1
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Daiß JL, Griesenbeck J, Tschochner H, Engel C. Synthesis of the ribosomal RNA precursor in human cells: mechanisms, factors and regulation. Biol Chem 2023; 404:1003-1023. [PMID: 37454246 DOI: 10.1515/hsz-2023-0214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/04/2023] [Indexed: 07/18/2023]
Abstract
The ribosomal RNA precursor (pre-rRNA) comprises three of the four ribosomal RNAs and is synthesized by RNA polymerase (Pol) I. Here, we describe the mechanisms of Pol I transcription in human cells with a focus on recent insights gained from structure-function analyses. The comparison of Pol I-specific structural and functional features with those of other Pols and with the excessively studied yeast system distinguishes organism-specific from general traits. We explain the organization of the genomic rDNA loci in human cells, describe the Pol I transcription cycle regarding structural changes in the enzyme and the roles of human Pol I subunits, and depict human rDNA transcription factors and their function on a mechanistic level. We disentangle information gained by direct investigation from what had apparently been deduced from studies of the yeast enzymes. Finally, we provide information about how Pol I mutations may contribute to developmental diseases, and why Pol I is a target for new cancer treatment strategies, since increased rRNA synthesis was correlated with rapidly expanding cell populations.
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Affiliation(s)
- Julia L Daiß
- Regensburg Center for Biochemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Joachim Griesenbeck
- Regensburg Center for Biochemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Herbert Tschochner
- Regensburg Center for Biochemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Christoph Engel
- Regensburg Center for Biochemistry, University of Regensburg, D-93053 Regensburg, Germany
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2
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Theophanous A, Christodoulou A, Mattheou C, Sibai DS, Moss T, Santama N. Transcription factor UBF depletion in mouse cells results in downregulation of both downstream and upstream elements of the rRNA transcription network. J Biol Chem 2023; 299:105203. [PMID: 37660911 PMCID: PMC10558777 DOI: 10.1016/j.jbc.2023.105203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 08/20/2023] [Accepted: 08/24/2023] [Indexed: 09/05/2023] Open
Abstract
Transcription/processing of the ribosomal RNA (rRNA) precursor, as part of ribosome biosynthesis, is intensively studied and characterized in eukaryotic cells. Here, we constructed shRNA-based mouse cell lines partially silenced for the Upstream Binding Factor UBF, the master regulator of rRNA transcription and organizer of open rDNA chromatin. Full Ubf silencing in vivo is not viable, and these new tools allow further characterization of rRNA transcription and its coordination with cellular signaling. shUBF cells display cell cycle G1 delay and reduced 47S rRNA precursor and 28S rRNA at baseline and serum-challenged conditions. Growth-related mTOR signaling is downregulated with the fractions of active phospho-S6 Kinase and pEIF4E translation initiation factor reduced, similar to phosphorylated cell cycle regulator retinoblastoma, pRB, positive regulator of UBF availability/rRNA transcription. Additionally, we find transcription-competent pUBF (Ser484) severely restricted and its interacting initiation factor RRN3 reduced and responsive to extracellular cues. Furthermore, fractional UBF occupancy on the rDNA unit is decreased in shUBF, and expression of major factors involved in different aspects of rRNA transcription is severely downregulated by UBF depletion. Finally, we observe reduced RNA Pol1 occupancy over rDNA promoter sequences and identified unexpected regulation of RNA Pol1 expression, relative to serum availability and under UBF silencing, suggesting that regulation of rRNA transcription may not be restricted to modulation of Pol1 promoter binding/elongation rate. Overall, this work reveals that UBF depletion has a critical downstream and upstream impact on the whole network orchestrating rRNA transcription in mammalian cells.
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Affiliation(s)
- Andria Theophanous
- Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus
| | | | | | - Dany S Sibai
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Quebec, Canada; Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Quebec, Canada
| | - Tom Moss
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Quebec, Canada; Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Quebec, Canada
| | - Niovi Santama
- Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus.
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3
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Abstract
The p-arms of the five human acrocentric chromosomes bear nucleolar organizer regions (NORs) comprising ribosomal gene (rDNA) repeats that are organized in a homogeneous tandem array and transcribed in a telomere-to-centromere direction. Precursor ribosomal RNA transcripts are processed and assembled into ribosomal subunits, the nucleolus being the physical manifestation of this process. I review current understanding of nucleolar chromosome biology and describe current exploration into a role for the NOR chromosomal context. Full DNA sequences for acrocentric p-arms are now emerging, aided by the current revolution in long-read sequencing and genome assembly. Acrocentric p-arms vary from 10.1 to 16.7 Mb, accounting for ∼2.2% of the genome. Bordering rDNA arrays, distal junctions, and proximal junctions are shared among the p-arms, with distal junctions showing evidence of functionality. The remaining p-arm sequences comprise multiple satellite DNA classes and segmental duplications that facilitate recombination between heterologous chromosomes, which is likely also involved in Robertsonian translocations.
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Affiliation(s)
- Brian McStay
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway, Ireland;
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4
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Moss T, LeDoux MS, Crane-Robinson C. HMG-boxes, ribosomopathies and neurodegenerative disease. Front Genet 2023; 14:1225832. [PMID: 37600660 PMCID: PMC10435976 DOI: 10.3389/fgene.2023.1225832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 07/19/2023] [Indexed: 08/22/2023] Open
Abstract
The UBTF E210K neuroregression syndrome is a predominantly neurological disorder caused by recurrent de novo dominant variants in Upstream Binding Factor, that is, essential for transcription of the ribosomal RNA genes. This unusual form of ribosomopathy is characterized by a slow decline in cognition, behavior, and sensorimotor functioning during the critical period of development. UBTF (or UBF) is a multi-HMGB-box protein that acts both as an epigenetic factor to establish "open" chromatin on the ribosomal genes and as a basal transcription factor in their RNA Polymerase I transcription. Here we review the possible mechanistic connections between the UBTF variants, ribosomal RNA gene transcription and the neuroregression syndrome, and suggest that DNA topology may play an important role.
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Affiliation(s)
- Tom Moss
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Québec, QC, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Québec, QC, Canada
| | - Mark S. LeDoux
- Department of Psychology, University of Memphis, Memphis, TN, United States
- Veracity Neuroscience LLC, Memphis, TN, United States
| | - Colyn Crane-Robinson
- Biophysics Laboratories, School of Biology, University of Portsmouth, Portsmouth, United Kingdom
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5
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Wu S, Chen J, Teo BHD, Wee SYK, Wong MHM, Cui J, Chen J, Leong KP, Lu J. The axis of complement C1 and nucleolus in antinuclear autoimmunity. Front Immunol 2023; 14:1196544. [PMID: 37359557 PMCID: PMC10288996 DOI: 10.3389/fimmu.2023.1196544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 05/19/2023] [Indexed: 06/28/2023] Open
Abstract
Antinuclear autoantibodies (ANA) are heterogeneous self-reactive antibodies that target the chromatin network, the speckled, the nucleoli, and other nuclear regions. The immunological aberration for ANA production remains partially understood, but ANA are known to be pathogenic, especially, in systemic lupus erythematosus (SLE). Most SLE patients exhibit a highly polygenic disease involving multiple organs, but in rare complement C1q, C1r, or C1s deficiencies, the disease can become largely monogenic. Increasing evidence point to intrinsic autoimmunogenicity of the nuclei. Necrotic cells release fragmented chromatins as nucleosomes and the alarmin HMGB1 is associated with the nucleosomes to activate TLRs and confer anti-chromatin autoimmunogenecity. In speckled regions, the major ANA targets Sm/RNP and SSA/Ro contain snRNAs that confer autoimmunogenecity to Sm/RNP and SSA/Ro antigens. Recently, three GAR/RGG-containing alarmins have been identified in the nucleolus that helps explain its high autoimmunogenicity. Interestingly, C1q binds to the nucleoli exposed by necrotic cells to cause protease C1r and C1s activation. C1s cleaves HMGB1 to inactive its alarmin activity. C1 proteases also degrade many nucleolar autoantigens including nucleolin, a major GAR/RGG-containing autoantigen and alarmin. It appears that the different nuclear regions are intrinsically autoimmunogenic by containing autoantigens and alarmins. However, the extracellular complement C1 complex function to dampen nuclear autoimmunogenecity by degrading these nuclear proteins.
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Affiliation(s)
- Shan Wu
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Immunology Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Junjie Chen
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Immunology Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Boon Heng Dennis Teo
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Immunology Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Seng Yin Kelly Wee
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Immunology Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Ming Hui Millie Wong
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Immunology Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Jianzhou Cui
- Immunology Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Jinmiao Chen
- Immunology Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Singapore Immunology Network, Agency for Science, Technology and Research, Singapore, Singapore
| | - Khai Pang Leong
- Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore, Singapore
| | - Jinhua Lu
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Immunology Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
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6
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Tsai HI, Wu Y, Huang R, Su D, Wu Y, Liu X, Wang L, Xu Z, Pang Y, Sun C, He C, Shu F, Zhu H, Wang D, Cheng F, Huang L, Chen H. PHF6 functions as a tumor suppressor by recruiting methyltransferase SUV39H1 to nucleolar region and offers a novel therapeutic target for PHF6-muntant leukemia. Acta Pharm Sin B 2022; 12:1913-1927. [PMID: 35847518 PMCID: PMC9279718 DOI: 10.1016/j.apsb.2021.10.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Revised: 09/24/2021] [Accepted: 10/14/2021] [Indexed: 11/22/2022] Open
Abstract
Mutations in the plant homeodomain-like finger protein 6 (PHF6) gene are strongly associated with acute myeloid (AML) and T-cell acute lymphoblastic leukemia (T-ALL). In this study, we demonstrated that PHF6 can bind to H3K9me3 and H3K27me1 on the nucleolar chromatin and recruit histone methyltransferase SUV39H1 to the rDNA locus. The deletion of PHF6 caused a decrease in the recruitment of SUV39H1 to rDNA gene loci, resulting in a reduction in the level of H3K9me3 and the promotion of rDNA transcription. The knockdown of either SUV39H1 or PHF6 significantly attenuated the effects of increase in H3K9me3 and suppressed the transcription of rDNA induced by the overexpression of the other interacting partner, thereby establishing an interdependent relationship between PHF6 and SUV39H1 in their control of rRNA transcription. The PHF6 clinical mutants significantly impaired the ability to bind and recruit SUV39H1 to the rDNA loci, resulting in an increase in rDNA transcription activity, the proliferation of in vitro leukemia cells, and the growth of in vivo mouse xenografts. Importantly, significantly elevated levels of pre-rRNA were observed in clinical AML patients who possessed a mutated version of PHF6. The specific rDNA transcription inhibitor CX5461 significantly reduced the resistance of U937 AML cells deficient in PHF6 to cytarabine, the drug that is most commonly used to treat AML. Collectively, we revealed a novel molecular mechanism by which PHF6 recruits methyltransferase SUV39H1 to the nucleolar region in leukemia and provided a potential therapeutic target for PHF6-mutant leukemia.
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Affiliation(s)
- Hsiang-i Tsai
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
- Department of Medical Imaging, the Affiliated Hospital of Jiangsu University, Zhenjiang 212001, China
| | - Yanping Wu
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
| | - Rui Huang
- Department of Hematology, Zhujiang Hospital, Southern Medical University, Guangzhou 510000, China
| | - Dandan Su
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
| | - Yingyi Wu
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
| | - Xiaoyan Liu
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
| | - Linglu Wang
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
| | - Zhanxue Xu
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
| | - Yuxin Pang
- School of Traditional Medicine Materials Resource, Guangdong Pharmaceutical University, Yunfu 527322, China
| | - Chong Sun
- Immune Regulation in Cancer, German Cancer Research Center, Heidelberg 69120, Germany
| | - Chao He
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
| | - Fan Shu
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
| | - Haitao Zhu
- Department of Medical Imaging, the Affiliated Hospital of Jiangsu University, Zhenjiang 212001, China
| | - Dongqing Wang
- Department of Medical Imaging, the Affiliated Hospital of Jiangsu University, Zhenjiang 212001, China
| | - Fang Cheng
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
- Corresponding authors.
| | - Laiqiang Huang
- The Shenzhen Key Lab of Gene and Antibody Therapy, Center for Biotechnology & Biomedicine, Division of Life and Health Sciences, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
- Corresponding authors.
| | - Hongbo Chen
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, China
- Corresponding authors.
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7
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Hornofova T, Pokorna B, Hubackova SS, Uvizl A, Kosla J, Bartek J, Hodny Z, Vasicova P. Phospho-SIM and exon8b of PML protein regulate formation of doxorubicin-induced rDNA-PML compartment. DNA Repair (Amst) 2022; 114:103319. [DOI: 10.1016/j.dnarep.2022.103319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 02/25/2022] [Accepted: 03/10/2022] [Indexed: 12/18/2022]
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8
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Rodriguez-Algarra F, Seaborne RAE, Danson AF, Yildizoglu S, Yoshikawa H, Law PP, Ahmad Z, Maudsley VA, Brew A, Holmes N, Ochôa M, Hodgkinson A, Marzi SJ, Pradeepa MM, Loose M, Holland ML, Rakyan VK. Genetic variation at mouse and human ribosomal DNA influences associated epigenetic states. Genome Biol 2022; 23:54. [PMID: 35164830 PMCID: PMC8842540 DOI: 10.1186/s13059-022-02617-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 01/24/2022] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Ribosomal DNA (rDNA) displays substantial inter-individual genetic variation in human and mouse. A systematic analysis of how this variation impacts epigenetic states and expression of the rDNA has thus far not been performed. RESULTS Using a combination of long- and short-read sequencing, we establish that 45S rDNA units in the C57BL/6J mouse strain exist as distinct genetic haplotypes that influence the epigenetic state and transcriptional output of any given unit. DNA methylation dynamics at these haplotypes are dichotomous and life-stage specific: at one haplotype, the DNA methylation state is sensitive to the in utero environment, but refractory to post-weaning influences, whereas other haplotypes entropically gain DNA methylation during aging only. On the other hand, individual rDNA units in human show limited evidence of genetic haplotypes, and hence little discernible correlation between genetic and epigenetic states. However, in both species, adjacent units show similar epigenetic profiles, and the overall epigenetic state at rDNA is strongly positively correlated with the total rDNA copy number. Analysis of different mouse inbred strains reveals that in some strains, such as 129S1/SvImJ, the rDNA copy number is only approximately 150 copies per diploid genome and DNA methylation levels are < 5%. CONCLUSIONS Our work demonstrates that rDNA-associated genetic variation has a considerable influence on rDNA epigenetic state and consequently rRNA expression outcomes. In the future, it will be important to consider the impact of inter-individual rDNA (epi)genetic variation on mammalian phenotypes and diseases.
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Affiliation(s)
| | - Robert A E Seaborne
- The Blizard Institute, School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Amy F Danson
- The Blizard Institute, School of Medicine and Dentistry, Queen Mary University of London, London, UK
- Present Address: German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany
| | - Selin Yildizoglu
- The Blizard Institute, School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Harunori Yoshikawa
- Fujii Memorial Institute of Medical Sciences, Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
| | - Pui Pik Law
- The Blizard Institute, School of Medicine and Dentistry, Queen Mary University of London, London, UK
- Department of Medical and Molecular Genetics, School of Basic and Medical Biosciences, King's College London, London, UK
| | - Zakaryya Ahmad
- The Blizard Institute, School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Victoria A Maudsley
- The Blizard Institute, School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Ama Brew
- The Blizard Institute, School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Nadine Holmes
- DeepSeq, School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Mateus Ochôa
- The Blizard Institute, School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Alan Hodgkinson
- Department of Medical and Molecular Genetics, School of Basic and Medical Biosciences, King's College London, London, UK
| | - Sarah J Marzi
- UK Dementia Research Institute, Imperial College London, London, UK
- Department of Brain Sciences, Imperial College London, London, UK
| | - Madapura M Pradeepa
- The Blizard Institute, School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Matthew Loose
- DeepSeq, School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Michelle L Holland
- Department of Medical and Molecular Genetics, School of Basic and Medical Biosciences, King's College London, London, UK.
| | - Vardhman K Rakyan
- The Blizard Institute, School of Medicine and Dentistry, Queen Mary University of London, London, UK.
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9
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Denisenko O. Epigenetics of Ribosomal RNA Genes. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:S103-S131. [PMID: 35501990 DOI: 10.1134/s0006297922140097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 10/11/2021] [Accepted: 10/12/2021] [Indexed: 06/14/2023]
Abstract
This review is focused on biology of genes encoding ribosomal RNA (rRNA) in mammals. rRNA is a structural component of the most abundant cellular molecule, the ribosome. There are many copies of rRNA genes per genome that are under tight transcriptional control by epigenetic mechanisms serving to meet cellular needs in protein synthesis. Curiously, only a fraction of rRNA genes is used even in the fast-growing cells, raising a question why unused copies of these genes have not been lost during evolution. Two plausible explanations are discussed. First, there is evidence that besides their direct function in production of rRNA, ribosomal RNA genes are involved in regulation of many other genes in the nucleus by forming either temporary or persistent complexes with these genes. Second, it seems that rRNA genes also play a role in the maintenance of genome stability, where lower copy number of rRNA genes destabilizes the genome. These "additional" functions of rRNA genes make them recurrent candidate drivers of chronic human diseases and aging. Experimental support for the involvement of these genes in human diseases and potential mechanisms are also discussed.
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Affiliation(s)
- Oleg Denisenko
- Department of Medicine, University of Washington, Seattle, WA, USA.
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10
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Schächner C, Merkl PE, Pilsl M, Schwank K, Hergert K, Kruse S, Milkereit P, Tschochner H, Griesenbeck J. Establishment and Maintenance of Open Ribosomal RNA Gene Chromatin States in Eukaryotes. Methods Mol Biol 2022; 2533:25-38. [PMID: 35796980 PMCID: PMC9761505 DOI: 10.1007/978-1-0716-2501-9_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
In growing eukaryotic cells, nuclear ribosomal (r)RNA synthesis by RNA polymerase (RNAP) I accounts for the vast majority of cellular transcription. This high output is achieved by the presence of multiple copies of rRNA genes in eukaryotic genomes transcribed at a high rate. In contrast to most of the other transcribed genomic loci, actively transcribed rRNA genes are largely devoid of nucleosomes adapting a characteristic "open" chromatin state, whereas a significant fraction of rRNA genes resides in a transcriptionally inactive nucleosomal "closed" chromatin state. Here, we review our current knowledge about the nature of open rRNA gene chromatin and discuss how this state may be established.
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Affiliation(s)
- Christopher Schächner
- Universität Regensburg, Regensburg Center for Biochemistry (RCB), Lehrstuhl Biochemie III, Regensburg, Germany
| | - Philipp E Merkl
- Universität Regensburg, Regensburg Center for Biochemistry (RCB), Lehrstuhl Biochemie III, Regensburg, Germany
- TUM ForTe, Technische Universität München, Munich, Germany
| | - Michael Pilsl
- Universität Regensburg, Regensburg Center for Biochemistry (RCB), Lehrstuhl Biochemie III, Regensburg, Germany
| | - Katrin Schwank
- Universität Regensburg, Regensburg Center for Biochemistry (RCB), Lehrstuhl Biochemie III, Regensburg, Germany
| | - Kristin Hergert
- Universität Regensburg, Regensburg Center for Biochemistry (RCB), Lehrstuhl Biochemie III, Regensburg, Germany
| | - Sebastian Kruse
- Universität Regensburg, Regensburg Center for Biochemistry (RCB), Lehrstuhl Biochemie III, Regensburg, Germany
| | - Philipp Milkereit
- Universität Regensburg, Regensburg Center for Biochemistry (RCB), Lehrstuhl Biochemie III, Regensburg, Germany.
| | - Herbert Tschochner
- Universität Regensburg, Regensburg Center for Biochemistry (RCB), Lehrstuhl Biochemie III, Regensburg, Germany.
| | - Joachim Griesenbeck
- Universität Regensburg, Regensburg Center for Biochemistry (RCB), Lehrstuhl Biochemie III, Regensburg, Germany.
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11
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Tchurikov NA, Kravatsky YV. The Role of rDNA Clusters in Global Epigenetic Gene Regulation. Front Genet 2021; 12:730633. [PMID: 34531902 PMCID: PMC8438155 DOI: 10.3389/fgene.2021.730633] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 08/02/2021] [Indexed: 12/26/2022] Open
Abstract
The regulation of gene expression has been studied for decades, but the underlying mechanisms are still not fully understood. As well as local and distant regulation, there are specific mechanisms of regulation during development and physiological modulation of gene activity in differentiated cells. Current research strongly supports a role for the 3D chromosomal structure in the regulation of gene expression. However, it is not known whether the genome structure reflects the formation of active or repressed chromosomal domains or if these structures play a primary role in the regulation of gene expression. During early development, heterochromatinization of ribosomal DNA (rDNA) is coupled with silencing or activation of the expression of different sets of genes. Although the mechanisms behind this type of regulation are not known, rDNA clusters shape frequent inter-chromosomal contacts with a large group of genes controlling development. This review aims to shed light on the involvement of clusters of ribosomal genes in the global regulation of gene expression. We also discuss the possible role of RNA-mediated and phase-separation mechanisms in the global regulation of gene expression by nucleoli.
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Affiliation(s)
- Nickolai A Tchurikov
- Engelhardt Institute of Molecular Biology Russian Academy of Sciences, Moscow, Russia
| | - Yuri V Kravatsky
- Engelhardt Institute of Molecular Biology Russian Academy of Sciences, Moscow, Russia
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12
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Ali MAM, Garcia-Vilas JA, Cromwell CR, Hubbard BP, Hendzel MJ, Schulz R. Matrix metalloproteinase-2 mediates ribosomal RNA transcription by cleaving nucleolar histones. FEBS J 2021; 288:6736-6751. [PMID: 34101354 DOI: 10.1111/febs.16061] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 05/09/2021] [Accepted: 06/07/2021] [Indexed: 02/06/2023]
Abstract
Cell proliferation and survival require continuous ribosome biogenesis and protein synthesis. Genes encoding ribosomal RNA are physically located in a specialized substructure within the nucleus known as the nucleolus, which has a central role in the biogenesis of ribosomes. Matrix metalloproteinase-2 was previously detected in the nucleus, however, its role there is elusive. Herein we report that matrix metalloproteinase-2 resides within the nucleolus to regulate ribosomal RNA transcription. Matrix metalloproteinase-2 is enriched at the promoter region of ribosomal RNA gene repeats, and its inhibition downregulates preribosomal RNA transcription. The N-terminal tail of histone H3 is clipped by matrix metalloproteinase-2 in the nucleolus, which is associated with increased ribosomal RNA transcription. Knocking down/out matrix metalloproteinase-2, or inhibiting its activity, prevents histone H3 cleavage and reduces both ribosomal RNA transcription and cell proliferation. In addition to the known extracellular roles of matrix metalloproteinase-2 in tumor growth, our data reveal an epigenetic mechanism whereby intranucleolar matrix metalloproteinase-2 regulates cell proliferation through histone clipping and facilitation of ribosomal RNA transcription.
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Affiliation(s)
- Mohammad A M Ali
- Department of Pediatrics, Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, AB, Canada.,Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, State University of New York, Binghamton, NY, USA
| | - Javier A Garcia-Vilas
- Department of Pediatrics, Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, AB, Canada.,Department of Pharmacology, Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, AB, Canada
| | - Christopher R Cromwell
- Department of Pharmacology, Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, AB, Canada
| | - Basil P Hubbard
- Department of Pharmacology, Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, AB, Canada
| | - Michael J Hendzel
- Department of Oncology, Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, AB, Canada
| | - Richard Schulz
- Department of Pediatrics, Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, AB, Canada.,Department of Pharmacology, Cancer Research Institute of Northern Alberta, University of Alberta, Edmonton, AB, Canada
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13
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Spt4 Promotes Pol I Processivity and Transcription Elongation. Genes (Basel) 2021; 12:genes12030413. [PMID: 33809333 PMCID: PMC8000598 DOI: 10.3390/genes12030413] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 03/03/2021] [Accepted: 03/09/2021] [Indexed: 01/25/2023] Open
Abstract
RNA polymerases (Pols) I, II, and III collectively synthesize most of the RNA in a eukaryotic cell. Transcription by Pols I, II, and III is regulated by hundreds of trans-acting factors. One such protein, Spt4, has been previously identified as a transcription factor that influences both Pols I and II. Spt4 forms a complex with Spt5, described as the Spt4/5 complex (or DSIF in mammalian cells). This complex has been shown previously to directly interact with Pol I and potentially affect transcription elongation. The previous literature identified defects in transcription by Pol I when SPT4 was deleted, but the necessary tools to characterize the mechanism of this effect were not available at the time. Here, we use a technique called Native Elongating Transcript Sequencing (NET-seq) to probe for the global occupancy of Pol I in wild-type (WT) and spt4△ Saccharomyces cerevisiae (yeast) cells at single nucleotide resolution in vivo. Analysis of NET-seq data reveals that Spt4 promotes Pol I processivity and enhances transcription elongation through regions of the ribosomal DNA that are particularly G-rich. These data suggest that Spt4/5 may directly affect transcription elongation by Pol I in vivo.
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14
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Smirnov E, Chmúrčiaková N, Liška F, Bažantová P, Cmarko D. Variability of Human rDNA. Cells 2021; 10:cells10020196. [PMID: 33498263 PMCID: PMC7909238 DOI: 10.3390/cells10020196] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 12/15/2022] Open
Abstract
In human cells, ribosomal DNA (rDNA) is arranged in ten clusters of multiple tandem repeats. Each repeat is usually described as consisting of two parts: the 13 kb long ribosomal part, containing three genes coding for 18S, 5.8S and 28S RNAs of the ribosomal particles, and the 30 kb long intergenic spacer (IGS). However, this standard scheme is, amazingly, often altered as a result of the peculiar instability of the locus, so that the sequence of each repeat and the number of the repeats in each cluster are highly variable. In the present review, we discuss the causes and types of human rDNA instability, the methods of its detection, its distribution within the locus, the ways in which it is prevented or reversed, and its biological significance. The data of the literature suggest that the variability of the rDNA is not only a potential cause of pathology, but also an important, though still poorly understood, aspect of the normal cell physiology.
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15
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Ide S, Imai R, Ochi H, Maeshima K. Transcriptional suppression of ribosomal DNA with phase separation. SCIENCE ADVANCES 2020; 6:6/42/eabb5953. [PMID: 33055158 PMCID: PMC7556839 DOI: 10.1126/sciadv.abb5953] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 08/25/2020] [Indexed: 05/21/2023]
Abstract
The nucleolus is a nuclear body with multiphase liquid droplets for ribosomal RNA (rRNA) transcription. How rRNA transcription is regulated in the droplets remains unclear. Here, using single-molecule tracking of RNA polymerase I (Pol I) and chromatin-bound upstream binding factor (UBF), we reveal suppression of transcription with phase separation. For transcription, active Pol I formed small clusters/condensates that constrained rDNA chromatin in the nucleolus fibrillar center (FC). Treatment with a transcription inhibitor induced Pol I to dissociate from rDNA chromatin and to move like a liquid within the nucleolar cap that transformed from the FC. Expression of a Pol I mutant associated with a craniofacial disorder inhibited transcription by competing with wild-type Pol I clusters and transforming the FC into the nucleolar cap. The cap droplet excluded an initiation factor, ensuring robust silencing. Our findings suggest a mechanism of rRNA transcription suppression via phase separation of intranucleolar molecules governed by Pol I.
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Affiliation(s)
- Satoru Ide
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan.
- Department of Genetics, Sokendai (Graduate University for Advanced Studies), Shizuoka 411-8540, Japan
| | - Ryosuke Imai
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
- Department of Genetics, Sokendai (Graduate University for Advanced Studies), Shizuoka 411-8540, Japan
| | - Hiroko Ochi
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Kazuhiro Maeshima
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan.
- Department of Genetics, Sokendai (Graduate University for Advanced Studies), Shizuoka 411-8540, Japan
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16
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Turi Z, Lacey M, Mistrik M, Moudry P. Impaired ribosome biogenesis: mechanisms and relevance to cancer and aging. Aging (Albany NY) 2020; 11:2512-2540. [PMID: 31026227 PMCID: PMC6520011 DOI: 10.18632/aging.101922] [Citation(s) in RCA: 109] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 04/04/2019] [Indexed: 02/06/2023]
Abstract
The biosynthesis of ribosomes is a complex process that requires the coordinated action of many factors and a huge energy investment from the cell. Ribosomes are essential for protein production, and thus for cellular survival, growth and proliferation. Ribosome biogenesis is initiated in the nucleolus and includes: the synthesis and processing of ribosomal RNAs, assembly of ribosomal proteins, transport to the cytoplasm and association of ribosomal subunits. The disruption of ribosome biogenesis at various steps, with either increased or decreased expression of different ribosomal components, can promote cell cycle arrest, senescence or apoptosis. Additionally, interference with ribosomal biogenesis is often associated with cancer, aging and age-related degenerative diseases. Here, we review current knowledge on impaired ribosome biogenesis, discuss the main factors involved in stress responses under such circumstances and focus on examples with clinical relevance.
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Affiliation(s)
- Zsofia Turi
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University, 779 00 Olomouc, Czech Republic
| | - Matthew Lacey
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University, 779 00 Olomouc, Czech Republic
| | - Martin Mistrik
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University, 779 00 Olomouc, Czech Republic
| | - Pavel Moudry
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University, 779 00 Olomouc, Czech Republic
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17
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Pang MYH, Sun X, Ausió J, Ishibashi T. Histone H4 variant, H4G, drives ribosomal RNA transcription and breast cancer cell proliferation by loosening nucleolar chromatin structure. J Cell Physiol 2020; 235:9601-9608. [PMID: 32385931 DOI: 10.1002/jcp.29770] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 04/09/2020] [Accepted: 04/25/2020] [Indexed: 02/06/2023]
Abstract
The hominidae-specific histone variant H4G is expressed in breast cancer patients in a stage-dependent manner. H4G localizes primarily in the nucleoli via its interaction with nucleophosmin (NPM1). H4G is involved in rDNA transcription and ribosome biogenesis, which facilitates breast cancer cell proliferation. However, the molecular mechanism underlying this process remains unknown. Here, we show that H4G is not stably incorporated into nucleolar chromatin, even with the chaperoning assistance of NPM1. H4G likely form transient nucleosome-like-structure that undergoes rapid dissociation. In addition, the nucleolar chromatin in H4GKO cells is more compact than WT cells. Altogether, our results suggest that H4G relaxes the nucleolar chromatin and enhances rRNA transcription by forming destabilized nucleosome in breast cancer cells.
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Affiliation(s)
- Matthew Y H Pang
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, NT, Hong Kong, HKSAR, China
| | - Xulun Sun
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, NT, Hong Kong, HKSAR, China
| | - Juan Ausió
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada
| | - Toyotaka Ishibashi
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, NT, Hong Kong, HKSAR, China
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18
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NORs on human acrocentric chromosome p-arms are active by default and can associate with nucleoli independently of rDNA. Proc Natl Acad Sci U S A 2020; 117:10368-10377. [PMID: 32332163 PMCID: PMC7229746 DOI: 10.1073/pnas.2001812117] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
A detailed description of how the genome is organized within the human nucleus is a major research goal. Nucleolar organizer regions (NORs) comprising ribosomal DNA (rDNA) arrays are located on the p-arms of the five human acrocentric chromosomes. Here we characterize the rules of engagement between NORs and nucleoli. We reveal variation in rDNA distribution, with some primary cell lines containing as many as four acrocentrics devoid of rDNA. We establish the default status of NORs as active and show that acrocentric p-arms devoid of rDNA retain nucleolar association potential. Based on our data, we propose that in diploid human cells, all 10 acrocentric chromosomes are nucleolar-associated, with involvement of non-rDNA sequences buffering against variable rDNA distribution. Nucleoli, the sites of ribosome biogenesis and the largest structures in human nuclei, form around nucleolar organizer regions (NORs) comprising ribosomal DNA (rDNA) arrays. NORs are located on the p-arms of the five human acrocentric chromosomes. Defining the rules of engagement between these p-arms and nucleoli takes on added significance as describing the three-dimensional organization of the human genome represents a major research goal. Here we used fluorescent in situ hybridization (FISH) and immuno-FISH on metaphase chromosomes from karyotypically normal primary and hTERT-immortalized human cell lines to catalog NORs in terms of their relative rDNA content and activity status. We demonstrate that a proportion of acrocentric p-arms in cell lines and from normal human donors have no detectable rDNA. Surprisingly, we found that all NORs with detectable rDNA are active, as defined by upstream binding factor loading. We determined the nucleolar association status of all NORs during interphase, and found that nucleolar association of acrocentric p-arms can occur independently of rDNA content, suggesting that sequences elsewhere on these chromosome arms drive nucleolar association. In established cancer lines, we characterize a variety of chromosomal rearrangements involving acrocentric p-arms and observe silent, rDNA-containing NORs that are dissociated from nucleoli. In conclusion, our findings indicate that within human nuclei, positioning of all 10 acrocentric chromosomes is dictated by nucleolar association. Furthermore, these nucleolar associations are buffered against interindividual variation in the distribution of rDNA.
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19
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Wang J, Zhang ZQ, Li FQ, Chen JN, Gong X, Cao BB, Wang W. Triptolide interrupts rRNA synthesis and induces the RPL23‑MDM2‑p53 pathway to repress lung cancer cells. Oncol Rep 2020; 43:1863-1874. [PMID: 32236588 PMCID: PMC7160537 DOI: 10.3892/or.2020.7569] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 03/09/2020] [Indexed: 12/15/2022] Open
Abstract
Lung cancer has one of the highest mortalities of any cancer worldwide. Triptolide (TP) is a promising tumor suppressor extracted from the Chinese herb Tripterygium wilfordii. Our previous proteomics analysis revealed that TP significantly interfered with the ribosome biogenesis pathway; however, the underlying molecular mechanism remains poorly understood. The aim of the present study was to determine the molecular mechanism of TP's anticancer effect by investigating the association between ribosomal stress and p53 activation. It was found that TP induces nucleolar disintegration together with RNA polymerase I (Pol I) and upstream binding factor (UBF) translocation. TP interrupted ribosomal (r)RNA synthesis through inhibition of RNA Pol I and UBF transcriptional activation. TP treatment increased the binding of ribosomal protein L23 (RPL23) to mouse double minute 2 protein (MDM2), resulting in p53 being released from MDM2 and stabilized. Activation of p53 induced apoptosis and cell cycle arrest by enhancing the activation of p53 upregulated modulator of apoptosis, caspase 9 and caspase 3, and suppressing BCL2. In vivo experiments showed that TP significantly reduced xenograft tumor size and increased mouse body weight. Immunohistochemical assays confirmed that TP significantly increased the p53 level and induced nucleolus disintegration, during which nucleolin distribution moved from the nucleolus to the nucleoplasm, and RPL23 clustered at the edge of the cell membrane. Therefore, it was proposed that TP induces ribosomal stress, which leads to nucleolus disintegration, and inhibition of rRNA transcription and synthesis, resulting in increased binding of RPL23 with MDM2. Consequently, p53 is activated, which induces apoptosis and cell cycle arrest.
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Affiliation(s)
- Juan Wang
- Department of Clinical Laboratory, Tongde Hospital of Zhejiang Province, Hangzhou, Zhejiang 310012, P.R. China
| | - Zhi-Qian Zhang
- College of Medical Technology, Zhejiang Chinese Medical University, Hangzhou, Zhejiang 310053, P.R. China
| | - Fang-Qiong Li
- Department of Clinical Laboratory, Tongde Hospital of Zhejiang Province, Hangzhou, Zhejiang 310012, P.R. China
| | - Jia-Ning Chen
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, P.R. China
| | - Xiaoting Gong
- Department of Clinical Laboratory, Tongde Hospital of Zhejiang Province, Hangzhou, Zhejiang 310012, P.R. China
| | - Bei-Bei Cao
- Department of Clinical Laboratory, Hangzhou Linan District People's Hospital, Hangzhou, Zhejiang 311300, P.R. China
| | - Wei Wang
- Department of Clinical Laboratory, Tongde Hospital of Zhejiang Province, Hangzhou, Zhejiang 310012, P.R. China
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20
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Izumikawa K, Ishikawa H, Yoshikawa H, Fujiyama S, Watanabe A, Aburatani H, Tachikawa H, Hayano T, Miura Y, Isobe T, Simpson RJ, Li L, Min J, Takahashi N. LYAR potentiates rRNA synthesis by recruiting BRD2/4 and the MYST-type acetyltransferase KAT7 to rDNA. Nucleic Acids Res 2019; 47:10357-10372. [PMID: 31504794 PMCID: PMC6821171 DOI: 10.1093/nar/gkz747] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 07/22/2019] [Accepted: 08/20/2018] [Indexed: 02/06/2023] Open
Abstract
Activation of ribosomal RNA (rRNA) synthesis is pivotal during cell growth and proliferation, but its aberrant upregulation may promote tumorigenesis. Here, we demonstrate that the candidate oncoprotein, LYAR, enhances ribosomal DNA (rDNA) transcription. Our data reveal that LYAR binds the histone-associated protein BRD2 without involvement of acetyl-lysine-binding bromodomains and recruits BRD2 to the rDNA promoter and transcribed regions via association with upstream binding factor. We show that BRD2 is required for the recruitment of the MYST-type acetyltransferase KAT7 to rDNA loci, resulting in enhanced local acetylation of histone H4. In addition, LYAR binds a complex of BRD4 and KAT7, which is then recruited to rDNA independently of the BRD2-KAT7 complex to accelerate the local acetylation of both H4 and H3. BRD2 also helps recruit BRD4 to rDNA. By contrast, LYAR has no effect on rDNA methylation or the binding of RNA polymerase I subunits to rDNA. These data suggest that LYAR promotes the association of the BRD2-KAT7 and BRD4-KAT7 complexes with transcription-competent rDNA loci but not to transcriptionally silent rDNA loci, thereby increasing rRNA synthesis by altering the local acetylation status of histone H3 and H4.
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Affiliation(s)
- Keiichi Izumikawa
- Department of Applied Life Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan.,Global Innovation Research Organizations, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan
| | - Hideaki Ishikawa
- Department of Applied Life Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan
| | - Harunori Yoshikawa
- Centre for Gene Regulation & Expression, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Sally Fujiyama
- Department of Applied Life Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan
| | - Akira Watanabe
- Department of Life Science Frontiers, Center for iPS Cell Research and Application, Kyoto University 53, Shogoin-kawahara-cho, Sakyo-ku, Kyoto-shi, Kyoto 606-8507, Japan
| | - Hiroyuki Aburatani
- Laboratory for System Biology and Medicine, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Hiroyuki Tachikawa
- Department of Applied Life Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Toshiya Hayano
- Department of Biomedical Sciences, College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu 525-8577, Japan
| | - Yutaka Miura
- Department of Applied Life Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan.,Global Innovation Research Organizations, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan
| | - Toshiaki Isobe
- Department of Chemistry, Graduate School of Sciences and Engineering, Tokyo Metropolitan University, 1-1 Minamiosawa, Hachiouji-shi, Tokyo 192-0397, Japan
| | - Richard J Simpson
- Global Innovation Research Organizations, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.,La Trobe Institute for Molecular Science (LIMS) LIMS Building 1, Room 412 La Trobe University, Bundoora Victoria 3086, Australia
| | - Li Li
- Structural Genomics Consortium, University of Toronto, 101 College St., Toronto, Ontario M5G 1L7, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Jinrong Min
- Global Innovation Research Organizations, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.,Structural Genomics Consortium, University of Toronto, 101 College St., Toronto, Ontario M5G 1L7, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Nobuhiro Takahashi
- Department of Applied Life Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan.,Global Innovation Research Organizations, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan
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21
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Lawrimore CJ, Bloom K. Common Features of the Pericentromere and Nucleolus. Genes (Basel) 2019; 10:E1029. [PMID: 31835574 PMCID: PMC6947172 DOI: 10.3390/genes10121029] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/05/2019] [Accepted: 12/07/2019] [Indexed: 12/20/2022] Open
Abstract
Both the pericentromere and the nucleolus have unique characteristics that distinguish them amongst the rest of genome. Looping of pericentromeric DNA, due to structural maintenance of chromosome (SMC) proteins condensin and cohesin, drives its ability to maintain tension during metaphase. Similar loops are formed via condensin and cohesin in nucleolar ribosomal DNA (rDNA). Condensin and cohesin are also concentrated in transfer RNA (tRNA) genes, genes which may be located within the pericentromere as well as tethered to the nucleolus. Replication fork stalling, as well as downstream consequences such as genomic recombination, are characteristic of both the pericentromere and rDNA. Furthermore, emerging evidence suggests that the pericentromere may function as a liquid-liquid phase separated domain, similar to the nucleolus. We therefore propose that the pericentromere and nucleolus, in part due to their enrichment of SMC proteins and others, contain similar domains that drive important cellular activities such as segregation, stability, and repair.
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Affiliation(s)
| | - Kerry Bloom
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA;
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22
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Papaioannou D, Petri A, Dovey OM, Terreri S, Wang E, Collins FA, Woodward LA, Walker AE, Nicolet D, Pepe F, Kumchala P, Bill M, Walker CJ, Karunasiri M, Mrózek K, Gardner ML, Camilotto V, Zitzer N, Cooper JL, Cai X, Rong-Mullins X, Kohlschmidt J, Archer KJ, Freitas MA, Zheng Y, Lee RJ, Aifantis I, Vassiliou G, Singh G, Kauppinen S, Bloomfield CD, Dorrance AM, Garzon R. The long non-coding RNA HOXB-AS3 regulates ribosomal RNA transcription in NPM1-mutated acute myeloid leukemia. Nat Commun 2019; 10:5351. [PMID: 31767858 PMCID: PMC6877618 DOI: 10.1038/s41467-019-13259-2] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 10/28/2019] [Indexed: 12/21/2022] Open
Abstract
Long non-coding RNAs (lncRNAs) are important regulatory molecules that are implicated in cellular physiology and pathology. In this work, we dissect the functional role of the HOXB-AS3 lncRNA in patients with NPM1-mutated (NPM1mut) acute myeloid leukemia (AML). We show that HOXB-AS3 regulates the proliferative capacity of NPM1mut AML blasts in vitro and in vivo. HOXB-AS3 is shown to interact with the ErbB3-binding protein 1 (EBP1) and guide EBP1 to the ribosomal DNA locus. Via this mechanism, HOXB-AS3 regulates ribosomal RNA transcription and de novo protein synthesis. We propose that in the context of NPM1 mutations, HOXB-AS3 overexpression acts as a compensatory mechanism, which allows adequate protein production in leukemic blasts.
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MESH Headings
- Acute Disease
- Animals
- Cell Line, Tumor
- Cell Proliferation
- HEK293 Cells
- Humans
- K562 Cells
- Leukemia, Myeloid/genetics
- Leukemia, Myeloid/pathology
- Mice, Inbred NOD
- Mice, Knockout
- Mice, SCID
- Mutation
- Nuclear Proteins/genetics
- Nucleophosmin
- Protein Biosynthesis/genetics
- RNA, Long Noncoding/genetics
- RNA, Ribosomal/genetics
- THP-1 Cells
- Transcription, Genetic
- Transplantation, Heterologous
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Affiliation(s)
| | - Andreas Petri
- Center for RNA Medicine, Department of Clinical Medicine, Aalborg University, Copenhagen, Denmark
| | - Oliver M Dovey
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, UK
| | - Sara Terreri
- Institute of Genetics and Biophysics (IGB-ABT), National Council of Research (CNR), Naples, Italy
| | - Eric Wang
- Department of Pathology, New York University School of Medicine, New York, NY, USA
| | - Frances A Collins
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
| | - Lauren A Woodward
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, OH, USA
| | - Allison E Walker
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
| | - Deedra Nicolet
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
- Alliance for Clinical Trials in Oncology Statistics and Data Center, The Ohio State University, Columbus, OH, USA
| | - Felice Pepe
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
| | - Prasanthi Kumchala
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
| | - Marius Bill
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
| | | | - Malith Karunasiri
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
| | - Krzysztof Mrózek
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
| | - Miranda L Gardner
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
- Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, USA
| | - Virginia Camilotto
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, UK
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Nina Zitzer
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
| | - Jonathan L Cooper
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, UK
| | - Xiongwei Cai
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, USA
| | - Xiaoqing Rong-Mullins
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
- Division of Biostatistics, College of Public Health, The Ohio State University, Columbus, OH, USA
| | - Jessica Kohlschmidt
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
- Alliance for Clinical Trials in Oncology Statistics and Data Center, The Ohio State University, Columbus, OH, USA
| | - Kellie J Archer
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
- Division of Biostatistics, College of Public Health, The Ohio State University, Columbus, OH, USA
| | - Michael A Freitas
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
- Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, USA
| | - Yi Zheng
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, USA
| | - Robert J Lee
- Division of Pharmaceutics, College of Pharmacy, The Ohio State University, Columbus, OH, USA
| | - Iannis Aifantis
- Department of Pathology, New York University School of Medicine, New York, NY, USA
| | - George Vassiliou
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, UK
- Department of Haematology, Cambridge University Hospitals NHS Trust, Cambridge, UK
| | - Guramrit Singh
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, OH, USA
| | - Sakari Kauppinen
- Center for RNA Medicine, Department of Clinical Medicine, Aalborg University, Copenhagen, Denmark
| | - Clara D Bloomfield
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA
| | | | - Ramiro Garzon
- The Ohio State University, Comprehensive Cancer Center, Columbus, OH, USA.
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23
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Cowell IG, Ling EM, Swan RL, Brooks MLW, Austin CA. The Deubiquitinating Enzyme Inhibitor PR-619 is a Potent DNA Topoisomerase II Poison. Mol Pharmacol 2019; 96:562-572. [PMID: 31515282 PMCID: PMC6776009 DOI: 10.1124/mol.119.117390] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 09/06/2019] [Indexed: 12/13/2022] Open
Abstract
2,6-Diaminopyridine-3,5-bis(thiocyanate) (PR-619) is a broad-spectrum deubiquitinating enzyme (DUB) inhibitor that has been employed in cell-based studies as a tool to investigate the role of ubiquitination in various cellular processes. Here, we demonstrate that in addition to its action as a DUB inhibitor, PR-619 is a potent DNA topoisomerase II (TOP2) poison, inducing both DNA topoisomerase IIα (TOP2A) and DNA topoisomerase IIβ (TOP2B) covalent DNA complexes with similar efficiency to the archetypal TOP2 poison etoposide. However, in contrast to etoposide, which induces TOP2-DNA complexes with a pan-nuclear distribution, PR-619 treatment results in nucleolar concentration of TOP2A and TOP2B. Notably, neither the induction of TOP2-DNA covalent complexes nor their nucleolar concentration are due to TOP2 hyperubiquitination since both occur even under conditions of depleted ubiquitin. Like etoposide, since PR-619 affected TOP2 enzyme activity in in vitro enzyme assays as well as in live cells, we conclude that PR-619 interacts directly with TOP2A and TOP2B. The concentration at which PR-619 exhibits robust cellular DUB inhibitor activity (5-20 μM) is similar to the lowest concentration at which TOP2 poison activity was detected (above 20 μM), which suggests that caution should be exercised when employing this DUB inhibitor in cell-based studies.
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Affiliation(s)
- Ian G Cowell
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Elise M Ling
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Rebecca L Swan
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Matilda L W Brooks
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Caroline A Austin
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom
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24
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Siebenwirth C, Greubel C, Drexler GA, Reindl J, Walsh DWM, Schwarz B, Sammer M, Baur I, Pospiech H, Schmid TE, Dollinger G, Friedl AA. Local inhibition of rRNA transcription without nucleolar segregation after targeted ion irradiation of the nucleolus. J Cell Sci 2019; 132:jcs.232181. [PMID: 31492757 PMCID: PMC6803363 DOI: 10.1242/jcs.232181] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 08/29/2019] [Indexed: 12/18/2022] Open
Abstract
Nucleoli have attracted interest for their role as cellular stress sensors and as potential targets for cancer treatment. The effect of DNA double-strand breaks (DSBs) in nucleoli on rRNA transcription and nucleolar organisation appears to depend on the agent used to introduce DSBs, DSB frequency and the presence (or not) of DSBs outside the nucleoli. To address the controversy, we targeted nucleoli with carbon ions at the ion microbeam SNAKE. Localized ion irradiation with 1-100 carbon ions per point (about 0.3-30 Gy per nucleus) did not lead to overall reduced ribonucleotide incorporation in the targeted nucleolus or other nucleoli of the same cell. However, both 5-ethynyluridine incorporation and Parp1 protein levels were locally decreased at the damaged nucleolar chromatin regions marked by γH2AX, suggesting localized inhibition of rRNA transcription. This locally restricted transcriptional inhibition was not accompanied by nucleolar segregation, a structural reorganisation observed after inhibition of rRNA transcription by treatment with actinomycin D or UV irradiation. The presented data indicate that even multiple complex DSBs do not lead to a pan-nucleolar response if they affect only a subnucleolar region.
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Affiliation(s)
- Christian Siebenwirth
- Bundeswehr Institute of Radiobiology, 80937 Munich, Germany .,Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577 Neubiberg, Germany.,Department of Radiation Therapy and Radiooncology, Technical University of Munich, 81675 Munich, Germany
| | - Christoph Greubel
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577 Neubiberg, Germany
| | - Guido A Drexler
- Department of Radiation Oncology, University Hospital, Ludwig Maximilians University of Munich, 81377 Munich, Germany
| | - Judith Reindl
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577 Neubiberg, Germany
| | - Dietrich W M Walsh
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577 Neubiberg, Germany
| | - Benjamin Schwarz
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577 Neubiberg, Germany
| | - Matthias Sammer
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577 Neubiberg, Germany
| | - Iris Baur
- Department of Radiation Oncology, University Hospital, Ludwig Maximilians University of Munich, 81377 Munich, Germany
| | - Helmut Pospiech
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), 07745 Jena, Germany
| | - Thomas E Schmid
- Department of Radiation Therapy and Radiooncology, Technical University of Munich, 81675 Munich, Germany
| | - Günther Dollinger
- Institute for Applied Physics and Metrology, Universität der Bundeswehr München, 85577 Neubiberg, Germany
| | - Anna A Friedl
- Department of Radiation Oncology, University Hospital, Ludwig Maximilians University of Munich, 81377 Munich, Germany
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25
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African trypanosomes expressing multiple VSGs are rapidly eliminated by the host immune system. Proc Natl Acad Sci U S A 2019; 116:20725-20735. [PMID: 31554700 PMCID: PMC6789922 DOI: 10.1073/pnas.1905120116] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many parasites escape the host immune system by undergoing antigenic variation, a process in which surface antigens are regularly shed and replaced by new ones. Trypanosoma brucei employs multiple sophisticated molecular mechanisms to ensure the expression of a homogeneous VSG coat. We generated a mutant parasite that expresses multiple distinct VSGs and studied the consequences of having a multi-VSG coat during an infection. We showed that expression of multiple VSGs makes the parasites more vulnerable to the immune response, which can now control the trypanosomes from the onset of the infection, allowing most mice to survive. In the future, trypanosome infections may be treated using drugs that generate parasites with multi-VSG coats. Trypanosoma brucei parasites successfully evade the host immune system by periodically switching the dense coat of variant surface glycoprotein (VSG) at the cell surface. Each parasite expresses VSGs in a monoallelic fashion that is tightly regulated. The consequences of exposing multiple VSGs during an infection, in terms of antibody response and disease severity, remain unknown. In this study, we overexpressed a high-mobility group box protein, TDP1, which was sufficient to open the chromatin of silent VSG expression sites, to disrupt VSG monoallelic expression, and to generate viable and healthy parasites with a mixed VSG coat. Mice infected with these parasites mounted a multi-VSG antibody response, which rapidly reduced parasitemia. Consequently, we observed prolonged survival in which nearly 90% of the mice survived a 30-d period of infection with undetectable parasitemia. Immunodeficient RAG2 knock-out mice were unable to control infection with TDP1-overexpressing parasites, showing that the adaptive immune response is critical to reducing disease severity. This study shows that simultaneous exposure of multiple VSGs is highly detrimental to the parasite, even at the very early stages of infection, suggesting that drugs that disrupt VSG monoallelic expression could be used to treat trypanosomiasis.
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26
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Jackobel AJ, Zeberl BJ, Glover DM, Fakhouri AM, Knutson BA. DNA binding preferences of S. cerevisiae RNA polymerase I Core Factor reveal a preference for the GC-minor groove and a conserved binding mechanism. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2019; 1862:194408. [PMID: 31382053 DOI: 10.1016/j.bbagrm.2019.194408] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 07/03/2019] [Accepted: 07/23/2019] [Indexed: 01/24/2023]
Abstract
In Saccharomyces cerevisiae, Core Factor (CF) is a key evolutionarily conserved transcription initiation factor that helps recruit RNA polymerase I (Pol I) to the ribosomal DNA (rDNA) promoter. Upregulated Pol I transcription has been linked to many cancers, and targeting Pol I is an attractive and emerging anti-cancer strategy. Using yeast as a model system, we characterized how CF binds to the Pol I promoter by electrophoretic mobility shift assays (EMSA). Synthetic DNA competitors along with anti-tumor drugs and nucleic acid stains that act as DNA groove blockers were used to discover the binding preference of yeast CF. Our results show that CF employs a unique binding mechanism where it prefers the GC-rich minor groove within the rDNA promoter. In addition, we show that yeast CF is able to bind to the human rDNA promoter sequence that is divergent in DNA sequence and demonstrate CF sensitivity to the human specific Pol I inhibitor, CX-5461. Finally, we show that the human Core Promoter Element (CPE) can functionally replace the yeast Core Element (CE) in vivo when aligned by conserved DNA structural features rather than DNA sequence. Together, these findings suggest that the yeast CF and the human ortholog Selectivity Factor 1 (SL1) use an evolutionarily conserved, structure-based mechanism to target DNA. Their shared mechanism may offer a new avenue in using yeast to explore current and future Pol I anti-cancer compounds.
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Affiliation(s)
- Ashleigh J Jackobel
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Brian J Zeberl
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Danea M Glover
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; School of Graduate Studies, Rutgers Biomedical and Health Sciences, Rutgers University, Piscataway, NJ 08854, USA
| | - Aula M Fakhouri
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Bruce A Knutson
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
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27
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Awasthi S, Verma M, Mahesh A, K Khan MI, Govindaraju G, Rajavelu A, Chavali PL, Chavali S, Dhayalan A. DDX49 is an RNA helicase that affects translation by regulating mRNA export and the levels of pre-ribosomal RNA. Nucleic Acids Res 2019; 46:6304-6317. [PMID: 29618122 PMCID: PMC6158705 DOI: 10.1093/nar/gky231] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 03/28/2018] [Indexed: 12/19/2022] Open
Abstract
Among the proteins predicted to be a part of the DExD box RNA helicase family, the functions of DDX49 are unknown. Here, we characterize the enzymatic activities and functions of DDX49 by comparing its properties with the well-studied RNA helicase, DDX39B. We find that DDX49 exhibits a robust ATPase and RNA helicase activity, significantly higher than that of DDX39B. DDX49 is required for the efficient export of poly (A)+ RNA from nucleus in a splicing-independent manner. Furthermore, DDX49 is a resident protein of nucleolus and regulates the steady state levels of pre-ribosomal RNA by regulating its transcription and stability. These dual functions of regulating mRNA export and pre-ribosomal RNA levels enable DDX49 to modulate global translation. Phenotypically, DDX49 promotes proliferation and colony forming potential of cells. Strikingly, DDX49 is significantly elevated in diverse cancer types suggesting that the increased abundance of DDX49 has a role in oncogenic transformation of cells. Taken together, this study shows the physiological role of DDX49 in regulating distinct steps of mRNA and pre-ribosomal RNA metabolism and hence translation and potential pathological role of its dysregulation, especially in cancers.
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Affiliation(s)
- Sharad Awasthi
- Department of Biotechnology, Pondicherry University, Puducherry 605 014, India
| | - Mamta Verma
- Department of Biotechnology, Pondicherry University, Puducherry 605 014, India
| | - Arun Mahesh
- Department of Biotechnology, Pondicherry University, Puducherry 605 014, India
| | - Mohd Imran K Khan
- Department of Biotechnology, Pondicherry University, Puducherry 605 014, India
| | - Gayathri Govindaraju
- Bacterial and Parasite Disease Biology, Rajiv Gandhi Center for Biotechnology, Trivandrum 695 014, India
| | - Arumugam Rajavelu
- Bacterial and Parasite Disease Biology, Rajiv Gandhi Center for Biotechnology, Trivandrum 695 014, India
| | - Pavithra L Chavali
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Sreenivas Chavali
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Arunkumar Dhayalan
- Department of Biotechnology, Pondicherry University, Puducherry 605 014, India
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28
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Nucleolar DNA Double-Strand Break Responses Underpinning rDNA Genomic Stability. Trends Genet 2019; 35:743-753. [PMID: 31353047 DOI: 10.1016/j.tig.2019.07.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 06/28/2019] [Accepted: 07/01/2019] [Indexed: 12/12/2022]
Abstract
Nucleoli, the sites of ribosome biogenesis, form around ribosomal gene (rDNA) arrays termed nucleolar organiser regions (NORs). These are the most transcriptionally active regions of the human genome and specialised responses have evolved to ensure their genomic stability. This review focuses on nucleolar responses to DNA double-strand breaks (DSBs) introduced into rDNA arrays using sequence-specific endonucleases, including CRISPR/Cas9. Repair of rDNA DSBs is predominantly carried out by the homology-directed repair (HDR) pathway that is facilitated by inhibition of transcription by RNA polymerase-I (Pol-I) and ensuing dramatic nucleolar reorganisation. Additionally, we review evidence that nucleoli can sense and respond to DSBs elsewhere in the genome.
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29
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Potapova TA, Unruh JR, Yu Z, Rancati G, Li H, Stampfer MR, Gerton JL. Superresolution microscopy reveals linkages between ribosomal DNA on heterologous chromosomes. J Cell Biol 2019; 218:2492-2513. [PMID: 31270138 PMCID: PMC6683752 DOI: 10.1083/jcb.201810166] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 03/14/2019] [Accepted: 06/03/2019] [Indexed: 12/15/2022] Open
Abstract
Potapova et al. use superresolution microscopy to describe linkages between ribosomal DNA on heterologous human chromosomes whose formation depends on the transcription factor UBF and topoisomerase II. Linkages persist in the absence of cohesion but require topoisomerase II for resolution. The spatial organization of the genome is enigmatic. Direct evidence of physical contacts between chromosomes and their visualization at nanoscale resolution has been limited. We used superresolution microscopy to demonstrate that ribosomal DNA (rDNA) can form linkages between chromosomes. We observed rDNA linkages in many different human cell types and demonstrated their resolution in anaphase. rDNA linkages are coated by the transcription factor UBF and their formation depends on UBF, indicating that they regularly occur between transcriptionally active loci. Overexpression of c-Myc increases rDNA transcription and the frequency of rDNA linkages, further suggesting that their formation depends on active transcription. Linkages persist in the absence of cohesion, but inhibition of topoisomerase II prevents their resolution in anaphase. We propose that linkages are topological intertwines occurring between transcriptionally active rDNA loci spatially colocated in the same nucleolar compartment. Our findings suggest that active DNA loci engage in physical interchromosomal connections that are an integral and pervasive feature of genome organization.
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Affiliation(s)
| | - Jay R Unruh
- Stowers Institute for Medical Research, Kansas City, MO
| | - Zulin Yu
- Stowers Institute for Medical Research, Kansas City, MO
| | - Giulia Rancati
- Institute of Medical Biology, Agency for Science, Technology and Research, Singapore
| | - Hua Li
- Stowers Institute for Medical Research, Kansas City, MO
| | - Martha R Stampfer
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA
| | - Jennifer L Gerton
- Stowers Institute for Medical Research, Kansas City, MO .,Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS
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30
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Nuclear Phosphoinositides-Versatile Regulators of Genome Functions. Cells 2019; 8:cells8070649. [PMID: 31261688 PMCID: PMC6678639 DOI: 10.3390/cells8070649] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 06/21/2019] [Accepted: 06/25/2019] [Indexed: 12/17/2022] Open
Abstract
The many functions of phosphoinositides in cytosolic signaling were extensively studied; however, their activities in the cell nucleus are much less clear. In this review, we summarize data about their nuclear localization and metabolism, and review the available literature on their involvements in chromatin remodeling, gene transcription, and RNA processing. We discuss the molecular mechanisms via which nuclear phosphoinositides, in particular phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2), modulate nuclear processes. We focus on PI(4,5)P2’s role in the modulation of RNA polymerase I activity, and functions of the nuclear lipid islets—recently described nucleoplasmic PI(4,5)P2-rich compartment involved in RNA polymerase II transcription. In conclusion, the high impact of the phosphoinositide–protein complexes on nuclear organization and genome functions is only now emerging and deserves further thorough studies.
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31
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Figueiredo VC, McCarthy JJ. Regulation of Ribosome Biogenesis in Skeletal Muscle Hypertrophy. Physiology (Bethesda) 2019; 34:30-42. [PMID: 30540235 PMCID: PMC6383632 DOI: 10.1152/physiol.00034.2018] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 09/11/2018] [Accepted: 09/13/2018] [Indexed: 01/22/2023] Open
Abstract
The ribosome is the enzymatic macromolecular machine responsible for protein synthesis. The rates of protein synthesis are primarily dependent on translational efficiency and capacity. Ribosome biogenesis has emerged as an important regulator of skeletal muscle growth and maintenance by altering the translational capacity of the cell. Here, we provide evidence to support a central role for ribosome biogenesis in skeletal muscle growth during postnatal development and in response to resistance exercise training. Furthermore, we discuss the cellular signaling pathways regulating ribosome biogenesis, discuss how myonuclear accretion affects translational capacity, and explore future areas of investigation within the field.
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Affiliation(s)
- Vandré Casagrande Figueiredo
- The Center for Muscle Biology, College of Health Sciences, University of Kentucky , Lexington, Kentucky
- Department of Rehabilitation Sciences, College of Medicine, University of Kentucky , Lexington, Kentucky
| | - John J McCarthy
- The Center for Muscle Biology, College of Health Sciences, University of Kentucky , Lexington, Kentucky
- Department of Physiology, University of Kentucky , Lexington, Kentucky
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32
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Awasthi S, Chakrapani B, Mahesh A, Chavali PL, Chavali S, Dhayalan A. DDX39B promotes translation through regulation of pre-ribosomal RNA levels. RNA Biol 2018; 15:1157-1166. [PMID: 30176153 DOI: 10.1080/15476286.2018.1517011] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
DDX39B, a DExD RNA helicase, is known to be involved in various cellular processes such as mRNA export, splicing and translation. Previous studies showed that the overexpression of DDX39B promotes the global translation but inhibits the mRNA export in a dominant negative manner. This presents a conundrum as to how DDX39B overexpression would increase the global translation if it inhibits the nuclear export of mRNAs. We resolve this by showing that DDX39B affects the levels of pre-ribosomal RNA by regulating its stability as well as synthesis. Furthermore, DDX39B promotes proliferation and colony forming potential of cells and its levels are significantly elevated in diverse cancer types. Thus, increase in DDX39B enhances global translation and cell proliferation through upregulation of pre-ribosomal RNA. This highlights a possible mechanism by which dysregulation of DDX39B expression could lead to oncogenesis.
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Affiliation(s)
- Sharad Awasthi
- a Department of Biotechnology , Pondicherry University , Puducherry , India
| | - Baskar Chakrapani
- a Department of Biotechnology , Pondicherry University , Puducherry , India
| | - Arun Mahesh
- a Department of Biotechnology , Pondicherry University , Puducherry , India
| | - Pavithra L Chavali
- b Structural Studies Division , MRC Laboratory of Molecular Biology , Cambridge , UK
| | - Sreenivas Chavali
- b Structural Studies Division , MRC Laboratory of Molecular Biology , Cambridge , UK
| | - Arunkumar Dhayalan
- a Department of Biotechnology , Pondicherry University , Puducherry , India
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33
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Abstract
Ribosome biogenesis is a complex and highly energy-demanding process that requires the concerted action of all three nuclear RNA polymerases (Pol I-III) in eukaryotes. The three largest ribosomal RNAs (rRNAs) originate from a precursor transcript (pre-rRNA) that is encoded by multicopy genes located in the nucleolus. Transcription of these rRNA genes (rDNA) by Pol I is the key regulation step in ribosome production and is tightly controlled by an intricate network of signaling pathways and epigenetic mechanisms. In this article, we give an overview of the composition of the basal Pol I machinery and rDNA chromatin. We discuss rRNA gene regulation in response to environmental signals and developmental cues and focus on perturbations occurring in diseases linked to either excessive or limited rRNA levels. Finally, we discuss the emerging view that rDNA integrity and activity may be involved in the aging process.
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Affiliation(s)
- Samim Sharifi
- Institute of Biochemistry and Biophysics, Center for Molecular Biomedicine, Friedrich Schiller University, 07745 Jena, Germany; , .,Leibniz-Institute on Aging-Fritz Lipmann Institute, 07745 Jena, Germany
| | - Holger Bierhoff
- Institute of Biochemistry and Biophysics, Center for Molecular Biomedicine, Friedrich Schiller University, 07745 Jena, Germany; , .,Leibniz-Institute on Aging-Fritz Lipmann Institute, 07745 Jena, Germany
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34
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Chen H, Duo Y, Hu B, Wang Z, Zhang F, Tsai H, Zhang J, Zhou L, Wang L, Wang X, Huang L. PICT-1 triggers a pro-death autophagy through inhibiting rRNA transcription and AKT/mTOR/p70S6K signaling pathway. Oncotarget 2018; 7:78747-78763. [PMID: 27729611 PMCID: PMC5346674 DOI: 10.18632/oncotarget.12288] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 09/16/2016] [Indexed: 01/05/2023] Open
Abstract
PICT-1 was originally identified as a tumor suppressor. Here, we found that PICT-1 overexpression triggered pro-death autophagy without nucleolar disruption or p53 accumulation in U251 and MCF7 cells. Truncated PICT-1 fragments 181-346 and 1-346, which partly or totally lack nucleolar localization, showed weaker autophagy-inducing effects than full-length PICT-1 and a well-defined nucleolar mutant (181-479). Furthermore, PICT-1 partly localizes to the nucleolar fibrillar center (FC) and directly binds to ribosomal DNA (rDNA) gene loci, where it interacts with upstream binding factor (UBF). Overexpression of PICT-1 or the 181-479 mutant, but not the 1-346 or 181-346 mutants, markedly inhibited the phosphorylation of UBF and the recruitment of rRNA polymerase I (Pol I) to the rDNA promoter in response to serum stimulation, thereby suppressing rRNA transcription, suggesting that rRNA transcription inhibition might be an important contributor to PICT-1-induced autophagy. This is supported by the finding that CX-5461, a specific Pol I inhibitor, also induced autophagy. In addition, both CX-5461 and PICT-1, but not the 1-346 or 181-346 mutants, significantly suppressed the activation of the Akt/mTOR/p70S6K signaling pathway. Our data show that PICT-1 triggers pro-death autophagy through inhibition of rRNA transcription and the inactivation of AKT/mTOR/p70S6K pathway, independent of nucleolar disruption and p53 activation.
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Affiliation(s)
- Hongbo Chen
- The Shenzhen Key Lab of Gene and Antibody Therapy, Center for Biotechnology & Biomedicine, Division of Life and Health Sciences, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China.,School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yanhong Duo
- Key Laboratory of Plant Cell Activities and Stress Adaptation, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Bo Hu
- Department of Laboratory Medicine, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou 510630, China
| | - Zhiwei Wang
- Department of Laboratory Medicine, The Fourth Affiliated Hospital of Guangzhou Medical University, Guangzhou 511447, China
| | - Fang Zhang
- The Shenzhen Key Laboratory of Gene and Antibody Therapy, Center for Biotechnology & Biomedicine, Division of Life and Health Sciences, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Hsiangi Tsai
- The Shenzhen Key Laboratory of Gene and Antibody Therapy, Center for Biotechnology & Biomedicine, Division of Life and Health Sciences, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China.,School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jianping Zhang
- Department of Quality Inspection, Shenzhen Weiguang Biological Products Co., Ltd, Shenzhen 518107, China
| | - Lanzhen Zhou
- Department of Quality Inspection, Shenzhen Weiguang Biological Products Co., Ltd, Shenzhen 518107, China
| | - Lijun Wang
- The Shenzhen Key Laboratory of Gene and Antibody Therapy, Center for Biotechnology & Biomedicine, Division of Life and Health Sciences, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Xinyu Wang
- Key Laboratory of Plant Cell Activities and Stress Adaptation, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Laiqiang Huang
- The Shenzhen Key Laboratory of Gene and Antibody Therapy, Center for Biotechnology & Biomedicine, Division of Life and Health Sciences, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China.,School of Life Sciences, Tsinghua University, Beijing 100084, China
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35
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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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36
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Lafita-Navarro MDC, Blanco R, Mata-Garrido J, Liaño-Pons J, Tapia O, García-Gutiérrez L, García-Alegría E, Berciano MT, Lafarga M, León J. MXD1 localizes in the nucleolus, binds UBF and impairs rRNA synthesis. Oncotarget 2018; 7:69536-69548. [PMID: 27588501 PMCID: PMC5342496 DOI: 10.18632/oncotarget.11766] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 08/26/2016] [Indexed: 12/16/2022] Open
Abstract
MXD1 is a protein that interacts with MAX, to form a repressive transcription factor. MXD1-MAX binds E-boxes. MXD1-MAX antagonizes the transcriptional activity of the MYC oncoprotein in most models. It has been reported that MYC overexpression leads to augmented RNA synthesis and ribosome biogenesis, which is a relevant activity in MYC-mediated tumorigenesis. Here we describe that MXD1, but not MYC or MNT, localizes to the nucleolus in a wide array of cell lines derived from different tissues (carcinoma, leukemia) as well as in embryonic stem cells. MXD1 also localizes in the nucleolus of primary tissue cells as neurons and Sertoli cells. The nucleolar localization of MXD1 was confirmed by co-localization with UBF. Co-immunoprecipitation experiments showed that MXD1 interacted with UBF and proximity ligase assays revealed that this interaction takes place in the nucleolus. Furthermore, chromatin immunoprecipitation assays showed that MXD1 was bound in the transcribed rDNA chromatin, where it co-localizes with UBF, but also in the ribosomal intergenic regions. The MXD1 involvement in rRNA synthesis was also suggested by the nucleolar segregation upon rRNA synthesis inhibition by actinomycin D. Silencing of MXD1 with siRNAs resulted in increased synthesis of pre-rRNA while enforced MXD1 expression reduces it. The results suggest a new role for MXD1, which is the control of ribosome biogenesis. This new MXD1 function would be important to curb MYC activity in tumor cells.
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Affiliation(s)
- Maria Del Carmen Lafita-Navarro
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), CSIC-Universidad de Cantabria, and Department of Molecular Biology, University of Cantabria, Santander, Spain.,Present address: Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Rosa Blanco
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), CSIC-Universidad de Cantabria, and Department of Molecular Biology, University of Cantabria, Santander, Spain
| | - Jorge Mata-Garrido
- Department of Anatomy and Cell Biology and Centro de Investigación en Red sobre Enfermedades Neurodegenerativas (CIBERNED), University of Cantabria-IDIVAL, Santander, Spain
| | - Judit Liaño-Pons
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), CSIC-Universidad de Cantabria, and Department of Molecular Biology, University of Cantabria, Santander, Spain
| | - Olga Tapia
- Department of Anatomy and Cell Biology and Centro de Investigación en Red sobre Enfermedades Neurodegenerativas (CIBERNED), University of Cantabria-IDIVAL, Santander, Spain
| | - Lucía García-Gutiérrez
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), CSIC-Universidad de Cantabria, and Department of Molecular Biology, University of Cantabria, Santander, Spain
| | - Eva García-Alegría
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), CSIC-Universidad de Cantabria, and Department of Molecular Biology, University of Cantabria, Santander, Spain.,Present address: Stem Cell Hematopoiesis Group, Cancer Research UK Manchester Institute, University of Manchester, Manchester, United Kingdom
| | - María T Berciano
- Department of Anatomy and Cell Biology and Centro de Investigación en Red sobre Enfermedades Neurodegenerativas (CIBERNED), University of Cantabria-IDIVAL, Santander, Spain
| | - Miguel Lafarga
- Department of Anatomy and Cell Biology and Centro de Investigación en Red sobre Enfermedades Neurodegenerativas (CIBERNED), University of Cantabria-IDIVAL, Santander, Spain
| | - Javier León
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), CSIC-Universidad de Cantabria, and Department of Molecular Biology, University of Cantabria, Santander, Spain
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37
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Chen J, Teo BHD, Cai Y, Wee SYK, Lu J. The linker histone H1.2 is a novel component of the nucleolar organizer regions. J Biol Chem 2018; 293:2358-2369. [PMID: 29301938 DOI: 10.1074/jbc.m117.810184] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 12/18/2017] [Indexed: 01/27/2023] Open
Abstract
The nucleoli accumulate rRNA genes and are the sites of rRNA synthesis and rRNA assembly into ribosomes. During mitosis, nucleoli dissociate, but nucleolar remnants remain on the rRNA gene loci, forming distinct nucleolar organizer regions (NORs). Little is known about the composition and structure of NORs, but upstream binding factor (UBF) has been established as its master organizer. In this study, we sought to establish new proteins in NORs. Using UBF-Sepharose to isolate UBF-binding proteins, we identified histone H1.2 as a candidate partner but were puzzled by this observation, given that UBF is known to be located predominantly in nucleoli, whereas H1.2 distributed broadly among the chromatins in interphase nuclei. We then examined cells undergoing mitosis and saw that both H1.2 and UBF were recruited into NORs in this state, reconciling the results of our UBF pulldowns. Inhibiting rRNA synthesis in interphase nuclei also induced NOR-like structures containing both UBF and H1.2. When chromosomes were isolated and spread on coverslips, NORs appeared separated from the chromosomes containing both UBF and H1.2. After chromosomes were fragmented by homogenization, intact NORs remained visible. Results collectively suggest that NORs are independent structures and that the linker histone H1.2 is a novel component of this structure.
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Affiliation(s)
- Junjie Chen
- From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine and Immunology Programme, National University of Singapore, Singapore 117697
| | - Boon Heng Dennis Teo
- From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine and Immunology Programme, National University of Singapore, Singapore 117697
| | - Yitian Cai
- From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine and Immunology Programme, National University of Singapore, Singapore 117697
| | - Seng Yin Kelly Wee
- From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine and Immunology Programme, National University of Singapore, Singapore 117697
| | - Jinhua Lu
- From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine and Immunology Programme, National University of Singapore, Singapore 117697
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38
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Jayaraman S, Chittiboyina S, Bai Y, Abad PC, Vidi PA, Stauffacher CV, Lelièvre SA. The nuclear mitotic apparatus protein NuMA controls rDNA transcription and mediates the nucleolar stress response in a p53-independent manner. Nucleic Acids Res 2017; 45:11725-11742. [PMID: 28981686 PMCID: PMC5714241 DOI: 10.1093/nar/gkx782] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 08/30/2017] [Indexed: 12/20/2022] Open
Abstract
The nuclear mitotic apparatus protein, NuMA, is involved in major cellular events such as DNA damage response, apoptosis and p53-mediated growth-arrest, all of which are under the control of the nucleolus upon stress. Proteomic investigation has identified NuMA among hundreds of nucleolar proteins. Yet, the precise link between NuMA and nucleolar function remains undetermined. We confirm that NuMA is present in the nucleolus and reveal redistribution of NuMA upon actinomycin D or doxorubicin-induced nucleolar stress. NuMA coimmunoprecipitates with RNA polymerase I, with ribosomal proteins RPL26 and RPL24, and with components of B-WICH, an ATP-dependent chromatin remodeling complex associated with rDNA transcription. NuMA also binds to 18S and 28S rRNAs and localizes to rDNA promoter regions. Downregulation of NuMA expression triggers nucleolar stress, as shown by decreased nascent pre-rRNA synthesis, fibrillarin perinucleolar cap formation and upregulation of p27kip1, but not p53. Physiologically relevant nucleolar stress induction with reactive oxygen species reaffirms a p53-independent p27kip1 response pathway and leads to nascent pre-rRNA reduction. It also promotes the decrease in the amount of NuMA. This previously uncharacterized function of NuMA in rDNA transcription and p53-independent nucleolar stress response supports a central role for this nuclear structural protein in cellular homeostasis.
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Affiliation(s)
- Swaathi Jayaraman
- Department of Basic Medical Sciences, Purdue University, West Lafayette, IN 47907-2026, USA.,Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-2026, USA
| | - Shirisha Chittiboyina
- Department of Basic Medical Sciences, Purdue University, West Lafayette, IN 47907-2026, USA
| | - Yunfeng Bai
- Department of Basic Medical Sciences, Purdue University, West Lafayette, IN 47907-2026, USA
| | - Patricia C Abad
- Department of Basic Medical Sciences, Purdue University, West Lafayette, IN 47907-2026, USA
| | - Pierre-Alexandre Vidi
- Department of Basic Medical Sciences, Purdue University, West Lafayette, IN 47907-2026, USA
| | - Cynthia V Stauffacher
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-2026, USA.,Center for Cancer Research, Purdue University, West Lafayette, IN 47907-2026, USA
| | - Sophie A Lelièvre
- Department of Basic Medical Sciences, Purdue University, West Lafayette, IN 47907-2026, USA.,Center for Cancer Research, Purdue University, West Lafayette, IN 47907-2026, USA
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39
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Internal Associations of the Acidic Region of Upstream Binding Factor Control Its Nucleolar Localization. Mol Cell Biol 2017; 37:MCB.00218-17. [PMID: 28874518 DOI: 10.1128/mcb.00218-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 08/25/2017] [Indexed: 01/24/2023] Open
Abstract
Upstream binding factor (UBF) is a member of the high-mobility group (HMG) box protein family, characterized by multiple HMG boxes and a C-terminal acidic region (AR). UBF is an essential transcription factor for rRNA genes and mediates the formation of transcriptionally active chromatin in the nucleolus. However, it remains unknown how UBF is specifically localized to the nucleolus. Here, we examined the molecular mechanisms that localize UBF to the nucleolus. We found that the first HMG box (HMG box 1), the linker region (LR), and the AR cooperatively regulate the nucleolar localization of UBF1. We demonstrated that the AR intramolecularly associates with and attenuates the DNA binding activity of HMG boxes and confers the structured DNA preference to HMG box 1. In contrast, the LR was found to serve as a nuclear localization signal and compete with HMG boxes to bind the AR, permitting nucleolar localization of UBF1. The LR sequence binds DNA and assists the stable chromatin binding of UBF. We also showed that the phosphorylation status of the AR does not clearly affect the localization of UBF1. Our results strongly suggest that associations of the AR with HMG boxes and the LR regulate UBF nucleolar localization.
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40
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Rajarajacholan UK, Thalappilly S, Riabowol K. ING1 regulates rRNA levels by altering nucleolar chromatin structure and mTOR localization. Nucleic Acids Res 2017; 45:1776-1792. [PMID: 27903908 PMCID: PMC5389678 DOI: 10.1093/nar/gkw1161] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 11/10/2016] [Indexed: 01/31/2023] Open
Abstract
Epigenetic, transcriptional and signaling processes in the nucleolus regulate rRNA transcription and cell growth. We report here that the tumor suppressor ING1b binds rDNA, regulates rDNA chromatin modifications and affects nucleolar localization of mTOR to modulate rRNA levels. ING1 represses rDNA transcription by recruiting HDAC1 to rDNA loci, increasing its association with the NoRC complex and deacetylating the histone H3K9 and H3K27 marks of active transcription. Loss of ING1 enhances nucleolar localization of phospho-mTOR and its association with Raptor and GβL, even during rapamycin treatment. ING1 inhibits rDNA transcription by inhibiting UBF activity and its interaction with mTOR. Regulation of rDNA heterochromatin and rRNA synthesis by ING1 is also apparent during normal cell growth and during cell stress. Moreover, this function was also important during PMA induced differentiation of THP1 cells, since knocking down ING1 affected the process by inhibiting rRNA transcriptional repression. These observations show that ING1 regulates the nucleolar epigenome and rDNA transcription suggesting that regulation of protein synthesis might serve as the basis for ING1 function as a type II tumor suppressor.
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Affiliation(s)
- Uma Karthika Rajarajacholan
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Subhash Thalappilly
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Karl Riabowol
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada.,Department of Oncology, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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41
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A role for Tau protein in maintaining ribosomal DNA stability and cytidine deaminase-deficient cell survival. Nat Commun 2017; 8:693. [PMID: 28947735 PMCID: PMC5612969 DOI: 10.1038/s41467-017-00633-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 07/14/2017] [Indexed: 12/20/2022] Open
Abstract
Cells from Bloom’s syndrome patients display genome instability due to a defective BLM and the downregulation of cytidine deaminase. Here, we use a genome-wide RNAi-synthetic lethal screen and transcriptomic profiling to identify genes enabling BLM-deficient and/or cytidine deaminase-deficient cells to tolerate constitutive DNA damage and replication stress. We found a synthetic lethal interaction between cytidine deaminase and microtubule-associated protein Tau deficiencies. Tau is overexpressed in cytidine deaminase-deficient cells, and its depletion worsens genome instability, compromising cell survival. Tau is recruited, along with upstream-binding factor, to ribosomal DNA loci. Tau downregulation decreases upstream binding factor recruitment, ribosomal RNA synthesis, ribonucleotide levels, and affects ribosomal DNA stability, leading to the formation of a new subclass of human ribosomal ultrafine anaphase bridges. We describe here Tau functions in maintaining survival of cytidine deaminase-deficient cells, and ribosomal DNA transcription and stability. Moreover, our findings for cancer tissues presenting concomitant cytidine deaminase underexpression and Tau upregulation open up new possibilities for anti-cancer treatment. Cytidine deaminase (CDA) deficiency leads to genome instability. Here the authors find a synthetic lethal interaction between CDA and the microtubule-associated protein Tau deficiencies, and report that Tau depletion affects rRNA synthesis, ribonucleotide pool balance, and rDNA stability.
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42
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Abstract
The nucleolus is a distinct compartment of the nucleus responsible for ribosome biogenesis. Mis-regulation of nucleolar functions and of the cellular translation machinery has been associated with disease, in particular with many types of cancer. Indeed, many tumor suppressors (p53, Rb, PTEN, PICT1, BRCA1) and proto-oncogenes (MYC, NPM) play a direct role in the nucleolus, and interact with the RNA polymerase I transcription machinery and the nucleolar stress response. We have identified Dicer and the RNA interference pathway as having an essential role in the nucleolus of quiescent Schizosaccharomyces pombe cells, distinct from pericentromeric silencing, by controlling RNA polymerase I release. We propose that this novel function is evolutionarily conserved and may contribute to the tumorigenic pre-disposition of DICER1 mutations in mammals.
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Affiliation(s)
- Benjamin Roche
- a Martienssen Lab, Cold Spring Harbor Laboratory , Cold Spring Harbor , NY , USA
| | - Benoît Arcangioli
- b Genome Dynamics Unit, UMR 3525 CNRS, Institut Pasteur , Paris , France
| | - Rob Martienssen
- a Martienssen Lab, Cold Spring Harbor Laboratory , Cold Spring Harbor , NY , USA.,c Howard Hughes Medical Institute, Cold Spring Harbor Laboratory , Cold Spring Harbor , NY , USA
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43
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The roles of RRP15 in nucleolar formation, ribosome biogenesis and checkpoint control in human cells. Oncotarget 2017; 8:13240-13252. [PMID: 28099941 PMCID: PMC5355092 DOI: 10.18632/oncotarget.14658] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 12/27/2016] [Indexed: 01/05/2023] Open
Abstract
The nucleolus controls ribosome biogenesis and its perturbation induces nucleolar stress that inhibits cell cycle progression and activates checkpoint responses. Here, we investigate the roles of ribosomal RNA processing protein, RRP15, in nucleolar formation, ribosome biogenesis, cell cycle progression and checkpoint control in human cells. RRP15 is localized in the nucleolus and required for nucleolar formation. In contrast to the budding yeast Rrp15p that was reported as a component of pre-60S subunits, RRP15 is found in both pre-40S and pre-60S subunits and involved in regulating rRNA transcription and ribosome biogenesis. Perturbation of RRP15 induces nucleolar stress that activates RPL5/RPL11/5S rRNA (RP)-Mdm2-p53 axis checkpoint response and arrests cells at G1-G1/S in p53-proficient non-transformed RPE1 cells but not in p53-deficient HeLa and MCF7 tumor cells. Instead, p53-deficient HeLa and MCF7 cells with RRP15-dependent nucleolar stress enter S-phase with S-phase perturbation that activates ATR-Chk1- γH2AX axis DNA replication/damage checkpoint response, delaying S-G2/M progression and, ultimately, causing cell death. The selective checkpoint response, cell cycle inhibition and/or cytotoxicity induced by RRP15-dependent nucleolar stress in p53-proficient non-transformed cells and p53-deficient tumor cells suggest that RRP15 might be a potential target for cancer therapy.
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44
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Gonyo P, Bergom C, Brandt AC, Tsaih SW, Sun Y, Bigley TM, Lorimer EL, Terhune SS, Rui H, Flister MJ, Long RM, Williams CL. SmgGDS is a transient nucleolar protein that protects cells from nucleolar stress and promotes the cell cycle by regulating DREAM complex gene expression. Oncogene 2017; 36:6873-6883. [PMID: 28806394 PMCID: PMC5730474 DOI: 10.1038/onc.2017.280] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 06/07/2017] [Accepted: 07/03/2017] [Indexed: 12/19/2022]
Abstract
The chaperone protein and guanine nucleotide exchange factor SmgGDS (RAP1GDS1) is a key promoter of cancer cell proliferation and tumorigenesis. SmgGDS undergoes nucleocytoplasmic shuttling, suggesting that it has both cytoplasmic and nuclear functions that promote cancer. Previous studies indicate that SmgGDS binds cytoplasmic small GTPases and promotes their trafficking to the plasma membrane. In contrast, little is known about the functions of SmgGDS in the nucleus, or how these nuclear functions might benefit cancer cells. Here we show unique nuclear localization and regulation of gene transcription pathways by SmgGDS. Strikingly, SmgGDS depletion significantly reduces expression of over 600 gene products that are targets of the DREAM complex, which is a transcription factor complex that regulates expression of proteins controlling the cell cycle. The cell cycle regulators E2F1, MYC, MYBL2 (B-Myb) and FOXM1 are among the DREAM targets that are diminished by SmgGDS depletion. E2F1 is well known to promote G1 cell cycle progression, and the loss of E2F1 in SmgGDS-depleted cells provides an explanation for previous reports that SmgGDS depletion characteristically causes a G1 cell cycle arrest. We show that SmgGDS localizes in nucleoli, and that RNAi-mediated depletion of SmgGDS in cancer cells disrupts nucleolar morphology, signifying nucleolar stress. We show that nucleolar SmgGDS interacts with the RNA polymerase I transcription factor upstream binding factor (UBF). The RNAi-mediated depletion of UBF diminishes nucleolar localization of SmgGDS and promotes proteasome-mediated degradation of SmgGDS, indicating that nucleolar sequestration of SmgGDS by UBF stabilizes SmgGDS protein. The ability of SmgGDS to interact with UBF and localize in the nucleolus is diminished by expressing DiRas1 or DiRas2, which are small GTPases that bind SmgGDS and act as tumor suppressors. Taken together, our results support a novel nuclear role for SmgGDS in protecting malignant cells from nucleolar stress, thus promoting cell cycle progression and tumorigenesis.
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Affiliation(s)
- P Gonyo
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - C Bergom
- Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - A C Brandt
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - S-W Tsaih
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Y Sun
- Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - T M Bigley
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Pediatrics, Washington University in St Louis, St Louis, MO, USA
| | - E L Lorimer
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - S S Terhune
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA.,Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - H Rui
- Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - M J Flister
- Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA.,Human and Molecular Genetics Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - R M Long
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA.,Medical College of Wisconsin Central Wisconsin Campus, Wausau, WI, USA
| | - C L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, USA
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45
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Xie Q, Li C, Song X, Wu L, Jiang Q, Qiu Z, Cao H, Yu K, Wan C, Li J, Yang F, Huang Z, Niu B, Jiang Z, Zhang T. Folate deficiency facilitates recruitment of upstream binding factor to hot spots of DNA double-strand breaks of rRNA genes and promotes its transcription. Nucleic Acids Res 2017; 45:2472-2489. [PMID: 27924000 PMCID: PMC5389733 DOI: 10.1093/nar/gkw1208] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 11/22/2016] [Indexed: 12/24/2022] Open
Abstract
The biogenesis of ribosomes in vivo is an essential process for cellular functions. Transcription of ribosomal RNA (rRNA) genes is the rate-limiting step in ribosome biogenesis controlled by environmental conditions. Here, we investigated the role of folate antagonist on changes of DNA double-strand breaks (DSBs) landscape in mouse embryonic stem cells. A significant DSB enhancement was detected in the genome of these cells and a large majority of these DSBs were found in rRNA genes. Furthermore, spontaneous DSBs in cells under folate deficiency conditions were located exclusively within the rRNA gene units, representing a H3K4me1 hallmark. Enrichment H3K4me1 at the hot spots of DSB regions enhanced the recruitment of upstream binding factor (UBF) to rRNA genes, resulting in the increment of rRNA genes transcription. Supplement of folate resulted in a restored UBF binding across DNA breakage sites of rRNA genes, and normal rRNA gene transcription. In samples from neural tube defects (NTDs) with low folate level, up-regulation of rRNA gene transcription was observed, along with aberrant UBF level. Our results present a new view by which alterations in folate levels affects DNA breakage through epigenetic control leading to the regulation of rRNA gene transcription during the early stage of development.
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Affiliation(s)
- Qiu Xie
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of Pediatrics-Peking University Teaching Hospital, Beijing 100020, China
| | - Caihua Li
- Genesky Biotechnologies Inc, Shanghai 200120, China
| | - Xiaozhen Song
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of Pediatrics-Peking University Teaching Hospital, Beijing 100020, China
| | - Lihua Wu
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of Pediatrics-Peking University Teaching Hospital, Beijing 100020, China
| | - Qian Jiang
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of Pediatrics-Peking University Teaching Hospital, Beijing 100020, China
| | - Zhiyong Qiu
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of Pediatrics-Peking University Teaching Hospital, Beijing 100020, China
| | - Haiyan Cao
- Department of Laboratory Medicine, The Fourth Affiliated Hospital of Harbin Medical University, Harbin 150081, China
| | - Kaihui Yu
- Department of Pathophysiology, Guangxi Medical University, Guangxi 530021, China
| | - Chunlei Wan
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of Pediatrics-Peking University Teaching Hospital, Beijing 100020, China
| | - Jianting Li
- Department of Biochemistry and Molecular Biology, Shanxi Medical University, Taiyuan 030001, China
| | - Feng Yang
- Genesky Biotechnologies Inc, Shanghai 200120, China
| | - Zebing Huang
- Genesky Biotechnologies Inc, Shanghai 200120, China
| | - Bo Niu
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of Pediatrics-Peking University Teaching Hospital, Beijing 100020, China
| | | | - Ting Zhang
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of Pediatrics-Peking University Teaching Hospital, Beijing 100020, China
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46
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Herdman C, Mars JC, Stefanovsky VY, Tremblay MG, Sabourin-Felix M, Lindsay H, Robinson MD, Moss T. A unique enhancer boundary complex on the mouse ribosomal RNA genes persists after loss of Rrn3 or UBF and the inactivation of RNA polymerase I transcription. PLoS Genet 2017; 13:e1006899. [PMID: 28715449 PMCID: PMC5536353 DOI: 10.1371/journal.pgen.1006899] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 07/31/2017] [Accepted: 06/27/2017] [Indexed: 11/19/2022] Open
Abstract
Transcription of the several hundred of mouse and human Ribosomal RNA (rRNA) genes accounts for the majority of RNA synthesis in the cell nucleus and is the determinant of cytoplasmic ribosome abundance, a key factor in regulating gene expression. The rRNA genes, referred to globally as the rDNA, are clustered as direct repeats at the Nucleolar Organiser Regions, NORs, of several chromosomes, and in many cells the active repeats are transcribed at near saturation levels. The rDNA is also a hotspot of recombination and chromosome breakage, and hence understanding its control has broad importance. Despite the need for a high level of rDNA transcription, typically only a fraction of the rDNA is transcriptionally active, and some NORs are permanently silenced by CpG methylation. Various chromatin-remodelling complexes have been implicated in counteracting silencing to maintain rDNA activity. However, the chromatin structure of the active rDNA fraction is still far from clear. Here we have combined a high-resolution ChIP-Seq protocol with conditional inactivation of key basal factors to better understand what determines active rDNA chromatin. The data resolve questions concerning the interdependence of the basal transcription factors, show that preinitiation complex formation is driven by the architectural factor UBF (UBTF) independently of transcription, and that RPI termination and release corresponds with the site of TTF1 binding. They further reveal the existence of an asymmetric Enhancer Boundary Complex formed by CTCF and Cohesin and flanked upstream by phased nucleosomes and downstream by an arrested RNA Polymerase I complex. We find that the Enhancer Boundary Complex is the only site of active histone modification in the 45kbp rDNA repeat. Strikingly, it not only delimits each functional rRNA gene, but also is stably maintained after gene inactivation and the re-establishment of surrounding repressive chromatin. Our data define a poised state of rDNA chromatin and place the Enhancer Boundary Complex as the likely entry point for chromatin remodelling complexes.
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Affiliation(s)
- Chelsea Herdman
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Québec, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Québec, Canada
| | - Jean-Clement Mars
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Québec, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Québec, Canada
| | - Victor Y. Stefanovsky
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Québec, 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, Québec, Canada
| | - Marianne Sabourin-Felix
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Québec, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Québec, Canada
| | - Helen Lindsay
- Institute of Molecular Life Sciences, University of Zürich, Zürich, Switzerland
- SIB Swiss Institute of Bioinformatics, University of Zürich, Zürich, Switzerland
| | - Mark D. Robinson
- Institute of Molecular Life Sciences, University of Zürich, Zürich, Switzerland
- SIB Swiss Institute of Bioinformatics, University of Zürich, Zürich, Switzerland
| | - Tom Moss
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Québec, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Québec, Canada
- * E-mail:
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47
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Bae N, Viviano M, Su X, Lv J, Cheng D, Sagum C, Castellano S, Bai X, Johnson C, Khalil MI, Shen J, Chen K, Li H, Sbardella G, Bedford MT. Developing Spindlin1 small-molecule inhibitors by using protein microarrays. Nat Chem Biol 2017; 13:750-756. [PMID: 28504676 PMCID: PMC5831360 DOI: 10.1038/nchembio.2377] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Accepted: 02/15/2017] [Indexed: 12/19/2022]
Abstract
The discovery of inhibitors of methyl- and acetyl-binding domains has provided evidence for the 'druggability' of epigenetic effector molecules. The small-molecule probe UNC1215 prevents methyl-dependent protein-protein interactions by engaging the aromatic cage of MBT domains and, with lower affinity, Tudor domains. Using a library of tagged UNC1215 analogs, we screened a protein-domain microarray of human methyllysine effector molecules to rapidly detect compounds with new binding profiles with either increased or decreased specificity. Using this approach, we identified a compound (EML405) that acquired a novel interaction with the Tudor-domain-containing protein Spindlin1 (SPIN1). Structural studies facilitated the rational synthesis of SPIN1 inhibitors with increased selectivity (EML631-633), which engage SPIN1 in cells, block its ability to 'read' H3K4me3 marks and inhibit its transcriptional-coactivator activity. Protein microarrays can thus be used as a platform to 'target-hop' and identify small molecules that bind and compete with domain-motif interactions.
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Affiliation(s)
- Narkhyun Bae
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Monica Viviano
- Dipartimento di Farmacia, Epigenetic Med Chem Lab, Università degli Studi di Salerno, Via Giovanni Paolo II 132, I-84084 Fisciano (SA), Italy
| | - Xiaonan Su
- Beijing Advanced Innovation Center for Structural Biology, MOE Key Laboratory of Protein Sciences, Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing 100084, China
- Tsinghua-Peking Joint Center for Life Sciences, Beijing, 100084, P.R. China
| | - Jie Lv
- Center for Regenerative Medicine, Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX 77030, USA & Department of Cardiothoracic Surgery, Weill Cornell Medical College, Cornell University
| | - Donghang Cheng
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Cari Sagum
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Sabrina Castellano
- Dipartimento di Farmacia, Epigenetic Med Chem Lab, Università degli Studi di Salerno, Via Giovanni Paolo II 132, I-84084 Fisciano (SA), Italy
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Salerno, Via Salvador Allende, I-84081 Baronissi (SA), Italy
| | - Xue Bai
- Beijing Advanced Innovation Center for Structural Biology, MOE Key Laboratory of Protein Sciences, Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing 100084, China
- Tsinghua-Peking Joint Center for Life Sciences, Beijing, 100084, P.R. China
| | - Claire Johnson
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Mahmoud Ibrahim Khalil
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
- Molecular Biology Unit, Department of Zoology, Faculty of Science, Alexandria University, Egypt
| | - Jianjun Shen
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Kaifu Chen
- Center for Regenerative Medicine, Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX 77030, USA & Department of Cardiothoracic Surgery, Weill Cornell Medical College, Cornell University
| | - Haitao Li
- Beijing Advanced Innovation Center for Structural Biology, MOE Key Laboratory of Protein Sciences, Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing 100084, China
- Tsinghua-Peking Joint Center for Life Sciences, Beijing, 100084, P.R. China
| | - Gianluca Sbardella
- Dipartimento di Farmacia, Epigenetic Med Chem Lab, Università degli Studi di Salerno, Via Giovanni Paolo II 132, I-84084 Fisciano (SA), Italy
| | - Mark T. Bedford
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
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48
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Mangan H, Gailín MÓ, McStay B. Integrating the genomic architecture of human nucleolar organizer regions with the biophysical properties of nucleoli. FEBS J 2017; 284:3977-3985. [PMID: 28500793 DOI: 10.1111/febs.14108] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 04/21/2017] [Accepted: 05/10/2017] [Indexed: 11/30/2022]
Abstract
Nucleoli are the sites of ribosome biogenesis and the largest membraneless subnuclear structures. They are intimately linked with growth and proliferation control and function as sensors of cellular stress. Nucleoli form around arrays of ribosomal gene (rDNA) repeats also called nucleolar organizer regions (NORs). In humans, NORs are located on the short arms of all five human acrocentric chromosomes. Multiple NORs contribute to the formation of large heterochromatin-surrounded nucleoli observed in most human cells. Here we will review recent findings about their genomic architecture. The dynamic nature of nucleoli began to be appreciated with the advent of photodynamic experiments using fluorescent protein fusions. We review more recent data on nucleoli in Xenopus germinal vesicles (GVs) which has revealed a liquid droplet-like behavior that facilitates nucleolar fusion. Further analysis in both XenopusGVs and Drosophila embryos indicates that the internal organization of nucleoli is generated by a combination of liquid-liquid phase separation and active processes involving rDNA. We will attempt to integrate these recent findings with the genomic architecture of human NORs to advance our understanding of how nucleoli form and respond to stress in human cells.
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Affiliation(s)
- Hazel Mangan
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Ireland
| | - Michael Ó Gailín
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Ireland
| | - Brian McStay
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Ireland
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49
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SHPRH regulates rRNA transcription by recognizing the histone code in an mTOR-dependent manner. Proc Natl Acad Sci U S A 2017; 114:E3424-E3433. [PMID: 28400511 DOI: 10.1073/pnas.1701978114] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Many DNA repair proteins have additional functions other than their roles in DNA repair. In addition to catalyzing PCNA polyubiquitylation in response to the stalling of DNA replication, SHPRH has the additional function of facilitating rRNA transcription by localizing to the ribosomal DNA (rDNA) promoter in the nucleoli. SHPRH was recruited to the rDNA promoter using its plant homeodomain (PHD), which interacts with histone H3 when the fourth lysine of H3 is not trimethylated. SHPRH enrichment at the rDNA promoter was inhibited by cell starvation, by treatment with actinomycin D or rapamycin, or by depletion of CHD4. SHPRH also physically interacted with the RNA polymerase I complex. Taken together, we provide evidence that SHPRH functions in rRNA transcription through its interaction with histone H3 in a mammalian target of rapamycin (mTOR)-dependent manner.
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50
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c-Myc co-ordinates mRNA cap methylation and ribosomal RNA production. Biochem J 2016; 474:377-384. [PMID: 27934633 PMCID: PMC5247799 DOI: 10.1042/bcj20160930] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 11/24/2016] [Accepted: 12/01/2016] [Indexed: 01/11/2023]
Abstract
The mRNA cap is a structure added to RNA pol II transcripts in eukaryotes, which recruits factors involved in RNA processing, nuclear export and translation initiation. RNA guanine-7 methyltransferase (RNMT)–RNA-activating miniprotein (RAM), the mRNA cap methyltransferase complex, completes the basic functional mRNA cap structure, cap 0, by methylating the cap guanosine. Here, we report that RNMT–RAM co-ordinates mRNA processing with ribosome production. Suppression of RNMT–RAM reduces synthesis of the 45S ribosomal RNA (rRNA) precursor. RNMT–RAM is required for c-Myc expression, a major regulator of RNA pol I, which synthesises 45S rRNA. Constitutive expression of c-Myc restores rRNA synthesis when RNMT–RAM is suppressed, indicating that RNMT–RAM controls rRNA production predominantly by controlling c-Myc expression. We report that RNMT–RAM is recruited to the ribosomal DNA locus, which may contribute to rRNA synthesis in certain contexts.
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