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Del Toro N, Fernandez-Ruiz A, Mignacca L, Kalegari P, Rowell MC, Igelmann S, Saint-Germain E, Benfdil M, Lopes-Paciencia S, Brakier-Gingras L, Bourdeau V, Ferbeyre G, Lessard F. Ribosomal protein RPL22/eL22 regulates the cell cycle by acting as an inhibitor of the CDK4-cyclin D complex. Cell Cycle 2019; 18:759-770. [PMID: 30874462 DOI: 10.1080/15384101.2019.1593708] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Senescence is a tumor suppressor program characterized by a stable growth arrest while maintaining cell viability. Senescence-associated ribogenesis defects (SARD) have been shown to regulate senescence through the ability of the ribosomal protein S14 (RPS14 or uS11) to bind and inhibit the cyclin-dependent kinase 4 (CDK4). Here we report another ribosomal protein that binds and inhibits CDK4 in senescent cells: L22 (RPL22 or eL22). Enforcing the expression of RPL22/eL22 is sufficient to induce an RB and p53-dependent cellular senescent phenotype in human fibroblasts. Mechanistically, RPL22/eL22 can interact with and inhibit CDK4-Cyclin D1 to decrease RB phosphorylation both in vitro and in cells. Briefly, we show that ribosome-free RPL22/eL22 causes a cell cycle arrest which could be relevant during situations of nucleolar stress such as cellular senescence or the response to cancer chemotherapy.
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Affiliation(s)
- Neylen Del Toro
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada
| | - Ana Fernandez-Ruiz
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada.,b CRCHUM , Montréal , QC , Canada
| | - Lian Mignacca
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada
| | - Paloma Kalegari
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada.,b CRCHUM , Montréal , QC , Canada
| | - Marie-Camille Rowell
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada.,b CRCHUM , Montréal , QC , Canada
| | - Sebastian Igelmann
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada
| | - Emmanuelle Saint-Germain
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada
| | - Mehdi Benfdil
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada
| | - Stéphane Lopes-Paciencia
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada.,b CRCHUM , Montréal , QC , Canada
| | - Léa Brakier-Gingras
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada
| | - Véronique Bourdeau
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada
| | - Gerardo Ferbeyre
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada.,b CRCHUM , Montréal , QC , Canada
| | - Frédéric Lessard
- a Department of Biochemistry and Molecular Medicine , Université de Montréal , Montréal , Québec , Canada
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52
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Dimitrova DG, Teysset L, Carré C. RNA 2'-O-Methylation (Nm) Modification in Human Diseases. Genes (Basel) 2019; 10:E117. [PMID: 30764532 PMCID: PMC6409641 DOI: 10.3390/genes10020117] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 01/28/2019] [Accepted: 01/30/2019] [Indexed: 12/24/2022] Open
Abstract
Nm (2'-O-methylation) is one of the most common modifications in the RNA world. It has the potential to influence the RNA molecules in multiple ways, such as structure, stability, and interactions, and to play a role in various cellular processes from epigenetic gene regulation, through translation to self versus non-self recognition. Yet, building scientific knowledge on the Nm matter has been hampered for a long time by the challenges in detecting and mapping this modification. Today, with the latest advancements in the area, more and more Nm sites are discovered on RNAs (tRNA, rRNA, mRNA, and small non-coding RNA) and linked to normal or pathological conditions. This review aims to synthesize the Nm-associated human diseases known to date and to tackle potential indirect links to some other biological defects.
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Affiliation(s)
- Dilyana G Dimitrova
- Sorbonne Université, Institut de Biologie Paris Seine, Centre National de la Recherche Scientifique, Transgenerational Epigenetics & Small RNA Biology, Laboratoire de Biologie du Développement, 75005 Paris, France.
| | - Laure Teysset
- Sorbonne Université, Institut de Biologie Paris Seine, Centre National de la Recherche Scientifique, Transgenerational Epigenetics & Small RNA Biology, Laboratoire de Biologie du Développement, 75005 Paris, France.
| | - Clément Carré
- Sorbonne Université, Institut de Biologie Paris Seine, Centre National de la Recherche Scientifique, Transgenerational Epigenetics & Small RNA Biology, Laboratoire de Biologie du Développement, 75005 Paris, France.
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53
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Lessard F, Brakier-Gingras L, Ferbeyre G. Ribosomal Proteins Control Tumor Suppressor Pathways in Response to Nucleolar Stress. Bioessays 2019; 41:e1800183. [PMID: 30706966 DOI: 10.1002/bies.201800183] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 12/18/2018] [Indexed: 01/05/2023]
Abstract
Ribosome biogenesis includes the making and processing of ribosomal RNAs, the biosynthesis of ribosomal proteins from their mRNAs in the cytosol and their transport to the nucleolus to assemble pre-ribosomal particles. Several stresses including cellular senescence reduce nucleolar rRNA synthesis and maturation increasing the availability of ribosome-free ribosomal proteins. Several ribosomal proteins can activate the p53 tumor suppressor pathway but cells without p53 can still arrest their proliferation in response to an imbalance between ribosomal proteins and mature rRNA production. Recent results on senescence-associated ribogenesis defects (SARD) show that the ribosomal protein S14 (RPS14 or uS11) can act as a CDK4/6 inhibitor linking ribosome biogenesis defects to the main engine of cell cycle progression. This work offers new insights into the regulation of the cell cycle and suggests novel avenues to design anticancer drugs.
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Affiliation(s)
- Frédéric Lessard
- Department of Biochemistry and Molecular Medicine, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, Québec H3C 3J7, Canada
| | - Léa Brakier-Gingras
- Department of Biochemistry and Molecular Medicine, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, Québec H3C 3J7, Canada
| | - Gerardo Ferbeyre
- Department of Biochemistry and Molecular Medicine, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, Québec H3C 3J7, Canada.,CRCHUM, 900 Saint-Denis - bureau R10.432, Montréal, Québec H2X 0A9, Canada
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54
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Penzo M, Montanaro L, Treré D, Derenzini M. The Ribosome Biogenesis-Cancer Connection. Cells 2019; 8:cells8010055. [PMID: 30650663 PMCID: PMC6356843 DOI: 10.3390/cells8010055] [Citation(s) in RCA: 139] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 01/08/2019] [Accepted: 01/14/2019] [Indexed: 01/05/2023] Open
Abstract
Multifaceted relations link ribosome biogenesis to cancer. Ribosome biogenesis takes place in the nucleolus. Clarifying the mechanisms involved in this nucleolar function and its relationship with cell proliferation: (1) allowed the understanding of the reasons for the nucleolar changes in cancer cells and their exploitation in tumor pathology, (2) defined the importance of the inhibition of ribosome biogenesis in cancer chemotherapy and (3) focused the attention on alterations of ribosome biogenesis in the pathogenesis of cancer. This review summarizes the research milestones regarding these relevant relationships between ribosome biogenesis and cancer. The structure and function of the nucleolus will also be briefly described.
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Affiliation(s)
- Marianna Penzo
- Department of Experimental, Diagnostic and Specialty Medicine, Alma Mater Studiorum-University of Bologna, 40138 Bologna, Italy.
- Center for Applied Biomedical Research (CRBA), Alma Mater Studiorum-University of Bologna, 40138 Bologna, Italy.
| | - Lorenzo Montanaro
- Department of Experimental, Diagnostic and Specialty Medicine, Alma Mater Studiorum-University of Bologna, 40138 Bologna, Italy.
- Center for Applied Biomedical Research (CRBA), Alma Mater Studiorum-University of Bologna, 40138 Bologna, Italy.
| | - Davide Treré
- Department of Experimental, Diagnostic and Specialty Medicine, Alma Mater Studiorum-University of Bologna, 40138 Bologna, Italy.
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55
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Agrawal S, Ganley ARD. The conservation landscape of the human ribosomal RNA gene repeats. PLoS One 2018; 13:e0207531. [PMID: 30517151 PMCID: PMC6281188 DOI: 10.1371/journal.pone.0207531] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 11/01/2018] [Indexed: 01/27/2023] Open
Abstract
Ribosomal RNA gene repeats (rDNA) encode ribosomal RNA, a major component of ribosomes. Ribosome biogenesis is central to cellular metabolic regulation, and several diseases are associated with rDNA dysfunction, notably cancer, However, its highly repetitive nature has severely limited characterization of the elements responsible for rDNA function. Here we make use of phylogenetic footprinting to provide a comprehensive list of novel, potentially functional elements in the human rDNA. Complete rDNA sequences for six non-human primate species were constructed using de novo whole genome assemblies. These new sequences were used to determine the conservation profile of the human rDNA, revealing 49 conserved regions in the rDNA intergenic spacer (IGS). To provide insights into the potential roles of these conserved regions, the conservation profile was integrated with functional genomics datasets. We find two major zones that contain conserved elements characterised by enrichment of transcription-associated chromatin factors, and transcription. Conservation of some IGS transcripts in the apes underpins the potential functional significance of these transcripts and the elements controlling their expression. Our results characterize the conservation landscape of the human IGS and suggest that noncoding transcription and chromatin elements are conserved and important features of this unique genomic region.
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Affiliation(s)
- Saumya Agrawal
- Institute of Natural and Mathematical Sciences, Massey University, Auckland, New Zealand
| | - Austen R. D. Ganley
- Institute of Natural and Mathematical Sciences, Massey University, Auckland, New Zealand
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
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56
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The Selective RNA Polymerase I Inhibitor CX-5461 Mitigates Neointimal Remodeling in a Modified Model of Rat Aortic Transplantation. Transplantation 2018; 102:1674-1683. [DOI: 10.1097/tp.0000000000002372] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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57
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Leung AWY, Anantha M, Dragowska WH, Wehbe M, Bally MB. Copper-CX-5461: A novel liposomal formulation for a small molecule rRNA synthesis inhibitor. J Control Release 2018; 286:1-9. [PMID: 30016731 DOI: 10.1016/j.jconrel.2018.07.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 07/04/2018] [Accepted: 07/13/2018] [Indexed: 12/23/2022]
Abstract
CX-5461 is currently in Phase I/II clinical trials for advanced hematologic malignancies and triple negative or BRCA-deficient breast cancer. The compound is currently administered to patients intravenously (i.v.) at low pH (3.5) due to solubility challenges. Reliance of low pH to enhance solubility of CX-5461 can adversely impact pharmacokinetics, biodistribution and therapeutic potential. We have addressed this solubility issue through a formulation method that relies on the interactions between CX-5461 and copper. Copper binds CX-5461 through the nitrogens of the pyrazine ring. Here, we describe synthesizing this copper-complexed CX-5461 (Cu(CX-5461)) within liposomes. CX-5461 was added to copper-containing liposomes and incubated at 60 °C for 30 min. The pharmacokinetics of CX-5461 was assessed in mice following a single i.v. injection at 30 mg/kg. Efficacy studies were completed in multiple subcutaneous mouse xenografts as well as in a bone marrow engraftment model of acute myeloid leukemia (AML). The novel Cu(CX-5461) formulation was stable at pH 7.4 and exhibited increased plasma circulation longevity, increasing the total exposure to CX5461 by an order of magnitude. Cu(CX-5461) was more active than CX-5461 in AML models in vivo. In HCT116-B46 and Capan-1 solid tumour models that are BRCA-deficient, the Cu(CX-5461) formulation engendered activity that was comparable to that of the low pH CX-5461 formulation. We have generated the first Cu(CX-5461) formulation suitable for i.v. administration that is more efficacious than the existing low-pH formulation in pre-clinical models of AML. The Cu(CX-5461) formulation may serve as an alternative formulation for CX-5461 in BRCA-deficient cancers.
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Affiliation(s)
- Ada W Y Leung
- Experimental Therapeutics, BC Cancer Research Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada; Department of Chemistry, University of British Columbia, Vancouver, BC, Canada; Cuprous Pharmaceuticals Inc., Vancouver, BC, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.
| | - Malathi Anantha
- Experimental Therapeutics, BC Cancer Research Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada
| | - Wieslawa H Dragowska
- Experimental Therapeutics, BC Cancer Research Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada
| | - Mohamed Wehbe
- Experimental Therapeutics, BC Cancer Research Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada; Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Marcel B Bally
- Experimental Therapeutics, BC Cancer Research Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada; Cuprous Pharmaceuticals Inc., Vancouver, BC, Canada; Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada; Centre for Drug Research and Development, Vancouver, BC, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada
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58
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Levin A, Minis A, Lalazar G, Rodriguez J, Steller H. PSMD5 Inactivation Promotes 26S Proteasome Assembly during Colorectal Tumor Progression. Cancer Res 2018; 78:3458-3468. [PMID: 29716915 PMCID: PMC6030489 DOI: 10.1158/0008-5472.can-17-2296] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 12/29/2017] [Accepted: 04/18/2018] [Indexed: 01/09/2023]
Abstract
Protein degradation by the ubiquitin-proteasome system (UPS) is central to protein homeostasis and cell survival. The active 26S proteasome is a large protease complex consisting of a catalytic 20S subunit and 19S regulatory particles. Cancer cells are exposed to considerable protein overload due to high metabolic rates, reprogrammed energy metabolism, and aneuploidy. Here we report a mechanism that facilitates the assembly of active 26S proteasomes in malignant cells. Upon tumorigenic transformation of the gut epithelium, 26S proteasome assembly was significantly enhanced, but levels of individual subunits were not changed. This enhanced assembly of 26S proteasomes increased further with tumor progression and was observed specifically in transformed cells, but not in other rapidly dividing cells. Moreover, expression of PSMD5, an inhibitor of proteasome assembly, was reduced in intestinal tumors and silenced with tumor progression. Reexpression of PSMD5 in tumor cells caused decreased 26S assembly and accumulation of polyubiquitinated proteins. These results suggest that inhibition of cancer-associated proteasome assembly may provide a novel therapeutic strategy to selectively kill cancer cells.Significance: Enhanced cancer-associated proteasome assembly is a major stress response that allows tumors to adapt to and to withstand protein overload.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/13/3458/F1.large.jpg Cancer Res; 78(13); 3458-68. ©2018 AACR.
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Affiliation(s)
- Avi Levin
- Strang Laboratory of Apoptosis and Cancer Biology, The Rockefeller University, New York, New York.
- Division of Gastroenterology, University of Iowa, Iowa City, Iowa
| | - Adi Minis
- Strang Laboratory of Apoptosis and Cancer Biology, The Rockefeller University, New York, New York
| | - Gadi Lalazar
- Laboratory of Cellular Biophysics, The Rockefeller University, New York, New York
| | - Jose Rodriguez
- Strang Laboratory of Apoptosis and Cancer Biology, The Rockefeller University, New York, New York
| | - Hermann Steller
- Strang Laboratory of Apoptosis and Cancer Biology, The Rockefeller University, New York, New York.
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59
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Derenzini E, Rossi A, Treré D. Treating hematological malignancies with drugs inhibiting ribosome biogenesis: when and why. J Hematol Oncol 2018; 11:75. [PMID: 29855342 PMCID: PMC5984324 DOI: 10.1186/s13045-018-0609-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 04/26/2018] [Indexed: 01/05/2023] Open
Abstract
It is well known that chemotherapy can cure only some cancers in advanced stage, mostly those with an intact p53 pathway. Hematological cancers such as lymphoma and certain forms of leukemia are paradigmatic examples of such scenario. Recent evidence indicates that the efficacy of many of the alkylating and intercalating agents, antimetabolites, topoisomerase, and kinase inhibitors used in cancer therapy is largely due to p53 stabilization and activation consequent to the inhibition of ribosome biogenesis. In this context, innovative drugs specifically hindering ribosome biogenesis showed preclinical activity and are currently in early clinical development in hematological malignancies. The mechanism of p53 stabilization after ribosome biogenesis inhibition is a multistep process, depending on specific factors that can be altered in tumor cells, which can affect the antitumor efficacy of ribosome biogenesis inhibitors (RiBi). In the present review, the basic mechanisms underlying the anticancer activity of RiBi are discussed based on the evidence deriving from available preclinical and clinical studies, with the purpose of defining when and why the treatment with drugs inhibiting ribosomal biogenesis could be highly effective in hematological malignancies.
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Affiliation(s)
- Enrico Derenzini
- European Institute of Oncology, Via Ripamonti 435, 20141, Milan, Italy.
| | - Alessandra Rossi
- European Institute of Oncology, Via Ripamonti 435, 20141, Milan, Italy
| | - Davide Treré
- DIMES, Università di Bologna, Via Massarenti 9, Bologna, Italy.
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60
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Molecular mechanism of promoter opening by RNA polymerase III. Nature 2018; 553:295-300. [PMID: 29345638 PMCID: PMC5777638 DOI: 10.1038/nature25440] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 12/08/2017] [Indexed: 01/03/2023]
Abstract
RNA polymerase III (Pol III) assembles together with transcription factor IIIB (TFIIIB) on different promoter types to initiate the transcription of small, structured RNAs. Here, we present structures of Pol III pre-initiation complexes comprising the 17-subunit Pol III and hetero-trimeric transcription factor TFIIIB with subunits TATA-binding protein (TBP), B-related factor 1 (Brf1) and B double prime 1 (Bdp1) bound to a natural promoter in different functional states. Electron cryo-microscopy (cryo-EM) reconstructions varying from 3.7 Å to 5.5 Å resolution include two early intermediates in which the DNA duplex is closed, an open DNA complex and an initially transcribing complex with RNA in the active site. Our structures reveal an extremely tight and multivalent interaction of TFIIIB with promoter DNA and explain how TFIIIB recruits Pol III. TFIIIB and Pol III subunit C37 together activate the intrinsic transcription factor-like activity of the Pol III-specific heterotrimer to initiate melting of double-stranded DNA in a mechanism similar as used in the Pol II system.
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61
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daSilva LF, Beckedorff FC, Ayupe AC, Amaral MS, Mesel V, Videira A, Reis EM, Setubal JC, Verjovski-Almeida S. Chromatin Landscape Distinguishes the Genomic Loci of Hundreds of Androgen-Receptor-Associated LincRNAs From the Loci of Non-associated LincRNAs. Front Genet 2018; 9:132. [PMID: 29875794 PMCID: PMC5985396 DOI: 10.3389/fgene.2018.00132] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 04/03/2018] [Indexed: 11/30/2022] Open
Abstract
Cell signaling events triggered by androgen hormone in prostate cells is dependent on activation of the androgen receptor (AR) transcription factor. Androgen hormone binding to AR promotes its displacement from the cytoplasm to the nucleus and AR binding to DNA motifs, thus inducing activatory and inhibitory transcriptional programs through a complex regulatory mechanism not yet fully understood. In this work, we performed RNA-seq deep-sequencing of LNCaP prostate cancer cells and found over 7000 expressed long intergenic non-coding RNAs (lincRNAs), of which ∼4000 are novel lincRNAs, and 258 lincRNAs have their expression activated by androgen. Immunoprecipitation of AR, followed by large-scale sequencing of co-immunoprecipitated RNAs (RIP-Seq) has identified in the LNCaP cell line a total of 619 lincRNAs that were significantly enriched (FDR < 10%, DESeq2) in the anti-Androgen Receptor (antiAR) fraction in relation to the control fraction (non-specific IgG), and we named them Androgen-Receptor-Associated lincRNAs (ARA-lincRNAs). A genome-wide analysis showed that protein-coding gene neighbors to ARA-lincRNAs had a significantly higher androgen-induced change in expression than protein-coding genes neighboring lincRNAs not associated to AR. To find relevant epigenetic signatures enriched at the ARA-lincRNAs’ transcription start sites (TSSs) we used a machine learning approach and identified that the ARA-lincRNA genomic loci in LNCaP cells are significantly enriched with epigenetic marks that are characteristic of in cis enhancer RNA regulators, and that the H3K27ac mark of active enhancers is conspicuously enriched at the TSS of ARA-lincRNAs adjacent to androgen-activated protein-coding genes. In addition, LNCaP topologically associating domains (TADs) that comprise chromatin regions with ARA-lincRNAs exhibit transcription factor contents, epigenetic marks and gene transcriptional activities that are significantly different from TADs not containing ARA-lincRNAs. This work highlights the possible involvement of hundreds of lincRNAs working in synergy with the AR on the genome-wide androgen-induced gene regulatory program in prostate cells.
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Affiliation(s)
- Lucas F daSilva
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.,Laboratório de Expressão Gênica em Eucariotos, Instituto Butantan, São Paulo, Brazil
| | - Felipe C Beckedorff
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.,Laboratório de Expressão Gênica em Eucariotos, Instituto Butantan, São Paulo, Brazil
| | - Ana C Ayupe
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Murilo S Amaral
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.,Laboratório de Expressão Gênica em Eucariotos, Instituto Butantan, São Paulo, Brazil
| | - Vinícius Mesel
- Laboratório de Expressão Gênica em Eucariotos, Instituto Butantan, São Paulo, Brazil
| | - Alexandre Videira
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.,Laboratório de Expressão Gênica em Eucariotos, Instituto Butantan, São Paulo, Brazil
| | - Eduardo M Reis
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - João C Setubal
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.,Biocomplexity Institute of Virginia Tech, Blacksburg, VA, United States
| | - Sergio Verjovski-Almeida
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.,Laboratório de Expressão Gênica em Eucariotos, Instituto Butantan, São Paulo, Brazil
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62
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Therapeutic dosages of aspirin counteract the IL-6 induced pro-tumorigenic effects by slowing down the ribosome biogenesis rate. Oncotarget 2018; 7:63226-63241. [PMID: 27557515 PMCID: PMC5325359 DOI: 10.18632/oncotarget.11441] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 08/13/2016] [Indexed: 02/07/2023] Open
Abstract
Chronic inflammation is a risk factor for the onset of cancer and the regular use of aspirin reduces the risk of cancer development. Here we showed that therapeutic dosages of aspirin counteract the pro-tumorigenic effects of the inflammatory cytokine interleukin(IL)-6 in cancer and non-cancer cell lines, and in mouse liver in vivo. We found that therapeutic dosages of aspirin prevented IL-6 from inducing the down-regulation of p53 expression and the acquisition of the epithelial mesenchymal transition (EMT) phenotypic changes in the cell lines. This was the result of a reduction in c-Myc mRNA transcription which was responsible for a down-regulation of the ribosomal protein S6 expression which, in turn, slowed down the rRNA maturation process, thus reducing the ribosome biogenesis rate. The perturbation of ribosome biogenesis hindered the Mdm2-mediated proteasomal degradation of p53, throughout the ribosomal protein-Mdm2-p53 pathway. P53 stabilization hindered the IL-6 induction of the EMT changes. The same effects were observed in livers from mice stimulated with IL-6 and treated with aspirin. It is worth noting that aspirin down-regulated ribosome biogenesis, stabilized p53 and up-regulated E-cadherin expression in unstimulated control cells also. In conclusion, these data showed that therapeutic dosages of aspirin increase the p53-mediated tumor-suppressor activity of the cells thus being in this way able to reduce the risk of cancer onset, either or not linked to chronic inflammatory processes.
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63
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Prosser KE, Leung AWY, Harrypersad S, Lewis AR, Bally MB, Walsby CJ. Transition Metal Ions Promote the Bioavailability of Hydrophobic Therapeutics: Cu and Zn Interactions with RNA Polymerase I Inhibitor CX5461. Chemistry 2018; 24:6334-6338. [PMID: 29490115 DOI: 10.1002/chem.201800289] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Indexed: 01/27/2023]
Abstract
Low aqueous solubility is a major barrier to the clinical application of otherwise promising drug candidates. We demonstrate that this issue can be resolved in medicinal molecules containing potential ligating groups, through the addition of labile transition-metal ions. Incubation of the chemotherapeutic CX5461 with Cu2+ or Zn2+ enables solubilization at neutral pH but does not affect intrinsic cytotoxicity. Spectroscopic and computational studies demonstrate that this arises from coordination to the pyrazine functionality of CX5461 and may involve bidentate coordination at physiological pH.
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Affiliation(s)
- Kathleen E Prosser
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada
| | - Ada W Y Leung
- Department of Experimental Therapeutics, British Columbia Cancer Agency, 675 West 10th Ave, Vancouver, BC, V5Z 4E6, Canada
| | - Shane Harrypersad
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada
| | - Andrew R Lewis
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada
| | - Marcel B Bally
- Department of Experimental Therapeutics, British Columbia Cancer Agency, 675 West 10th Ave, Vancouver, BC, V5Z 4E6, Canada
| | - Charles J Walsby
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada
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64
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Graczyk D, Cieśla M, Boguta M. Regulation of tRNA synthesis by the general transcription factors of RNA polymerase III - TFIIIB and TFIIIC, and by the MAF1 protein. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1861:320-329. [DOI: 10.1016/j.bbagrm.2018.01.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 01/20/2018] [Accepted: 01/21/2018] [Indexed: 01/03/2023]
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65
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Johnston R, D'Costa Z, Ray S, Gorski J, Harkin DP, Mullan P, Panov KI. The identification of a novel role for BRCA1 in regulating RNA polymerase I transcription. Oncotarget 2018; 7:68097-68110. [PMID: 27589844 PMCID: PMC5356541 DOI: 10.18632/oncotarget.11770] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 08/24/2016] [Indexed: 12/22/2022] Open
Abstract
The unrestrained proliferation of cancer cells requires a high level of ribosome biogenesis. The first stage of ribosome biogenesis is the transcription of the large ribosomal RNAs (rRNAs); the structural and functional components of the ribosome. Transcription of rRNA is carried out by RNA polymerase I (Pol-I) and its associated holoenzyme complex.Here we report that BRCA1, a nuclear phosphoprotein, and a known tumour suppressor involved in variety of cellular processes such as DNA damage response, transcriptional regulation, cell cycle control and ubiquitylation, is associated with rDNA repeats, in particular with the regulatory regions of the rRNA gene.We demonstrate that BRCA1 interacts directly with the basal Pol-I transcription factors; upstream binding factor (UBF), selectivity factor-1 (SL1) as well as interacting with RNA Pol-I itself. We show that in response to DNA damage, BRCA1 occupancy at the rDNA repeat is decreased and the observed BRCA1 interactions with the Pol-I transcription machinery are weakened.We propose, therefore, that there is a rDNA associated fraction of BRCA1 involved in DNA damage dependent regulation of Pol-I transcription, regulating the stability and formation of the Pol-I holoenzyme during initiation and/or elongation in response to DNA damage.
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Affiliation(s)
- Rebecca Johnston
- School of Biological Sciences, Queen's University Belfast, Belfast, BT9 7BL, UK
| | - Zenobia D'Costa
- The Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT9 7BL, UK.,Department of Oncology, University of Oxford, Oxford, OX3 7DQ, UK
| | - Swagat Ray
- School of Biological Sciences, Queen's University Belfast, Belfast, BT9 7BL, UK.,Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
| | - Julia Gorski
- The Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT9 7BL, UK
| | - D Paul Harkin
- The Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT9 7BL, UK
| | - Paul Mullan
- The Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT9 7BL, UK
| | - Konstantin I Panov
- School of Biological Sciences, Queen's University Belfast, Belfast, BT9 7BL, UK.,The Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT9 7BL, UK
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66
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Zhang S, Li X, Wang HY, Steven Zheng XF. Beyond regulation of pol III: Role of MAF1 in growth, metabolism, aging and cancer. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1861:338-343. [PMID: 29407795 DOI: 10.1016/j.bbagrm.2018.01.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Revised: 01/24/2018] [Accepted: 01/28/2018] [Indexed: 11/24/2022]
Abstract
MAF1 was discovered as a master repressor of Pol III-dependent transcription in response to diverse extracellular signals, including growth factor, nutrient and stress. It is regulated through posttranslational mechanisms such as phosphorylation. A prominent upstream regulator of MAF1 is the mechanistic target of rapamycin (mTOR) pathway. mTOR kinase directly phosphorylates MAF1, controlling its localization and transcriptional activity. In mammals, MAF1 has also been shown to regulate Pol I- and Pol II-dependent transcription. Interestingly, MAF1 modulates Pol II activity both as a repressor and activator, depending on specific target genes, to impact on cellular growth and metabolism. While MAF1 represses genes such as TATA-binding protein (TBP) and fatty acid synthase (FASN), it activates the expression of PTEN, a major tumor suppressor and an inhibitor of the mTOR signaling. Increasing evidence indicates that MAF1 plays an important role in different aspects of normal physiology, lifespan and oncogenesis. Here we will review the current knowledge on MAF1 in growth, metabolism, aging and cancer. This article is part of a Special Issue entitled: SI: Regulation of tRNA synthesis and modification in physiological conditions and disease edited by Dr. Boguta Magdalena.
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Affiliation(s)
- Shanshan Zhang
- State Key Laboratory of Oncology in South China, and Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou 510060, China
| | - Xiaoxing Li
- State Key Laboratory of Oncology in South China, and Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou 510060, China
| | - Hui-Yun Wang
- State Key Laboratory of Oncology in South China, and Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou 510060, China; Rutgers Cancer Institute of New Jersey and Department of Pharmacology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, New Brunswick, NJ 08903, USA
| | - X F Steven Zheng
- State Key Laboratory of Oncology in South China, and Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou 510060, China; Rutgers Cancer Institute of New Jersey and Department of Pharmacology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, New Brunswick, NJ 08903, USA.
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67
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Willis IM, Moir RD. Signaling to and from the RNA Polymerase III Transcription and Processing Machinery. Annu Rev Biochem 2018; 87:75-100. [PMID: 29328783 DOI: 10.1146/annurev-biochem-062917-012624] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
RNA polymerase (Pol) III has a specialized role in transcribing the most abundant RNAs in eukaryotic cells, transfer RNAs (tRNAs), along with other ubiquitous small noncoding RNAs, many of which have functions related to the ribosome and protein synthesis. The high energetic cost of producing these RNAs and their central role in protein synthesis underlie the robust regulation of Pol III transcription in response to nutrients and stress by growth regulatory pathways. Downstream of Pol III, signaling impacts posttranscriptional processes affecting tRNA function in translation and tRNA cleavage into smaller fragments that are increasingly attributed with novel cellular activities. In this review, we consider how nutrients and stress control Pol III transcription via its factors and its negative regulator, Maf1. We highlight recent work showing that the composition of the tRNA population and the function of individual tRNAs is dynamically controlled and that unrestrained Pol III transcription can reprogram central metabolic pathways.
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Affiliation(s)
- Ian M Willis
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA; , .,Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Robyn D Moir
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA; ,
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68
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Chen X, Dickman D. Development of a tissue-specific ribosome profiling approach in Drosophila enables genome-wide evaluation of translational adaptations. PLoS Genet 2017; 13:e1007117. [PMID: 29194454 PMCID: PMC5728580 DOI: 10.1371/journal.pgen.1007117] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 12/13/2017] [Accepted: 11/16/2017] [Indexed: 01/19/2023] Open
Abstract
Recent advances in next-generation sequencing approaches have revolutionized our understanding of transcriptional expression in diverse systems. However, measurements of transcription do not necessarily reflect gene translation, the process of ultimate importance in understanding cellular function. To circumvent this limitation, biochemical tagging of ribosome subunits to isolate ribosome-associated mRNA has been developed. However, this approach, called TRAP, lacks quantitative resolution compared to a superior technology, ribosome profiling. Here, we report the development of an optimized ribosome profiling approach in Drosophila. We first demonstrate successful ribosome profiling from a specific tissue, larval muscle, with enhanced resolution compared to conventional TRAP approaches. We next validate the ability of this technology to define genome-wide translational regulation. This technology is leveraged to test the relative contributions of transcriptional and translational mechanisms in the postsynaptic muscle that orchestrate the retrograde control of presynaptic function at the neuromuscular junction. Surprisingly, we find no evidence that significant changes in the transcription or translation of specific genes are necessary to enable retrograde homeostatic signaling, implying that post-translational mechanisms ultimately gate instructive retrograde communication. Finally, we show that a global increase in translation induces adaptive responses in both transcription and translation of protein chaperones and degradation factors to promote cellular proteostasis. Together, this development and validation of tissue-specific ribosome profiling enables sensitive and specific analysis of translation in Drosophila. Recent advances in next-generation sequencing approaches have revolutionized our understanding of transcriptional expression in diverse systems. However, transcriptional expression alone does not necessarily report gene translation, the process of ultimate importance in understanding cellular function. Ribosome profiling is a powerful approach to quantify the number of ribosomes associated with each mRNA to determine rates of gene translation. However, ribosome profiling requires large quantities of starting material, limiting progress in developing tissue-specific approaches. Here, we have developed the first tissue-specific ribosome profiling system in Drosophila to reveal genome-wide changes in translation. We first demonstrate successful ribosome profiling from muscle cells that exhibit superior resolution compared to other translational profiling methods. We then use transcriptional and ribosome profiling to define whether transcriptional or translational mechanisms are necessary for synaptic signaling at the neuromuscular junction. Finally, we utilize ribosome profiling to reveal adaptive changes in cellular translation following cellular stress to muscle tissue. Together, this now enables the power of Drosophila genetics to be leveraged with ribosome profiling in specific tissues.
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Affiliation(s)
- Xun Chen
- Department of Neurobiology, University of Southern California, Los Angeles, California, United States of America
- USC Neuroscience Graduate Program, University of Southern California, Los Angeles, California, United States of America
| | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, California, United States of America
- * E-mail:
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69
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Kostopoulou ON, Wilhelmi V, Raiss S, Ananthaseshan S, Lindström MS, Bartek J, Söderberg-Naucler C. Human cytomegalovirus and Herpes Simplex type I virus can engage RNA polymerase I for transcription of immediate early genes. Oncotarget 2017; 8:96536-96552. [PMID: 29228551 PMCID: PMC5722503 DOI: 10.18632/oncotarget.22106] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 10/13/2017] [Indexed: 12/22/2022] Open
Abstract
Human cytomegalovirus (HCMV) utilizes RNA polymerase II to transcribe viral genes and produce viral mRNAs. It can specifically target the nucleolus to facilitate viral transcription and translation. As RNA polymerase I (Pol I)-mediated transcription is active in the nucleolus, we investigated the role of Pol I, along with relative contributions of the human Pol II and Pol III, to early phases of viral transcription in HCMV infected cells, compared with Herpes Simplex Virus-1 (HSV-1) and Murine cytomegalovirus (MCMV). Inhibition of Pol I with siRNA or the Pol I inhibitors CX-5461 or Actinomycin D (5nM) resulted in significantly decreased IE and pp65 mRNA and protein levels in human fibroblasts at early times post infection. This initially delayed replication was compensated for later during the replication process, at which stage it didn't significantly affect virus production. Pol I inhibition also reduced HSV-1 ICP0 and gB transcripts, suggesting that some herpesviruses engage Pol I for their early transcription. In contrast, inhibition of Pol I failed to affect MCMV transcription. Collectively, our results contribute to better understanding of the functional interplay between RNA Pol I-mediated nucleolar events and the Herpes viruses, particularly HCMV whose pathogenic impact ranges from congenital malformations and potentially deadly infections among immunosuppressed patients, up to HCMV's emerging oncomodulatory role in human tumors.
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Affiliation(s)
- Ourania N Kostopoulou
- Department of Medicine, Center for Molecular Medicine L8:03, Karolinska University Hospital, Stockholm, Sweden
| | - Vanessa Wilhelmi
- Department of Medicine, Center for Molecular Medicine L8:03, Karolinska University Hospital, Stockholm, Sweden
| | - Sina Raiss
- Department of Medicine, Center for Molecular Medicine L8:03, Karolinska University Hospital, Stockholm, Sweden
| | - Sharan Ananthaseshan
- Department of Medicine, Center for Molecular Medicine L8:03, Karolinska University Hospital, Stockholm, Sweden
| | - Mikael S Lindström
- Department of Medical Biochemistry and Biophysics, Science For Life Laboratory, Division of Genome Biology, Karolinska Institute, Solna, Sweden
| | - Jiri Bartek
- Department of Medical Biochemistry and Biophysics, Science For Life Laboratory, Division of Genome Biology, Karolinska Institute, Solna, Sweden
| | - Cecilia Söderberg-Naucler
- Department of Medicine, Center for Molecular Medicine L8:03, Karolinska University Hospital, Stockholm, Sweden
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70
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Zhang J, Shao J, Zhu L, Zhao R, Xing J, Wang J, Guo X, Tu S, Han B, Yu K. Molecular profiling identifies prognostic markers of stage IA lung adenocarcinoma. Oncotarget 2017; 8:74846-74855. [PMID: 29088828 PMCID: PMC5650383 DOI: 10.18632/oncotarget.20420] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 06/16/2017] [Indexed: 12/29/2022] Open
Abstract
We previously showed that different pathologic subtypes were associated with different prognostic values in patients with stage IA lung adenocarcinoma (AC). We hypothesize that differential gene expression profiles of different subtypes may be valuable factors for prognosis in stage IA lung adenocarcinoma. We performed microarray gene expression profiling on tumor tissues micro-dissected from patients with acinar and solid predominant subtypes of stage IA lung adenocarcinoma. These patients had undergone a lobectomy and mediastinal lymph node dissection at the Shanghai Chest Hospital, Shanghai, China in 2012. No patient had preoperative treatment. We performed the Gene Set Enrichment Analysis (GSEA) analysis to look for gene expression signatures associated with tumor subtypes. The histologic subtypes of all patients were classified according to the 2015 WHO lung Adenocarcinoma classification. We found that patients with the solid predominant subtype are enriched for genes involved in RNA polymerase activity as well as inactivation of the p53 pathway. Further, we identified a list of genes that may serve as prognostic markers for stage IA lung adenocarcinoma. Validation in the TCGA database shows that these genes are correlated with survival, suggesting that they are novel prognostic factors for stage IA lung adenocarcinoma. In conclusion, we have uncovered novel prognostic factors for stage IA lung adenocarcinoma using gene expression profiling in combination with histopathology subtyping.
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Affiliation(s)
- Jie Zhang
- Shanghai Chest Hospital, Shanghai JiaoTong University, Department of Pathology, Shanghai, China
| | - Jinchen Shao
- Shanghai Chest Hospital, Shanghai JiaoTong University, Department of Pathology, Shanghai, China
| | - Lei Zhu
- Shanghai Chest Hospital, Shanghai JiaoTong University, Department of Pathology, Shanghai, China
| | - Ruiying Zhao
- Shanghai Chest Hospital, Shanghai JiaoTong University, Department of Pathology, Shanghai, China
| | - Jie Xing
- Shanghai Chest Hospital, Shanghai JiaoTong University, Department of Pathology, Shanghai, China
| | - Jun Wang
- Tumor Initiation & Maintenance Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla
| | - Xiaohui Guo
- Bioinformatics Core, Sanford Burnham Prebys Medical Discovery Institute, La Jolla
| | - Shichun Tu
- Allele Biotechnology & Pharmaceuticals, Inc., Nancy Ridge Drive, San Diego, USA
| | - Baohui Han
- Shanghai Chest Hospital, Shanghai JiaoTong University, Department of Pulmonary Medicine, Shanghai, China
| | - Keke Yu
- Shanghai Chest Hospital, Shanghai JiaoTong University, Department of Pathology, Shanghai, China.,Shanghai Chest Hospital, Shanghai JiaoTong University, Department of Biobank, Shanghai, China
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71
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Kim Y, Lee J, Shin H, Jang S, Kim SC, Lee Y. Biosynthesis of brain cytoplasmic 200 RNA. Sci Rep 2017; 7:6884. [PMID: 28761139 PMCID: PMC5537265 DOI: 10.1038/s41598-017-05097-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 05/10/2017] [Indexed: 12/13/2022] Open
Abstract
Brain cytoplasmic 200 RNA (BC200 RNA), a neuron-specific non-coding RNA, is also highly expressed in a number of tumors of non-neuronal origin. However, the biosynthesis of BC200 RNA remains poorly understood. In this study, we show that the efficient transcription of BC200 RNA requires both internal and upstream promoter elements in cancer cells. The transcription complex seems to interact with a broad range of sequences within the upstream 100-bp region. The cellular levels and half-lives of BC200 RNA were found to differ across various cancer cell types, but there was no significant correlation between these parameters. Exogenously expressed BC200 RNA had a shorter half-life than that observed for the endogenous version in cancer cells, suggesting that BC200 RNA might be protected by some limiting factor(s) in cancer cells. Transient transfection experiments showed that the transcriptional activity of the exogenous BC200 RNA promoter element varied depending on the cancer cell type. However, the promoter activities together with the half-life data could not explain the differences in the levels of BC200 RNA among different cell types, suggesting that there is another level of transcriptional regulation beyond that detected by our transient transfection experiments.
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Affiliation(s)
- Youngmi Kim
- Department of Chemistry, KAIST, Daejeon, 34141, Korea
| | - Jungmin Lee
- Department of Chemistry, KAIST, Daejeon, 34141, Korea
| | - Heegwon Shin
- Department of Chemistry, KAIST, Daejeon, 34141, Korea
| | - Seonghui Jang
- Department of Chemistry, KAIST, Daejeon, 34141, Korea
| | - Sun Chang Kim
- Department of Biological Sciences, KAIST, Daejeon, 34141, Korea
| | - Younghoon Lee
- Department of Chemistry, KAIST, Daejeon, 34141, Korea.
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72
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Chen Y, Wen H, Wu CI. A mathematical theory of the transcription repression (TR) therapy of cancer - whether and how it may work. Oncotarget 2017; 8:38642-38649. [PMID: 28454100 PMCID: PMC5503560 DOI: 10.18632/oncotarget.16957] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 03/29/2017] [Indexed: 12/14/2022] Open
Abstract
Transcription repression (TR) therapy of cancer has been widely discussed. Here, TR refers to global repression of transcription rather than specific targeting of cancer-causing genes such as MYC. TR drugs inhibit transcription by binding to the transcribed DNA or to RNA polymerase; for example, actinomycin D has been extensively used in research and therapy to shut down transcription globally [1-7]. As proliferating cells demand a high rate of transcription, restricting transcript production could be effective in slowing down cell proliferation. However, TR also deprives other less proliferative cells of new transcripts, thus leading to substantial toxicity [1, 8, 9]. We now develop a mathematical theory to exploit the greater demand for transcription in highly proliferating cells. A new strategy, referred to as the TRR (transcript repression-recovery) model, would insert a recovery phase to allow the more slowly proliferating cells to recover. It is most effective to have strong blocking for a short period (a few hours) followed by a longer recovery phase in each cell cycle. Hence, TRR can potentially achieve selective killing of cells based on their global transcription needs but precise fine-tuning is necessary.
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Affiliation(s)
- Yuxin Chen
- State Key Laboratory of Bio-control, School of Life Science, Sun Yat-Sen University, Guangzhou, China
| | - Haijun Wen
- State Key Laboratory of Bio-control, School of Life Science, Sun Yat-Sen University, Guangzhou, China
| | - Chung-I Wu
- State Key Laboratory of Bio-control, School of Life Science, Sun Yat-Sen University, Guangzhou, China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, USA
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73
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Brun S, Abella N, Berciano MT, Tapia O, Jaumot M, Freire R, Lafarga M, Agell N. SUMO regulates p21Cip1 intracellular distribution and with p21Cip1 facilitates multiprotein complex formation in the nucleolus upon DNA damage. PLoS One 2017; 12:e0178925. [PMID: 28582471 PMCID: PMC5459497 DOI: 10.1371/journal.pone.0178925] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 05/22/2017] [Indexed: 01/06/2023] Open
Abstract
We previously showed that p21Cip1 transits through the nucleolus on its way from the nucleus to the cytoplasm and that DNA damage inhibits this transit and induces the formation of p21Cip1-containing intranucleolar bodies (INoBs). Here, we demonstrate that these INoBs also contain SUMO-1 and UBC9, the E2 SUMO-conjugating enzyme. Furthermore, whereas wild type SUMO-1 localized in INoBs, a SUMO-1 mutant, which is unable to conjugate with proteins, does not, suggesting the presence of SUMOylated proteins at INoBs. Moreover, depletion of the SUMO-conjugating enzyme UBC9 or the sumo hydrolase SENP2 changed p21Cip1 intracellular distribution. In addition to SUMO-1 and p21Cip1, cell cycle regulators and DNA damage checkpoint proteins, including Cdk2, Cyclin E, PCNA, p53 and Mdm2, and PML were also detected in INoBs. Importantly, depletion of UBC9 or p21Cip1 impacted INoB biogenesis and the nucleolar accumulation of the cell cycle regulators and DNA damage checkpoint proteins following DNA damage. The impact of p21Cip1 and SUMO-1 on the accumulation of proteins in INoBs extends also to CRM1, a nuclear exportin that is also important for protein translocation from the cytoplasm to the nucleolus. Thus, SUMO and p21Cip1 regulate the transit of proteins through the nucleolus, and that disruption of nucleolar export by DNA damage induces SUMO and p21Cip1 to act as hub proteins to form a multiprotein complex in the nucleolus.
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Affiliation(s)
- Sonia Brun
- Departament Biomedicina, Universitat de Barcelona, IDIBAPS, Barcelona, Spain
| | - Neus Abella
- Departament Biomedicina, Universitat de Barcelona, IDIBAPS, Barcelona, Spain
| | - Maria T. Berciano
- Departamento de Anatomía y Biología Celular, Universidad de Cantabria-IDIVAL, Santander, Spain
| | - Olga Tapia
- Departamento de Anatomía y Biología Celular, Universidad de Cantabria-IDIVAL, Santander, Spain
| | - Montserrat Jaumot
- Departament Biomedicina, Universitat de Barcelona, IDIBAPS, Barcelona, Spain
| | - Raimundo Freire
- Unidad de Investigación, Hospital Universitario de Canarias, Instituto de Tecnologías Biomédicas, Tenerife, Spain
| | - Miguel Lafarga
- Departamento de Anatomía y Biología Celular, Universidad de Cantabria-IDIVAL, Santander, Spain
| | - Neus Agell
- Departament Biomedicina, Universitat de Barcelona, IDIBAPS, Barcelona, Spain
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74
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Derenzini M, Montanaro L, Trerè D. Ribosome biogenesis and cancer. Acta Histochem 2017; 119:190-197. [PMID: 28168996 DOI: 10.1016/j.acthis.2017.01.009] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 01/27/2017] [Indexed: 12/21/2022]
Abstract
There is growing evidence indicating that the human pathological conditions characterized by an up-regulated ribosome biogenesis are at an increased risk of cancer onset. At the basis of this relationship is the close interconnection between the ribosome biogenesis and cell proliferation. Cell proliferation-stimulating factors also stimulate ribosome production, while the ribosome biogenesis rate controls the cell cycle progression. The major tumour suppressor, the p53 protein, plays an important balancing role between the ribosome biogenesis rate and the cell progression through the cell cycle phases. The perturbation of ribosome biogenesis stabilizes and activates p53, with a consequent cell cycle arrest and/or apoptotic cell death, whereas an up-regulated ribosome production down-regulates p53 expression and activity, thus facilitating neoplastic transformation. In the present review we describe the interconnection between ribosome biogenesis and cell proliferation, while highlighting the mechanisms by which quantitative changes in ribosome biogenesis may induce cancer.
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Affiliation(s)
- Massimo Derenzini
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna 40138, Italy.
| | - Lorenzo Montanaro
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna 40138, Italy.
| | - Davide Trerè
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna 40138, Italy.
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75
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Ye Q, Pang S, Zhang W, Guo X, Wang J, Zhang Y, Liu Y, Wu X, Jiang F. Therapeutic Targeting of RNA Polymerase I With the Small-Molecule CX-5461 for Prevention of Arterial Injury-Induced Neointimal Hyperplasia. Arterioscler Thromb Vasc Biol 2017; 37:476-484. [PMID: 28062495 DOI: 10.1161/atvbaha.116.308401] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 12/21/2016] [Indexed: 01/09/2023]
Abstract
OBJECTIVE RNA polymerase I (Pol I)-dependent rRNA synthesis is a determinant factor in ribosome biogenesis and thus cell proliferation. The importance of dysregulated Pol I activity in cardiovascular disease, however, has not been recognized. Here, we tested the hypothesis that specific inhibition of Pol I might prevent arterial injury-induced neointimal hyperplasia. APPROACH AND RESULTS CX-5461 is a novel selective Pol I inhibitor. Using this tool, we demonstrated that local inhibition of Pol I blocked balloon injury-induced neointima formation in rat carotid arteries in vivo. Neointimal development was associated with augmented rDNA transcriptional activity as evidenced by the increased phosphorylation of upstream binding factor-1. The beneficial effect of CX-5461 was mainly mediated by inducing G2/M cell cycle arrest of proliferating smooth muscle cells without obvious apoptosis. CX-5461 did not induce p53 stabilization but increased p53 phosphorylation and acetylation and activated the ataxia telangiectasia mutated/ataxia telangiectasia and Rad3-related (ATR) pathway. Inhibition of ATR, but not of ataxia telangiectasia mutated, abolished the cytostatic effect of CX-5461 and p53 phosphorylation. In addition, inhibition of p53 or knockdown of the p53 target GADD45 mimicked the effect of ATR inhibition. In vivo experiments showed that the levels of phospho-p53 and acetyl-p53, and activity of the ataxia telangiectasia mutated/ATR pathway were all augmented in CX-5461-treated vessels. CONCLUSIONS Pol I can be therapeutically targeted to inhibit the growth of neointima, supporting that Pol I is a novel biological target for preventing arterial restenosis. Mechanistically, Pol I inhibition elicited G2/M cell cycle arrest in smooth muscle cells via activation of the ATR-p53 axis.
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Affiliation(s)
- Qing Ye
- From the School of Basic Medicine, Shandong University, Jinan, Shandong Province, China (Q.Y., S.P., W.Z., X.G., J.W., Y.L., F.J.); Key Laboratory of Cardiovascular Remodeling and Function Research & The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China (X.W.); and Department of Cardiology, Qing Dao Central Hospital, Qing Dao, Shandong Province, China (Y.Z.)
| | - Shu Pang
- From the School of Basic Medicine, Shandong University, Jinan, Shandong Province, China (Q.Y., S.P., W.Z., X.G., J.W., Y.L., F.J.); Key Laboratory of Cardiovascular Remodeling and Function Research & The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China (X.W.); and Department of Cardiology, Qing Dao Central Hospital, Qing Dao, Shandong Province, China (Y.Z.)
| | - Wenjing Zhang
- From the School of Basic Medicine, Shandong University, Jinan, Shandong Province, China (Q.Y., S.P., W.Z., X.G., J.W., Y.L., F.J.); Key Laboratory of Cardiovascular Remodeling and Function Research & The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China (X.W.); and Department of Cardiology, Qing Dao Central Hospital, Qing Dao, Shandong Province, China (Y.Z.)
| | - Xiaotong Guo
- From the School of Basic Medicine, Shandong University, Jinan, Shandong Province, China (Q.Y., S.P., W.Z., X.G., J.W., Y.L., F.J.); Key Laboratory of Cardiovascular Remodeling and Function Research & The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China (X.W.); and Department of Cardiology, Qing Dao Central Hospital, Qing Dao, Shandong Province, China (Y.Z.)
| | - Jianli Wang
- From the School of Basic Medicine, Shandong University, Jinan, Shandong Province, China (Q.Y., S.P., W.Z., X.G., J.W., Y.L., F.J.); Key Laboratory of Cardiovascular Remodeling and Function Research & The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China (X.W.); and Department of Cardiology, Qing Dao Central Hospital, Qing Dao, Shandong Province, China (Y.Z.)
| | - Yongtao Zhang
- From the School of Basic Medicine, Shandong University, Jinan, Shandong Province, China (Q.Y., S.P., W.Z., X.G., J.W., Y.L., F.J.); Key Laboratory of Cardiovascular Remodeling and Function Research & The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China (X.W.); and Department of Cardiology, Qing Dao Central Hospital, Qing Dao, Shandong Province, China (Y.Z.)
| | - Yang Liu
- From the School of Basic Medicine, Shandong University, Jinan, Shandong Province, China (Q.Y., S.P., W.Z., X.G., J.W., Y.L., F.J.); Key Laboratory of Cardiovascular Remodeling and Function Research & The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China (X.W.); and Department of Cardiology, Qing Dao Central Hospital, Qing Dao, Shandong Province, China (Y.Z.)
| | - Xiao Wu
- From the School of Basic Medicine, Shandong University, Jinan, Shandong Province, China (Q.Y., S.P., W.Z., X.G., J.W., Y.L., F.J.); Key Laboratory of Cardiovascular Remodeling and Function Research & The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China (X.W.); and Department of Cardiology, Qing Dao Central Hospital, Qing Dao, Shandong Province, China (Y.Z.)
| | - Fan Jiang
- From the School of Basic Medicine, Shandong University, Jinan, Shandong Province, China (Q.Y., S.P., W.Z., X.G., J.W., Y.L., F.J.); Key Laboratory of Cardiovascular Remodeling and Function Research & The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China (X.W.); and Department of Cardiology, Qing Dao Central Hospital, Qing Dao, Shandong Province, China (Y.Z.).
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76
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Cell cycle and growth stimuli regulate different steps of RNA polymerase I transcription. Gene 2016; 612:36-48. [PMID: 27989772 DOI: 10.1016/j.gene.2016.12.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 12/09/2016] [Accepted: 12/14/2016] [Indexed: 12/20/2022]
Abstract
Transcription of the ribosomal RNA genes (rDNA) by RNA polymerase I (Pol I) is a major control step for ribosome synthesis and is tightly linked to cellular growth. However, the question of whether this process is modulated primarily at the level of transcription initiation or elongation is controversial. Studies in markedly different cell types have identified either initiation or elongation as the major control point. In this study, we have re-examined this question in NIH3T3 fibroblasts using a combination of metabolic labeling of the 47S rRNA, chromatin immunoprecipitation analysis of Pol I and overexpression of the transcription initiation factor Rrn3. Acute manipulation of growth factor levels altered rRNA synthesis rates over 8-fold without changing Pol I loading onto the rDNA. In fact, robust changes in Pol I loading were only observed under conditions where inhibition of rDNA transcription was associated with chronic serum starvation or cell cycle arrest. Overexpression of the transcription initiation factor Rrn3 increased loading of Pol I on the rDNA but failed to enhance rRNA synthesis in either serum starved, serum treated or G0/G1 arrested cells. Together these data suggest that transcription elongation is rate limiting for rRNA synthesis. We propose that transcription initiation is required for rDNA transcription in response to cell cycle cues, whereas elongation controls the dynamic range of rRNA synthesis output in response to acute growth factor modulation.
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77
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Brighenti E, Treré D, Derenzini M. Targeted cancer therapy with ribosome biogenesis inhibitors: a real possibility? Oncotarget 2016; 6:38617-27. [PMID: 26415219 PMCID: PMC4770724 DOI: 10.18632/oncotarget.5775] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 09/04/2015] [Indexed: 12/13/2022] Open
Abstract
The effects of many chemotherapeutic drugs on ribosome biogenesis have been underestimated for a long time. Indeed, many drugs currently used for cancer treatment--and which are known to either damage DNA or hinder DNA synthesis--have been shown to exert their toxic action mainly by inhibiting rRNA synthesis or maturation. Moreover, there are new drugs that have been proposed recently for cancer chemotherapy, which only hinder ribosome biogenesis without any genotoxic activity. Even though ribosome biogenesis occurs in both normal and cancer cells, whether resting or proliferating, there is evidence that the selective inhibition of ribosome biogenesis may, in some instances, result in a selective damage to neoplastic cells. The higher sensitivity of cancer cells to inhibitors of rRNA synthesis appears to be the consequence of either the loss of the mechanisms controlling the cell cycle progression or the acquisition of activating oncogene and inactivating tumor suppressor gene mutations that up-regulate the ribosome biogenesis rate. This article reviews those cancer cell characteristics on which the selective cancer cell cytotoxicity induced by the inhibitors of ribosome biogenesis is based.
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Affiliation(s)
- Elisa Brighenti
- Department of Experimental, Diagnostic and Specialty Medicine, Bologna University, Bologna, Italy
| | - Davide Treré
- Department of Experimental, Diagnostic and Specialty Medicine, Bologna University, Bologna, Italy
| | - Massimo Derenzini
- Department of Experimental, Diagnostic and Specialty Medicine, Bologna University, Bologna, Italy
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78
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Birch J, Clarke CJ, Campbell AD, Campbell K, Mitchell L, Liko D, Kalna G, Strathdee D, Sansom OJ, Neilson M, Blyth K, Norman JC. The initiator methionine tRNA drives cell migration and invasion leading to increased metastatic potential in melanoma. Biol Open 2016; 5:1371-1379. [PMID: 27543055 PMCID: PMC5087684 DOI: 10.1242/bio.019075] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 08/12/2016] [Indexed: 12/19/2022] Open
Abstract
The cell's repertoire of transfer RNAs (tRNAs) has been linked to cancer. Recently, the level of the initiator methionine tRNA (tRNAiMet) in stromal fibroblasts has been shown to influence extracellular matrix (ECM) secretion to drive tumour growth and angiogenesis. Here we show that increased tRNAiMet within cancer cells does not influence tumour growth, but drives cell migration and invasion via a mechanism that is independent from ECM synthesis and dependent on α5β1 integrin and levels of the translation initiation ternary complex. In vivo and ex vivo migration (but not proliferation) of melanoblasts is significantly enhanced in transgenic mice which express additional copies of the tRNAiMet gene. We show that increased tRNAiMet in melanoma drives migratory, invasive behaviour and metastatic potential without affecting cell proliferation and primary tumour growth, and that expression of RNA polymerase III-associated genes (which drive tRNA expression) are elevated in metastases by comparison with primary tumours. Thus, specific alterations to the cancer cell tRNA repertoire drive a migration/invasion programme that may lead to metastasis.
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Affiliation(s)
- Joanna Birch
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Cassie J Clarke
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Andrew D Campbell
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Kirsteen Campbell
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Louise Mitchell
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Dritan Liko
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Gabriela Kalna
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Douglas Strathdee
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Owen J Sansom
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Matthew Neilson
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Karen Blyth
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
| | - Jim C Norman
- Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, Scotland
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79
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Kotsantis P, Silva LM, Irmscher S, Jones RM, Folkes L, Gromak N, Petermann E. Increased global transcription activity as a mechanism of replication stress in cancer. Nat Commun 2016; 7:13087. [PMID: 27725641 PMCID: PMC5062618 DOI: 10.1038/ncomms13087] [Citation(s) in RCA: 201] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 08/31/2016] [Indexed: 12/28/2022] Open
Abstract
Cancer is a disease associated with genomic instability that often results from oncogene activation. This in turn leads to hyperproliferation and replication stress. However, the molecular mechanisms that underlie oncogene-induced replication stress are still poorly understood. Oncogenes such as HRASV12 promote proliferation by upregulating general transcription factors to stimulate RNA synthesis. Here we investigate whether this increase in transcription underlies oncogene-induced replication stress. We show that in cells overexpressing HRASV12, elevated expression of the general transcription factor TATA-box binding protein (TBP) leads to increased RNA synthesis, which together with R-loop accumulation results in replication fork slowing and DNA damage. Furthermore, overexpression of TBP alone causes the hallmarks of oncogene-induced replication stress, including replication fork slowing, DNA damage and senescence. Consequently, we reveal that increased transcription can be a mechanism of oncogene-induced DNA damage, providing a molecular link between upregulation of the transcription machinery and genomic instability in cancer. Cancer cells proliferate at high rates and incur replication stress. Here, the authors show that this can be the consequence of oncogene-induced higher transcriptional activity, which, through increased RNA synthesis and R-loop accumulation, results in replication fork slowing and DNA damage.
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Affiliation(s)
- Panagiotis Kotsantis
- Institute of Cancer and Genomic Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Lara Marques Silva
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Sarah Irmscher
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Rebecca M Jones
- Institute of Cancer and Genomic Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Lisa Folkes
- Department of Oncology, CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Natalia Gromak
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Eva Petermann
- Institute of Cancer and Genomic Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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80
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Overexpression of Ribosomal RNA in the Development of Human Cervical Cancer Is Associated with rDNA Promoter Hypomethylation. PLoS One 2016; 11:e0163340. [PMID: 27695092 PMCID: PMC5047480 DOI: 10.1371/journal.pone.0163340] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 09/07/2016] [Indexed: 12/30/2022] Open
Abstract
The ribosomal RNA (rRNA) gene encodes rRNA for protein synthesis. Aberrant expression of the rRNA gene has been generally observed in tumor cells and levels of its promoter methylation as an epigenetic regulator affect rRNA gene transcription. The possible relationship between expression and promoter methylation of rDNA has not been examined in human clinical cervical cancer. Here we investigate rRNA gene expression by quantitative real time PCR, and promoter methylation levels by HpaII/MspI digestion and sodium bisulfite sequencing in the development of human cervical cancer. We find that indeed rRNA levels are elevated in most of cervical intraepithelial neoplasia (CIN) specimens as compared with non-cancer tissues. The rDNA promoter region in cervical intraepithelial neoplasia (CIN) tissues reveals significant hypomethylation at cytosines in the context of CpG dinucleotides, accompanied with rDNA chromatin decondensation. Furthermore treatment of HeLa cells with the methylation inhibitor drug 5-aza-2’-deoxycytidine (DAC) demonstrates the negative correlation between the expression of 45S rDNA and the methylation level in the rDNA promoter region. These data suggest that a decrease in rDNA promoter methylation levels can result in an increase of rRNA synthesis in the development of human cervical cancer.
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81
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Johnson DL, Stiles BL. Maf1, A New PTEN Target Linking RNA and Lipid Metabolism. Trends Endocrinol Metab 2016; 27:742-750. [PMID: 27296319 PMCID: PMC5035567 DOI: 10.1016/j.tem.2016.04.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 04/22/2016] [Accepted: 04/29/2016] [Indexed: 01/07/2023]
Abstract
PTEN is a critical tumor suppressor whose dysregulation leads to metabolic disease and cancer. How these diseases are linked at a molecular level is poorly understood. Maf1 is a novel PTEN target that connects PTEN's ability to repress intracellular lipid accumulation with its tumor suppressor function. Maf1 represses the expression of rRNAs and tRNAs to restrain biosynthetic capacity and oncogenic transformation. Recent studies demonstrate that Maf1 also controls intracellular lipid accumulation. In animal models, dysregulation of RNA polymerase I- and III-dependent transcription, and subsequent upregulation of rRNAs and tRNAs, leads to altered lipid metabolism and storage. Together these results identify unexpected connections between RNA and lipid metabolism that may help explain the strong epidemiological association between obesity and cancer.
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82
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Li L, Li Y, Zhao J, Fan S, Wang L, Li X. CX-5461 induces autophagy and inhibits tumor growth via mammalian target of rapamycin-related signaling pathways in osteosarcoma. Onco Targets Ther 2016; 9:5985-5997. [PMID: 27729807 PMCID: PMC5047727 DOI: 10.2147/ott.s104513] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Osteosarcoma (OS) is the most common primary bone tumor, but molecular mechanisms of the disease have not been well understood, and treatment of metastatic OS remains a challenge. Rapid ribosomal RNA synthesis in cancer is transcribed by RNA polymerase I, which results in unbridled cell growth. The recent discovery of CX-5461, a selective RNA polymerase I inhibitor, exerted its inhibitory effect of ribosomal RNA synthesis and antiproliferative potency. Here, we demonstrate that CX-5461 induces G2 arrest in the cell cycle and expression of microtubule-associated protein 1 light chain 3 II isoform in OS cell lines. Autophagic vacuoles could be observed in electron microscopy and 3-methyladenine prevented cell death mediated by CX-5461. Moreover, it significantly augmented phosphorylated AMP-Activated Protein Kinases α (p-AMPK α). (Thr172) expression in U2-OS cells and decreased p-Akt (Ser473) expression in MNNG cells, respectively, which repressed their downstream effector, mammalian target of rapamycin. On the other hand, CX-5461 increased p53 accumulation and messenger RNA level of its target genes, p21, MDM2, and Sestrin1/2 in U2-OS cells. Knockdown of p53 expression markedly impaired cell death as well as the expression of light chain 3-II and p21 induced by CX-5461. It also significantly enhanced doxorubicin-mediated cytotoxic effect in vitro and in vivo together with additive expression of p53, p21, and light chain 3-II in U2-OS cells. Our data indicate that CX-5461 might induce autophagy via mammalian target of rapamycin-associated signaling pathways dependent on p53 status and exert p53-dependent synergistic antitumor effect combined with doxorubicin in OS. These results suggest that CX-5461 might be promising in clinical therapy for OS, especially cases harboring wild-type p53.
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Affiliation(s)
- Leiming Li
- Department of Joint Surgery and Sports Medicine, The First Affiliated Hospital
| | - Yan Li
- Department of Spine and Joint Surgery, Sheng Jing Hospital
| | - Jiansong Zhao
- Department of Spine and Joint Surgery, Sheng Jing Hospital
| | - Shuli Fan
- Department of Geriatrics, The First Affiliated Hospital, China Medical University, Shenyang, People's Republic of China
| | - Liguo Wang
- Department of Joint Surgery and Sports Medicine, The First Affiliated Hospital
| | - Xu Li
- Department of Joint Surgery and Sports Medicine, The First Affiliated Hospital
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83
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Figueiredo VC, Roberts LA, Markworth JF, Barnett MPG, Coombes JS, Raastad T, Peake JM, Cameron-Smith D. Impact of resistance exercise on ribosome biogenesis is acutely regulated by post-exercise recovery strategies. Physiol Rep 2016; 4:4/2/e12670. [PMID: 26818586 PMCID: PMC4760384 DOI: 10.14814/phy2.12670] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Muscle hypertrophy occurs following increased protein synthesis, which requires activation of the ribosomal complex. Additionally, increased translational capacity via elevated ribosomal RNA (rRNA) synthesis has also been implicated in resistance training-induced skeletal muscle hypertrophy. The time course of ribosome biogenesis following resistance exercise (RE) and the impact exerted by differing recovery strategies remains unknown. In the present study, the activation of transcriptional regulators, the expression levels of pre-rRNA, and mature rRNA components were measured through 48 h after a single-bout RE. In addition, the effects of either low-intensity cycling (active recovery, ACT) or a cold-water immersion (CWI) recovery strategy were compared. Nine male subjects performed two bouts of high-load RE randomized to be followed by 10 min of either ACT or CWI. Muscle biopsies were collected before RE and at 2, 24, and 48 h after RE. RE increased the phosphorylation of the p38-MNK1-eIF4E axis, an effect only evident with ACT recovery. Downstream, cyclin D1 protein, total eIF4E, upstream binding factor 1 (UBF1), and c-Myc proteins were all increased only after RE with ACT. This corresponded with elevated abundance of the pre-rRNAs (45S, ITS-28S, ITS-5.8S, and ETS-18S) from 24 h after RE with ACT. In conclusion, coordinated upstream signaling and activation of transcriptional factors stimulated pre-rRNA expression after RE. CWI, as a recovery strategy, markedly blunted these events, suggesting that suppressed ribosome biogenesis may be one factor contributing to the impaired hypertrophic response observed when CWI is used regularly after exercise.
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Affiliation(s)
| | - Llion A Roberts
- School of Human Movement and Nutrition Sciences The University of Queensland, Brisbane, Australia Centre of Excellence for Applied Sport Science Research, Queensland Academy of Sport, Brisbane, Australia
| | - James F Markworth
- The Liggins Institute, The University of Auckland, Auckland, New Zealand
| | - Matthew P G Barnett
- AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | - Jeff S Coombes
- School of Human Movement and Nutrition Sciences The University of Queensland, Brisbane, Australia
| | | | - Jonathan M Peake
- Centre of Excellence for Applied Sport Science Research, Queensland Academy of Sport, Brisbane, Australia School of Biomedical Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia
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84
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Transient rRNA synthesis inhibition with CX-5461 is sufficient to elicit growth arrest and cell death in acute lymphoblastic leukemia cells. Oncotarget 2016; 6:34846-58. [PMID: 26472108 PMCID: PMC4741494 DOI: 10.18632/oncotarget.5413] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 09/30/2015] [Indexed: 11/25/2022] Open
Abstract
Enhanced rRNA synthesis is a downstream effect of many of the signaling pathways that are aberrantly activated in cancer, such as the PI3K/mTOR and MAP kinase pathways. Recently, two new rRNA synthesis inhibitors have demonstrated therapeutic effects on cancer cells while sparing normal cells. One of them, CX-5461, is currently in phase 1 clinical trials for hematological malignancies. Here, we investigate the effectiveness of transient treatment with this drug on acute lymphoblastic leukemia cells. Our results show that short exposure to CX-5461 followed by drug washout is sufficient to induce persistent G2 cell-cycle arrest and irreversible commitment to cell death, in spite of rRNA synthesis returning to normal within 24 hours of drug washout. The magnitude of cell death after transient exposure is similar to continuous exposure, but the time to cell death is relatively delayed with transient exposure. In this report, we also investigate rational drug combinations that can potentiate the effect of continuous CX-5461 treatment. We show that the checkpoint abrogator UCN-01 can relieve CX-5461-induced G2 arrest and potentiate the cytotoxic effects of CX-5461. Finally, we show that ERK1/2 is activated upon CX-5461 treatment, and that pharmacological inhibition of MEK1/2 leads to enhanced cell death in combination with CX-5461. In summary, our results provide evidence for the effectiveness of CX-5461 pulse treatment, which may minimize drug related toxicity, and evidence for enhanced effectiveness of CX-5461 in combination with other targeted agents.
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85
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Regulation of energy homeostasis by the ubiquitin-independent REGγ proteasome. Nat Commun 2016; 7:12497. [PMID: 27511885 PMCID: PMC4987533 DOI: 10.1038/ncomms12497] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 07/07/2016] [Indexed: 12/30/2022] Open
Abstract
Maintenance of energy homeostasis is essential for cell survival. Here, we report that the ATP- and ubiquitin-independent REGγ-proteasome system plays a role in maintaining energy homeostasis and cell survival during energy starvation via repressing rDNA transcription, a major intracellular energy-consuming process. Mechanistically, REGγ-proteasome limits cellular rDNA transcription and energy consumption by targeting the rDNA transcription activator SirT7 for ubiquitin-independent degradation under normal conditions. Moreover, energy starvation induces an AMPK-directed SirT7 phosphorylation and subsequent REGγ-dependent SirT7 subcellular redistribution and degradation, thereby further reducing rDNA transcription to save energy to overcome cell death. Energy starvation is a promising strategy for cancer therapy. Our report also shows that REGγ knockdown markedly improves the anti-tumour activity of energy metabolism inhibitors in mice. Our results underscore a control mechanism for an ubiquitin-independent process in maintaining energy homeostasis and cell viability under starvation conditions, suggesting that REGγ-proteasome inhibition has a potential to provide tumour-starving benefits. In conditions of energy stress cells reduce transcription of ribosomal RNA (rRNA) to maintain cell survival. Here, the authors show that energy stress induces an AMPK-dependent phosphorylation of Sirt7, which promotes its ubiquitin-independent degradation by REGγ, resulting in the down-regulation of rRNA transcription and cell survival.
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86
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Dass RA, Sarshad AA, Carson BB, Feenstra JM, Kaur A, Obrdlik A, Parks MM, Prakash V, Love DK, Pietras K, Serra R, Blanchard SC, Percipalle P, Brown AMC, Vincent CT. Wnt5a Signals through DVL1 to Repress Ribosomal DNA Transcription by RNA Polymerase I. PLoS Genet 2016; 12:e1006217. [PMID: 27500936 PMCID: PMC4976976 DOI: 10.1371/journal.pgen.1006217] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 07/05/2016] [Indexed: 11/19/2022] Open
Abstract
Ribosome biogenesis is essential for cell growth and proliferation and is commonly elevated in cancer. Accordingly, numerous oncogene and tumor suppressor signaling pathways target rRNA synthesis. In breast cancer, non-canonical Wnt signaling by Wnt5a has been reported to antagonize tumor growth. Here, we show that Wnt5a rapidly represses rDNA gene transcription in breast cancer cells and generates a chromatin state with reduced transcription of rDNA by RNA polymerase I (Pol I). These effects were specifically dependent on Dishevelled1 (DVL1), which accumulates in nucleolar organizer regions (NORs) and binds to rDNA regions of the chromosome. Upon DVL1 binding, the Pol I transcription activator and deacetylase Sirtuin 7 (SIRT7) releases from rDNA loci, concomitant with disassembly of Pol I transcription machinery at the rDNA promoter. These findings reveal that Wnt5a signals through DVL1 to suppress rRNA transcription. This provides a novel mechanism for how Wnt5a exerts tumor suppressive effects and why disruption of Wnt5a signaling enhances mammary tumor growth in vivo.
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Affiliation(s)
- Randall A. Dass
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, New York, United States of America
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
| | - Aishe A. Sarshad
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
- Biology Program, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Brittany B. Carson
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
| | - Jennifer M. Feenstra
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
| | - Amanpreet Kaur
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, New York, United States of America
| | - Ales Obrdlik
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
- Biology Program, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Matthew M. Parks
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
| | - Varsha Prakash
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
| | - Damon K. Love
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, New York, United States of America
| | - Kristian Pietras
- Department of Laboratory Medicine, Center for Molecular Pathology, Lund University, Lund, Sweden
| | - Rosa Serra
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Scott C. Blanchard
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
- Tri-Institutional PhD program in Chemical Biology, Weill Cornell Medical College, New York, New York, United States of America
| | - Piergiorgio Percipalle
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
- Biology Program, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
- * E-mail: (PP); (AMCB); (CTV)
| | - Anthony M. C. Brown
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail: (PP); (AMCB); (CTV)
| | - C. Theresa Vincent
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, New York, United States of America
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
- * E-mail: (PP); (AMCB); (CTV)
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87
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Li Y, Tsang CK, Wang S, Li X, Yang Y, Fu L, Huang W, Li M, Wang H, Zheng XS. MAF1 suppresses AKT-mTOR signaling and liver cancer through activation of PTEN transcription. Hepatology 2016; 63:1928-42. [PMID: 26910647 PMCID: PMC5021206 DOI: 10.1002/hep.28507] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 02/17/2016] [Indexed: 12/12/2022]
Abstract
UNLABELLED The phosphatidylinositol 3-kinase/phosphatidylinositol 3,4,5-trisphosphate 3-phosphatase/protein kinase B/mammalian target of rapamycin (PI3K-PTEN-AKT-mTOR) pathway is a central controller of cell growth and a key driver for human cancer. MAF1 is an mTOR downstream effector and transcriptional repressor of ribosomal and transfer RNA genes. MAF1 expression is markedly reduced in hepatocellular carcinomas, which is correlated with disease progression and poor prognosis. Consistently, MAF1 displays tumor-suppressor activity toward in vitro and in vivo cancer models. Surprisingly, blocking the synthesis of ribosomal and transfer RNAs is insufficient to account for MAF1's tumor-suppressor function. Instead, MAF1 down-regulation paradoxically leads to activation of AKT-mTOR signaling, which is mediated by decreased PTEN expression. MAF1 binds to the PTEN promoter, enhancing PTEN promoter acetylation and activity. CONCLUSION In contrast to its canonical function as a transcriptional repressor, MAF1 can also act as a transcriptional activator for PTEN, which is important for MAF1's tumor-suppressor function. These results have implications in disease staging, prognostic prediction, and AKT-mTOR-targeted therapy in liver cancer. (Hepatology 2016;63:1928-1942).
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Affiliation(s)
- Yue Li
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer MedicineSun Yat‐sen University Cancer CenterGuangzhouChina
| | - Chi Kwan Tsang
- Rutgers Cancer Institute of New Jersey and Department of Pharmacology, Robert Wood Johnson Medical School, Rutgersthe State University of New JerseyNew BrunswickNJ
| | - Suihai Wang
- State Key Laboratory of Organ Failure Research, Institute of Antibody Engineering, School of BiotechnologySouthern Medical UniversityGuangzhouChina
| | - Xiao‐Xing Li
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer MedicineSun Yat‐sen University Cancer CenterGuangzhouChina
| | - Yang Yang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer MedicineSun Yat‐sen University Cancer CenterGuangzhouChina
| | - Liwu Fu
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer MedicineSun Yat‐sen University Cancer CenterGuangzhouChina
| | - Wenlin Huang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer MedicineSun Yat‐sen University Cancer CenterGuangzhouChina
| | - Ming Li
- State Key Laboratory of Organ Failure Research, Institute of Antibody Engineering, School of BiotechnologySouthern Medical UniversityGuangzhouChina
| | - Hui‐Yun Wang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer MedicineSun Yat‐sen University Cancer CenterGuangzhouChina,Rutgers Cancer Institute of New Jersey and Department of Pharmacology, Robert Wood Johnson Medical School, Rutgersthe State University of New JerseyNew BrunswickNJ
| | - X.F. Steven Zheng
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer MedicineSun Yat‐sen University Cancer CenterGuangzhouChina,Rutgers Cancer Institute of New Jersey and Department of Pharmacology, Robert Wood Johnson Medical School, Rutgersthe State University of New JerseyNew BrunswickNJ
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88
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Reuter LM, Sträßer K. Falling for the dark side of transcription: Nab2 fosters RNA polymerase III transcription. Transcription 2016; 7:69-74. [PMID: 27049816 PMCID: PMC4984684 DOI: 10.1080/21541264.2016.1170252] [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] [Indexed: 11/16/2022] Open
Abstract
RNA polymerase III (RNAPIII) synthesizes diverse, small, non-coding RNAs with many important roles in the cellular metabolism. One of the open questions of RNAPIII transcription is whether and how additional factors are involved. Recently, Nab2 was identified as the first messenger ribonucleoprotein particle (mRNP) biogenesis factor with a function in RNAPIII transcription.
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Affiliation(s)
- L Maximilian Reuter
- a Institute of Biochemistry, Justus Liebig University Giessen , Giessen , Germany
| | - Katja Sträßer
- a Institute of Biochemistry, Justus Liebig University Giessen , Giessen , Germany
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89
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Stępiński D. Nucleolus-derived mediators in oncogenic stress response and activation of p53-dependent pathways. Histochem Cell Biol 2016; 146:119-39. [PMID: 27142852 DOI: 10.1007/s00418-016-1443-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/25/2016] [Indexed: 12/12/2022]
Abstract
Rapid growth and division of cells, including tumor ones, is correlated with intensive protein biosynthesis. The output of nucleoli, organelles where translational machineries are formed, depends on a rate of particular stages of ribosome production and on accessibility of elements crucial for their effective functioning, including substrates, enzymes as well as energy resources. Different factors that induce cellular stress also often lead to nucleolar dysfunction which results in ribosome biogenesis impairment. Such nucleolar disorders, called nucleolar or ribosomal stress, usually affect cellular functioning which in fact is a result of p53-dependent pathway activation, elicited as a response to stress. These pathways direct cells to new destinations such as cell cycle arrest, damage repair, differentiation, autophagy, programmed cell death or aging. In the case of impaired nucleolar functioning, nucleolar and ribosomal proteins mediate activation of the p53 pathways. They are also triggered as a response to oncogenic factor overexpression to protect tissues and organs against extensive proliferation of abnormal cells. Intentional impairment of any step of ribosome biosynthesis which would direct the cells to these destinations could be a strategy used in anticancer therapy. This review presents current knowledge on a nucleolus, mainly in relation to cancer biology, which is an important and extremely sensitive element of the mechanism participating in cellular stress reaction mediating activation of the p53 pathways in order to counteract stress effects, especially cancer development.
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Affiliation(s)
- Dariusz Stępiński
- Department of Cytophysiology, Faculty of Biology and Environmental Protection, University of Łódź, Pomorska 141/143, 90-236, Łódź, Poland.
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90
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Hoffmann NA, Jakobi AJ, Vorländer MK, Sachse C, Müller CW. Transcribing RNA polymerase III observed by electron cryomicroscopy. FEBS J 2016; 283:2811-9. [PMID: 27059519 PMCID: PMC5053293 DOI: 10.1111/febs.13732] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 03/26/2016] [Accepted: 04/04/2016] [Indexed: 12/21/2022]
Abstract
Electron cryomicroscopy reconstructions of elongating RNA polymerase (Pol) III at 3.9 Å resolution and of unbound Pol III (apo Pol III) in two distinct conformations at 4.6 Å and 4.7 Å resolution allow the construction of complete atomic models of Pol III and provide new functional insights into the adaption of Pol III to fulfill its specific transcription tasks.
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Affiliation(s)
- Niklas A Hoffmann
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, Germany
| | - Arjen J Jakobi
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, Germany
| | - Matthias K Vorländer
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, Germany
| | - Carsten Sachse
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, Germany
| | - Christoph W Müller
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, Germany
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91
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RNA Polymerase III Advances: Structural and tRNA Functional Views. Trends Biochem Sci 2016; 41:546-559. [PMID: 27068803 DOI: 10.1016/j.tibs.2016.03.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 03/03/2016] [Accepted: 03/09/2016] [Indexed: 12/25/2022]
Abstract
RNA synthesis in eukaryotes is divided among three RNA polymerases (RNAPs). RNAP III transcribes hundreds of tRNA genes and fewer additional short RNA genes. We survey recent work on transcription by RNAP III including an atomic structure, mechanisms of action, interactions with chromatin and retroposons, and a conserved link between its activity and a tRNA modification that enhances mRNA decoding. Other new work suggests important mechanistic connections to oxidative stress, autoimmunity and cancer, embryonic stem cell pluripotency, and tissue-specific developmental effects. We consider that, for some of its complex functions, variation in RNAP III activity levels lead to nonuniform changes in tRNAs that can shift the translation profiles of key codon-biased mRNAs with resultant phenotypes or disease states.
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92
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Liu C, Stonestrom AJ, Christian T, Yong J, Takase R, Hou YM, Yang X. Molecular Basis and Consequences of the Cytochrome c-tRNA Interaction. J Biol Chem 2016; 291:10426-36. [PMID: 26961879 DOI: 10.1074/jbc.m115.697789] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Indexed: 11/06/2022] Open
Abstract
The intrinsic apoptosis pathway occurs through the release of mitochondrial cytochrome c to the cytosol, where it promotes activation of the caspase family of proteases. The observation that tRNA binds to cytochrome c revealed a previously unexpected mode of apoptotic regulation. However, the molecular characteristics of this interaction, and its impact on each interaction partner, are not well understood. Using a novel fluorescence assay, we show here that cytochrome c binds to tRNA with an affinity comparable with other tRNA-protein binding interactions and with a molecular ratio of ∼3:1. Cytochrome c recognizes the tertiary structural features of tRNA, particularly in the core region. This binding is independent of the charging state of tRNA but is regulated by the redox state of cytochrome c. Compared with reduced cytochrome c, oxidized cytochrome c binds to tRNA with a weaker affinity, which correlates with its stronger pro-apoptotic activity. tRNA binding both facilitates cytochrome c reduction and inhibits the peroxidase activity of cytochrome c, which is involved in its release from mitochondria. Together, these findings provide new insights into the cytochrome c-tRNA interaction and apoptotic regulation.
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Affiliation(s)
- Cuiping Liu
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Aaron J Stonestrom
- the Department of Cancer Biology and Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and
| | - Thomas Christian
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Jeongsik Yong
- the Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455
| | - Ryuichi Takase
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Ya-Ming Hou
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107,
| | - Xiaolu Yang
- the Department of Cancer Biology and Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and
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93
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Pawlowska R, Janicka M, Jedrzejczyk D, Chworos A. RNA fragments mimicking tRNA analogs interact with cytochrome c. Mol Biol Rep 2016; 43:295-304. [DOI: 10.1007/s11033-016-3954-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 02/11/2016] [Indexed: 01/08/2023]
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94
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RNA Polymerase III Output Is Functionally Linked to tRNA Dimethyl-G26 Modification. PLoS Genet 2015; 11:e1005671. [PMID: 26720005 PMCID: PMC4697793 DOI: 10.1371/journal.pgen.1005671] [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: 08/27/2015] [Accepted: 10/26/2015] [Indexed: 11/19/2022] Open
Abstract
Control of the differential abundance or activity of tRNAs can be important determinants of gene regulation. RNA polymerase (RNAP) III synthesizes all tRNAs in eukaryotes and it derepression is associated with cancer. Maf1 is a conserved general repressor of RNAP III under the control of the target of rapamycin (TOR) that acts to integrate transcriptional output and protein synthetic demand toward metabolic economy. Studies in budding yeast have indicated that the global tRNA gene activation that occurs with derepression of RNAP III via maf1-deletion is accompanied by a paradoxical loss of tRNA-mediated nonsense suppressor activity, manifested as an antisuppression phenotype, by an unknown mechanism. We show that maf1-antisuppression also occurs in the fission yeast S. pombe amidst general activation of RNAP III. We used tRNA-HydroSeq to document that little changes occurred in the relative levels of different tRNAs in maf1Δ cells. By contrast, the efficiency of N2,N2-dimethyl G26 (m(2)2G26) modification on certain tRNAs was decreased in response to maf1-deletion and associated with antisuppression, and was validated by other methods. Over-expression of Trm1, which produces m(2)2G26, reversed maf1-antisuppression. A model that emerges is that competition by increased tRNA levels in maf1Δ cells leads to m(2)2G26 hypomodification due to limiting Trm1, reducing the activity of suppressor-tRNASerUCA and accounting for antisuppression. Consistent with this, we show that RNAP III mutations associated with hypomyelinating leukodystrophy decrease tRNA transcription, increase m(2)2G26 efficiency and reverse antisuppression. Extending this more broadly, we show that a decrease in tRNA synthesis by treatment with rapamycin leads to increased m(2)2G26 modification and that this response is conserved among highly divergent yeasts and human cells.
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95
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Ponti D, Bastianelli D, Rosa P, Pacini L, Ibrahim M, Rendina EA, Ragona G, Calogero A. The expression of B23 and EGR1 proteins is functionally linked in tumor cells under stress conditions. BMC Cell Biol 2015; 16:27. [PMID: 26577150 PMCID: PMC4650859 DOI: 10.1186/s12860-015-0073-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 11/12/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The nucleolus is a multi-domain enriched with proteins involved in ribosome biogenesis, cell cycle and apoptosis control, viral replication and differentiation of stem cells. Several authors have suggested a role for the nucleolus also in malignant transformation. We have recently demonstrated that under specific circumstances the transcriptional factor EGR1 is shuttled to the nucleolus where it functions as a negative regulator of RNA polymerase I. Since this activity is hampered in ARF -/- cells, and ARF transcription is regulated by EGR1 while the turnover of ARF protein is under the control of B23, we speculated that some sort of cooperation between EGR1 and B23 might also exist. RESULTS In this work we identified a canonical EGR1 binding site on the B23 promoter through experiments of transactivation and in vitro DNA binding assay. We then found that the levels of B23 expression are directly correlated with those of EGR1, and that this correlation applies to several cellular types and to different stress conditions. Furthermore, we showed that EGR1 stability and accumulation within the nucleolus is in turn regulated by B23 through proteasome involvement, similarly to ARF turnover. CONCLUSION Our results highlight EGR1 as a regulator of B23 expression actively playing within the newly discovered nucleolar B23-ARF-EGR1 network.
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Affiliation(s)
- Donatella Ponti
- Department of Medico-Surgical Sciences and Biotechnologies, University of Rome Sapienza, Corso della Repubblica 79, 04100, Latina, Italy.
| | - Daniela Bastianelli
- Division of Thoracic Surgery, Department of Medical-Surgical Science and Translational Medicine, University Sapienza, S. Andrea Hospital, via di Grottarossa 1035, 00189, Rome, Italy.
| | - Paolo Rosa
- Department of Medico-Surgical Sciences and Biotechnologies, University of Rome Sapienza, Corso della Repubblica 79, 04100, Latina, Italy.
| | - Luca Pacini
- Department of Medico-Surgical Sciences and Biotechnologies, University of Rome Sapienza, Corso della Repubblica 79, 04100, Latina, Italy.
| | - Mohsen Ibrahim
- Division of Thoracic Surgery, Department of Medical-Surgical Science and Translational Medicine, University Sapienza, S. Andrea Hospital, via di Grottarossa 1035, 00189, Rome, Italy.
| | - Erino Angelo Rendina
- Division of Thoracic Surgery, Department of Medical-Surgical Science and Translational Medicine, University Sapienza, S. Andrea Hospital, via di Grottarossa 1035, 00189, Rome, Italy.
| | - Giuseppe Ragona
- Department of Medico-Surgical Sciences and Biotechnologies, University of Rome Sapienza, Corso della Repubblica 79, 04100, Latina, Italy.
| | - Antonella Calogero
- Department of Medico-Surgical Sciences and Biotechnologies, University of Rome Sapienza, Corso della Repubblica 79, 04100, Latina, Italy.
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96
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Arimbasseri AG, Rijal K, Maraia RJ. Comparative overview of RNA polymerase II and III transcription cycles, with focus on RNA polymerase III termination and reinitiation. Transcription 2015; 5:e27639. [PMID: 25764110 DOI: 10.4161/trns.27369] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In eukaryotes, RNA polymerase (RNAP) III transcribes hundreds of genes for tRNAs and 5S rRNA, among others, which share similar promoters and stable transcription initiation complexes (TIC), which support rapid RNAP III recycling. In contrast, RNAP II transcribes a large number of genes with highly variable promoters and interacting factors, which exert fine regulatory control over TIC lability and modifications of RNAP II at different transitional points in the transcription cycle. We review data that illustrate a relatively smooth continuity of RNAP III initiation-elongation-termination and reinitiation toward its function to produce high levels of tRNAs and other RNAs that support growth and development.
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Affiliation(s)
- Aneeshkumar G Arimbasseri
- a Intramural Research Program; Eunice Kennedy Shriver National Institute of Child Health and Human Development; National Institutes of Health; Bethesda, MD USA
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97
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Kardos GR, Robertson GP. Therapeutic interventions to disrupt the protein synthetic machinery in melanoma. Pigment Cell Melanoma Res 2015; 28:501-19. [PMID: 26139519 PMCID: PMC4716672 DOI: 10.1111/pcmr.12391] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 06/30/2015] [Indexed: 01/23/2023]
Abstract
Control of the protein synthetic machinery is deregulated in many cancers, including melanoma, to increase the protein production. Tumor suppressors and oncogenes play key roles in protein synthesis from the transcription of rRNA and ribosome biogenesis to mRNA translation initiation and protein synthesis. Major signaling pathways are altered in melanoma to modulate the protein synthetic machinery, thereby promoting tumor development. However, despite the importance of this process in melanoma development, involvement of the protein synthetic machinery in this cancer type is an underdeveloped area of study. Here, we review the coupling of melanoma development to deregulation of the protein synthetic machinery. We examine existing knowledge regarding RNA polymerase I inhibition and mRNA translation focusing on their inhibition for therapeutic applications in melanoma. Furthermore, the contribution of amino acid biosynthesis and involvement of ribosomal proteins are also reviewed as future therapeutic strategies to target deregulated protein production in melanoma.
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Affiliation(s)
- Gregory R. Kardos
- Department of Pharmacology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, USA, 17033
- The Melanoma and Skin Cancer Center, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, USA, 17033
- The Melanoma Therapeutics Program, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, USA, 17033
| | - Gavin P. Robertson
- Department of Pharmacology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, USA, 17033
- Department of Pathology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, USA, 17033
- Department of Dermatology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, USA, 17033
- Department of Surgery, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, USA, 17033
- The Melanoma and Skin Cancer Center, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, USA, 17033
- The Melanoma Therapeutics Program, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, USA, 17033
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98
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Fang ZP, Jiang BG, Zhang FB, Wang AD, Ji YM, Xu YF, Li JC, Zhou WP, Zhou WJ, Han HX. Rpb3 promotes hepatocellular carcinoma through its N-terminus. Oncotarget 2015; 5:9256-68. [PMID: 25211001 PMCID: PMC4253432 DOI: 10.18632/oncotarget.2389] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The expression of RNA polymerase II subunit 3 (Rpb3) was found frequent up-regulation in Hepatocellular carcinoma (HCC) tumors. Significant associations could also be drawn between increased expressions of Rpb3 and advance HCC staging and shorter disease-free survival of patients. Overexpression of Rpb3 increased HCC cell proliferation, migratory rate and tumor growth in nude mice, whereas suppression of Rpb3 using shRNA inhibited these effects. For mechanism study, we found that Rpb3 bound directly to Snail, downregulated E-cadherin, induced HCC cells epithelial-mesenchymal transition (EMT). In particular, N-terminus of Rpb3 blocked Rpb3 binding to Snail, inhibited Rpb3-high-expression HCC cells proliferation, migration, tumor growth in nude mice, and also inhibited DEN-induced liver tumorigenesis. Furthermore, N-terminus of Rpb3 did not inhibit normal liver cells or Rpb3-low-expression HCC cells proliferation. These findings suggest that N-terminus of Rpb3 selectively inhibits Rpb3-high-expression HCC cells proliferation. N-terminus of Rpb3 may be useful in treating patients diagnosed with Rpb3-high-expression HCC.
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Affiliation(s)
- Zhe-Ping Fang
- Department of Hepatobiliary Surgery, Taizhou Hospital of Zhejiang Province, Wenzhou Medical University, Linhai 317000, China
| | - Bei-Ge Jiang
- Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai 200438, China
| | - Fa-Biao Zhang
- Department of Hepatobiliary Surgery, Taizhou Hospital of Zhejiang Province, Wenzhou Medical University, Linhai 317000, China
| | - Ai-Dong Wang
- Department of Hepatobiliary Surgery, Taizhou Hospital of Zhejiang Province, Wenzhou Medical University, Linhai 317000, China
| | - Yi-Ming Ji
- Department of Hepatobiliary Surgery, Taizhou Hospital of Zhejiang Province, Wenzhou Medical University, Linhai 317000, China
| | - Yong-Fu Xu
- Department of Hepatobiliary Surgery, Taizhou Hospital of Zhejiang Province, Wenzhou Medical University, Linhai 317000, China
| | - Ji-Cheng Li
- Institute of Cell Biology, Zhejiang University, 866 Yu-Hang-Tang Road, Hangzhou 310058, China
| | - Wei-Ping Zhou
- Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai 200438, China
| | - Wei-Jie Zhou
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI 48109, USA
| | - Hai-Xiong Han
- Department of Hepatobiliary Surgery, Taizhou Hospital of Zhejiang Province, Wenzhou Medical University, Linhai 317000, China
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99
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Khanna A, Pradhan A, Curran SP. Emerging Roles for Maf1 beyond the Regulation of RNA Polymerase III Activity. J Mol Biol 2015; 427:2577-85. [PMID: 26173035 DOI: 10.1016/j.jmb.2015.06.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 06/26/2015] [Accepted: 06/30/2015] [Indexed: 01/17/2023]
Abstract
Maf1 was first identified in yeast, and studies in metazoans have primarily focused on examining its role in the repression of transcription that is dependent on RNA polymerase III. Recent work has revealed a novel and conserved function for Maf1 in the maintenance of intracellular lipid pools in Caenorhabditis elegans, mice, and cancer cell lines. Although additional Maf1 targets are likely, they have not been identified, and these recent findings begin to define specific activities for Maf1 in multicellular organisms beyond the regulation of RNA polymerase III transcription and suggest that Maf1 plays a more diverse role in organismal physiology. We will discuss these newly defined physiological roles of Maf1 that point to its placement as an important new player in lipid metabolism with implications in human metabolic diseases such as obesity and cancer, which display prominent defects in lipid homeostasis.
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Affiliation(s)
- Akshat Khanna
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA; Department of Molecular and Computational Biology, Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Ajay Pradhan
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA
| | - Sean P Curran
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA; Department of Molecular and Computational Biology, Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA 90089, USA; Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA.
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100
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Genome-Wide Analysis of Drosophila RBf2 Protein Highlights the Diversity of RB Family Targets and Possible Role in Regulation of Ribosome Biosynthesis. G3-GENES GENOMES GENETICS 2015; 5:1503-15. [PMID: 25999584 PMCID: PMC4502384 DOI: 10.1534/g3.115.019166] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
RBf2 is a recently evolved retinoblastoma family member in Drosophila that differs from RBf1, especially in the C-terminus. To investigate whether the unique features of RBf2 contribute to diverse roles in gene regulation, we performed chromatin immunoprecipitation sequencing for both RBf2 and RBf1 in embryos. A previous model for RB−E2F interactions suggested that RBf1 binds dE2F1 or dE2F2, whereas RBf2 is restricted to binding to dE2F2; however, we found that RBf2 targets approximately twice as many genes as RBf1. Highly enriched among the RBf2 targets were ribosomal protein genes. We tested the functional significance of this finding by assessing RBf activity on ribosomal protein promoters and the endogenous genes. RBf1 and RBf2 significantly repressed expression of some ribosomal protein genes, although not all bound genes showed transcriptional effects. Interestingly, many ribosomal protein genes are similarly targeted in human cells, indicating that these interactions may be relevant for control of ribosome biosynthesis and growth. We carried out bioinformatic analysis to investigate the basis for differential targeting by these two proteins and found that RBf2-specific promoters have distinct sequence motifs, suggesting unique targeting mechanisms. Association of RBf2 with these promoters appears to be independent of dE2F2/dDP, although promoters bound by both RBf1 and RBf2 require dE2F2/dDP. The presence of unique RBf2 targets suggest that evolutionary appearance of this corepressor represents the acquisition of potentially novel roles in gene regulation for the RB family.
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