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Regulation of ribosomal RNA gene copy number, transcription and nucleolus organization in eukaryotes. Nat Rev Mol Cell Biol 2023; 24:414-429. [PMID: 36732602 DOI: 10.1038/s41580-022-00573-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2022] [Indexed: 02/04/2023]
Abstract
One of the first biological machineries to be created seems to have been the ribosome. Since then, organisms have dedicated great efforts to optimize this apparatus. The ribosomal RNA (rRNA) contained within ribosomes is crucial for protein synthesis and maintenance of cellular function in all known organisms. In eukaryotic cells, rRNA is produced from ribosomal DNA clusters of tandem rRNA genes, whose organization in the nucleolus, maintenance and transcription are strictly regulated to satisfy the substantial demand for rRNA required for ribosome biogenesis. Recent studies have elucidated mechanisms underlying the integrity of ribosomal DNA and regulation of its transcription, including epigenetic mechanisms and a unique recombination and copy-number control system to stably maintain high rRNA gene copy number. In this Review, we disucss how the crucial maintenance of rRNA gene copy number through control of gene amplification and of rRNA production by RNA polymerase I are orchestrated. We also discuss how liquid-liquid phase separation controls the architecture and function of the nucleolus and the relationship between rRNA production, cell senescence and disease.
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2
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Tiwari K, Singh G, Singh SK. Purification and Structural Characterization of N-Terminal 190 Amino Acid Deleted Essential Mammalian Protein; Transcription Termination Factor 1. ACS OMEGA 2022; 7:45165-45173. [PMID: 36530226 PMCID: PMC9753541 DOI: 10.1021/acsomega.2c05603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Abstract
The mammalian transcription termination factor 1 (TTF1) is an essential protein that plays diverse cellular physiological functions like transcription regulation (both initiation and termination), replication fork blockage, chromatin remodeling, and DNA damage repair. Hence, understanding the structure and mechanism conferred by its variable conformations is important. However, so far, almost nothing is known about the structure of either the full-length protein or any of its domains in isolation. Since the full-length protein even after multiple attempts could not be purified in soluble form, we have codon optimized, expressed, and purified the N-terminal 190 amino acid deleted TTF1 (ΔN190TTF1) protein. In this study, we characterized this essential protein by studying its homogeneity, molecular size, and secondary structure using tools like dynamic light scattering (DLS), circular dichroism (CD) spectroscopy, Raman spectroscopy, and atomic force microscopy (AFM). By CD spectroscopy and DLS, we confirmed that the purified protein is homogeneous and soluble. CD spectroscopy also revealed that ΔN190TTF1 is a helical protein, which was further established by analysis of Raman spectra and amide I region deconvolution studies. The DLS study estimated the size of a single protein molecule to be 17.2 nm (in aqueous solution). Our structural and biophysical characterization of this essential protein will open avenues toward solving the structure to atomic resolution and will also encourage researchers to investigate the mechanism behind its diverse functions attributed to its various domains.
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3
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Tiwari K, Gangopadhyay A, Singh G, Singh VK, Singh SK. Ab initio modelling of an essential mammalian protein: Transcription Termination Factor 1 (TTF1). J Biomol Struct Dyn 2022:1-10. [PMID: 35947129 DOI: 10.1080/07391102.2022.2109754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Abstract
Transcription Termination Factor 1 (TTF1) is an essential mammalian protein that regulates transcription, replication fork arrest, DNA damage repair, chromatin remodelling etc. TTF1 interacts with numerous cellular proteins to regulate various cellular phenomena which play a crucial role in maintaining normal cellular physiology, and dysregulation of this protein has been reported to induce oncogenic transformation of the cells. However, despite its key role in many cellular processes, the complete structure of human TTF1 has not been elucidated to date, neither experimentally nor computationally. Therefore, understanding the structure of human TTF1 is crucial for studying its functions and interactions with other cellular factors. The aim of this study was to construct the complete structure of human TTF1 protein, using molecular modelling approaches. Owing to the lack of suitable homologues in the Protein Data Bank (PDB), the complete structure of human TTF1 was constructed by ab initio modelling. The structural stability was determined with molecular dynamics (MD) simulations in explicit solvent, and trajectory analyses. The frequently occurring conformation of human TTF1 was selected by trajectory clustering, and the central residues of this conformation were determined by centrality analyses of the Residue Interaction Network (RIN) of TTF1. Two residue clusters, one in the oligomerization domain and other in the C-terminal domain, were found to be central to the structural stability of human TTF1. To the best of our knowledge, this study is the first to report the complete structure of this essential mammalian protein, and the results obtained herein will provide structural insights for future research including that in cancer biology and related studies.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Kumud Tiwari
- School of Biotechnology, Institute of Science, Banaras Hindu University, Varanasi, India
| | - Aditi Gangopadhyay
- Department of Chemical Technology, University of Calcutta, Kolkata, India
| | | | - Vinay Kumar Singh
- School of Biotechnology, Institute of Science, Banaras Hindu University, Varanasi, India.,Center for Bioinformatics, School of Biotechnology, Institute of Science, Banaras Hindu University, Varanasi, India
| | - Samarendra Kumar Singh
- School of Biotechnology, Institute of Science, Banaras Hindu University, Varanasi, India
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4
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Samejima I, Spanos C, Samejima K, Rappsilber J, Kustatscher G, Earnshaw WC. Mapping the invisible chromatin transactions of prophase chromosome remodeling. Mol Cell 2022; 82:696-708.e4. [PMID: 35090599 PMCID: PMC8823707 DOI: 10.1016/j.molcel.2021.12.039] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 11/03/2021] [Accepted: 12/28/2021] [Indexed: 02/07/2023]
Abstract
We have used a combination of chemical genetics, chromatin proteomics, and imaging to map the earliest chromatin transactions during vertebrate cell entry into mitosis. Chicken DT40 CDK1as cells undergo synchronous mitotic entry within 15 min following release from a 1NM-PP1-induced arrest in late G2. In addition to changes in chromatin association with nuclear pores and the nuclear envelope, earliest prophase is dominated by changes in the association of ribonucleoproteins with chromatin, particularly in the nucleolus, where pre-rRNA processing factors leave chromatin significantly before RNA polymerase I. Nuclear envelope barrier function is lost early in prophase, and cytoplasmic proteins begin to accumulate on the chromatin. As a result, outer kinetochore assembly appears complete by nuclear envelope breakdown (NEBD). Most interphase chromatin proteins remain associated with chromatin until NEBD, after which their levels drop sharply. An interactive proteomic map of chromatin transactions during mitotic entry is available as a resource at https://mitoChEP.bio.ed.ac.uk.
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Affiliation(s)
- Itaru Samejima
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK
| | - Christos Spanos
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK
| | - Kumiko Samejima
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK
| | - Juri Rappsilber
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK; Technische Universität Berlin, Chair of Bioanalytics, 10623 Berlin, Germany
| | - Georg Kustatscher
- Institute of Quantitative Biology, Biochemistry and Biotechnology, University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK.
| | - William C Earnshaw
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK.
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5
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Defining the Influence of the A12.2 Subunit on Transcription Elongation and Termination by RNA Polymerase I In Vivo. Genes (Basel) 2021; 12:genes12121939. [PMID: 34946888 PMCID: PMC8701712 DOI: 10.3390/genes12121939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 11/26/2021] [Accepted: 11/29/2021] [Indexed: 11/16/2022] Open
Abstract
Saccharomyces cerevisiae has approximately 200 copies of the 35S rDNA gene, arranged tandemly on chromosome XII. This gene is transcribed by RNA polymerase I (Pol I) and the 35S rRNA transcript is processed to produce three of the four rRNAs required for ribosome biogenesis. An intergenic spacer (IGS) separates each copy of the 35S gene and contains the 5S rDNA gene, the origin of DNA replication, and the promoter for the adjacent 35S gene. Pol I is a 14-subunit enzyme responsible for the majority of rRNA synthesis, thereby sustaining normal cellular function and growth. The A12.2 subunit of Pol I plays a crucial role in cleavage, termination, and nucleotide addition during transcription. Deletion of this subunit causes alteration of nucleotide addition kinetics and read-through of transcription termination sites. To interrogate both of these phenomena, we performed native elongating transcript sequencing (NET-seq) with an rpa12Δ strain of S. cerevisiae and evaluated the resultant change in Pol I occupancy across the 35S gene and the IGS. Compared to wild-type (WT), we observed template sequence-specific changes in Pol I occupancy throughout the 35S gene. We also observed rpa12Δ Pol I occupancy downstream of both termination sites and throughout most of the IGS, including the 5S gene. Relative occupancy of rpa12Δ Pol I increased upstream of the promoter-proximal Reb1 binding site and dropped significantly downstream, implicating this site as a third terminator for Pol I transcription. Collectively, these high-resolution results indicate that the A12.2 subunit of Pol I plays an important role in transcription elongation and termination.
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Zhu Y, Wang Y, Tao B, Han J, Chen H, Zhu Q, Huang L, He Y, Hong J, Li Y, Chen J, Huang J, Lo LJ, Peng J. Nucleolar GTPase Bms1 displaces Ttf1 from RFB-sites to balance progression of rDNA transcription and replication. J Mol Cell Biol 2021; 13:902-917. [PMID: 34791311 PMCID: PMC8800533 DOI: 10.1093/jmcb/mjab074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 10/30/2021] [Accepted: 11/02/2021] [Indexed: 11/24/2022] Open
Abstract
18S, 5.8S, and 28S ribosomal RNAs (rRNAs) are cotranscribed as a pre-ribosomal RNA (pre-rRNA) from the rDNA by RNA polymerase I whose activity is vigorous during the S-phase, leading to a conflict with rDNA replication. This conflict is resolved partly by replication-fork-barrier (RFB)-sites sequences located downstream of the rDNA and RFB-binding proteins such as Ttf1. However, how Ttf1 is displaced from RFB-sites to allow replication fork progression remains elusive. Here, we reported that loss-of-function of Bms1l, a nucleolar GTPase, upregulates rDNA transcription, causes replication-fork stall, and arrests cell cycle at the S-to-G2 transition; however, the G1-to-S transition is constitutively active characterized by persisting DNA synthesis. Concomitantly, ubf, tif-IA, and taf1b marking rDNA transcription, Chk2, Rad51, and p53 marking DNA-damage response, and Rpa2, PCNA, Fen1, and Ttf1 marking replication fork stall are all highly elevated in bms1l mutants. We found that Bms1 interacts with Ttf1 in addition to Rc1l. Finally, we identified RFB-sites for zebrafish Ttf1 through chromatin immunoprecipitation sequencing and showed that Bms1 disassociates the Ttf1‒RFB complex with its GTPase activity. We propose that Bms1 functions to balance rDNA transcription and replication at the S-phase through interaction with Rcl1 and Ttf1, respectively. TTF1 and Bms1 together might impose an S-phase checkpoint at the rDNA loci.
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Affiliation(s)
- Yanqing Zhu
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058 China
| | - Yong Wang
- Taizhou Hospital, Zhejiang University, Taizhou, 317000 China
| | - Boxiang Tao
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058 China
| | - Jinhua Han
- Life Sciences Institute, Zhejiang University, Hangzhou, 310058 China
| | - Hong Chen
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058 China
| | - Qinfang Zhu
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058 China
| | - Ling Huang
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058 China
| | - Yinan He
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058 China
| | - Jian Hong
- Institute of Biotechnology, Zhejiang University, Hangzhou, 310058 China
| | - Yunqin Li
- Institute of Biotechnology, Zhejiang University, Hangzhou, 310058 China
| | - Jun Chen
- College of Life Sciences, Zhejiang University, Hangzhou, 310058 China
| | - Jun Huang
- Life Sciences Institute, Zhejiang University, Hangzhou, 310058 China
| | - Li Jan Lo
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058 China
| | - Jinrong Peng
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058 China
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Kalish BT, Kim E, Finander B, Duffy EE, Kim H, Gilman CK, Yim YS, Tong L, Kaufman RJ, Griffith EC, Choi GB, Greenberg ME, Huh JR. Maternal immune activation in mice disrupts proteostasis in the fetal brain. Nat Neurosci 2021; 24:204-213. [PMID: 33361822 PMCID: PMC7854524 DOI: 10.1038/s41593-020-00762-9] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 11/18/2020] [Indexed: 12/21/2022]
Abstract
Maternal infection and inflammation during pregnancy are associated with neurodevelopmental disorders in offspring, but little is understood about the molecular mechanisms underlying this epidemiologic phenomenon. Here, we leveraged single-cell RNA sequencing to profile transcriptional changes in the mouse fetal brain in response to maternal immune activation (MIA) and identified perturbations in cellular pathways associated with mRNA translation, ribosome biogenesis and stress signaling. We found that MIA activates the integrated stress response (ISR) in male, but not female, MIA offspring in an interleukin-17a-dependent manner, which reduced global mRNA translation and altered nascent proteome synthesis. Moreover, blockade of ISR activation prevented the behavioral abnormalities as well as increased cortical neural activity in MIA male offspring. Our data suggest that sex-specific activation of the ISR leads to maternal inflammation-associated neurodevelopmental disorders.
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Affiliation(s)
- Brian T Kalish
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
- Division of Newborn Medicine, Department of Pediatrics, Boston Children's Hospital, Boston, MA, USA.
| | - Eunha Kim
- Department of Immunology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Benjamin Finander
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Division of Newborn Medicine, Department of Pediatrics, Boston Children's Hospital, Boston, MA, USA
| | - Erin E Duffy
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Hyunju Kim
- Department of Immunology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Casey K Gilman
- Department of Immunology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Yeong Shin Yim
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Lilin Tong
- Division of Newborn Medicine, Department of Pediatrics, Boston Children's Hospital, Boston, MA, USA
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Randal J Kaufman
- Degenerative Disease Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - Eric C Griffith
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Gloria B Choi
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Michael E Greenberg
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
| | - Jun R Huh
- Department of Immunology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
- Evergrande Center for Immunologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, MA, USA.
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8
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Boutin J, Lessard F, Tremblay MG, Moss T. The Short N-Terminal Repeats of Transcription Termination Factor 1 Contain Semi-Redundant Nucleolar Localization Signals and P19-ARF Tumor Suppressor Binding Sites. THE YALE JOURNAL OF BIOLOGY AND MEDICINE 2019; 92:385-396. [PMID: 31543703 PMCID: PMC6747939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The p14/p19ARF (ARF) tumor suppressor provides an important link in the activation of p53 (TP53) by inhibiting its targeted degradation via the E3 ligases MDM2/HDM2. However, ARF also limits tumor growth by directly inhibiting ribosomal RNA synthesis and processing. Initial studies of the ARF tumor suppressor were compounded by overlap between the INK4A and ARF genes encoded by the CDKN2A locus, but mouse models of pure ARF-loss and its inactivation in human cancers identified it as a distinct tumor suppressor even in the absence of p53. We previously demonstrated that both human and mouse ARF interact with Transcription Termination Factor 1 (TTF1, TTF-I), an essential factor implicated in transcription termination and silencing of the ribosomal RNA genes. Accumulation of ARF upon oncogenic stress was shown to inhibit ribosomal RNA synthesis by depleting nucleolar TTF1. Here we have mapped the functional nucleolar localization sequences (NoLS) of mouse TTF1 and the sequences responsible for interaction with ARF. We find that both sequences lie within the 25 amino acid N-terminal repeats of TTF1. Nucleolar localization depends on semi-redundant lysine-arginine motifs in each repeat and to a minor extent on binding to target DNA sequences by the Myb homology domain of TTF1. While nucleolar localization of TTF1 predominantly correlates with its interaction with ARF, NoLS activity and ARF binding are mediated by distinct sequences within each N-terminal repeat. The data suggest that the N-terminal repeats of mouse TTF1, and by analogy those of human TTF1, cooperate to mediate both nucleolar localization and ARF binding.
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Affiliation(s)
- Joël Boutin
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre (Axe Cancer, CR-CHU de Québec), Quebec, QC, Canada,Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Université Laval, Quebec, QC, Canada,Endocrinology and Nephrology Division of the Quebec University Hospital Research Centre (Axe endocrinologie et néphrologie, CR-CHU de Québec), Quebec, QC, Canada
| | - Frédéric Lessard
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre (Axe Cancer, CR-CHU de Québec), Quebec, QC, Canada,Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Université Laval, Quebec, QC, Canada,Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, QC, Canada
| | - Michel G. Tremblay
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre (Axe Cancer, CR-CHU de Québec), Quebec, QC, Canada
| | - Tom Moss
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre (Axe Cancer, CR-CHU de Québec), Quebec, QC, Canada,Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Université Laval, Quebec, QC, Canada,To whom all correspondence should be addressed: Tom Moss, Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Université Laval, Quebec, QC, Canada; Tel: 418-525-4444 ext. 15549; Fax: 418-691-5439;
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9
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Park SH, Yu KL, Jung YM, Lee SD, Kim MJ, You JC. Investigation of functional roles of transcription termination factor-1 (TTF-I) in HIV-1 replication. BMB Rep 2018; 51:338-343. [PMID: 29555014 PMCID: PMC6089867 DOI: 10.5483/bmbrep.2018.51.7.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2018] [Indexed: 11/25/2022] Open
Abstract
Transcription termination factor-1 (TTF-I) is an RNA polymerase 1-mediated transcription terminator and consisting of a C-terminal DNA-binding domain, central domain, and N-terminal regulatory domain. This protein binds to a so-called ‘Sal box’ composed of an 11-base pair motif. The interaction of TTF-I with the ‘Sal box’ is important for many cellular events, including efficient termination of RNA polymerase-1 activity involved in pre-rRNA synthesis and formation of a chromatin loop. To further understand the role of TTF-I in human immunodeficiency virus (HIV)-I virus production, we generated various TTF-I mutant forms. Through a series of studies of the over-expression of TTF-I and its derivatives along with co-transfection with either proviral DNA or HIV-I long terminal repeat (LTR)-driven reporter vectors, we determined that wild-type TTF-I downregulates HIV-I LTR activity and virus production, while the TTF-I Myb-like domain alone upregulated virus production, suggesting that wild-type TTF-I inhibits virus production and trans-activation of the LTR sequence; the Myb-like domain of TTF-I increased virus production and trans-activated LTR activity.
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Affiliation(s)
- Seong-Hyun Park
- National Research Laboratory for Molecular Virology, Department of Pathology, School of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Kyung-Lee Yu
- National Research Laboratory for Molecular Virology, Department of Pathology, School of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Yu-Mi Jung
- National Research Laboratory for Molecular Virology, Department of Pathology, School of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Seong-Deok Lee
- National Research Laboratory for Molecular Virology, Department of Pathology, School of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | | | - Ji-Chang You
- National Research Laboratory for Molecular Virology, Department of Pathology, School of Medicine, The Catholic University of Korea, Seoul 06591, Korea; Avixgen Inc., Seoul 06649, Korea
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10
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Functional architecture of the Reb1-Ter complex of Schizosaccharomyces pombe. Proc Natl Acad Sci U S A 2016; 113:E2267-76. [PMID: 27035982 DOI: 10.1073/pnas.1525465113] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Reb1 ofSchizosaccharomyces pomberepresents a family of multifunctional proteins that bind to specific terminator sites (Ter) and cause polar termination of transcription catalyzed by RNA polymerase I (pol I) and arrest of replication forks approaching the Ter sites from the opposite direction. However, it remains to be investigated whether the same mechanism causes arrest of both DNA transactions. Here, we present the structure of Reb1 as a complex with a Ter site at a resolution of 2.7 Å. Structure-guided molecular genetic analyses revealed that it has distinct and well-defined DNA binding and transcription termination (TTD) domains. The region of the protein involved in replication termination is distinct from the TTD. Mechanistically, the data support the conclusion that transcription termination is not caused by just high affinity Reb1-Ter protein-DNA interactions. Rather, protein-protein interactions between the TTD with the Rpa12 subunit of RNA pol I seem to be an integral part of the mechanism. This conclusion is further supported by the observation that double mutations in TTD that abolished its interaction with Rpa12 also greatly reduced transcription termination thereby revealing a conduit for functional communications between RNA pol I and the terminator protein.
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11
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Komatsu H, Iguchi T, Ueda M, Nambara S, Saito T, Hirata H, Sakimura S, Takano Y, Uchi R, Shinden Y, Eguchi H, Masuda T, Sugimachi K, Eguchi H, Doki Y, Mori M, Mimori K. Clinical and biological significance of transcription termination factor, RNA polymerase I in human liver hepatocellular carcinoma. Oncol Rep 2016; 35:2073-80. [PMID: 26821084 DOI: 10.3892/or.2016.4593] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 12/04/2015] [Indexed: 11/06/2022] Open
Abstract
Recent studies have indicated that increased ribosomal activity contributes to cancer progression. Transcription termination factor, RNA polymerase I (TTF1) acts as a transcription factor for RNA polymerase I. However, the role which TTF1 plays in cancer progression still remains unknown. The present study aimed to determine whether TTF1 plays a critical role in the progression of human liver hepatocellular carcinoma (HCC). In the present study, quantitative real-time reverse transcription polymerase chain reaction was conducted to evaluate TTF1 mRNA expression in 60 HCC tissue samples in order to determine the clinicopathological significance of TTF1. To investigate whether the expression levels of TTF1 were associated known gene signatures which represented ribosomal activity, we applied gene set enrichment analysis (GSEA) to HCC cases in The Cancer Genome Atlas (TCGA) a. We also performed in vitro proliferation assays using TTF1‑overexpressing HCC cells. TTF1 expression was significantly higher in HCC tumor tissues than in adjacent liver tissues (P<0.001). The overall survival (OS) of patients with high TTF1 expression levels was significantly shorter than that of patients with low TTF1 expression (P=0.027). Multivariate analysis indicated that TTF1 expression was an independent prognostic factor for OS (P=0.020). GSEA revealed significant associations between TTF1 expression and gene sets involved in ribosomal function. In vitro, cell proliferation and rRNA transcription were significantly promoted by overexpression of TTF1 in the HCC cell lines HuH-7 and HepG2. From these results, it was suggested that TTF1 participate in poor prognoses and play a role in tumor cell growth in HCC, possibly by upregulating ribosomal activity. In conclusion, we first propose that TTF1 may be a novel biomarker and therapeutic target in HCC. Increased expression of TTF1 was significantly associated with poor prognosis in two independent sets of HCC cases. Furthermore, in vitro experiments provided an explanation for clinical data showing that overexpression of TTF1 contributed to the proliferation of cancer cells.
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Affiliation(s)
- Hisateru Komatsu
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Tomohiro Iguchi
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Masami Ueda
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Sho Nambara
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Tomoko Saito
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Hidenari Hirata
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Shotaro Sakimura
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Yuki Takano
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Ryutaro Uchi
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Yoshiaki Shinden
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Hidetoshi Eguchi
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Takaaki Masuda
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Keishi Sugimachi
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
| | - Hidetoshi Eguchi
- Department of Gastroenterological Surgery, Graduate School of Medicine, Suita, Osaka, Japan
| | - Yuichiro Doki
- Department of Gastroenterological Surgery, Graduate School of Medicine, Suita, Osaka, Japan
| | - Masaki Mori
- Department of Gastroenterological Surgery, Graduate School of Medicine, Suita, Osaka, Japan
| | - Koshi Mimori
- Department of Surgery, Kyushu University, Beppu Hospital, Beppu, Oita, Japan
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12
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Ueda M, Iguchi T, Nambara S, Saito T, Komatsu H, Sakimura S, Hirata H, Uchi R, Takano Y, Shinden Y, Eguchi H, Masuda T, Sugimachi K, Yamamoto H, Doki Y, Mori M, Mimori K. Overexpression of Transcription Termination Factor 1 is Associated with a Poor Prognosis in Patients with Colorectal Cancer. Ann Surg Oncol 2015; 22 Suppl 3:S1490-8. [PMID: 26036188 DOI: 10.1245/s10434-015-4652-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Indexed: 01/10/2023]
Abstract
BACKGROUND RNA polymerase 1 transcription termination factor (TTF1) mediates the transcription of ribosomal RNA (rRNA). In the current study, we investigated the clinical and biological significance of the TTF1 gene in colorectal cancer (CRC). METHODS The expression of TTF1 messenger RNA (mRNA) in tumor and normal tissues from 136 patients with CRC was examined by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). We also performed in vitro cell proliferation and migration assays in TTF1-expressing CRC cells. The biological role of TTF1 in CRC was further elucidated using gene set enrichment analysis (GSEA) with CRC samples. RESULTS TTF1 expression was significantly higher in tumor tissues than in corresponding normal tissues (p = 0.016). In clinicopathological analysis, the high-TTF1 expression group showed a higher incidence of liver metastasis and lymphatic invasion than the low-TTF1 expression group (p < 0.05), and tended to have more frequent venous invasion than the low-TTF1 expression group. Furthermore, the high-TTF1 expression group had a significantly poorer prognosis than the low-TTF1 expression group (p = 0.011). Moreover, overexpression of TTF1 enhanced the proliferation and migration capacity of CRC cells in vitro. GSEA revealed that TTF1 was significantly associated with the RAS and MYC pathways, and this observation was confirmed in samples from 136 patients with CRC. CONCLUSION TTF1 was involved in cancer progression via the RAS and MYC pathways in CRC, suggesting that TTF1 may be a prognostic indicator and therapeutic target in CRC.
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Affiliation(s)
- Masami Ueda
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan. .,Department of Gastroenterological Surgery, Graduate School of Medicine, Osaka University, Suita, Japan.
| | - Tomohiro Iguchi
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Sho Nambara
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Tomoko Saito
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Hisateru Komatsu
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan.,Department of Gastroenterological Surgery, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Shotaro Sakimura
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Hidenari Hirata
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Ryutaro Uchi
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Yuki Takano
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Yoshiaki Shinden
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Hidetoshi Eguchi
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Takaaki Masuda
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Keishi Sugimachi
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan
| | - Hirofumi Yamamoto
- Department of Gastroenterological Surgery, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Yuichiro Doki
- Department of Gastroenterological Surgery, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Masaki Mori
- Department of Gastroenterological Surgery, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Koshi Mimori
- Department of Surgery, Kyushu University Beppu Hospital, Beppu, Japan.
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13
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The Human RNA Polymerase I Transcription Terminator Complex Acts as a Replication Fork Barrier That Coordinates the Progress of Replication with rRNA Transcription Activity. Mol Cell Biol 2015; 35:1871-81. [PMID: 25776556 DOI: 10.1128/mcb.01521-14] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Accepted: 03/09/2015] [Indexed: 01/28/2023] Open
Abstract
In S phase, the replication and transcription of genomic DNA need to accommodate each other, otherwise their machineries collide, with chromosomal instability as a possible consequence. Here, we characterized the human replication fork barrier (RFB) that is present downstream from the 47S pre-rRNA gene (ribosomal DNA [rDNA]). We found that the most proximal transcription terminator, Sal box T1, acts as a polar RFB, while the other, Sal box T4/T5, arrests replication forks bidirectionally. The fork-arresting activity at these sites depends on polymerase I (Pol I) transcription termination factor 1 (TTF-1) and a replisome component, TIMELESS (TIM). We also found that the RFB activity was linked to rDNA copies with hypomethylated CpG and coincided with the time that actively transcribed rRNA genes are replicated. Failed fork arrest at RFB sites led to a slowdown of fork progression moving in the opposite direction to rRNA transcription. Chemical inhibition of transcription counteracted this deceleration of forks, indicating that rRNA transcription impedes replication in the absence of RFB activity. Thus, our results reveal a role of RFB for coordinating the progression of replication and transcription activity in highly transcribed rRNA genes.
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14
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Colin J, Candelli T, Porrua O, Boulay J, Zhu C, Lacroute F, Steinmetz LM, Libri D. Roadblock termination by reb1p restricts cryptic and readthrough transcription. Mol Cell 2015; 56:667-80. [PMID: 25479637 DOI: 10.1016/j.molcel.2014.10.026] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 06/09/2014] [Accepted: 10/29/2014] [Indexed: 02/09/2023]
Abstract
Widely transcribed compact genomes must cope with the major challenge of frequent overlapping or concurrent transcription events. Efficient and timely transcription termination is crucial to control pervasive transcription and prevent transcriptional interference. In yeast, transcription termination of RNA polymerase II (RNAPII) occurs via two possible pathways that both require recognition of termination signals on nascent RNA by specific factors. We describe here an additional mechanism of transcription termination for RNAPII and demonstrate its biological significance. We show that the transcriptional activator Reb1p bound to DNA is a roadblock for RNAPII, which pauses and is ubiquitinated, thus triggering termination. Reb1p-dependent termination generates a class of cryptic transcripts that are degraded in the nucleus by the exosome. We also observed transcriptional interference between neighboring genes in the absence of Reb1p. This work demonstrates the importance of roadblock termination for controlling pervasive transcription and preventing transcription through gene regulatory regions.
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Affiliation(s)
- Jessie Colin
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France
| | - Tito Candelli
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France
| | - Odil Porrua
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France
| | - Jocelyne Boulay
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France
| | - Chenchen Zhu
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, 69117 Heidelberg, Germany
| | - François Lacroute
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France
| | - Lars M Steinmetz
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, 69117 Heidelberg, Germany; Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Domenico Libri
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France.
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15
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Binding of the termination factor Nsi1 to its cognate DNA site is sufficient to terminate RNA polymerase I transcription in vitro and to induce termination in vivo. Mol Cell Biol 2014; 34:3817-27. [PMID: 25092870 DOI: 10.1128/mcb.00395-14] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Different models have been proposed explaining how eukaryotic gene transcription is terminated. Recently, Nsi1, a factor involved in silencing of ribosomal DNA (rDNA), was shown to be required for efficient termination of rDNA transcription by RNA polymerase I (Pol I) in the yeast Saccharomyces cerevisiae. Nsi1 contains Myb-like DNA binding domains and associates in vivo near the 3' end of rRNA genes to rDNA, but information about which and how DNA sequences might influence Nsi1-dependent termination is lacking. Here, we show that binding of Nsi1 to a stretch of 11 nucleotides in the correct orientation was sufficient to pause elongating Pol I shortly upstream of the Nsi1 binding site and to release the transcripts in vitro. The same minimal DNA element triggered Nsi1-dependent termination of pre-rRNA synthesis using an in vivo reporter assay. Termination efficiency in the in vivo system could be enhanced by inclusion of specific DNA sequences downstream of the Nsi1 binding site. These data and the finding that Nsi1 blocks efficiently only Pol I-dependent RNA synthesis in an in vitro transcription system improve our understanding of a unique mechanism of transcription termination.
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16
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Németh A, Perez-Fernandez J, Merkl P, Hamperl S, Gerber J, Griesenbeck J, Tschochner H. RNA polymerase I termination: Where is the end? BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:306-17. [PMID: 23092677 DOI: 10.1016/j.bbagrm.2012.10.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 10/10/2012] [Accepted: 10/17/2012] [Indexed: 01/01/2023]
Abstract
The synthesis of ribosomal RNA (rRNA) precursor molecules by RNA polymerase I (Pol I) terminates with the dissociation of the protein-DNA-RNA ternary complex. Based on in vitro results the mechanism of Pol I termination appeared initially to be rather conserved and simple until this process was more thoroughly re-investigated in vivo. A picture emerged that Pol I termination seems to be connected to co-transcriptional processing, re-initiation of transcription and, possibly, other processes downstream of Pol I transcription units. In this article, our current understanding of the mechanism of Pol I termination and how this process might be implicated in other biological processes in yeast and mammals is summarized and discussed. This article is part of a Special Issue entitled: Transcription by Odd Pols.
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Affiliation(s)
- Attila Németh
- Universität Regensburg, Biochemie-Zentrum Regensburg (BZR), Lehrstuhl Biochemie III, 93053 Regensburg, Germany.
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17
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Hochstatter J, Hölzel M, Rohrmoser M, Schermelleh L, Leonhardt H, Keough R, Gonda TJ, Imhof A, Eick D, Längst G, Németh A. Myb-binding protein 1a (Mybbp1a) regulates levels and processing of pre-ribosomal RNA. J Biol Chem 2012; 287:24365-77. [PMID: 22645127 DOI: 10.1074/jbc.m111.303719] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Ribosomal RNA gene transcription, co-transcriptional processing, and ribosome biogenesis are highly coordinated processes that are tightly regulated during cell growth. In this study we discovered that Mybbp1a is associated with both the RNA polymerase I complex and the ribosome biogenesis machinery. Using a reporter assay that uncouples transcription and RNA processing, we show that Mybbp1a represses rRNA gene transcription. In addition, overexpression of the protein reduces RNA polymerase I loading on endogenous rRNA genes as revealed by chromatin immunoprecipitation experiments. Accordingly, depletion of Mybbp1a results in an accumulation of the rRNA precursor in vivo but surprisingly also causes growth arrest of the cells. This effect can be explained by the observation that the modulation of Mybbp1a protein levels results in defects in pre-rRNA processing within the cell. Therefore, the protein may play a dual role in the rRNA metabolism, potentially linking and coordinating ribosomal DNA transcription and pre-rRNA processing to allow for the efficient synthesis of ribosomes.
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Affiliation(s)
- Julia Hochstatter
- Biochemistry Center Regensburg, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
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18
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Lessard F, Stefanovsky V, Tremblay MG, Moss T. The cellular abundance of the essential transcription termination factor TTF-I regulates ribosome biogenesis and is determined by MDM2 ubiquitinylation. Nucleic Acids Res 2012; 40:5357-67. [PMID: 22383580 PMCID: PMC3384320 DOI: 10.1093/nar/gks198] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The ARF tumour suppressor stabilizes p53 by negatively regulating the E3 ubiquitin ligase MDM2 to promote cell cycle arrest and cell death. However, ARF is also able to arrest cell proliferation by inhibiting ribosome biogenesis. In greater part this is achieved by targeting the transcription termination factor I (TTF-I) for nucleolar export, leading to an inhibition of both ribosomal RNA synthesis and processing. We now show that in the absence of ARF, TTF-I is ubiquitinylated by MDM2. MDM2 interacts directly with TTF-I and regulates its cellular abundance by targeting it for degradation by the proteasome. Enhanced TTF-I levels inhibit ribosome biogenesis by suppressing ribosomal RNA synthesis and processing, strongly suggesting that exact TTF-I levels are critical for efficient ribosome biogenesis. We further show that concomitant with its ability to displace TTF-I from the nucleolus, ARF inhibits MDM2 ubiquitinylation of TTF-I by competitively binding to a site overlapping the MDM2 interaction site. Thus, both the sub-nuclear localization and the abundance of TTF-I are key regulators of ribosome biogenesis.
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Affiliation(s)
- Frédéric Lessard
- Cancer Research Centre and Department of Molecular Biology, Medical Biochemistry and Pathology of Laval University, CHUQ Research Centre, Pavillon St Patrick, 9 rue McMahon, Québec, G1R 3S3 Québec, Canada
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19
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Lessard F, Morin F, Ivanchuk S, Langlois F, Stefanovsky V, Rutka J, Moss T. The ARF Tumor Suppressor Controls Ribosome Biogenesis by Regulating the RNA Polymerase I Transcription Factor TTF-I. Mol Cell 2010; 38:539-50. [DOI: 10.1016/j.molcel.2010.03.015] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Revised: 02/24/2010] [Accepted: 03/25/2010] [Indexed: 11/29/2022]
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20
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Richard P, Manley JL. Transcription termination by nuclear RNA polymerases. Genes Dev 2009; 23:1247-69. [PMID: 19487567 DOI: 10.1101/gad.1792809] [Citation(s) in RCA: 246] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Gene transcription in the cell nucleus is a complex and highly regulated process. Transcription in eukaryotes requires three distinct RNA polymerases, each of which employs its own mechanisms for initiation, elongation, and termination. Termination mechanisms vary considerably, ranging from relatively simple to exceptionally complex. In this review, we describe the present state of knowledge on how each of the three RNA polymerases terminates and how mechanisms are conserved, or vary, from yeast to human.
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Affiliation(s)
- Patricia Richard
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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21
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Eydmann T, Sommariva E, Inagawa T, Mian S, Klar AJS, Dalgaard JZ. Rtf1-mediated eukaryotic site-specific replication termination. Genetics 2008; 180:27-39. [PMID: 18723894 PMCID: PMC2535681 DOI: 10.1534/genetics.108.089243] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Accepted: 06/30/2008] [Indexed: 11/18/2022] Open
Abstract
The molecular mechanisms mediating eukaryotic replication termination and pausing remain largely unknown. Here we present the molecular characterization of Rtf1 that mediates site-specific replication termination at the polar Schizosaccharomyces pombe barrier RTS1. We show that Rtf1 possesses two chimeric myb/SANT domains: one is able to interact with the repeated motifs encoded by the RTS1 element as well as the elements enhancer region, while the other shows only a weak DNA binding activity. In addition we show that the C-terminal tail of Rtf1 mediates self-interaction, and deletion of this tail has a dominant phenotype. Finally, we identify a point mutation in Rtf1 domain I that converts the RTS1 element into a replication barrier of the opposite polarity. Together our data establish that multiple protein DNA and protein-protein interactions between Rtf1 molecules and both the repeated motifs and the enhancer region of RTS1 are required for site-specific termination at the RTS1 element.
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Affiliation(s)
- T Eydmann
- Marie Curie Research Institute, The Chart, Oxted RH8 0TL, United Kingdom
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22
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Affiliation(s)
- Brian McStay
- Biomedical Research Centre, University of Dundee, Ninewells Hospital, Dundee DD1 9SY, United Kingdom.
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23
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Asin-Cayuela J, Helm M, Attardi G. A Monomer-to-Trimer Transition of the Human Mitochondrial Transcription Termination Factor (mTERF) Is Associated with a Loss of in Vitro Activity. J Biol Chem 2004; 279:15670-7. [PMID: 14744862 DOI: 10.1074/jbc.m312537200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human mitochondrial transcription termination factor (mTERF) is a nuclear-encoded 39-kDa protein that recognizes a mtDNA segment within the mitochondrial tRNA(Leu(UUR)) gene immediately adjacent to and downstream of the 16 S rRNA gene. Binding of mTERF to this site promotes termination of rDNA transcription. Despite the fact that mTERF binds DNA as a monomer, the presence in its sequence of three leucine-zipper motifs suggested the possibility of mTERF establishing intermolecular interactions with proteins of the same or different type. When a mitochondrial lysate from HeLa cells was submitted to gel filtration chromatography, mTERF was eluted in two peaks, as detected by immunoblotting. The first peak, which varied in proportion between 30 and 50%, appeared at the position expected from the molecular mass of the monomer (41 +/- 2 kDa), and the gel filtration fractions that contained it exhibited DNA binding activity. Most interestingly, the material in this peak had a strong stimulating activity on in vitro transcription of the mitochondrial rDNA. The second peak eluted at a position corresponding to an estimated molecular mass of 111 +/- 5 kDa. No mTERF DNA binding activity could be detected in the corresponding gel filtration fractions. Therefore, we propose that mTERF exists in mitochondria in two forms, an active monomer and an inactive large size complex. The estimated molecular weight of this complex and the fact that purified mTERF can be eluted from a gel filtration column as a complex of the same molecular weight strongly suggest that this inactive complex is a homotrimer of mTERF.
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Affiliation(s)
- Jordi Asin-Cayuela
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
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24
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Guffanti E, Corradini R, Ottonello S, Dieci G. Functional dissection of RNA polymerase III termination using a peptide nucleic acid as a transcriptional roadblock. J Biol Chem 2004; 279:20708-16. [PMID: 14970213 DOI: 10.1074/jbc.m311295200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have shown previously that a T(10) peptide nucleic acid (PNA) bound to the transcriptional terminator of a Saccharomyces cerevisiae tDNA(Ile)(TAT) gene arrests elongating yeast RNA polymerase (pol) III at a position that precedes by 20 bp the upstream end of the PNA roadblock (Dieci, G., Corradini, R., Sforza, S., Marchelli, R., and Ottonello, S. (2001) J. Biol. Chem. 276, 5720-5725). Here, a PNA-binding cassette was placed at various distances downstream of a functional tDNA(Ile) transcriptional terminator (T(6)) that is not bound by the T(10) PNA, and the effect of the PNA roadblock on RNA 3'-end formation, transcript release, and transcription reinitiation was examined. With a PNA roadblock placed as close as 5 bp downstream of the T(6) terminator, pol III could still reach the termination site and complete pre-tRNA synthesis, implying that the catalytic site-to-front edge (C-F) distance of the polymerase can shorten by >10 bp upon recognition of the terminator element. In addition, transcripts synthesized by a PNA-roadblocked terminating pol III were found to be released from transcription complexes. Interestingly, however, the same roadblock dramatically reduced the rate of transcription reinitiation. Also, when placed 5 bp downstream of a mutationally inactivated terminator element (T(3)GT(2)), the PNA roadblock restored transcription termination, thus indicating that the inactivated terminator is compromised in its ability to cause pol III pausing, but can still induce C-F distance shortening and transcript release. The latter two activities were found to be further impaired in variants of the inactivated terminator bearing fewer than three consecutive T residues (T(2)G(2)T(2) and TG(2)TGT). The data indicate that RNA polymerase pausing, C-F distance shortening, and transcript release are functionally distinguishable features of the termination process and point to the RNA release propensity of pol III as a major determinant of its remarkably high termination efficiency.
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Affiliation(s)
- Elisa Guffanti
- Dipartimento di Biochimica e Biologia Molecolare and Dipartimento di Chimica Organica e Industriale, Università degli Studi di Parma, 43100 Parma, Italy
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25
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Barak O, Lazzaro MA, Lane WS, Speicher DW, Picketts DJ, Shiekhattar R. Isolation of human NURF: a regulator of Engrailed gene expression. EMBO J 2004; 22:6089-100. [PMID: 14609955 PMCID: PMC275440 DOI: 10.1093/emboj/cdg582] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The modification of chromatin structure is an important regulatory mechanism for developmental gene expression. Differential expression of the mammalian ISWI genes, SNF2H and SNF2L, has suggested that they possess distinct developmental roles. Here we describe the purification and characterization of the first human SNF2L-containing complex. The subunit composition suggests that it represents the human ortholog of the Drosophila nucleosome-remodeling factor (NURF) complex. Human NURF (hNURF) is enriched in brain, and we demonstrate that it regulates human Engrailed, a homeodomain protein that regulates neuronal development in the mid-hindbrain. Furthermore, we show that hNURF potentiates neurite outgrowth in cell culture. Taken together, our data suggess a role for an ISWI complex in neuronal growth.
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Affiliation(s)
- Orr Barak
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
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26
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Gromak N, Rideau A, Southby J, Scadden ADJ, Gooding C, Hüttelmaier S, Singer RH, Smith CWJ. The PTB interacting protein raver1 regulates alpha-tropomyosin alternative splicing. EMBO J 2003; 22:6356-64. [PMID: 14633994 PMCID: PMC291850 DOI: 10.1093/emboj/cdg609] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2003] [Revised: 09/19/2003] [Accepted: 10/13/2003] [Indexed: 01/09/2023] Open
Abstract
Regulated switching of the mutually exclusive exons 2 and 3 of alpha-tropomyosin (TM) involves repression of exon 3 in smooth muscle cells. Polypyrimidine tract-binding protein (PTB) is necessary but not sufficient for regulation of TM splicing. Raver1 was identified in two-hybrid screens by its interactions with the cytoskeletal proteins actinin and vinculin, and was also found to interact with PTB. Consistent with these interactions raver1 can be localized in either the nucleus or cytoplasm. Here we show that raver1 is able to promote the smooth muscle-specific alternative splicing of TM by enhancing PTB-mediated repression of exon 3. This activity of raver1 is dependent upon characterized PTB-binding regulatory elements and upon a region of raver1 necessary for interaction with PTB. Heterologous recruitment of raver1, or just its C-terminus, induced very high levels of exon 3 skipping, bypassing the usual need for PTB binding sites downstream of exon 3. This suggests a novel mechanism for PTB-mediated splicing repression involving recruitment of raver1 as a potent splicing co-repressor.
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Affiliation(s)
- Natalia Gromak
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
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27
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Pedersen TX, Leethanakul C, Patel V, Mitola D, Lund LR, Danø K, Johnsen M, Gutkind JS, Bugge TH. Laser capture microdissection-based in vivo genomic profiling of wound keratinocytes identifies similarities and differences to squamous cell carcinoma. Oncogene 2003; 22:3964-76. [PMID: 12813470 DOI: 10.1038/sj.onc.1206614] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Keratinocytes undergo a dramatic phenotypic conversion during reepithelialization of skin wounds to become hyperproliferative, migratory, and invasive. This transient healing response phenotypically resembles malignant transformation of keratinocytes during squamous cell carcinoma progression. Here we present the first analysis of global changes in keratinocyte gene expression during skin wound healing in vivo, and compare these changes to changes in gene expression during malignant conversion of keratinized epithelium. Laser capture microdissection was used to isolate RNA from wound keratinocytes from incisional mouse skin wounds and adjacent normal skin keratinocytes. Changes in gene expression were determined by comparative cDNA array analyses, and the approach was validated by in situ hybridization. The analyses identified 48 candidate genes not previously associated with wound reepithelialization. Furthermore, the analyses revealed that the phenotypic resemblance of wound keratinocytes to squamous cell carcinoma is mimicked at the level of gene expression, but notable differences between the two tissue-remodeling processes were also observed. The combination of laser capture microdissection and cDNA array analysis provides a powerful new tool to unravel the complex changes in gene expression that underlie physiological and pathological remodeling of keratinized epithelium.
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Affiliation(s)
- Tanja Xenia Pedersen
- Proteases and Tissue Remodeling Unit, Oral & Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, 30 Convent Drive, Room 211, Bethesda, MD 20892, USA
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28
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Sim EUH, Smith A, Szilagi E, Rae F, Ioannou P, Lindsay MH, Little MH. Wnt-4 regulation by the Wilms' tumour suppressor gene, WT1. Oncogene 2002; 21:2948-60. [PMID: 12082525 DOI: 10.1038/sj.onc.1205373] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2001] [Revised: 01/31/2002] [Accepted: 01/31/2002] [Indexed: 11/08/2022]
Abstract
The Wilms' tumour suppressor gene, WT1, encodes multiple nuclear protein isoforms, all containing four C-terminal zinc finger motifs. WT1 proteins can both activate and repress putative target genes in vitro, although the in vivo relevance of these putative target genes is often unverified. WT1 mutations can result in Wilms' tumour and the Denys-Drash Syndrome (DDS) of infantile nephropathy, XY pseudohermaphroditism and predisposition to Wilms' tumour. We have established stable transfectants of the mouse mesonephric cell line, M15, which express WT1 harbouring a common DDS point mutation (R394W). A comparison of the expression profiles of M15 and transfectant C2A was performed using Nylon-based arrays. Very few genes showed differential expression. However Wnt-4, a member of the Wnt gene family of secreted glycoproteins, was downregulated in C2A and other similar clones. Doxycycline induction of WT1-A or WT1-D expression in HEK293 stable transfectants also elicited an elevation in Wnt4 expression. Wnt4 is critical for the mesenchyme-to-epithelial transition during kidney development, making it an attractive putative WT1 target. We have mapped human Wnt-4 gene to chromosome 1p35-36, a region of frequent LOH in WT, have characterized the genomic structure of the human Wnt-4 gene and isolated 9 kb of immediate promoter. While several potential WT1 binding sites exist within this promoter, reporter analysis does not strongly support the direct regulation of Wnt4 by WT1. We propose that Wnt-4 regulation by WT1 occurs at a more distant promoter or enhancer site, or is indirect.
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Affiliation(s)
- Edmund U-H Sim
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
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Roger B, Moisand A, Amalric F, Bouvet P. Repression of RNA polymerase I transcription by nucleolin is independent of the RNA sequence that is transcribed. J Biol Chem 2002; 277:10209-19. [PMID: 11773064 DOI: 10.1074/jbc.m106412200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nucleolin is one of the most abundant non-ribosomal proteins of the nucleolus. Several studies in vitro have shown that nucleolin is involved in several steps of ribosome biogenesis, including the regulation of rDNA transcription, rRNA processing, and ribosome assembly. However, the different steps of ribosome biogenesis are highly coordinated, and therefore it is not clear to what extent nucleolin is involved in each of these steps. It has been proposed that the interaction of nucleolin with the rDNA sequence and with nascent pre-rRNA leads to the blocking of RNA polymerase I (RNA pol I) transcription. To test this model and to get molecular insights into the role of nucleolin in RNA pol I transcription, we studied the function of nucleolin in Xenopus oocytes. We show that injection of a 2-4-fold excess of Xenopus or hamster nucleolin in stage VI Xenopus oocytes reduces the accumulation of 40 S pre-rRNA 3-fold, whereas transcription by RNA polymerase II and III is not affected. Direct analysis of rDNA transcription units by electron microscopy reveals that the number of polymerase complexes/rDNA unit is drastically reduced in the presence of increased amounts of nucleolin and corresponds to the level of reduction of 40 S pre-rRNA. Transcription from DNA templates containing various combinations of RNA polymerase I or II promoters in fusion with rDNA or CAT sequences was analyzed in the presence of elevated amounts of nucleolin. It was shown that nucleolin leads to transcription repression from a minimal polymerase I promoter, independently of the nature of the RNA sequence that is transcribed. Therefore, we propose that nucleolin affects RNA pol I transcription by acting directly on the transcription machinery or on the rDNA promoter sequences and not, as previously thought, through interaction with the nascent pre-rRNA.
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Affiliation(s)
- Benoit Roger
- Laboratoire de Pharmacologie et de Biologie Structurale, CNRS UMR 5089, 205 route de Narbonne, 31077 Toulouse Cedex, France
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31
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Hoffmann E, Neumann G, Hobom G, Webster RG, Kawaoka Y. "Ambisense" approach for the generation of influenza A virus: vRNA and mRNA synthesis from one template. Virology 2000; 267:310-7. [PMID: 10662626 DOI: 10.1006/viro.1999.0140] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We present a system for creating influenza virus by generating viral RNA (vRNA) and mRNA from one template. Recently, a system for the generation of influenza A virus entirely from cloned cDNAs was established (Neumann et al., 1999, Proc. Natl. Acad. Sci. USA 96, 9345-9350). Cells were transfected with plasmids for RNA polymerase I-driven intracellular synthesis of all eight viral RNAs, and with protein expression plasmids for the synthesis of viral structural proteins. Although this system is highly efficient in virus generation, the construction and cotransfection of 17 plasmids is cumbersome and may limit the use of this system to cell lines that can be transfected with high efficiencies. Synthesizing both vRNA and mRNA from one template would reduce the number of plasmids required for virus generation. Therefore, we generated a bidirectional transcription construct that contains cDNA encoding PB1 flanked by an RNA polymerase I (pol I) promoter for vRNA synthesis and an RNA polymerase II (pol II) promoter for mRNA synthesis. The utility of this approach is proved by the generation of virus after transfecting the pol I/pol II-promoter-PB1 construct together with vRNA- and protein-expression constructs for the remaining seven segments. Because this approach reduces the number of plasmids required for virus generation, it also reduces the work necessary for cloning, probably enhances the efficiency of virus generation, and expands the use of the reverse-genetics system to cell lines for which efficient cotransfection of 17 plasmids cannot be achieved.
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Affiliation(s)
- E Hoffmann
- Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, 332 North Lauderdale, Memphis, Tennessee 38105-2794, USA
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32
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Affiliation(s)
- B Ganter
- Department of Pathology, Stanford University School of Medicine, California 94305, USA
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33
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Grummt I. Regulation of mammalian ribosomal gene transcription by RNA polymerase I. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1999; 62:109-54. [PMID: 9932453 DOI: 10.1016/s0079-6603(08)60506-1] [Citation(s) in RCA: 190] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
All cells, from prokaryotes to vertebrates, synthesize vast amounts of ribosomal RNA to produce the several million new ribosomes per generation that are required to maintain the protein synthetic capacity of the daughter cells. Ribosomal gene (rDNA) transcription is governed by RNA polymerase I (Pol I) assisted by a dedicated set of transcription factors that mediate the specificity of transcription and are the targets of the pleiotrophic pathways the cell uses to adapt rRNA synthesis to cell growth. In the past few years we have begun to understand the specific functions of individual factors involved in rDNA transcription and to elucidate on a molecular level how transcriptional regulation is achieved. This article reviews our present knowledge of the molecular mechanism of rDNA transcriptional regulation.
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Affiliation(s)
- I Grummt
- Division of Molecular Biology of the Cell II, German Cancer Research Center, Heidelberg, Germany
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34
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Wagner DS, Gan L, Klein WH. Expression of a gene trap reporter construct in a subset of cells in embryonic sites of hematopoiesis: evidence for alternative rRNA production in hematopoietic cells. Biochem Biophys Res Commun 1998; 250:674-81. [PMID: 9784405 DOI: 10.1006/bbrc.1998.9309] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Three mouse lines were generated from independent gene trap events in embryonic stem cells. These lines express a betageo reporter gene in a subset of cells at sites of embryonic hematopoiesis. The 5' breakpoints of all three lines were found to lie in 45S ribosomal RNA transcription units. Expression was apparently linked to metabolic activity in these cells, since the kinetics of expression during embryogenesis matched that of cycling cells with colony forming unit spleen (CFU-S) potential. Expression was not seen in adult tissues unless the animals were treated with hydroxyurea, inducing synchronous entry of quiescent CFU-S into the cell cycle. Our results suggest that there is a subset of hematopoietic stem cells, which when actively proliferating, express the SAbetageo reporter construct from RNA polymerase I transcription units.
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Affiliation(s)
- D S Wagner
- Department of Biochemistry and Molecular Biology, University of Texas M.D. Anderson Cancer Center, Houston, Texas, 77030, USA
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35
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Wang KL, Warner JR. Positive and negative autoregulation of REB1 transcription in Saccharomyces cerevisiae. Mol Cell Biol 1998; 18:4368-76. [PMID: 9632820 PMCID: PMC109020 DOI: 10.1128/mcb.18.7.4368] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/1998] [Accepted: 04/07/1998] [Indexed: 02/07/2023] Open
Abstract
Reb1p is a DNA binding protein of Saccharomyces cerevisiae that has been implicated in the activation of transcription by polymerase (Pol) II, in the termination of transcription by Pol I, and in the organization of nucleosomes. Studies of the transcriptional control of the REB1 gene have led us to identify three Reb1p binding sites in the 5' region of the its gene, termed A, B, and C, at positions -110, -80, and +30 with respect to transcription initiation. In vitro, Reb1p binds to the three sites with the relative affinity of A >/= C > B. Kinetic parameters suggest that when both A and C sites are present on the same DNA molecule, the C site may recruit Reb1p for the A site. In vivo the A and B sites each contribute to the transcription activity of REB1 in roughly additive fashion. Mutation of both A and B sites abolishes transcription. On the other hand, the C site is a negative element, reducing transcription by 40%. In cells overexpressing Reb1p, the C site reduces transcription by more than 80%. This effect can be transposed to another transcription unit, demonstrating that the effect of Reb1p binding at the C site does not depend on interaction with upstream Reb1p molecules. Relocation of the C site to a position 105 bp downstream of the transcription initiation site abolishes its effect, suggesting that it does not act as a conventional attenuator of transcription. We conclude that binding of Reb1p at the C site hinders formation of the initiation complex. This arrangement of Reb1p binding sites provides a positive and negative mechanism to autoregulate the expression of REB1. Such an arrangement could serve to dampen the inevitable fluctuation in Rep1p levels caused by the intermittent presence of its mRNA within an individual cell.
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Affiliation(s)
- K L Wang
- Department of Cell Biology, Albert Einstein College of Medicine, The Bronx, New York 10461, USA
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36
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Affiliation(s)
- R J Planta
- Department of Biochemistry and Molecular Biology, IMBW, BioCentrum Amsterdam, Vrije Universiteit, The Netherlands.
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37
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Reeder RH, Lang WH. Terminating transcription in eukaryotes: lessons learned from RNA polymerase I. Trends Biochem Sci 1997; 22:473-7. [PMID: 9433127 DOI: 10.1016/s0968-0004(97)01133-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Within the past few years, the genes encoding transcription terminator proteins for RNA polymerase I (pol I) have been cloned from organisms as diverse as yeast and mammals. The availability of terminator proteins has allowed construction of in vitro transcription systems that terminate pol I at the same sites as used in vivo and thus allows study of termination mechanisms. This has resulted in a burst of information concerning pol I termination mechanisms, which this review will attempt to summarize.
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Affiliation(s)
- R H Reeder
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
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38
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Gerber JK, Gögel E, Berger C, Wallisch M, Müller F, Grummt I, Grummt F. Termination of mammalian rDNA replication: polar arrest of replication fork movement by transcription termination factor TTF-I. Cell 1997; 90:559-67. [PMID: 9267035 DOI: 10.1016/s0092-8674(00)80515-2] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A replication fork barrier (RFB) at the 3' end of eukaryotic ribosomal RNA genes blocks bidirectional fork progression and limits DNA replication to the same direction as transcription. We have reproduced the RFB in vitro in HeLa cell extracts using 3' terminal murine rDNA fused to an SV40 origin-based vector. The RFB is polar and modularly organized, requiring both the Sal box transcription terminator and specific flanking sequences. Mutations within the terminator element, depletion of the RNA polymerase I-specific transcription termination factor TTF-I, or deletion of the termination domain of TTF-I abolishes RFB activity. Thus, the same factor that blocks elongating RNA polymerase I prevents head-on collision between the DNA replication apparatus and the transcription machinery.
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Affiliation(s)
- J K Gerber
- Institute of Biochemistry, University of Würzburg, Germany
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39
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Caparros-Ruiz D, Lahmy S, Piersanti S, Echeverría M. Two ribosomal DNA-binding factors interact with a cluster of motifs on the 5' external transcribed spacer, upstream from the primary pre-rRNA processing site in a higher plant. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 247:981-9. [PMID: 9288923 DOI: 10.1111/j.1432-1033.1997.00981.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In radish the primary processing site in pre-rRNA has been mapped to a TTTTCGCGC sequence (motif P) in the 5' external transcribed spacer (5' ETS) of the ribosomal DNA (rDNA) [Delcasso-Tremousaygue, D., Grellet, F., Panabières, F., Ananiev, E. & Delseny, M. (1988) Eur. J. Biochem. 172, 767-776]. The processing site is just downstream of four similar motifs named A1, A2, A3 and B. The five motifs constitute cluster A123BP. We have described previously that in radish extracts a nuclear protein, nuclear factor B (NF B) specifically binds to motif B [Echeverría, M., Penon, P. & Delseny, M. (1994) Mol. Gen. Genet. 243, 442-452]. Here, by means of electrophoretic-mobility-shift assays, we describe an rDNA-binding activity, nuclear factor D (NF D), that interacts with the A123BP cluster. Using various rDNA probes and competitors we show that NF D binds specifically to the A123 clustered motifs but not to similar B or P motifs. We used sequence-specific DNA-affinity chromatography to separate NF D from NF B. DNase I footprinting was used to map the binding site of NF D on the A123BP cluster and we compared it with that of NF B on the same probe. The footprint of NF D extends from the A1 motif to the 5' end of the NF B-binding site and includes motifs A2 and A3 on each strand. The footprinting of NF B is restricted to motif B and adjacent nucleotides. Thus the NF D-binding and NF B-binding sites are distinct but overlap. These two factors bind with a high specificity to the A123BP cluster in the radish 5' ETS. The possibility that these factors regulate rDNA transcription elongation at the level of the primary pre-rRNA processing site in crucifers is discussed.
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Affiliation(s)
- D Caparros-Ruiz
- Laboratoire de Physiologie et Biologie Moléculaire des Plantes, UMR CNRS 5545, Université de Perpignan, France
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40
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Tschochne H, Milkereit P. RNA polymerase I from S. cerevisiae depends on an additional factor to release terminated transcripts from the template. FEBS Lett 1997; 410:461-6. [PMID: 9237683 DOI: 10.1016/s0014-5793(97)00636-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Terminated transcripts were generated at the ends of linearized DNA templates and at DNA-bound lac repressor by in vitro transcription with highly enriched or purified yeast RNA polymerase I (pol I). The release of the synthesized transcripts from the DNA was analyzed using immobilized DNA as template for the transcription reaction. An additional activity distinguishable from pol I was necessary to remove the terminated RNA from the template. Efficiency of transcript release could be improved if a thymidine-rich DNA fragment was located upstream of the transcriptional arrest caused by the DNA-bound lac repressor. The release activity interacted with different forms of polymerases, pol I able to initiate on the ribosomal gene promoter and pol I only active in non-specific transcription.
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41
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Lapi P, Macchia PE, Chiovato L, Biffali E, Moschini L, Larizza D, Baserga M, Pinchera A, Fenzi G, Di Lauro R. Mutations in the gene encoding thyroid transcription factor-1 (TTF-1) are not a frequent cause of congenital hypothyroidism (CH) with thyroid dysgenesis. Thyroid 1997; 7:383-7. [PMID: 9226207 DOI: 10.1089/thy.1997.7.383] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Permanent congenital hypothyroidism (CH) has an incidence of 1/3000-4000 newborns and is among the most frequent cause of mental retardation and neurological alterations in children. In 80% to 85% of cases CH is associated with thyroid dysgenesis. A group of 61 patients with CH (22 with agenesis, 18 with ectopy, 1 with hypoplasia, and 20 cases with CH without thyroid enlargement but not further characterized) and 30 normal subjects were examined for the presence of mutations in the gene encoding the thyroid transcription factor 1 (TTF-1). The coding-region of the TTF-1 gene was analyzed in all cases by the single stranded conformational polymorphism (SSCP) and no mutations were detected. Direct sequencing also carried out in patients with thyroid agenesis confirmed the absence of mutations or polymorphisms in the TTF-1 gene. The absence of mutations in the TTF-1 gene in our samples indicates that the mutations in the TTF-1 gene are not a frequent cause of CH.
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Affiliation(s)
- P Lapi
- Stazione Zoologica A. Dohrn, Napoli, Naples, Italy
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42
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Mason SW, Wallisch M, Grummt I. RNA polymerase I transcription termination: similar mechanisms are employed by yeast and mammals. J Mol Biol 1997; 268:229-34. [PMID: 9159465 DOI: 10.1006/jmbi.1997.0976] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Termination of RNA polymerase I (Pol I) transcription requires the interaction of a specific DNA binding factor with terminator elements downstream of the pre-rRNA coding region. Both the terminator elements and the respective termination factors are distinct in yeast and mammals, and differences in the mechanism of transcription termination have been postulated. We have compared in vitro transcription termination of yeast and mouse Pol I using both the murine factor TTF-I, and the yeast homolog Reb1p. We show that, similar to TTF-I, Reb1p was sufficient for pausing of Pol I from either species, but was unable to cause release of the nascent transcripts from the paused ternary complex. The deficiency of Reb1p to mediate transcript release from Pol I of either species was complemented by the recently characterized murine release factor. Thus, both yeast and mouse Pol I termination requires a trans-acting factor that, in conjunction with the T-rich flanking sequence, releases the transcripts and Pol I from the template. The observation that the murine factor causes dissociation of ternary transcription complexes arrested by Reb1p suggests that the mechanism of Pol I termination is highly conserved from yeast to mammals.
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Affiliation(s)
- S W Mason
- German Cancer Research Center, Division of Molecular Biology of the Cell II, Heidelberg
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43
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Zhao A, Guo A, Liu Z, Pape L. Molecular cloning and analysis of Schizosaccharomyces pombe Reb1p: sequence-specific recognition of two sites in the far upstream rDNA intergenic spacer. Nucleic Acids Res 1997; 25:904-10. [PMID: 9016645 PMCID: PMC146519 DOI: 10.1093/nar/25.4.904] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The coding sequences for a Schizosaccharomyces pombe sequence-specific DNA binding protein, Reb1p, have been cloned. The predicted S. pombe Reb1p is 24-29% identical to mouse TTF-1 (transcription termination factor-1) and Saccharomyces cerevisiae REB1 protein, both of which direct termination of RNA polymerase I catalyzed transcripts. The S.pombe Reb1 cDNA encodes a predicted polypeptide of 504 amino acids with a predicted molecular weight of 58.4 kDa. The S. pombe Reb1p is unusual in that the bipartite DNA binding motif identified originally in S.cerevisiae and Klyveromyces lactis REB1 proteins is uninterrupted and thus S.pombe Reb1p may contain the smallest natural REB1 homologous DNA binding domain. Its genomic coding sequences were shown to be interrupted by two introns. A recombinant histidine-tagged Reb1 protein bearing the rDNA binding domain has two homologous, sequence-specific binding sites in the S. pomber DNA intergenic spacer, located between 289 and 480 nt downstream of the end of the approximately 25S rRNA coding sequences. Each binding site is 13-14 bp downstream of two of the three proposed in vivo termination sites. The core of this 17 bp site, AGGTAAGGGTAATGCAC, is specifically protected by Reb1p in footprinting analysis.
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Affiliation(s)
- A Zhao
- Department of Chemistry, New York University 10003, USA
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44
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Jeong SW, Lang WH, Reeder RH. The yeast transcription terminator for RNA polymerase I is designed to prevent polymerase slippage. J Biol Chem 1996; 271:16104-10. [PMID: 8663252 DOI: 10.1074/jbc.271.27.16104] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A transcription terminator for RNA polymerase I (polI) in the yeast, Saccharomyces cerevisiae, is composed of two essential elements, the 11bp binding site for Reb1p and an upstream T-rich element coding for the last 10-12 nucleotides of the terminated transcript. We now show that, if the upstream element is changed to homopolymer T residues, polI undergoes iterative slippage, long poly(U) tails are added to the transcript, and termination is impaired. Reinsertion of one or two non-T residues within a critical region prevents iterative slippage and reinstates termination. A survey of naturally occurring terminators reveals that many contain T-rich upstream regions with non-T residues situated appropriately to prevent slippage. We discuss the possibility that the first step in slippage, backward sliding of both the transcript and the catalytic center of the polymerase, may be an obligatory step in the normal termination process.
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Affiliation(s)
- S W Jeong
- Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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45
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Schnapp A, Grummt I. Purification, assay, and properties of RNA polymerase I and class I-specific transcription factors in mouse. Methods Enzymol 1996; 273:233-48. [PMID: 8791616 DOI: 10.1016/s0076-6879(96)73023-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- A Schnapp
- Division of Molecular Biology of the Cell II/0120, German Cancer Research Center, Heidelberg, Germany
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