gene copy number, transcription and nucleolus organization in eukaryotes. Nat Rev Mol Cell Biol 2023; 24:414-429. [PMID: 36732602 DOI: 10.1038/s41580-022-00573-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2022] [Indexed: 02/04/2023]
Abstract
One of the first biological machineries to be created seems to have been the ribosome. Since then, organisms have dedicated great efforts to optimize this apparatus. The ribosomal RNA (rRNA) contained within ribosomes is crucial for protein synthesis and maintenance of cellular function in all known organisms. In eukaryotic cells, rRNA is produced from ribosomal DNA clusters of tandem rRNA genes, whose organization in the nucleolus, maintenance and transcription are strictly regulated to satisfy the substantial demand for rRNA required for ribosome biogenesis. Recent studies have elucidated mechanisms underlying the integrity of ribosomal DNA and regulation of its transcription, including epigenetic mechanisms and a unique recombination and copy-number control system to stably maintain high rRNA gene copy number. In this Review, we disucss how the crucial maintenance of rRNA gene copy number through control of gene amplification and of rRNA production by RNA polymerase I are orchestrated. We also discuss how liquid-liquid phase separation controls the architecture and function of the nucleolus and the relationship between rRNA production, cell senescence and disease.
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Nucleolus and Nucleolar Stress: From Cell Fate Decision to Disease Development. Cells 2022; 11:cells11193017. [PMID: 36230979 PMCID: PMC9563748 DOI: 10.3390/cells11193017] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 09/19/2022] [Accepted: 09/22/2022] [Indexed: 11/30/2022] Open
Abstract
Besides the canonical function in ribosome biogenesis, there have been significant recent advances towards the fascinating roles of the nucleolus in stress response, cell destiny decision and disease progression. Nucleolar stress, an emerging concept describing aberrant nucleolar structure and function as a result of impaired rRNA synthesis and ribosome biogenesis under stress conditions, has been linked to a variety of signaling transductions, including but not limited to Mdm2-p53, NF-κB and HIF-1α pathways. Studies have uncovered that nucleolus is a stress sensor and signaling hub when cells encounter various stress conditions, such as nutrient deprivation, DNA damage and oxidative and thermal stress. Consequently, nucleolar stress plays a pivotal role in the determination of cell fate, such as apoptosis, senescence, autophagy and differentiation, in response to stress-induced damage. Nucleolar homeostasis has been involved in the pathogenesis of various chronic diseases, particularly tumorigenesis, neurodegenerative diseases and metabolic disorders. Mechanistic insights have revealed the indispensable role of nucleolus-initiated signaling in the progression of these diseases. Accordingly, the intervention of nucleolar stress may pave the path for developing novel therapies against these diseases. In this review, we systemically summarize recent findings linking the nucleolus to stress responses, signaling transduction and cell-fate decision, set the spotlight on the mechanisms by which nucleolar stress drives disease progression, and highlight the merit of the intervening nucleolus in disease treatment.
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Ravaioli F, Zampieri M, Morandi L, Pirazzini C, Pellegrini C, De Fanti S, Gensous N, Pirazzoli GL, Sambati L, Ghezzo A, Ciccarone F, Reale A, Monti D, Salvioli S, Caiafa P, Capri M, Bürkle A, Moreno-Villanueva M, Garagnani P, Franceschi C, Bacalini MG. DNA Methylation Analysis of Ribosomal DNA in Adults With Down Syndrome. Front Genet 2022; 13:792165. [PMID: 35571061 PMCID: PMC9094685 DOI: 10.3389/fgene.2022.792165] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Accepted: 03/18/2022] [Indexed: 01/08/2023] Open
Abstract
Control of ribosome biogenesis is a critical aspect of the regulation of cell metabolism. As ribosomal genes (rDNA) are organized in repeated clusters on chromosomes 13, 14, 15, 21, and 22, trisomy of chromosome 21 confers an excess of rDNA copies to persons with Down syndrome (DS). Previous studies showed an alteration of ribosome biogenesis in children with DS, but the epigenetic regulation of rDNA genes has not been investigated in adults with DS so far. In this study, we used a targeted deep-sequencing approach to measure DNA methylation (DNAm) of rDNA units in whole blood from 69 adults with DS and 95 euploid controls. We further evaluated the expression of the precursor of ribosomal RNAs (RNA45S) in peripheral blood mononuclear cells (PBMCs) from the same subjects. We found that the rDNA promoter tends to be hypermethylated in DS concerning the control group. The analysis of epihaplotypes (the combination of methylated and unmethylated CpG sites along the same DNA molecule) showed a significantly lower intra-individual diversity in the DS group, which at the same time was characterized by a higher interindividual variability. Finally, we showed that RNA45S expression is lower in adults with DS. Collectively, our results suggest a rearrangement of the epigenetic profile of rDNA in DS, possibly to compensate for the extranumerary rDNA copies. Future studies should assess whether the regulation of ribosome biogenesis can contribute to the pathogenesis of DS and explain the clinical heterogeneity characteristic of the syndrome.
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Affiliation(s)
- Francesco Ravaioli
- Department of Experimental, Diagnostic and Specialty Medicine (DIMES), University of Bologna, Bologna, Italy
| | - Michele Zampieri
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Luca Morandi
- Functional and Molecular Neuroimaging Unit, IRCCS Istituto Delle Scienze Neurologiche di Bologna, Bologna, Italy
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Chiara Pirazzini
- IRCCS Istituto Delle Scienze Neurologiche di Bologna, Bologna, Italy
| | | | - Sara De Fanti
- Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy
- Interdepartmental Centre Alma Mater Research Institute on Global Challenges and Climate Change, University of Bologna, Bologna, Italy
| | - Noémie Gensous
- Department of Internal Medicine and Clinical Immunology, CHU Bordeaux (Groupe Hospitalier Saint-André), Bordeaux, France
- UMR/CNRS 5164, ImmunoConcEpT, CNRS, University of Bordeaux, Bordeaux, France
| | | | - Luisa Sambati
- IRCCS Istituto Delle Scienze Neurologiche di Bologna, U.O.C. Clinica Neurologica Rete Neurologica Metropolitana (NEUROMET), Bologna, Italy
| | | | - Fabio Ciccarone
- IRCCS San Raffaele Roma, Department of Human Sciences and Promotion of the Quality of Life, San Raffaele Roma Open University, Rome, Italy
| | - Anna Reale
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Daniela Monti
- Department of Experimental and Clinical Biomedical Sciences “Mario Serio”, University of Florence, Florence, Italy
| | - Stefano Salvioli
- Department of Experimental, Diagnostic and Specialty Medicine (DIMES), University of Bologna, Bologna, Italy
| | - Paola Caiafa
- Department of Cellular Biotechnologies and Haematology, Sapienza University of Rome, Rome, Italy
| | - Miriam Capri
- Department of Experimental, Diagnostic and Specialty Medicine (DIMES), University of Bologna, Bologna, Italy
| | - Alexander Bürkle
- Molecular Toxicology Group, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Maria Moreno-Villanueva
- Molecular Toxicology Group, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Paolo Garagnani
- Department of Experimental, Diagnostic and Specialty Medicine (DIMES), University of Bologna, Bologna, Italy
- Applied Biomedical Research Center (CRBA), S. Orsola-Malpighi Polyclinic, Bologna, Italy
- CNR Institute of Molecular Genetics “Luigi Luca Cavalli-Sforza”—Unit of Bologna, Bologna, Italy
- Department of Laboratory Medicine, Clinical Chemistry, Karolinska Institutet, Karolinska University Hospital, Huddinge, Sweden
| | - Claudio Franceschi
- Laboratory of Systems Medicine of Healthy Aging, Department of Applied Mathematics, Lobachevsky University, Nizhny Novgorod, Russia
| | - Maria Giulia Bacalini
- IRCCS Istituto Delle Scienze Neurologiche di Bologna, Bologna, Italy
- *Correspondence: Maria Giulia Bacalini,
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Ripmeester EGJ, Welting TJM, van den Akker GGH, Surtel DAM, Steijns JSJ, Cremers A, van Rhijn LW, Caron MMJ. BMP7 increases protein synthesis in SW1353 cells and determines rRNA levels in a NKX3-2-dependent manner. PLoS One 2022; 17:e0263430. [PMID: 35139106 PMCID: PMC8827423 DOI: 10.1371/journal.pone.0263430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 01/19/2022] [Indexed: 11/18/2022] Open
Abstract
BMP7 is a morphogen capable of counteracting the OA chondrocyte hypertrophic phenotype via NKX3-2. NKX3-2 represses expression of RUNX2, an important transcription factor for chondrocyte hypertrophy. Since RUNX2 has previously been described as an inhibitor for 47S pre-rRNA transcription, we hypothesized that BMP7 positively influences 47S pre-rRNA transcription through NKX3-2, resulting in increased protein translational capacity. Therefor SW1353 cells and human primary chondrocytes were exposed to BMP7 and rRNA (18S, 5.8S, 28S) expression was determined by RT-qPCR. NKX3-2 knockdown was achieved via transfection of a NKX3-2-specific siRNA duplex. Translational capacity was assessed by the SUNsET assay, and 47S pre-rRNA transcription was determined by transfection of a 47S gene promoter-reporter plasmid. BMP7 treatment increased protein translational capacity. This was associated by increased 18S and 5.8S rRNA and NKX3-2 mRNA expression, as well as increased 47S gene promotor activity. Knockdown of NKX3-2 led to increased expression of RUNX2, accompanied by decreased 47S gene promotor activity and rRNA expression, an effect BMP7 was unable to restore. Our data demonstrate that BMP7 positively influences protein translation capacity of SW1353 cells and chondrocytes. This is likely caused by an NKX3-2-dependent activation of 47S gene promotor activity. This finding connects morphogen-mediated changes in cellular differentiation to an aspect of ribosome biogenesis via key transcription factors central to determining the chondrocyte phenotype.
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Affiliation(s)
- Ellen G. J. Ripmeester
- Laboratory for Experimental Orthopedics, Department of Orthopedic Surgery, Maastricht University, Maastricht, the Netherlands
| | - Tim J. M. Welting
- Laboratory for Experimental Orthopedics, Department of Orthopedic Surgery, Maastricht University, Maastricht, the Netherlands
- Laboratory for Experimental Orthopedics, Department of Orthopedic Surgery, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Guus G. H. van den Akker
- Laboratory for Experimental Orthopedics, Department of Orthopedic Surgery, Maastricht University, Maastricht, the Netherlands
| | - Don A. M. Surtel
- Laboratory for Experimental Orthopedics, Department of Orthopedic Surgery, Maastricht University, Maastricht, the Netherlands
| | - Jessica S. J. Steijns
- Laboratory for Experimental Orthopedics, Department of Orthopedic Surgery, Maastricht University, Maastricht, the Netherlands
| | - Andy Cremers
- Laboratory for Experimental Orthopedics, Department of Orthopedic Surgery, Maastricht University, Maastricht, the Netherlands
| | - Lodewijk W. van Rhijn
- Laboratory for Experimental Orthopedics, Department of Orthopedic Surgery, Maastricht University, Maastricht, the Netherlands
- Laboratory for Experimental Orthopedics, Department of Orthopedic Surgery, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Marjolein M. J. Caron
- Laboratory for Experimental Orthopedics, Department of Orthopedic Surgery, Maastricht University, Maastricht, the Netherlands
- * E-mail:
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5
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Morovicz AP, Mazloumi Gavgani F, Jacobsen RG, Skuseth Slinning M, Turcu DC, Lewis AE. Phosphoinositide 3-kinase signalling in the nucleolus. Adv Biol Regul 2021; 83:100843. [PMID: 34920983 DOI: 10.1016/j.jbior.2021.100843] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 11/20/2021] [Indexed: 12/26/2022]
Abstract
The phosphoinositide 3-kinase (PI3K) signalling pathway plays key roles in many cellular processes and is altered in many diseases. The function and mode of action of the pathway have mostly been elucidated in the cytoplasm. However, many of the components of the PI3K pathway are also present in the nucleus at specific sub-nuclear sites including nuclear speckles, nuclear lipid islets and the nucleolus. Nucleoli are membrane-less subnuclear structures where ribosome biogenesis occurs. Processes leading to ribosome biogenesis are tightly regulated to maintain protein translation capacity of cells. This review focuses on nucleolar PI3K signalling and how it regulates rRNA synthesis, as well as on the identification of downstream phosphatidylinositol (3,4,5)trisphosphate effector proteins.
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Affiliation(s)
| | | | - Rhîan G Jacobsen
- Department of Biological Sciences, University of Bergen, 5008, Bergen, Norway
| | | | - Diana C Turcu
- Department of Biological Sciences, University of Bergen, 5008, Bergen, Norway
| | - Aurélia E Lewis
- Department of Biological Sciences, University of Bergen, 5008, Bergen, Norway.
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6
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Maity P, Singh K, Krug L, Koroma A, Hainzl A, Bloch W, Kochanek S, Wlaschek M, Schorpp-Kistner M, Angel P, Ignatius A, Geiger H, Scharffetter-Kochanek K. Persistent JunB activation in fibroblasts disrupts stem cell niche interactions enforcing skin aging. Cell Rep 2021; 36:109634. [PMID: 34469740 DOI: 10.1016/j.celrep.2021.109634] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 06/15/2021] [Accepted: 08/09/2021] [Indexed: 01/02/2023] Open
Abstract
Fibroblasts residing in the connective tissues constitute the stem cell niche, particularly in organs such as skin. Although the effect of fibroblasts on stem cell niches and organ aging is an emerging concept, the underlying mechanisms are largely unresolved. We report a mechanism of redox-dependent activation of transcription factor JunB, which, through concomitant upregulation of p16INK4A and repression of insulin growth factor-1 (IGF-1), initiates the installment of fibroblast senescence. Fibroblast senescence profoundly disrupts the metabolic and structural niche, and its essential interactions with different stem cells thus enforces depletion of stem cells pools and skin tissue decline. In fact, silencing of JunB in a fibroblast-niche-specific manner-by reinstatement of IGF-1 and p16 levels-restores skin stem cell pools and overall skin tissue integrity. Here, we report a role of JunB in the control of connective tissue niche and identified targets to combat skin aging and associated pathologies.
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Affiliation(s)
- Pallab Maity
- Department of Dermatology and Allergic Diseases, Ulm University, 89081 Ulm, Germany; Aging Research Center (ARC), 89081 Ulm, Germany.
| | - Karmveer Singh
- Department of Dermatology and Allergic Diseases, Ulm University, 89081 Ulm, Germany; Aging Research Center (ARC), 89081 Ulm, Germany
| | - Linda Krug
- Department of Dermatology and Allergic Diseases, Ulm University, 89081 Ulm, Germany
| | - Albert Koroma
- Department of Dermatology and Allergic Diseases, Ulm University, 89081 Ulm, Germany; Aging Research Center (ARC), 89081 Ulm, Germany
| | - Adelheid Hainzl
- Department of Dermatology and Allergic Diseases, Ulm University, 89081 Ulm, Germany
| | - Wilhelm Bloch
- Institute of Cardiology and Sports Medicine, Molecular and cellular Sports Medicine, German Sport University Cologne, 50933 Cologne, Germany
| | - Stefan Kochanek
- Department of Gene Therapy, University of Ulm, 89081 Ulm, Germany
| | - Meinhard Wlaschek
- Department of Dermatology and Allergic Diseases, Ulm University, 89081 Ulm, Germany
| | - Marina Schorpp-Kistner
- Division of Signal Transduction and Growth Control, German Cancer Research Center (DKFZ) and DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany
| | - Peter Angel
- Division of Signal Transduction and Growth Control, German Cancer Research Center (DKFZ) and DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany
| | - Anita Ignatius
- Institute of Orthopaedic Research and Biomechanics, Ulm University, 89081 Ulm, Germany
| | - Hartmut Geiger
- Aging Research Center (ARC), 89081 Ulm, Germany; Institute of Molecular Medicine and Stem Cell Aging, Ulm University, 89081 Ulm, Germany; Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center and University of Cincinnati, Cincinnati, OH 45229, USA
| | - Karin Scharffetter-Kochanek
- Department of Dermatology and Allergic Diseases, Ulm University, 89081 Ulm, Germany; Aging Research Center (ARC), 89081 Ulm, Germany.
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7
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Tang C, Li W, Klosterman SJ, Wang Y. Transcriptome Variations in Verticillium dahliae in Response to Two Different Inorganic Nitrogen Sources. Front Microbiol 2021; 12:712701. [PMID: 34394062 PMCID: PMC8355529 DOI: 10.3389/fmicb.2021.712701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 07/01/2021] [Indexed: 11/16/2022] Open
Abstract
The fungus Verticillium dahliae causes vascular wilt disease on hundreds of plant species. The main focus of the research to control this fungus has been aimed at infection processes such as penetration peg formation and effector secretion, but the ability of the fungus to acquire and utilize nutrients are often overlooked and may hold additional potential to formulate new disease control approaches. Little is known about the molecular mechanisms of nitrogen acquisition and assimilation processes in V. dahliae. In this present study, RNA sequencing and gene expression analysis were used to examine differentially expressed genes in response to the different nitrogen sources, nitrate and ammonium, in V. dahliae. A total of 3244 and 2528 differentially expressed genes were identified in response to nitrate and ammonium treatments, respectively. The data indicated nitrate metabolism requires additional energy input while ammonium metabolism is accompanied by reductions in particular cellular processes. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses of DEGs during nitrate metabolism revealed that many of the genes encoded those involved in protein biosynthetic and metabolic processes, especially ribosome and RNA polymerase biosynthesis, but also other processes including transport and organonitrogen compound metabolism. Analysis of DEGs in the ammonium treatment indicated that cell cycle, oxidoreductase, and certain metabolic activities were reduced. In addition, DEGs participating in the utilization of both nitrate and ammonium were related to L-serine biosynthesis, energy-dependent multidrug efflux pump activity, and glycerol transport. We further showed that the mutants of three differentially expressed transcription factors (VdMcm1, VdHapX, and VDAG_08640) exhibited abnormal phenotypes under nitrate and ammonium treatment compared with the wild type strain. Deletion of VdMcm1 displayed slower growth when utilizing both nitrogen sources, while deletion of VdHapX and VDAG_08640 only affected nitrate metabolism, inferring that nitrogen assimilation required regulation of bZIP transcription factor family and participation of cell cycle. Taken together, our findings illustrate the convergent and distinctive regulatory mechanisms between preferred (ammonium) and alternative nitrogen (nitrate) metabolism at the transcriptome level, leading to better understanding of inorganic nitrogen metabolism in V. dahliae.
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Affiliation(s)
- Chen Tang
- Beijing Key Laboratory for Forest Pest Control, College of Forestry, Beijing Forestry University, Beijing, China
| | - Wenwen Li
- Beijing Key Laboratory for Forest Pest Control, College of Forestry, Beijing Forestry University, Beijing, China
| | - Steven J Klosterman
- Agricultural Research Service, United States Department of Agriculture, Salinas, CA, United States
| | - Yonglin Wang
- Beijing Key Laboratory for Forest Pest Control, College of Forestry, Beijing Forestry University, Beijing, China
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8
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Kofuji S, Sasaki AT. GTP metabolic reprogramming by IMPDH2: unlocking cancer cells' fuelling mechanism. J Biochem 2021; 168:319-328. [PMID: 32702086 DOI: 10.1093/jb/mvaa085] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Accepted: 07/16/2020] [Indexed: 12/15/2022] Open
Abstract
Growing cells increase multiple biosynthetic processes in response to the high metabolic demands needed to sustain proliferation. The even higher metabolic requirements in the setting of cancer provoke proportionately greater biosynthesis. Underappreciated key aspects of this increased metabolic demand are guanine nucleotides and adaptive mechanisms to regulate their concentration. Using the malignant brain tumour, glioblastoma, as a model, we have demonstrated that one of the rate-limiting enzymes for guanosine triphosphate (GTP) synthesis, inosine monophosphate dehydrogenase-2 (IMPDH2), is increased and IMPDH2 expression is necessary for the activation of de novo GTP biosynthesis. Moreover, increased IMPDH2 enhances RNA polymerase I and III transcription directly linking GTP metabolism to both anabolic capacity as well as nucleolar enlargement historically observed as associated with cancer. In this review, we will review in detail the basis of these new discoveries and, more generally, summarize the current knowledge on the role of GTP metabolism in cancer.
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Affiliation(s)
- Satoshi Kofuji
- Department of Developmental and Regenerative Biology, Medical Research Institute, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Atsuo T Sasaki
- Division of Hematology and Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, 3125 Eden Ave., Cincinnati, OH 45267-0508, USA.,Department of Cancer Biology, University of Cincinnati College of Medicine, 3125 Eden Ave., OH 45267-0508, USA.,Department of Neurosurgery, Brain Tumor Center at UC Gardner Neuroscience Institute, 3113 Bellevue Ave, Cincinnati, OH 45267-0508, USA.,Institute for Advanced Biosciences, Keio University, Kakuganji 246-2, Mizukami, Tsuruoka City, Yamagata 997-0052, Japan
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9
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Mazloumi Gavgani F, Karlsson T, Tangen IL, Morovicz AP, Arnesen VS, Turcu DC, Ninzima S, Spang K, Krakstad C, Guillermet-Guibert J, Lewis AE. Nuclear upregulation of class I phosphoinositide 3-kinase p110β correlates with high 47S rRNA levels in cancer cells. J Cell Sci 2021; 134:jcs.246090. [PMID: 33536247 DOI: 10.1242/jcs.246090] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 12/24/2020] [Indexed: 12/12/2022] Open
Abstract
The class I phosphoinositide 3-kinase (PI3K) catalytic subunits p110α and p110β are ubiquitously expressed but differently targeted in tumours. In cancer, PIK3CB (encoding p110β) is seldom mutated compared with PIK3CA (encoding p110α) but can contribute to tumorigenesis in certain PTEN-deficient tumours. The underlying molecular mechanisms are, however, unclear. We have previously reported that p110β is highly expressed in endometrial cancer (EC) cell lines and at the mRNA level in primary patient tumours. Here, we show that p110β protein levels are high in both the cytoplasmic and nuclear compartments in EC cells. Moreover, high nuclear:cytoplasmic staining ratios were detected in high-grade primary tumours. High levels of phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P 3] were measured in the nucleus of EC cells, and pharmacological and genetic approaches showed that its production was partly dependent upon p110β activity. Using immunofluorescence staining, p110β and PtdIns(3,4,5)P 3 were localised in the nucleolus, which correlated with high levels of 47S pre-rRNA. p110β inhibition led to a decrease in both 47S rRNA levels and cell proliferation. In conclusion, these results present a nucleolar role for p110β that may contribute to tumorigenesis in EC.This article has an associated First Person interview with Fatemeh Mazloumi Gavgani, joint first author of the paper.
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Affiliation(s)
| | - Thomas Karlsson
- Department of Biological Sciences, University of Bergen, Bergen 5008, Norway
| | - Ingvild L Tangen
- Centre for Cancer Biomarkers, Department of Clinical Science, University of Bergen, Bergen 5021, Norway.,Department of Gynaecology and Obstetrics, Haukeland University Hospital, Bergen 5021, Norway
| | | | | | - Diana C Turcu
- Department of Biological Sciences, University of Bergen, Bergen 5008, Norway
| | - Sandra Ninzima
- Department of Biological Sciences, University of Bergen, Bergen 5008, Norway
| | - Katharina Spang
- Department of Biological Sciences, University of Bergen, Bergen 5008, Norway
| | - Camilla Krakstad
- Centre for Cancer Biomarkers, Department of Clinical Science, University of Bergen, Bergen 5021, Norway.,Department of Gynaecology and Obstetrics, Haukeland University Hospital, Bergen 5021, Norway
| | - Julie Guillermet-Guibert
- Inserm U1037, Centre de Recherches en Cancérologie de Toulouse (CRCT), Institut National de la Santé et de la Recherche Médicale (INSERM), Université Toulouse III Paul Sabatier, 31037 Toulouse, France
| | - Aurélia E Lewis
- Department of Biological Sciences, University of Bergen, Bergen 5008, Norway
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10
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IGF-1 Upregulates Biglycan and Decorin by Increasing Translation and Reducing ADAMTS5 Expression. Int J Mol Sci 2021; 22:ijms22031403. [PMID: 33573338 PMCID: PMC7866853 DOI: 10.3390/ijms22031403] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 01/22/2021] [Accepted: 01/28/2021] [Indexed: 12/11/2022] Open
Abstract
Proteoglycan (PG) is a glycosaminoglycan (GAG)-conjugated protein essential for maintaining tissue strength and elasticity. The most abundant skin PGs, biglycan and decorin, have been reported to decrease as skin ages. Insulin-like growth factor-1 (IGF-1) is important in various physiological functions such as cell survival, growth, and apoptosis. It is well known that the serum level of IGF-1 decreases with age. Therefore, we investigated whether and how IGF-1 affects biglycan and decorin. When primary cultured normal human dermal fibroblasts (NHDFs) were treated with IGF-1, protein levels of biglycan and decorin increased, despite no difference in mRNA expression. This increase was not inhibited by transcription blockade using actinomycin D, suggesting that it is mediated by IGF-1-induced enhanced translation. Additionally, both mRNA and protein expression of ADAMTS5, a PG-degrading enzyme, were decreased in IGF-1-treated NHDFs. Knockdown of ADAMTS5 via RNA interference increased protein expression of biglycan and decorin. Moreover, mRNA and protein expression of ADAMTS5 increased in aged human skin tissues compared to young tissue. Overall, IGF-1 increases biglycan and decorin, which is achieved by improving protein translation to increase synthesis and preventing ADAMTS5-mediated degradation. This suggests a new role of IGF-1 as a regulator for biglycan and decorin in skin aging process.
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11
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Elsharawy KA, Toss MS, Raafat S, Ball G, Green AR, Aleskandarany MA, Dalton LW, Rakha EA. Prognostic significance of nucleolar assessment in invasive breast cancer. Histopathology 2020; 76:671-684. [PMID: 31736094 DOI: 10.1111/his.14036] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 11/07/2019] [Accepted: 11/14/2019] [Indexed: 12/17/2022]
Abstract
AIMS Nucleolar morphometric features have a potential role in the assessment of the aggressiveness of many cancers. However, the role of nucleoli in invasive breast cancer (BC) is still unclear. The aims of this study were to investigate the optimal method for scoring nucleoli in IBC and their prognostic significance, and to refine the grading of breast cancer (BC) by incorporating nucleolar score. METHODS AND RESULTS Digital images acquired from haematoxylin and eosin-stained sections from a large BC cohort were divided into training (n = 400) and validation (n = 1200) sets for use in this study. Four different assessment methods were evaluated in the training set to identify the optimal method associated with the best performance and significant prognostic value. These were: (i) a modified Helpap method; (ii) counting prominent nucleoli (size ≥2.5 µm) in 10 field views (FVs); (iii) counting prominent nucleoli in five FVs; and (iv) counting prominent nucleoli in one FV. The optimal method was applied to the validation set and to an external validation set, i.e. data from The Cancer Genome Atlas (n = 743). Scoring prominent nucleoli in five FVs showed the highest interobserver concordance rate (intraclass correlation coefficient of 0.8) and a significant association with BC-specific survival (P < 0.0001). A high nucleolar score was associated with younger age, larger tumour size, and higher grade. Incorporation of nucleolar score in the Nottingham grading system resulted in a higher significant association with survival than the conventional grade. CONCLUSIONS Quantification of nucleolar prominence in five FVs is a cost-efficient and reproducible morphological feature that can predict BC behaviour and can provide an alternative to pleomorphism to improve BC grading performance.
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Affiliation(s)
- Khloud A Elsharawy
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, UK.,Department of Zoology, Faculty of Science, Damietta University, Damietta, Egypt
| | - Michael S Toss
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, UK
| | - Sara Raafat
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, UK
| | - Graham Ball
- School of Science and Technology, Nottingham Trent University, Nottingham, UK
| | - Andrew R Green
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, UK
| | - Mohammed A Aleskandarany
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, UK
| | - Leslie W Dalton
- Department of Histopathology, South Austin Hospital, Austin, TX, USA
| | - Emad A Rakha
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, UK
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12
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Aldiss P, Lewis JE, Lupini I, Bloor I, Chavoshinejad R, Boocock DJ, Miles AK, Ebling FJP, Budge H, Symonds ME. Exercise Training in Obese Rats Does Not Induce Browning at Thermoneutrality and Induces a Muscle-Like Signature in Brown Adipose Tissue. Front Endocrinol (Lausanne) 2020; 11:97. [PMID: 32265830 PMCID: PMC7099615 DOI: 10.3389/fendo.2020.00097] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 02/14/2020] [Indexed: 01/08/2023] Open
Abstract
Aim: Exercise training elicits diverse effects on brown (BAT) and white adipose tissue (WAT) physiology in rodents housed below their thermoneutral zone (i.e., 28-32°C). In these conditions, BAT is chronically hyperactive and, unlike human residence, closer to thermoneutrality. Therefore, we set out to determine the effects of exercise training in obese animals at 28°C (i.e., thermoneutrality) on BAT and WAT in its basal (i.e., inactive) state. Methods: Sprague-Dawley rats (n = 12) were housed at thermoneutrality from 3 weeks of age and fed a high-fat diet. At 12 weeks of age half these animals were randomized to 4-weeks of swim-training (1 h/day, 5 days per week). Following a metabolic assessment interscapular and perivascular BAT and inguinal (I)WAT were taken for analysis of thermogenic genes and the proteome. Results: Exercise attenuated weight gain but did not affect total fat mass or thermogenic gene expression. Proteomics revealed an impact of exercise training on 2-oxoglutarate metabolic process, mitochondrial respiratory chain complex IV, carbon metabolism, and oxidative phosphorylation. This was accompanied by an upregulation of multiple proteins involved in skeletal muscle physiology in BAT and an upregulation of muscle specific markers (i.e., Myod1, CkM, Mb, and MyoG). UCP1 mRNA was undetectable in IWAT with proteomics highlighting changes to DNA binding, the positive regulation of apoptosis, HIF-1 signaling and cytokine-cytokine receptor interaction. Conclusion: Exercise training reduced weight gain in obese animals at thermoneutrality and is accompanied by an oxidative signature in BAT which is accompanied by a muscle-like signature rather than induction of thermogenic genes. This may represent a new, UCP1-independent pathway through which BAT physiology is regulated by exercise training.
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Affiliation(s)
- Peter Aldiss
- The Early Life Research Unit, Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Jo E. Lewis
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
| | - Irene Lupini
- School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy
| | - Ian Bloor
- The Early Life Research Unit, Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Ramyar Chavoshinejad
- The Early Life Research Unit, Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - David J. Boocock
- John van Geest Cancer Research Centre, Nottingham Trent University, Nottingham, United Kingdom
| | - Amanda K. Miles
- John van Geest Cancer Research Centre, Nottingham Trent University, Nottingham, United Kingdom
| | - Francis J. P. Ebling
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
| | - Helen Budge
- The Early Life Research Unit, Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Michael E. Symonds
- The Early Life Research Unit, Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, United Kingdom
- Nottingham Digestive Disease Centre and Biomedical Research Unit, School of Medicine, University of Nottingham, Nottingham, United Kingdom
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13
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Aging and Caloric Restriction Modulate the DNA Methylation Profile of the Ribosomal RNA Locus in Human and Rat Liver. Nutrients 2020; 12:nu12020277. [PMID: 31973116 PMCID: PMC7070571 DOI: 10.3390/nu12020277] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 01/13/2020] [Accepted: 01/17/2020] [Indexed: 12/21/2022] Open
Abstract
A growing amount of evidence suggests that the downregulation of protein synthesis is an adaptive response during physiological aging, which positively contributes to longevity and can be modulated by nutritional interventions like caloric restriction (CR). The expression of ribosomal RNA (rRNA) is one of the main determinants of translational rate, and epigenetic modifications finely contribute to its regulation. Previous reports suggest that hypermethylation of ribosomal DNA (rDNA) locus occurs with aging, although with some species- and tissue- specificity. In the present study, we experimentally measured DNA methylation of three regions (the promoter, the 5′ of the 18S and the 5′ of 28S sequences) in the rDNA locus in liver tissues from rats at two, four, 10, and 18 months. We confirm previous findings, showing age-related hypermethylation, and describe, for the first time, that this gain in methylation also occurs in human hepatocytes. Furthermore, we show that age-related hypermethylation is enhanced in livers of rat upon CR at two and 10 months, and that at two months a trend towards the reduction of rRNA expression occurs. Collectively, our results suggest that CR modulates age-related regulation of methylation at the rDNA locus, thus providing an epigenetic readout of the pro-longevity effects of CR.
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14
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Weeks SE, Metge BJ, Samant RS. The nucleolus: a central response hub for the stressors that drive cancer progression. Cell Mol Life Sci 2019; 76:4511-4524. [PMID: 31338556 PMCID: PMC6841648 DOI: 10.1007/s00018-019-03231-0] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 06/25/2019] [Accepted: 07/15/2019] [Indexed: 01/17/2023]
Abstract
The nucleolus is a sub-nuclear body known primarily for its role in ribosome biogenesis. Increased number and/or size of nucleoli have historically been used by pathologists as a prognostic indicator of cancerous lesions. This increase in nucleolar number and/or size is classically attributed to the increased need for protein synthesis in cancer cells. However, evidences suggest that the nucleolus plays critical roles in many cellular functions in both normal cell biology and disease pathologies, including cancer. As new functions of the nucleolus are elucidated, there is mounting evidence to support the role of the nucleolus in regulating additional cellular functions, particularly response to cellular stressors, maintenance of genome stability, and DNA damage repair, as well as the regulation of gene expression and biogenesis of several ribonucleoproteins. This review highlights the central role of the nucleolus in carcinogenesis and cancer progression and discusses how cancer cells may become "addicted" to nucleolar functions.
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Affiliation(s)
- Shannon E Weeks
- Department of Pathology, University of Alabama at Birmingham, WTI 320E, 1824 6th Ave South, Birmingham, AL, 35233, USA
| | - Brandon J Metge
- Department of Pathology, University of Alabama at Birmingham, WTI 320E, 1824 6th Ave South, Birmingham, AL, 35233, USA
| | - Rajeev S Samant
- Department of Pathology, University of Alabama at Birmingham, WTI 320E, 1824 6th Ave South, Birmingham, AL, 35233, USA.
- O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, USA.
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15
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von Walden F. Ribosome biogenesis in skeletal muscle: coordination of transcription and translation. J Appl Physiol (1985) 2019; 127:591-598. [PMID: 31219775 DOI: 10.1152/japplphysiol.00963.2018] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Skeletal muscle mass responds in a remarkable manner to alterations in loading and use. It has long been clear that skeletal muscle hypertrophy can be prevented by inhibiting RNA synthesis. Since 80% of the cell's total RNA has been estimated to be rRNA, this finding indicates that de novo production of rRNA via transcription of the corresponding genes is important for such hypertrophy to occur. Transcription of rDNA by RNA Pol I is the rate-limiting step in ribosome biogenesis, indicating in turn that this biogenesis strongly influences the hypertrophic response. The present minireview focuses on 1) a brief description of the key steps in ribosome biogenesis and the relationship of this process to skeletal muscle mass and 2) the coordination of ribosome biogenesis and protein synthesis for growth or atrophy, as exemplified by the intracellular AMPK and mTOR pathways.
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Affiliation(s)
- Ferdinand von Walden
- Division of Pediatric Neurology, Department of Women's and Children's Health, Karolinska Institute, Stockholm, Sweden
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16
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Abetov DA, Kiyan VS, Zhylkibayev AA, Sarbassova DA, Alybayev SD, Spooner E, Song MS, Bersimbaev RI, Sarbassov DD. Formation of mammalian preribosomes proceeds from intermediate to composed state during ribosome maturation. J Biol Chem 2019; 294:10746-10757. [PMID: 31076509 DOI: 10.1074/jbc.ac119.008378] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 05/07/2019] [Indexed: 12/28/2022] Open
Abstract
In eukaryotes, ribosome assembly is a rate-limiting step in ribosomal biogenesis that takes place in a distinctive subnuclear organelle, the nucleolus. How ribosomes get assembled at the nucleolar site by forming initial preribosomal complexes remains poorly characterized. In this study, using several human and murine cell lines, we developed a method for isolation of native mammalian preribosomal complexes by lysing cell nuclei through mild sonication. A sucrose gradient fractionation of the nuclear lysate resolved several ribonucleoprotein (RNP) complexes containing rRNAs and ribosomal proteins. Characterization of the RNP complexes with MS-based protein identification and Northern blotting-based rRNA detection approaches identified two types of preribosomes we named here as intermediate preribosomes (IPRibs) and composed preribosome (CPRib). IPRib complexes comprised large preribosomes (105S to 125S in size) containing the rRNA modification factors and premature rRNAs. We further observed that a distinctive CPRib complex consists of an 85S preribosome assembled with mature rRNAs and a ribosomal biogenesis factor, Ly1 antibody-reactive (LYAR), that does not associate with premature rRNAs and rRNA modification factors. rRNA-labeling experiments uncovered that IPRib assembly precedes CPRib complex formation. We also found that formation of the preribosomal complexes is nutrient-dependent because the abundances of IPRib and CPRib decreased substantially when cells were either deprived of amino acids or exposed to an mTOR kinase inhibitor. These findings indicate that preribosomes form via dynamic and nutrient-dependent processing events and progress from an intermediate to a composed state during ribosome maturation.
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Affiliation(s)
- Danysh A Abetov
- Department of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Vladimir S Kiyan
- Department of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Assylbek A Zhylkibayev
- Department of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Dilara A Sarbassova
- Department of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Sanzhar D Alybayev
- Department of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Eric Spooner
- Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142
| | - Min Sup Song
- Department of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas 77030; MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, Texas 77030
| | - Rakhmetkazhy I Bersimbaev
- Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Nur-Sultan 010000, Kazakhstan, and
| | - Dos D Sarbassov
- Department of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas 77030; MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, Texas 77030,; Department of Biology, Nazarbayev University, Nur-Sultan 010000, Kazakhstan.
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17
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Figueiredo VC, McCarthy JJ. Regulation of Ribosome Biogenesis in Skeletal Muscle Hypertrophy. Physiology (Bethesda) 2019; 34:30-42. [PMID: 30540235 PMCID: PMC6383632 DOI: 10.1152/physiol.00034.2018] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 09/11/2018] [Accepted: 09/13/2018] [Indexed: 01/22/2023] Open
Abstract
The ribosome is the enzymatic macromolecular machine responsible for protein synthesis. The rates of protein synthesis are primarily dependent on translational efficiency and capacity. Ribosome biogenesis has emerged as an important regulator of skeletal muscle growth and maintenance by altering the translational capacity of the cell. Here, we provide evidence to support a central role for ribosome biogenesis in skeletal muscle growth during postnatal development and in response to resistance exercise training. Furthermore, we discuss the cellular signaling pathways regulating ribosome biogenesis, discuss how myonuclear accretion affects translational capacity, and explore future areas of investigation within the field.
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Affiliation(s)
- Vandré Casagrande Figueiredo
- The Center for Muscle Biology, College of Health Sciences, University of Kentucky , Lexington, Kentucky
- Department of Rehabilitation Sciences, College of Medicine, University of Kentucky , Lexington, Kentucky
| | - John J McCarthy
- The Center for Muscle Biology, College of Health Sciences, University of Kentucky , Lexington, Kentucky
- Department of Physiology, University of Kentucky , Lexington, Kentucky
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18
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Tiku V, Antebi A. Nucleolar Function in Lifespan Regulation. Trends Cell Biol 2018; 28:662-672. [PMID: 29779866 DOI: 10.1016/j.tcb.2018.03.007] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 03/26/2018] [Accepted: 03/29/2018] [Indexed: 12/12/2022]
Abstract
The nucleolus is a prominent membraneless organelle residing within the nucleus. The nucleolus has been regarded as a housekeeping structure mainly known for its role in ribosomal RNA (rRNA) production and ribosome assembly. However, accumulating evidence has revealed its functions in numerous cellular processes that control organismal physiology, thereby taking the nucleolus much beyond its conventional role in ribosome biogenesis. Perturbations in nucleolar functions have been associated with severe diseases such as cancer and progeria. Recent studies have also uncovered the role of the nucleolus in development and aging. In this review we discuss major nucleolar functions that impact organismal aging.
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Affiliation(s)
- Varnesh Tiku
- Max Planck Institute for Biology of Ageing, Joseph Stelzmann Strasse 9b, 50931 Cologne, Germany; Present Address: Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Adam Antebi
- Max Planck Institute for Biology of Ageing, Joseph Stelzmann Strasse 9b, 50931 Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50674 Cologne, Germany.
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19
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Kang J, Kusnadi EP, Ogden AJ, Hicks RJ, Bammert L, Kutay U, Hung S, Sanij E, Hannan RD, Hannan KM, Pearson RB. Amino acid-dependent signaling via S6K1 and MYC is essential for regulation of rDNA transcription. Oncotarget 2018; 7:48887-48904. [PMID: 27385002 PMCID: PMC5226478 DOI: 10.18632/oncotarget.10346] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 06/15/2016] [Indexed: 12/25/2022] Open
Abstract
Dysregulation of RNA polymerase I (Pol I)-dependent ribosomal DNA (rDNA) transcription is a consistent feature of malignant transformation that can be targeted to treat cancer. Understanding how rDNA transcription is coupled to the availability of growth factors and nutrients will provide insight into how ribosome biogenesis is maintained in a tumour environment characterised by limiting nutrients. We demonstrate that modulation of rDNA transcription initiation, elongation and rRNA processing is an immediate, co-regulated response to altered amino acid abundance, dependent on both mTORC1 activation of S6K1 and MYC activity. Growth factors regulate rDNA transcription initiation while amino acids modulate growth factor-dependent rDNA transcription by primarily regulating S6K1-dependent rDNA transcription elongation and processing. Thus, we show for the first time amino acids regulate rRNA synthesis by a distinct, post-initiation mechanism, providing a novel model for integrated control of ribosome biogenesis that has implications for understanding how this process is dysregulated in cancer.
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Affiliation(s)
- Jian Kang
- Oncogenic Signaling and Growth Control Program, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne, Victoria, Australia
| | - Eric P Kusnadi
- Oncogenic Signaling and Growth Control Program, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne, Victoria, Australia
| | - Allison J Ogden
- Oncogenic Signaling and Growth Control Program, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne, Victoria, Australia
| | - Rodney J Hicks
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia.,Molecular Imaging and Targeted Therapeutics Laboratory, Cancer Therapeutics Program, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
| | - Lukas Bammert
- Institute of Biochemistry, Department of Biology, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
| | - Ulrike Kutay
- Institute of Biochemistry, Department of Biology, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
| | - Sandy Hung
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital & Department of Ophthalmology, University of Melbourne, East Melbourne, Victoria, Australia
| | - Elaine Sanij
- Oncogenic Signaling and Growth Control Program, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne, Victoria, Australia
| | - Ross D Hannan
- Oncogenic Signaling and Growth Control Program, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne, Victoria, Australia.,Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia.,Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.,School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia.,Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberaa, ACT, Australia
| | - Katherine M Hannan
- Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia.,Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, Canberaa, ACT, Australia
| | - Richard B Pearson
- Oncogenic Signaling and Growth Control Program, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne, Victoria, Australia.,Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia.,Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
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20
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Giguère V. Canonical signaling and nuclear activity of mTOR-a teamwork effort to regulate metabolism and cell growth. FEBS J 2018; 285:1572-1588. [PMID: 29337437 DOI: 10.1111/febs.14384] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 12/21/2017] [Accepted: 01/10/2018] [Indexed: 01/07/2023]
Abstract
Mechanistic (or mammalian) target of rapamycin (mTOR) is a kinase that regulates almost all functions related to cell growth and metabolism in response to extra- and intracellular stimuli, such as availability of nutrients, the presence of growth factors, or the energy status of the cell. As part of two distinct protein complexes, mTORC1 and mTORC2, the kinase has been shown to influence cell growth and proliferation by controlling ribosome biogenesis, mRNA translation, carbohydrate and lipid metabolism, protein degradation, autophagy as well as microtubule and actin dynamics. In addition to these well-characterized functions, mTOR can also influence gene transcription. While most studies focused on investigating how canonical mTOR signaling regulates the activity of transcription factors outside the nucleus, recent findings point to a more direct role for mTOR as a transcription factor operating on chromatin in the nucleus. In particular, recent genome-wide identification of mTOR targets on chromatin reveals that its activities in the nucleus and cytoplasm are functionally and biologically linked, thus uncovering a novel paradigm in mTOR function.
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Affiliation(s)
- Vincent Giguère
- Departments of Biochemistry, Medicine and Oncology, Faculty of Medicine, Goodman Cancer Research Centre, McGill University, Montréal, Canada
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21
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Abstract
The nucleolus is a distinct compartment of the nucleus responsible for ribosome biogenesis. Mis-regulation of nucleolar functions and of the cellular translation machinery has been associated with disease, in particular with many types of cancer. Indeed, many tumor suppressors (p53, Rb, PTEN, PICT1, BRCA1) and proto-oncogenes (MYC, NPM) play a direct role in the nucleolus, and interact with the RNA polymerase I transcription machinery and the nucleolar stress response. We have identified Dicer and the RNA interference pathway as having an essential role in the nucleolus of quiescent Schizosaccharomyces pombe cells, distinct from pericentromeric silencing, by controlling RNA polymerase I release. We propose that this novel function is evolutionarily conserved and may contribute to the tumorigenic pre-disposition of DICER1 mutations in mammals.
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Affiliation(s)
- Benjamin Roche
- a Martienssen Lab, Cold Spring Harbor Laboratory , Cold Spring Harbor , NY , USA
| | - Benoît Arcangioli
- b Genome Dynamics Unit, UMR 3525 CNRS, Institut Pasteur , Paris , France
| | - Rob Martienssen
- a Martienssen Lab, Cold Spring Harbor Laboratory , Cold Spring Harbor , NY , USA.,c Howard Hughes Medical Institute, Cold Spring Harbor Laboratory , Cold Spring Harbor , NY , USA
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22
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von Walden F, Liu C, Aurigemma N, Nader GA. mTOR signaling regulates myotube hypertrophy by modulating protein synthesis, rDNA transcription, and chromatin remodeling. Am J Physiol Cell Physiol 2016; 311:C663-C672. [DOI: 10.1152/ajpcell.00144.2016] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 08/30/2016] [Indexed: 01/15/2023]
Abstract
Ribosome production is an early event during skeletal muscle hypertrophy and precedes muscle protein accretion. Signaling via mTOR is crucial for ribosome production and hypertrophy; however, the mechanisms by which it regulates these processes remain to be identified. Herein, we investigated the activation of mTOR signaling in hypertrophying myotubes and determined that mTOR coordinates various aspects of gene expression important for ribosome production. First, inhibition of translation with cycloheximide had a more potent effect on protein synthesis than rapamycin indicating that mTOR function during hypertrophy is not on general, but rather on specific protein synthesis. Second, blocking Pol II transcription had a similar effect as Rapamycin and, unexpectedly, revealed the necessity of Pol II transcription for Pol I transcription, suggesting that mTOR may regulate ribosome production also by controlling Class II genes at the transcriptional level. Third, Pol I activity is essential for rDNA transcription and, surprisingly, for protein synthesis as selective Pol I inhibition blunted rDNA transcription, protein synthesis, and the hypertrophic response of myotubes. Finally, mTOR has nuclear localization in muscle, which is not sensitive to rapamycin. Inhibition of mTOR signaling by rapamycin disrupted mTOR-rDNA promoter interaction and resulted in altered histone marks indicative of repressed transcription and formation of higher-order chromatin structure. Thus mTOR signaling appears to regulate muscle hypertrophy by affecting protein synthesis, Class I and II gene expression, and chromatin remodeling.
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Affiliation(s)
- Ferdinand von Walden
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
| | - Chang Liu
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
| | - Nicole Aurigemma
- Noll Laboratory, Department of Kinesiology and Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania; and
| | - Gustavo A. Nader
- Noll Laboratory, Department of Kinesiology and Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania; and
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
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23
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Rajput P, Pandey V, Kumar V. Stimulation of ribosomal RNA gene promoter by transcription factor Sp1 involves active DNA demethylation by Gadd45-NER pathway. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1859:953-63. [PMID: 27156884 DOI: 10.1016/j.bbagrm.2016.05.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 04/23/2016] [Accepted: 05/04/2016] [Indexed: 01/29/2023]
Abstract
The well-studied Pol II transcription factor Sp1 has not been investigated for its regulatory role in rDNA transcription. Here, we show that Sp1 bound to specific sites on rDNA and localized into the nucleoli during the G1 phase of cell cycle to activate rDNA transcription. It facilitated the recruitment of Pol I pre-initiation complex and impeded the binding of nucleolar remodeling complex (NoRC) to rDNA resulting in the formation of euchromatin active state. More importantly, Sp1 also orchestrated the site-specific binding of Gadd45a-nucleotide excision repair (NER) complex resulting in active demethylation and transcriptional activation of rDNA. Interestingly, knockdown of Sp1 impaired rDNA transcription due to reduced engagement of the Gadd45a-NER complex and hypermethylation of rDNA. Thus, the present study unveils a novel role of Sp1 in rDNA transcription involving promoter demethylation.
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MESH Headings
- A549 Cells
- Cell Cycle Proteins/genetics
- Cell Cycle Proteins/metabolism
- Cell Nucleolus/metabolism
- DNA Methylation
- DNA Repair
- DNA, Ribosomal/genetics
- DNA, Ribosomal/metabolism
- Epigenesis, Genetic
- Euchromatin/chemistry
- Euchromatin/metabolism
- G1 Phase
- Genes, Reporter
- Green Fluorescent Proteins/genetics
- Green Fluorescent Proteins/metabolism
- HCT116 Cells
- HEK293 Cells
- Humans
- Nuclear Proteins/genetics
- Nuclear Proteins/metabolism
- Promoter Regions, Genetic
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- Signal Transduction
- Sp1 Transcription Factor/antagonists & inhibitors
- Sp1 Transcription Factor/genetics
- Sp1 Transcription Factor/metabolism
- Transcription, Genetic
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Affiliation(s)
- Pallavi Rajput
- Virology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Vijaya Pandey
- Virology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Vijay Kumar
- Virology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067, India.
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24
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Grassi ML, Palma CDS, Thomé CH, Lanfredi GP, Poersch A, Faça VM. Proteomic analysis of ovarian cancer cells during epithelial-mesenchymal transition (EMT) induced by epidermal growth factor (EGF) reveals mechanisms of cell cycle control. J Proteomics 2016; 151:2-11. [PMID: 27394697 DOI: 10.1016/j.jprot.2016.06.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 05/20/2016] [Accepted: 06/07/2016] [Indexed: 12/11/2022]
Abstract
Epithelial to mesenchymal transition (EMT) is a well-orchestrated process that culminates with loss of epithelial phenotype and gain of a mesenchymal and migratory phenotype. EMT enhances cancer cell invasiveness and drug resistance, favoring metastasis. Dysregulation of transcription factors, signaling pathways, miRNAs and growth factors including EGF, TGF-beta and HGF can trigger EMT. In ovarian cancer, overexpression of the EGFR family is associated with more aggressive clinical behavior. Here, the ovarian adenocarcinoma cell line Caov-3 was induced to EMT with EGF in order to identify specific mechanisms controlled by this process. Caov-3 cells induced to EMT were thoroughly validated and a combination of subcellular proteome enrichment, GEL-LC-MS/MS and SILAC strategy allowed consistent proteome identification and quantitation. Protein network analysis of differentially expressed proteins highlighted regulation of metabolism and cell cycle. Activation of relevant signaling pathways, such as PI3K/Akt/mTOR and Ras/Erk MAPK, in response to EGF-induced EMT was validated. Also, EMT did not affected the proliferation rate of Caov-3 cells, but led to cell cycle arrest in G1 phase regulated by increased levels of p21Waf1/Cip1, independently of p53. Furthermore, a decrease in G1 and G2 checkpoint proteins was observed, supporting the involvement of EGF-induced EMT in cell cycle control. BIOLOGICAL SIGNIFICANCE Cancer is a complex multistep process characterized by accumulation of several hallmarks including epithelial to mesenchymal transition (EMT), which promotes cellular and microenvironmental changes resulting in invasion and migration to distant sites, favoring metastasis. EMT can be triggered by different extracellular stimuli, including growth factors such as EGF. In ovarian cancer, the most lethal gynecological cancer, overexpression of the EGFR family is associated with more aggressive clinical behavior, increasing mortality rate caused by metastasis. Our proteomic data, together with specific validation of specific cellular mechanisms demonstrated that EGF-induced EMT in Caov-3 cells leads to important alterations in metabolic process (protein synthesis) and cell cycle control, supporting the implication of EGF/EMT in cancer metastasis, cancer stem cell generation and, therefore, poor prognosis for the disease.
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Affiliation(s)
- Mariana Lopes Grassi
- Dept. Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil; Cell-Based Therapy Center, Ribeirão Preto Blood Center, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Camila de Souza Palma
- Dept. Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil; Cell-Based Therapy Center, Ribeirão Preto Blood Center, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Carolina Hassibe Thomé
- Dept. Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil; Cell-Based Therapy Center, Ribeirão Preto Blood Center, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Guilherme Pauperio Lanfredi
- Dept. Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil; Cell-Based Therapy Center, Ribeirão Preto Blood Center, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Aline Poersch
- Dept. Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Vitor Marcel Faça
- Dept. Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil; Cell-Based Therapy Center, Ribeirão Preto Blood Center, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
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25
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Gizak A, Grenda M, Mamczur P, Wisniewski J, Sucharski F, Silberring J, McCubrey JA, Wisniewski JR, Rakus D. Insulin/IGF1-PI3K-dependent nucleolar localization of a glycolytic enzyme--phosphoglycerate mutase 2, is necessary for proper structure of nucleolus and RNA synthesis. Oncotarget 2016; 6:17237-50. [PMID: 26033454 PMCID: PMC4627304 DOI: 10.18632/oncotarget.4044] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 04/30/2015] [Indexed: 12/31/2022] Open
Abstract
Phosphoglycerate mutase (PGAM), a conserved, glycolytic enzyme has been found in nucleoli of cancer cells. Here, we present evidence that accumulation of PGAM in the nucleolus is a universal phenomenon concerning not only neoplastically transformed but also non-malignant cells. Nucleolar localization of the enzyme is dependent on the presence of the PGAM2 (muscle) subunit and is regulated by insulin/IGF-1–PI3K signaling pathway as well as drugs influencing ribosomal biogenesis. We document that PGAM interacts with several 40S and 60S ribosomal proteins and that silencing of PGAM2 expression results in disturbance of nucleolar structure, inhibition of RNA synthesis and decrease of the mitotic index of squamous cell carcinoma cells. We conclude that presence of PGAM in the nucleolus is a prerequisite for synthesis and initial assembly of new pre-ribosome subunits.
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Affiliation(s)
- Agnieszka Gizak
- Department of Animal Molecular Physiology, Wroclaw University, Cybulskiego, Wroclaw, Poland
| | - Marcin Grenda
- Department of Animal Molecular Physiology, Wroclaw University, Cybulskiego, Wroclaw, Poland
| | - Piotr Mamczur
- Department of Animal Molecular Physiology, Wroclaw University, Cybulskiego, Wroclaw, Poland
| | - Janusz Wisniewski
- Department of Animal Molecular Physiology, Wroclaw University, Cybulskiego, Wroclaw, Poland
| | - Filip Sucharski
- Department of Biochemistry and Neurobiology, Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Kraków, Poland
| | - Jerzy Silberring
- Department of Biochemistry and Neurobiology, Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Kraków, Poland
| | - James A McCubrey
- Department of Microbiology and Immunology, Brody School of Medicine at East Carolina University, Greenville, NC, USA
| | - Jacek R Wisniewski
- Biochemical Proteomics Group, Department of Proteomics and Signal Transduction, Max-Planck-Institute of Biochemistry, Martinsried, Germany
| | - Dariusz Rakus
- Department of Animal Molecular Physiology, Wroclaw University, Cybulskiego, Wroclaw, Poland
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26
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Salifou K, Ray S, Verrier L, Aguirrebengoa M, Trouche D, Panov KI, Vandromme M. The histone demethylase JMJD2A/KDM4A links ribosomal RNA transcription to nutrients and growth factors availability. Nat Commun 2016; 7:10174. [PMID: 26729372 PMCID: PMC5157185 DOI: 10.1038/ncomms10174] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 11/11/2015] [Indexed: 12/15/2022] Open
Abstract
The interplay between methylation and demethylation of histone lysine residues is an essential component of gene expression regulation and there is considerable interest in elucidating the roles of proteins involved. Here we report that histone demethylase KDM4A/JMJD2A, which is involved in the regulation of cell proliferation and is overexpressed in some cancers, interacts with RNA Polymerase I, associates with active ribosomal RNA genes and is required for serum-induced activation of rDNA transcription. We propose that KDM4A controls the initial stages of transition from 'poised', non-transcribed rDNA chromatin into its active form. We show that PI3K, a major signalling transducer central for cell proliferation and survival, controls cellular localization of KDM4A and consequently its association with ribosomal DNA through the SGK1 downstream kinase. We propose that the interplay between PI3K/SGK1 signalling cascade and KDM4A constitutes a mechanism by which cells adapt ribosome biogenesis level to the availability of growth factors and nutrients.
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Affiliation(s)
- Kader Salifou
- Centre for Integrative Biology, Université de Toulouse, UT3 Toulouse, France
- Centre for Integrative Biology, CNRS, UT3 Toulouse, France
| | - Swagat Ray
- School of Biological Sciences, Queen's University Belfast, Belfast BT9 7BL, UK
| | - Laure Verrier
- Centre for Integrative Biology, Université de Toulouse, UT3 Toulouse, France
- Centre for Integrative Biology, CNRS, UT3 Toulouse, France
| | - Marion Aguirrebengoa
- Centre for Integrative Biology, Université de Toulouse, UT3 Toulouse, France
- Centre for Integrative Biology, CNRS, UT3 Toulouse, France
| | - Didier Trouche
- Centre for Integrative Biology, Université de Toulouse, UT3 Toulouse, France
- Centre for Integrative Biology, CNRS, UT3 Toulouse, France
| | - Konstantin I. Panov
- School of Biological Sciences, Queen's University Belfast, Belfast BT9 7BL, UK
- Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast BT9 7AE, UK
| | - Marie Vandromme
- Centre for Integrative Biology, Université de Toulouse, UT3 Toulouse, France
- Centre for Integrative Biology, CNRS, UT3 Toulouse, France
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mTORC1 directly phosphorylates and activates ERα upon estrogen stimulation. Oncogene 2015; 35:3535-43. [PMID: 26522726 PMCID: PMC4853282 DOI: 10.1038/onc.2015.414] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 09/09/2015] [Accepted: 09/28/2015] [Indexed: 01/08/2023]
Abstract
Breast cancer is the leading cause of cancer-related deaths among women. Approximately 75% of breast cancers are estrogen receptor α (ERα) positive, underscoring the dependence of cancer cells on estrogen for growth and survival. Patients treated with endocrine therapy often develop resistance, either de novo or acquired, which in some cases is caused by aberrations within the growth factor signaling pathways. The mechanistic target of rapamycin complex 1 (mTORC1) has emerged as a critical node in estrogenic signaling. We have previously shown that mTORC1 can phosphorylate and activate ERα on S167 via its effector the 40S ribosomal S6 kinase 1 (S6K1). Presently, we have uncovered a direct link between mTORC1 and ERα. We found that ERα binds to regulatory-associated protein of mTOR (Raptor) and causes it to translocate to the nucleus upon estrogen stimulation. Additionally, we identified mTOR as the kinase that phosphorylates ERα on S104/106 and activates transcription of ER target genes. Our findings show a direct link between mTORC1 and ERα, which further implicates mTORC1 signaling in the pathogenesis of ER-positive breast cancer and provides rationale for FDA-approved use of mTORC1 inhibitors in combination with endocrine agents for treatment of this disease.
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28
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de Las Heras-Rubio A, Perucho L, Paciucci R, Vilardell J, LLeonart ME. Ribosomal proteins as novel players in tumorigenesis. Cancer Metastasis Rev 2015; 33:115-41. [PMID: 24375388 DOI: 10.1007/s10555-013-9460-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Ribosome biogenesis is the most demanding energetic and metabolic expenditure of the cell. The nucleolus, a nuclear compartment, coordinates rRNA transcription, maturation, and assembly into ribosome subunits. The transcription process is highly coordinated with ribosome biogenesis. In this context, ribosomal proteins (RPs) play a crucial role. In the last decade, an increasing number of studies have associated RPs with extraribosomal functions related to proliferation. Importantly, the expression of RPs appears to be deregulated in several human disorders due, at least in part, to genetic mutations. Although the deregulation of RPs in human malignancies is commonly observed, a more complex mechanism is believed to be involved, favoring the tumorigenic process, its progression and metastasis. This review explores the roles of the most frequently mutated oncogenes and tumor suppressor genes in human cancer that modulate ribosome biogenesis, including their interaction with RPs. In this regard, we propose a new focus for novel therapies.
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Affiliation(s)
- A de Las Heras-Rubio
- Oncology and Pathology Group, Institut de Recerca Hospital Vall d'Hebron, Passeig Vall d'Hebron 119-129, 08035, Barcelona, Spain
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29
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Davis WJ, Lehmann PZ, Li W. Nuclear PI3K signaling in cell growth and tumorigenesis. Front Cell Dev Biol 2015; 3:24. [PMID: 25918701 PMCID: PMC4394695 DOI: 10.3389/fcell.2015.00024] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 03/27/2015] [Indexed: 12/12/2022] Open
Abstract
The PI3K/Akt signaling pathway is a major driving force in a variety of cellular functions. Dysregulation of this pathway has been implicated in many human diseases including cancer. While the activity of the cytoplasmic PI3K/Akt pathway has been extensively studied, the functions of these molecules and their effector proteins within the nucleus are poorly understood. Harboring key cellular processes such as DNA replication and repair as well as nascent messenger RNA transcription, the nucleus provides a unique compartmental environment for protein–protein and protein–DNA/RNA interactions required for cell survival, growth, and proliferation. Here we summarize recent advances made toward elucidating the nuclear PI3K/Akt signaling cascade and its key components within the nucleus as they pertain to cell growth and tumorigenesis. This review covers the spatial and temporal localization of the major nuclear kinases having PI3K activities and the counteracting phosphatases as well as the role of nuclear PI3K/Akt signaling in mRNA processing and exportation, DNA replication and repair, ribosome biogenesis, cell survival, and tumorigenesis.
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Affiliation(s)
- William J Davis
- College of Medical Sciences, Washington State University Spokane, WA, USA
| | - Peter Z Lehmann
- College of Medical Sciences, Washington State University Spokane, WA, USA
| | - Weimin Li
- College of Medical Sciences, Washington State University Spokane, WA, USA
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30
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Nguyen LXT, Raval A, Garcia JS, Mitchell BS. Regulation of Ribosomal Gene Expression in Cancer. J Cell Physiol 2015; 230:1181-8. [DOI: 10.1002/jcp.24854] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 10/16/2014] [Indexed: 12/20/2022]
Affiliation(s)
- Le Xuan Truong Nguyen
- Departments of Medicine and Chemical and Systems Biology; Stanford Cancer Institute; Stanford University School of Medicine; Stanford California
| | - Aparna Raval
- Departments of Medicine and Chemical and Systems Biology; Stanford Cancer Institute; Stanford University School of Medicine; Stanford California
| | - Jacqueline S. Garcia
- Departments of Medicine and Chemical and Systems Biology; Stanford Cancer Institute; Stanford University School of Medicine; Stanford California
| | - Beverly S. Mitchell
- Departments of Medicine and Chemical and Systems Biology; Stanford Cancer Institute; Stanford University School of Medicine; Stanford California
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31
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p53- and ERK7-dependent ribosome surveillance response regulates Drosophila insulin-like peptide secretion. PLoS Genet 2014; 10:e1004764. [PMID: 25393288 PMCID: PMC4230838 DOI: 10.1371/journal.pgen.1004764] [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: 01/28/2014] [Accepted: 09/19/2014] [Indexed: 01/05/2023] Open
Abstract
Insulin-like signalling is a conserved mechanism that coordinates animal growth and metabolism with nutrient status. In Drosophila, insulin-producing median neurosecretory cells (IPCs) regulate larval growth by secreting insulin-like peptides (dILPs) in a diet-dependent manner. Previous studies have shown that nutrition affects dILP secretion through humoral signals derived from the fat body. Here we uncover a novel mechanism that operates cell autonomously in the IPCs to regulate dILP secretion. We observed that impairment of ribosome biogenesis specifically in the IPCs strongly inhibits dILP secretion, which consequently leads to reduced body size and a delay in larval development. This response is dependent on p53, a known surveillance factor for ribosome biogenesis. A downstream effector of this growth inhibitory response is an atypical MAP kinase ERK7 (ERK8/MAPK15), which is upregulated in the IPCs following impaired ribosome biogenesis as well as starvation. We show that ERK7 is sufficient and essential to inhibit dILP secretion upon impaired ribosome biogenesis, and it acts epistatically to p53. Moreover, we provide evidence that p53 and ERK7 contribute to the inhibition of dILP secretion upon starvation. Thus, we conclude that a cell autonomous ribosome surveillance response, which leads to upregulation of ERK7, inhibits dILP secretion to impede tissue growth under limiting dietary conditions. Ribosome biogenesis is a major consumer of cellular energy and a rate-limiting process during cell growth. The ribosome biogenesis pathway is tightly connected with signaling pathways that regulate tissue growth. For example, nutrient-regulated signaling cues adjust the rate of ribosome biogenesis. On the other hand, the process of ribosome biogenesis is closely monitored by so-called surveillance mechanisms. The best-known ribosome surveillance factor is the transcription factor and tumor suppressor p53. In proliferating cells, activation of p53 upon disturbed ribosome biogenesis leads to cell cycle arrest and inhibition of proliferation. Here we show that ribosome surveillance not only regulates growth locally in proliferating cells, but is also coupled to hormonal growth control through regulation of insulin like peptide (dILPs) secretion. We observed that inhibition of ribosome biogenesis in the Drosophila insulin-producing cells generates a strong cell autonomous signal to inhibit dILP secretion. We identify two downstream effectors of this ribosome surveillance response by showing that p53 as well as an atypical MAP kinase ERK7 are mediators of the inhibition of dILP secretion. We also provide evidence that this ribosome surveillance mechanism contributes to nutrient-dependent regulation of dILP secretion.
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32
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Regulation of rDNA transcription in response to growth factors, nutrients and energy. Gene 2014; 556:27-34. [PMID: 25447905 DOI: 10.1016/j.gene.2014.11.010] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 11/04/2014] [Accepted: 11/06/2014] [Indexed: 11/21/2022]
Abstract
Exquisite control of ribosome biogenesis is fundamental for the maintenance of cellular growth and proliferation. Importantly, synthesis of ribosomal RNA by RNA polymerase I is a key regulatory step in ribosome biogenesis and a major biosynthetic and energy consuming process. Consequently, ribosomal RNA gene transcription is tightly coupled to the availability of growth factors, nutrients and energy. Thus cells have developed an intricate sensing network to monitor the cellular environment and modulate ribosomal DNA transcription accordingly. Critical controllers in these sensing networks, which mediate growth factor activation of ribosomal DNA transcription, include the PI3K/AKT/mTORC1, RAS/RAF/ERK pathways and MYC transcription factor. mTORC1 also responds to amino acids and energy status, making it a key hub linking all three stimuli to the regulation of ribosomal DNA transcription, although this is achieved via overlapping and distinct mechanisms. This review outlines the current knowledge of how cells respond to environmental cues to control ribosomal RNA synthesis. We also highlight the critical points within this network that are providing new therapeutic opportunities for treating cancers through modulation of RNA polymerase I activity and potential novel imaging strategies.
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33
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Ghosh A, Rideout EJ, Grewal SS. TIF-IA-dependent regulation of ribosome synthesis in drosophila muscle is required to maintain systemic insulin signaling and larval growth. PLoS Genet 2014; 10:e1004750. [PMID: 25356674 PMCID: PMC4214618 DOI: 10.1371/journal.pgen.1004750] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 09/15/2014] [Indexed: 02/06/2023] Open
Abstract
The conserved TOR kinase signaling network links nutrient availability to cell, tissue and body growth in animals. One important growth-regulatory target of TOR signaling is ribosome biogenesis. Studies in yeast and mammalian cell culture have described how TOR controls rRNA synthesis—a limiting step in ribosome biogenesis—via the RNA Polymerase I transcription factor TIF-IA. However, the contribution of TOR-dependent ribosome synthesis to tissue and body growth in animals is less clear. Here we show in Drosophila larvae that ribosome synthesis in muscle is required non-autonomously to maintain normal body growth and development. We find that amino acid starvation and TOR inhibition lead to reduced levels of TIF-IA, and decreased rRNA synthesis in larval muscle. When we mimic this decrease in muscle ribosome synthesis using RNAi-mediated knockdown of TIF-IA, we observe delayed larval development and reduced body growth. This reduction in growth is caused by lowered systemic insulin signaling via two endocrine responses: reduced expression of Drosophila insulin-like peptides (dILPs) from the brain and increased expression of Imp-L2—a secreted factor that binds and inhibits dILP activity—from muscle. We also observed that maintaining TIF-IA levels in muscle could partially reverse the starvation-mediated suppression of systemic insulin signaling. Finally, we show that activation of TOR specifically in muscle can increase overall body size and this effect requires TIF-IA function. These data suggest that muscle ribosome synthesis functions as a nutrient-dependent checkpoint for overall body growth: in nutrient rich conditions, TOR is required to maintain levels of TIF-IA and ribosome synthesis to promote high levels of systemic insulin, but under conditions of starvation stress, reduced muscle ribosome synthesis triggers an endocrine response that limits systemic insulin signaling to restrict growth and maintain homeostasis. All animals need adequate nutrition to grow and develop. Studies in tissue culture and model organisms have identified the TOR kinase signaling pathway as a key nutrient-dependent regulator of growth. Under nutrient rich conditions, TOR kinase is active and stimulates metabolic processes that drive growth. Under nutrient poor conditions, TOR is inhibited and animals alter their metabolism to maintain homeostasis and survival. Here we use Drosophila larvae to identify a role for ribosome synthesis—a key metabolic process—in mediating nutrient and TOR effects on body growth. In particular, we show that ribosome synthesis specifically in larval muscle is necessary to maintain organismal growth. We find that inhibition of muscle ribosome synthesis leads to reduced systemic insulin-like growth factor signaling via two endocrine responses—decreased expression of brain derived Drosophila insulin-like peptides (dILPs) and increased expression of Imp-L2, an inhibitor of insulin signaling. As a result of these effects, body growth is reduced and larval development is delayed. These findings suggest that control of ribosome synthesis, and hence protein synthesis, in specific tissues can exert control on overall body growth.
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Affiliation(s)
- Abhishek Ghosh
- Department of Biochemistry and Molecular Biology, and Clark H. Smith Brain Tumour Centre, Southern Alberta Cancer Research Institute, University of Calgary, Health Research Innovation Center, Calgary, Alberta, Canada
| | - Elizabeth J. Rideout
- Department of Biochemistry and Molecular Biology, and Clark H. Smith Brain Tumour Centre, Southern Alberta Cancer Research Institute, University of Calgary, Health Research Innovation Center, Calgary, Alberta, Canada
| | - Savraj S. Grewal
- Department of Biochemistry and Molecular Biology, and Clark H. Smith Brain Tumour Centre, Southern Alberta Cancer Research Institute, University of Calgary, Health Research Innovation Center, Calgary, Alberta, Canada
- * E-mail:
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34
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mTORC1 signaling controls multiple steps in ribosome biogenesis. Semin Cell Dev Biol 2014; 36:113-20. [PMID: 25148809 DOI: 10.1016/j.semcdb.2014.08.004] [Citation(s) in RCA: 180] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 08/07/2014] [Accepted: 08/11/2014] [Indexed: 02/06/2023]
Abstract
Ribosome biogenesis is critical for cells to generate the ribosomes they need for protein synthesis in order to survive, grow and proliferate. It is a complex process, involving the coordinated production of four different RNA species and about 80 proteins, as well as their assembly into functional ribosomal subunits. Given its high demand for amino acids and nucleotides, it is also a metabolically expensive process for the cell. The mammalian target of rapamycin complex 1 (mTORC1) is a protein kinases which is activated by nutrients, anabolic hormones and oncogenic signaling pathways. mTORC1 positively regulates several steps in ribosome biogenesis, including ribosomal RNA transcription, the synthesis of ribosomal proteins and other components required for ribosome assembly. mTORC1 can thus coordinate stimuli which promote ribosome production with the various steps involved in this process. Although important advances have been made in our understanding of mTORC1 signaling, major questions remain about the molecular mechanisms by which it regulates ribosome biogenesis.
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35
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Fuentes EN, Zuloaga R, Valdes JA, Molina A, Alvarez M. Skeletal muscle plasticity induced by seasonal acclimatization involves IGF1 signaling: implications in ribosomal biogenesis and protein synthesis. Comp Biochem Physiol B Biochem Mol Biol 2014; 176:48-57. [PMID: 25088252 DOI: 10.1016/j.cbpb.2014.07.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 07/11/2014] [Accepted: 07/22/2014] [Indexed: 12/15/2022]
Abstract
One of the most fundamental biological processes in living organisms that are affected by environmental fluctuations is growth. In fish, skeletal muscle accounts for the largest proportion of body mass, and the growth of this tissue is mainly controlled by the insulin-like growth factor (IGF) system. By using the carp (Cyprinus carpio), a fish that inhabits extreme conditions during winter and summer, we assessed the skeletal muscle plasticity induced by seasonal acclimatization and the relation of IGF signaling with protein synthesis and ribosomal biogenesis. The expression of igf1 in muscle decreased during winter in comparison with summer, whereas the expression for both paralogues of igf2 did not change significantly between seasons. The expression of igf1 receptor a (igf1ra), but not of igf1rb, was down-regulated in muscle during the winter as compared to the summer. A decrease in protein contents and protein phosphorylation for IGF signaling molecules in muscle was observed in winter-acclimatized carp. This was related with a decreased expression in muscle for markers of myogenesis (myoblast determination factor (myod), myogenic factor 5 (myf5), and myogenin (myog)); protein synthesis (myosin heavy chain (mhc) and myosin light chain (mlc3 and mlc1b)); and ribosomal biogenesis (pre-rRNA and ribosomal proteins). IGF signaling, and key markers of ribosomal biogenesis, protein synthesis, and myogenesis were affected by seasonal acclimatization, with differential regulation in gene expression and signaling pathway activation observed in muscle between both seasons. This suggests that these molecules are responsible for the muscle plasticity induced by seasonal acclimatization in carp.
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Affiliation(s)
- Eduardo N Fuentes
- Laboratorio de Biotecnología Molecular, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Av. Republica 217, Santiago, Chile; Interdisciplinary Center for Aquaculture Research (INCAR), Víctor Lamas 1290, PO Box 160-C, Concepción, Chile.
| | - Rodrigo Zuloaga
- Laboratorio de Biotecnología Molecular, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Av. Republica 217, Santiago, Chile
| | - Juan Antonio Valdes
- Laboratorio de Biotecnología Molecular, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Av. Republica 217, Santiago, Chile; Interdisciplinary Center for Aquaculture Research (INCAR), Víctor Lamas 1290, PO Box 160-C, Concepción, Chile
| | - Alfredo Molina
- Laboratorio de Biotecnología Molecular, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Av. Republica 217, Santiago, Chile; Interdisciplinary Center for Aquaculture Research (INCAR), Víctor Lamas 1290, PO Box 160-C, Concepción, Chile
| | - Marco Alvarez
- Interdisciplinary Center for Aquaculture Research (INCAR), Víctor Lamas 1290, PO Box 160-C, Concepción, Chile; Laboratorio de Biología Celular y Molecular, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Quillota 980, Viña del Mar, Chile.
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36
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Abstract
Key Points
Akt/FLNA/TIF-90 signaling regulates rRNA synthesis in acute myelogenous leukemia cells. Direct targeting of Akt has potential therapeutic applications in acute myelogenous leukemia treatment.
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37
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Nguyen LXT, Sesay A, Mitchell BS. Effect of CAL-101, a PI3Kδ inhibitor, on ribosomal rna synthesis and cell proliferation in acute myeloid leukemia cells. Blood Cancer J 2014; 4:e228. [PMID: 25014775 PMCID: PMC4219447 DOI: 10.1038/bcj.2014.49] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- L X T Nguyen
- Departments of Medicine and Chemical and Systems Biology, Stanford Cancer Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - A Sesay
- Departments of Medicine and Chemical and Systems Biology, Stanford Cancer Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - B S Mitchell
- Departments of Medicine and Chemical and Systems Biology, Stanford Cancer Institute, Stanford University School of Medicine, Stanford, CA, USA
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Aramburu J, Ortells MC, Tejedor S, Buxadé M, López-Rodríguez C. Transcriptional regulation of the stress response by mTOR. Sci Signal 2014; 7:re2. [PMID: 24985347 DOI: 10.1126/scisignal.2005326] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The kinase mammalian target of rapamycin (mTOR) is a central regulator of cell growth and proliferation that integrates inputs from growth factor receptors, nutrient availability, intracellular ATP (adenosine 5'-triphosphate), and a variety of stressors. Since early works in the mid-1990s uncovered the role of mTOR in stimulating protein translation, this kinase has emerged as a rather multifaceted regulator of numerous processes. Whereas mTOR is generally activated by growth- and proliferation-stimulating signals, its activity can be reduced and even suppressed when cells are exposed to a variety of stress conditions. However, cells can also adapt to stress while maintaining their growth capacity and mTOR function. Despite knowledge accumulated on how stress represses mTOR, less is known about mTOR influencing stress responses. In this review, we discuss the capability of mTOR, in particular mTOR complex 1 (mTORC1), to activate stress-responsive transcription factors, and we outline open questions for future investigation.
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Affiliation(s)
- Jose Aramburu
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain.
| | - M Carmen Ortells
- Centre for Genomic Regulation and Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Sonia Tejedor
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Maria Buxadé
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Cristina López-Rodríguez
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain.
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Akt activation enhances ribosomal RNA synthesis through casein kinase II and TIF-IA. Proc Natl Acad Sci U S A 2013; 110:20681-6. [PMID: 24297901 DOI: 10.1073/pnas.1313097110] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Transcription initiation factor I (TIF-IA) plays an essential role in regulating ribosomal RNA (rRNA) synthesis by tethering RNA polymerase I (Pol I) to the rDNA promoter. We have found that activated Akt enhances rRNA synthesis through the phosphorylation of casein kinase IIα (CK2α) on a threonine residue near its N terminus. CK2 in turn phosphorylates TIF-IA, thereby increasing rDNA transcription. Activated Akt also stabilizes TIF-IA, induces its translocation to the nucleolus, and enhances its interaction with Pol I. Treatment with AZD8055, an inhibitor of both Akt and mammalian target of rapamycin phosphorylation, but not with rapamycin, disrupts Akt-mediated TIF-IA stability, translocation, and activity. These data support a model in which activated Akt enhances rRNA synthesis both by preventing TIF-IA degradation and phosphorylating CK2α, which in turn phosphorylates TIF-IA. This model provides an explanation for the ability of activated Akt to promote cell proliferation and, potentially, transformation.
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Bruhn MA, Pearson RB, Hannan RD, Sheppard KE. AKT-independent PI3-K signaling in cancer - emerging role for SGK3. Cancer Manag Res 2013; 5:281-92. [PMID: 24009430 PMCID: PMC3762672 DOI: 10.2147/cmar.s35178] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The phosphoinositide 3-kinase (PI3-K) signaling pathway plays an important role in a wide variety of fundamental cellular processes, largely mediated via protein kinase B/v-akt murine thymoma viral oncogene homolog (PKB/AKT) signaling. Given the crucial role of PI3-K/AKT signaling in regulating processes such as cell growth, proliferation, and survival, it is not surprising that components of this pathway are frequently dysregulated in cancer, making the AKT kinase family members important therapeutic targets. The large number of clinical trials currently evaluating PI3-K pathway inhibitors as a therapeutic strategy further emphasizes this. The serum- and glucocorticoid-inducible protein kinase (SGK) family is made up of three isoforms, SGK1, 2, and 3, that are PI3-K-dependent, serine/threonine kinases, with similar substrate specificity to AKT. Consequently, the SGK family also regulates similar cell processes to the AKT kinases, including cell proliferation and survival. Importantly, there is emerging evidence demonstrating that SGK3 plays a critical role in AKT-independent oncogenic signaling. This review will focus on the role of SGK3 as a key effector of AKT-independent PI3-K oncogenic signaling.
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Affiliation(s)
- Maressa A Bruhn
- Division of Cancer Research, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia ; School of Biological Sciences, Flinders University, Bedford Park, South Australia, Australia
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41
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Kellenberger AJ, Tauchi M. Mammalian target of rapamycin complex 1 (mTORC1) may modulate the timing of anagen entry in mouse hair follicles. Exp Dermatol 2013; 22:77-80. [PMID: 23278901 DOI: 10.1111/exd.12062] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/29/2012] [Indexed: 12/31/2022]
Abstract
Mammalian target of rapamycin (mTOR) is a central regulator of cell proliferation and survival. There is limited evidence that mTOR influences hair follicles (HFs), which undergo cycles of quiescence (telogen), growth (anagen) and regression (catagen). We sought to investigate whether mTOR, in particular mTOR complex 1 (mTORC1), regulates the hair growth cycle by employing biochemical, immunohistochemical and functional approaches in vivo. Here, we demonstrate that quantitative analysis of mTORC1 kinase activity shows phase-dependent changes, and phosphorylated mTOR at S2448 (p-mTOR) was localized in certain sites of HFs in a phase-dependent manner. These results were indicative of mTOR's role in hair growth initiation. Finally, in a pharmacological challenge in vivo using the specific mTORC1 inhibitor, rapamycin, hair cycle initiation was delayed, suggesting a functional relevance of mTORC1 in anagen entry. Based on our findings, we propose that mTORC1 may participate in hair cycle regulation, namely the timing of anagen initiation.
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Ray S, Panova T, Miller G, Volkov A, Porter ACG, Russell J, Panov KI, Zomerdijk JCBM. Topoisomerase IIα promotes activation of RNA polymerase I transcription by facilitating pre-initiation complex formation. Nat Commun 2013; 4:1598. [PMID: 23511463 PMCID: PMC3615473 DOI: 10.1038/ncomms2599] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Accepted: 02/09/2013] [Indexed: 11/15/2022] Open
Abstract
Type II DNA topoisomerases catalyse DNA double-strand cleavage, passage and re-ligation to effect topological changes. There is considerable interest in elucidating topoisomerase II roles, particularly as these proteins are targets for anti-cancer drugs. Here we uncover a role for topoisomerase IIα in RNA polymerase I-directed ribosomal RNA gene transcription, which drives cell growth and proliferation and is upregulated in cancer cells. Our data suggest that topoisomerase IIα is a component of the initiation-competent RNA polymerase Iβ complex and interacts directly with RNA polymerase I-associated transcription factor RRN3, which targets the polymerase to promoter-bound SL1 in pre-initiation complex formation. In cells, activation of rDNA transcription is reduced by inhibition or depletion of topoisomerase II, and this is accompanied by reduced transient double-strand DNA cleavage in the rDNA-promoter region and reduced pre-initiation complex formation. We propose that topoisomerase IIα functions in RNA polymerase I transcription to produce topological changes at the rDNA promoter that facilitate efficient de novo pre-initiation complex formation.
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Affiliation(s)
- Swagat Ray
- School of Biological Sciences and the Centre for Cancer Research and Cell Biology, Queen’s University Belfast, Belfast BT9 7BL, UK
| | - Tatiana Panova
- School of Biological Sciences and the Centre for Cancer Research and Cell Biology, Queen’s University Belfast, Belfast BT9 7BL, UK
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Gail Miller
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Arsen Volkov
- Gene Targeting Group, Centre for Haematology, Imperial College Faculty of Medicine, Du Cane Road, London W12 0NN, UK
| | - Andrew C. G. Porter
- Gene Targeting Group, Centre for Haematology, Imperial College Faculty of Medicine, Du Cane Road, London W12 0NN, UK
| | - Jackie Russell
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Konstantin I. Panov
- School of Biological Sciences and the Centre for Cancer Research and Cell Biology, Queen’s University Belfast, Belfast BT9 7BL, UK
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
- These authors contributed equally to this work
| | - Joost C. B. M. Zomerdijk
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
- These authors contributed equally to this work
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Bailey CE, Hammers DW, Deford JH, Dimayuga VL, Amaning JK, Farrar R, Papaconstantinou J. Ishemia-reperfusion enhances GAPDH nitration in aging skeletal muscle. Aging (Albany NY) 2012; 3:1003-17. [PMID: 22027257 PMCID: PMC3229964 DOI: 10.18632/aging.100394] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Aging and skeletal muscle ischemia/reperfusion (I/R) injury leads to decreased contractile force generation that increases severely with age. Our studies show that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) protein expression is significantly decreased at 3 and 5 days reperfusion in the young mouse muscle and at 1, 3, 5, and 7 days in the aged muscle. Using PCR, we have shown that GAPDH mRNA levels in young and old muscle increase at 5 days reperfusion compared to control, suggesting that the protein deficit is not transcriptional. Furthermore, while total tyrosine nitration did not increase in the young muscle, GAPDH nitration increased significantly at 1 and 3 days reperfusion. In contrast, total tyrosine nitration in aged muscle increased significantly at 1, 3, and 5 days of reperfusion, with increases in GAPDH nitration at the same time points. We conclude that GAPDH protein levels decrease following I/R, that this is not transcriptionally mediated, that the aged muscle experiences greater oxidative stress, protein modification and GAPDH degradation, possibly contributing to decreased muscle function. We propose that tyrosine nitration enhances GAPDH degradation following I/R and that the persistent decrease of GAPDH in aged muscle is due to the prolonged increase in oxidative modification in this age group.
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Affiliation(s)
- C Eric Bailey
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, USA
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Hetman M, Pietrzak M. Emerging roles of the neuronal nucleolus. Trends Neurosci 2012; 35:305-14. [PMID: 22305768 DOI: 10.1016/j.tins.2012.01.002] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2011] [Revised: 12/15/2011] [Accepted: 01/03/2012] [Indexed: 12/22/2022]
Abstract
Although, the nucleolus has been observed for almost 200 years in neurons, studies that directly address the neuronal roles of this subnuclear structure have appeared only recently. The aim of this review is to discuss recent progress and identify some critical questions that remain to be answered. As expected for the cellular center of ribosome biogenesis, the nucleolus is essential for the growth of developing neurons, including neurite morphogenesis and long-term maintenance of mature neurons. In addition, the nucleolus contributes to neuronal stress responses, including the regulation of apoptosis. Hence, disrupted neurodevelopment or neurodegeneration are among the likely consequences of nucleolar dysfunction. Conversely, the presence of active nucleoli may determine the potential for neurorepair.
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Affiliation(s)
- Michal Hetman
- Kentucky Spinal Cord Injury Research Center and Department of Neurological Surgery, University of Louisville, Louisville, Kentucky 40292, USA.
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Ortells MC, Morancho B, Drews-Elger K, Viollet B, Laderoute KR, López-Rodríguez C, Aramburu J. Transcriptional regulation of gene expression during osmotic stress responses by the mammalian target of rapamycin. Nucleic Acids Res 2012; 40:4368-84. [PMID: 22287635 PMCID: PMC3378878 DOI: 10.1093/nar/gks038] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Although stress can suppress growth and proliferation, cells can induce adaptive responses that allow them to maintain these functions under stress. While numerous studies have focused on the inhibitory effects of stress on cell growth, less is known on how growth-promoting pathways influence stress responses. We have approached this question by analyzing the effect of mammalian target of rapamycin (mTOR), a central growth controller, on the osmotic stress response. Our results showed that mammalian cells exposed to moderate hypertonicity maintained active mTOR, which was required to sustain their cell size and proliferative capacity. Moreover, mTOR regulated the induction of diverse osmostress response genes, including targets of the tonicity-responsive transcription factor NFAT5 as well as NFAT5-independent genes. Genes sensitive to mTOR-included regulators of stress responses, growth and proliferation. Among them, we identified REDD1 and REDD2, which had been previously characterized as mTOR inhibitors in other stress contexts. We observed that mTOR facilitated transcription-permissive conditions for several osmoresponsive genes by enhancing histone H4 acetylation and the recruitment of RNA polymerase II. Altogether, these results reveal a previously unappreciated role of mTOR in regulating transcriptional mechanisms that control gene expression during cellular stress responses.
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Affiliation(s)
- M Carmen Ortells
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain
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Abstract
Studies of epilepsy have mainly focused on the membrane proteins that control neuronal excitability. Recently, attention has been shifting to intracellular proteins and their interactions, signaling cascades and feedback regulation as they relate to epilepsy. The mTOR (mammalian target of rapamycin) signal transduction pathway, especially, has been suggested to play an important role in this regard. These pathways are involved in major physiological processes as well as in numerous pathological conditions. Here, involvement of the mTOR pathway in epilepsy will be reviewed by presenting; an overview of the pathway, a brief description of key signaling molecules, a summary of independent reports and possible implications of abnormalities of those molecules in epilepsy, a discussion of the lack of experimental data, and questions raised for the understanding its epileptogenic mechanism.
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Affiliation(s)
- Chang Hoon Cho
- Epilepsy Research Laboratory Department of Pediatrics Children's Hospital of Philadelphia, Pennsylvania 19104, USA.
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Boulon S, Westman BJ, Hutten S, Boisvert FM, Lamond AI. The nucleolus under stress. Mol Cell 2010; 40:216-27. [PMID: 20965417 PMCID: PMC2987465 DOI: 10.1016/j.molcel.2010.09.024] [Citation(s) in RCA: 755] [Impact Index Per Article: 53.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 08/16/2010] [Accepted: 09/22/2010] [Indexed: 12/16/2022]
Abstract
Cells typically respond quickly to stress, altering their metabolism to compensate. In mammalian cells, stress signaling usually leads to either cell-cycle arrest or apoptosis, depending on the severity of the insult and the ability of the cell to recover. Stress also often leads to reorganization of nuclear architecture, reflecting the simultaneous inhibition of major nuclear pathways (e.g., replication and transcription) and activation of specific stress responses (e.g., DNA repair). In this review, we focus on how two nuclear organelles, the nucleolus and the Cajal body, respond to stress. The nucleolus senses stress and is a central hub for coordinating the stress response. We review nucleolar function in the stress-induced regulation of p53 and the specific changes in nucleolar morphology and composition that occur upon stress. Crosstalk between nucleoli and CBs is also discussed in the context of stress responses.
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Affiliation(s)
- Séverine Boulon
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dundee DD1 5EH, UK
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Gomes C, Smith SC, Youssef MN, Zheng JJ, Hagg T, Hetman M. RNA polymerase 1-driven transcription as a mediator of BDNF-induced neurite outgrowth. J Biol Chem 2010; 286:4357-63. [PMID: 21098478 DOI: 10.1074/jbc.m110.170134] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Neurite outgrowth is essential for development of the nervous system. Neurotrophins including BDNF are among extracellular signals that regulate neurite outgrowth. The ERK1/2 pathway contributes to intracellular signaling networks transducing the pro-neuritic effects of BDNF. In the nucleolus, RNA polymerase-1 (Pol1)-mediated transcription regulates ribosomal biogenesis, enabling cellular protein synthesis and growth. Hence, we tested the possibility that Pol1 is an effector for pro-neuritic signals such as BDNF. We report that Pol1-mediated nucleolar transcription was increased by BDNF in an ERK1/2-dependent manner in rat forebrain neurons. Conversely, in cultured hippocampal neurons, knockdown of a Pol1 coactivator, transcription initiation factor 1A (TIF1A), attenuated BDNF- or ERK1/2-induced neurite outgrowth. Also, upon overexpression, a constitutively active mutant of TIF1A strongly promoted neurite outgrowth, including increases in total neurite length and branching. Finally, overexpression of wild-type TIF1A enhanced the pro-neuritic effects of ERK1/2 activation. These observations indicate that the Pol1-mediated nucleolar transcription regulates neurite outgrowth and serves as a major pro-neuritic effector of the BDNF-activated ERK1/2 pathway. Thus, development of the nervous system appears critically dependent on the nucleolus.
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Affiliation(s)
- Cynthia Gomes
- Department of Neurological Surgery, University of Louisville, Kentucky Spinal Cord Injury Research Center, Louisville, Kentucky 40292, USA
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Moreno-Igoa M, Manzano R, Oliván S, Calvo AC, Toivonen JM, Osta R. Effects of gene therapy on muscle 18S rRNA expression in mouse model of ALS. BMC Res Notes 2010; 3:275. [PMID: 21044297 PMCID: PMC2987871 DOI: 10.1186/1756-0500-3-275] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 11/02/2010] [Indexed: 01/14/2023] Open
Abstract
Background The efficiency of gene therapy experiments is frequently evaluated by measuring the impact of the treatment on the expression of genes of interest by quantitative real time PCR (qRT-PCR) and by normalizing these values to those of housekeeping (HK) genes constitutively expressed throughout the experiment. The objective of this work was to study the effects of muscle gene therapy on the expression of 18 S ribosomal RNA (Rn18S), a commonly used HK gene. Findings Mouse model of motor neuron disease (SOD1-G93A) was injected intramuscularly with Brain-derived neurotrophic factor (BDNF-TTC) encoding or control naked DNA plasmids. qRT-PCR expression analysis was performed for BDNF and HK genes Rn18 S, glyceraldehyde-3-phosphate dehydrogenase (Gapdh) and β-actin (Actb). We report that elevated BDNF expression in the injected muscle was accompanied with increased Rn18 S expression, whereas Gapdh and Actb were not affected. Increased "ribosomal output" upon BDNF stimulation was supported by increased steady-state levels of ribosomal protein mRNAs. Conclusions Ribosomal RNA transcription may be directly stimulated by administration of trophic factors. Caution should be taken in using Rn18 S as a HK gene in experiments where muscle metabolism is likely to be altered by therapeutic intervention.
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Affiliation(s)
- María Moreno-Igoa
- LAGENBIO-I3A, Veterinary Faculty, Aragon Institute of Health Sciences (IACS), Universidad de Zaragoza, Miguel Servet 177, 50013 Zaragoza, Spain.
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Philippi A, Steinbauer R, Reiter A, Fath S, Leger-Silvestre I, Milkereit P, Griesenbeck J, Tschochner H. TOR-dependent reduction in the expression level of Rrn3p lowers the activity of the yeast RNA Pol I machinery, but does not account for the strong inhibition of rRNA production. Nucleic Acids Res 2010; 38:5315-26. [PMID: 20421203 PMCID: PMC2938223 DOI: 10.1093/nar/gkq264] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Ribosome biogenesis is tightly linked to cellular growth. A crucial step in the regulation of ribosomal RNA (rRNA) gene transcription is the formation of the complex between RNA polymerase I (Pol I) and the Pol I-dependent transcription factor Rrn3p. We found that TOR inactivation leads to proteasome-dependent degradation of Rrn3p and a strong reduction in initiation competent Pol I-Rrn3p complexes affecting yeast rRNA gene transcription. Using a mutant expressing non-degradable Rrn3p or a strain in which defined endogenous Rrn3p levels can be adjusted by the Tet-off system, we can demonstrate that Rrn3p levels influence the number of Pol I-Rrn3p complexes and consequently rRNA gene transcription. However, our analysis reveals that the dramatic reduction of rRNA synthesis in the immediate cellular response to impaired TOR signalling cannot be explained by the simple down-regulation of Rrn3p and Pol I-Rrn3p levels.
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Affiliation(s)
- Anja Philippi
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany
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