1
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Lu YY, Krebber H. Nuclear mRNA Quality Control and Cytoplasmic NMD Are Linked by the Guard Proteins Gbp2 and Hrb1. Int J Mol Sci 2021; 22:ijms222011275. [PMID: 34681934 PMCID: PMC8541090 DOI: 10.3390/ijms222011275] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/13/2021] [Accepted: 10/17/2021] [Indexed: 12/23/2022] Open
Abstract
Pre-mRNA splicing is critical for cells, as defects in this process can lead to altered open reading frames and defective proteins, potentially causing neurodegenerative diseases and cancer. Introns are removed in the nucleus and splicing is documented by the addition of exon-junction-complexes (EJCs) at exon-exon boundaries. This “memory” of splicing events is important for the ribosome, which translates the RNAs in the cytoplasm. In case a stop codon was detected before an EJC, translation is blocked and the RNA is eliminated by the nonsense-mediated decay (NMD). In the model organism Saccharomyces cerevisiae, two guard proteins, Gbp2 and Hrb1, have been identified as nuclear quality control factors for splicing. In their absence, intron-containing mRNAs leak into the cytoplasm. Their presence retains transcripts until the process is completed and they release the mRNAs by recruitment of the export factor Mex67. On transcripts that experience splicing problems, these guard proteins recruit the nuclear RNA degradation machinery. Interestingly, they continue their quality control function on exported transcripts. They support NMD by inhibiting translation and recruiting the cytoplasmic degradation factors. In this way, they link the nuclear and cytoplasmic quality control systems. These discoveries are also intriguing for humans, as homologues of these guard proteins are present also in multicellular organisms. Here, we provide an overview of the quality control mechanisms of pre-mRNA splicing, and present Gbp2 and Hrb1, as well as their human counterparts, as important players in these pathways.
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2
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Chanarat S. UBL5/Hub1: An Atypical Ubiquitin-Like Protein with a Typical Role as a Stress-Responsive Regulator. Int J Mol Sci 2021; 22:ijms22179384. [PMID: 34502293 PMCID: PMC8431670 DOI: 10.3390/ijms22179384] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 08/25/2021] [Accepted: 08/29/2021] [Indexed: 11/23/2022] Open
Abstract
Members of the ubiquitin-like protein family are known for their ability to modify substrates by covalent conjugation. The highly conserved ubiquitin relative UBL5/Hub1, however, is atypical because it lacks a carboxy-terminal di-glycine motif required for conjugation, and the whole E1-E2-E3 enzyme cascade is likely absent. Though the conjugation-mediated role of UBL5/Hub1 is controversial, it undoubtedly functions by interacting non-covalently with its partners. Several interactors of UBL5/Hub1 identified to date have suggested broad stress-responsive functions of the protein, for example, stress-induced control of pre-mRNA splicing, Fanconi anemia pathway of DNA damage repair, and mitochondrial unfolded protein response. While having an atypical mode of function, UBL5/Hub1 is still a stress protein that regulates feedback to various stimuli in a similar manner to other ubiquitin-like proteins. In this review, I discuss recent progress in understanding the functions of UBL5/Hub1 and the fundamental questions which remain to be answered.
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Affiliation(s)
- Sittinan Chanarat
- Laboratory of Molecular Cell Biology, Department of Biochemistry and Center for Excellence in Protein and Enzyme Technology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
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3
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Lee M, Jain P, Wang F, Ma PC, Borczuk A, Halmos B. MET alterations and their impact on the future of non-small cell lung cancer (NSCLC) targeted therapies. Expert Opin Ther Targets 2021; 25:249-268. [PMID: 33945380 DOI: 10.1080/14728222.2021.1925648] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Introduction: The MET gene and its pathway normally plays a crucial role in cell homeostasis, motility, and apoptosis. However, when the MET gene is altered, there is an imbalance toward cell proliferation and invasion commonly seen in numerous different types of cancers. The heterogeneous group of MET alterations that includes MET amplification, MET exon 14 skipping mutation, and MET fusions has been difficult to diagnose and treat. Currently, treatments are focused on tyrosine kinase inhibitors but now there is emerging data on novel MET-targeted therapies including monoclonal antibodies and antibody-drug conjugates that have emerged.Areas covered: We introduce new emerging data on MET alterations in non-small cell lung cancer (NSCLC) that has contributed to advances in MET targeted therapeutics. We offer our perspective and examine new information on the mechanisms of the MET alterations in this review.Expert opinion: Given the trends currently involving the targeting of MET altered malignancies, there will most likely be a continued rapid expansion of testing, novel tyrosine kinase inhibitors and potent antibody approaches. Combination treatments will be necessary to optimize management of advanced and early disease.
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Affiliation(s)
- Matthew Lee
- Department of Oncology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, NY, USA
| | - Prantesh Jain
- Division of Medical Oncology, Department of Medicine, University Hospitals Cleveland Medical Center, Case Comprehensive Cancer Center, Cleveland, OH, USA
| | - Feng Wang
- Department of Oncology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, NY, USA
| | - Patrick C Ma
- Penn State CancerInstitute, PennState College of Medicine, Penn State Health Milton S Hershey Medical Center, Hershey, PA, USA
| | - Alain Borczuk
- Department of Pathology, NewYork-Presbyterian Hospital/Weill Cornell Medical Center, New York, NY, USA
| | - Balazs Halmos
- Department of Oncology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, NY, USA
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4
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Aguado C, Teixido C, Román R, Reyes R, Giménez-Capitán A, Marin E, Cabrera C, Viñolas N, Castillo S, Muñoz S, Arcocha A, López-Vilaró L, Sullivan I, Aldeguer E, Rodríguez S, Moya I, Viteri S, Cardona AF, Palmero R, Sainz C, Mesa-Guzmán M, Lozano MD, Aguilar-Hernández A, Martínez-Bueno A, González-Cao M, Gonzalvo E, Leenders WPJ, Rosell R, Montuenga LM, Prat A, Molina-Vila MA, Reguart N. Multiplex RNA-based detection of clinically relevant MET alterations in advanced non-small cell lung cancer. Mol Oncol 2020; 15:350-363. [PMID: 33236532 PMCID: PMC7858100 DOI: 10.1002/1878-0261.12861] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 10/23/2020] [Accepted: 11/20/2020] [Indexed: 12/13/2022] Open
Abstract
MET inhibitors have shown activity in non‐small‐cell lung cancer patients (NSCLC) with MET amplification and exon 14 skipping (METΔex14). However, patient stratification is imperfect, and thus, response rates have varied widely. Here, we studied MET alterations in 474 advanced NSCLC patients by nCounter, an RNA‐based technique, together with next‐generation sequencing (NGS), fluorescence in situ hybridization (FISH), immunohistochemistry (IHC), and reverse transcriptase polymerase chain reaction (RT–PCR), exploring correlation with clinical benefit. Of the 474 samples analyzed, 422 (89%) yielded valid results by nCounter, which identified 13 patients (3%) with METΔex14 and 15 patients (3.5%) with very‐high MET mRNA expression. These two subgroups were mutually exclusive, displayed distinct phenotypes and did not generally coexist with other drivers. For METΔex14, 3/8 (37.5%) samples positive by nCounter tested negative by NGS. Regarding patients with very‐high MET mRNA, 92% had MET amplification by FISH and/or NGS. However, FISH failed to identify three patients (30%) with very‐high MET RNA expression, among which one received MET tyrosine kinase inhibitor treatment deriving clinical benefit. Our results indicate that quantitative mRNA‐based techniques can improve the selection of patients for MET‐targeted therapies.
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Affiliation(s)
- Cristina Aguado
- Laboratory of Oncology, Pangaea Oncology, Quirón Dexeus University Hospital, Barcelona, Spain
| | - Cristina Teixido
- Thoracic Oncology Unit, Department of Pathology, Hospital Clínic, Barcelona, Spain.,Translational Genomics and Targeted Therapeutics in Solid Tumors, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Ruth Román
- Laboratory of Oncology, Pangaea Oncology, Quirón Dexeus University Hospital, Barcelona, Spain
| | - Roxana Reyes
- Thoracic Oncology Unit, Department of Medical Oncology, Hospital Clínic, Barcelona, Spain
| | - Ana Giménez-Capitán
- Laboratory of Oncology, Pangaea Oncology, Quirón Dexeus University Hospital, Barcelona, Spain
| | - Elba Marin
- Translational Genomics and Targeted Therapeutics in Solid Tumors, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Thoracic Oncology Unit, Department of Medical Oncology, Hospital Clínic, Barcelona, Spain
| | - Carlos Cabrera
- Dr Rosell Oncology Institute, Dexeus University Hospital Quiron Salud Group, Barcelona, Spain
| | - Nuria Viñolas
- Thoracic Oncology Unit, Department of Medical Oncology, Hospital Clínic, Barcelona, Spain
| | - Sergi Castillo
- Division of Medical Oncology, Hospital General de Granollers, Barcelona, Spain
| | - Silvia Muñoz
- Division of Medical Oncology, Hospital General de Granollers, Barcelona, Spain
| | - Ainara Arcocha
- Thoracic Oncology Unit, Department of Medical Oncology, Hospital Clínic, Barcelona, Spain
| | - Laura López-Vilaró
- Department of Pathology, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Ivana Sullivan
- Division of Medical Oncology, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Erika Aldeguer
- Laboratory of Oncology, Pangaea Oncology, Quirón Dexeus University Hospital, Barcelona, Spain
| | - Sonia Rodríguez
- Laboratory of Oncology, Pangaea Oncology, Quirón Dexeus University Hospital, Barcelona, Spain
| | - Irene Moya
- Dr Rosell Oncology Institute, Dexeus University Hospital Quiron Salud Group, Barcelona, Spain
| | - Santiago Viteri
- Dr Rosell Oncology Institute, Dexeus University Hospital Quiron Salud Group, Barcelona, Spain.,Dr Rosell Oncology Institute, Teknon Medical Center, Quiron Salud Group, Barcelona, Spain
| | - Andrés Felipe Cardona
- Foundation for Clinical and Applied Cancer Research-FICMAC, Bogotá, Colombia.,Clinical and Translational Oncology Group, Institute of Oncology, Clínica del Country, Bogotá, Colombia
| | - Ramon Palmero
- Division of Medical Oncology, Catalan Institute of Oncology, L'Hospitalet, Barcelona, Spain
| | - Cristina Sainz
- Center for Applied Medical Research (CIMA), University of Navarra, Spain.,CIBERONC, Madrid, Spain
| | | | - Maria D Lozano
- CIBERONC, Madrid, Spain.,IDISNA, Pamplona, Spain.,Department of Pathology, Anatomy and Physiology, School of Medicine, University of Navarra, Pamplona, Spain
| | | | | | - María González-Cao
- Dr Rosell Oncology Institute, Dexeus University Hospital Quiron Salud Group, Barcelona, Spain
| | - Elena Gonzalvo
- Thoracic Oncology Unit, Department of Pathology, Hospital Clínic, Barcelona, Spain
| | - William P J Leenders
- Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Nijmegen, The Netherlands
| | - Rafael Rosell
- Dr Rosell Oncology Institute, Dexeus University Hospital Quiron Salud Group, Barcelona, Spain.,Institut d'Investigació en Ciències de la Salut Germans Trias i Pujol, Badalona, Spain.,Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Luis M Montuenga
- Center for Applied Medical Research (CIMA), University of Navarra, Spain.,CIBERONC, Madrid, Spain.,IDISNA, Pamplona, Spain.,Department of Pathology, Anatomy and Physiology, School of Medicine, University of Navarra, Pamplona, Spain
| | - Aleix Prat
- Translational Genomics and Targeted Therapeutics in Solid Tumors, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Thoracic Oncology Unit, Department of Medical Oncology, Hospital Clínic, Barcelona, Spain
| | - Miguel A Molina-Vila
- Laboratory of Oncology, Pangaea Oncology, Quirón Dexeus University Hospital, Barcelona, Spain
| | - Noemi Reguart
- Translational Genomics and Targeted Therapeutics in Solid Tumors, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Thoracic Oncology Unit, Department of Medical Oncology, Hospital Clínic, Barcelona, Spain
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5
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Zhang D, Meng F. A Comprehensive Overview of Structure-Activity Relationships of Small-Molecule Splicing Modulators Targeting SF3B1 as Anticancer Agents. ChemMedChem 2020; 15:2098-2120. [PMID: 33037739 DOI: 10.1002/cmdc.202000642] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 09/19/2020] [Indexed: 02/06/2023]
Abstract
The pre-mRNA splicing factor SF3B1 shows recurrent mutations among hematologic malignancies and some solid tumors. In 2007, the identification of two cytotoxic natural products, which showed splicing inhibition by binding to SF3b, prompted the development of small-molecule splicing modulators of SF3B1 as therapeutics for cancer. Recent studies suggested that spliceosome-mutant cells are preferentially sensitive to pharmacologic splicing modulation; therefore, exploring the clinical utility of splicing modulator therapies in patients with spliceosome-mutant hematologic malignancies who have failed current therapies is greatly needed, as these patients have few treatment options. H3B-8800 had unique pharmacological activity and exhibited favorable data in phase I clinical trials to treat patients with advanced myeloid malignancies, indicating that further clinical trials are promising. The most established small-molecule modulators of SF3B1 can be categorized into three classes: the bicycles, the monopyranes, and the 12-membered macrolides. This review provides a comprehensive overview of the structure-activity relationships of small-molecule SF3B1 modulators, with a detailed analysis of interactions between modulators and protein binding pocket. The future strategy for splicing modulators development is also discussed.
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Affiliation(s)
- Datong Zhang
- School of Chemistry and Chemical Engineering, Qilu University of Technology (Shandong Academy of Sciences), 3501 Daxue Road, Jinan, 250353, P. R. China
| | - Fancui Meng
- Tianjin Institute of Pharmaceutical Research, 306 Huiren Road, Tianjin, 300301, P. R. China
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6
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Abstract
Single-cell analyses have revealed a tremendous variety among cells in the abundance and chemical composition of RNA. Much of this heterogeneity is due to alternative splicing by the spliceosome. Little is known about how many of the resulting isoforms are biologically functional or just provide noise with little to no impact. The dynamic nature of the spliceosome provides numerous opportunities for regulation but is also the source of stochastic fluctuations. We discuss possible origins of splicing stochasticity, the experimental approaches for studying heterogeneity in isoforms, and the potential biological significance of noisy splicing in development and disease.
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Affiliation(s)
- Yihan Wan
- Laboratory of Receptor Biology and Gene Expression, Center for Cancer Research, National Cancer Institute, Bethesda, MD, 20892, USA
| | - Daniel R Larson
- Laboratory of Receptor Biology and Gene Expression, Center for Cancer Research, National Cancer Institute, Bethesda, MD, 20892, USA.
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7
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Björk P, Wieslander L. Integration of mRNP formation and export. Cell Mol Life Sci 2017; 74:2875-2897. [PMID: 28314893 PMCID: PMC5501912 DOI: 10.1007/s00018-017-2503-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 03/06/2017] [Accepted: 03/07/2017] [Indexed: 12/13/2022]
Abstract
Expression of protein-coding genes in eukaryotes relies on the coordinated action of many sophisticated molecular machineries. Transcription produces precursor mRNAs (pre-mRNAs) and the active gene provides an environment in which the pre-mRNAs are processed, folded, and assembled into RNA–protein (RNP) complexes. The dynamic pre-mRNPs incorporate the growing transcript, proteins, and the processing machineries, as well as the specific protein marks left after processing that are essential for export and the cytoplasmic fate of the mRNPs. After release from the gene, the mRNPs move by diffusion within the interchromatin compartment, making up pools of mRNPs. Here, splicing and polyadenylation can be completed and the mRNPs recruit the major export receptor NXF1. Export competent mRNPs interact with the nuclear pore complex, leading to export, concomitant with compositional and conformational changes of the mRNPs. We summarize the integrated nuclear processes involved in the formation and export of mRNPs.
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Affiliation(s)
- Petra Björk
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden
| | - Lars Wieslander
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden
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8
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Eckert D, Andrée N, Razanau A, Zock-Emmenthal S, Lützelberger M, Plath S, Schmidt H, Guerra-Moreno A, Cozzuto L, Ayté J, Käufer NF. Prp4 Kinase Grants the License to Splice: Control of Weak Splice Sites during Spliceosome Activation. PLoS Genet 2016; 12:e1005768. [PMID: 26730850 PMCID: PMC4701394 DOI: 10.1371/journal.pgen.1005768] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 12/03/2015] [Indexed: 12/02/2022] Open
Abstract
The genome of the fission yeast Schizosaccharomyces pombe encodes 17 kinases that are essential for cell growth. These include the cell-cycle regulator Cdc2, as well as several kinases that coordinate cell growth, polarity, and morphogenesis during the cell cycle. In this study, we further characterized another of these essential kinases, Prp4, and showed that the splicing of many introns is dependent on Prp4 kinase activity. For detailed characterization, we chose the genes res1 and ppk8, each of which contains one intron of typical size and position. Splicing of the res1 intron was dependent on Prp4 kinase activity, whereas splicing of the ppk8 intron was not. Extensive mutational analyses of the 5’ splice site of both genes revealed that proper transient interaction with the 5’ end of snRNA U1 governs the dependence of splicing on Prp4 kinase activity. Proper transient interaction between the branch sequence and snRNA U2 was also important. Therefore, the Prp4 kinase is required for recognition and efficient splicing of introns displaying weak exon1/5’ splice sites and weak branch sequences. Prp4 is an essential protein kinase that is involved in the splicing of some introns. Using a conditional mutant of Prp4, we showed that a subset of genes, including several cell cycle–regulatory genes, are dependent on Prp4 for splicing. Furthermore, we could convert genes between Prp4-dependent and -independent states by introducing single-nucleotide mutations in the exon1/5’ splice sites and branch sequence of introns. This work shows that Prp4 activity is required for splicing surveillance in a subset of mRNAs.
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Affiliation(s)
- Daniela Eckert
- Institute of Genetics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Nicole Andrée
- Institute of Genetics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Aleh Razanau
- Department of Physiology and Pathophysiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada
| | | | - Martin Lützelberger
- Institute of Genetics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Susann Plath
- Institute of Genetics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Henning Schmidt
- Institute of Genetics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Angel Guerra-Moreno
- Oxidative Stress and Cell Cycle Group, Universitat Pompeu Fabra, Barcelona, Spain
| | - Luca Cozzuto
- CRG Bioinformatics Core, Centre de Regulació Genòmica (CRG), and Universitat Pompeu Fabra, Barcelona, Spain
| | - José Ayté
- Oxidative Stress and Cell Cycle Group, Universitat Pompeu Fabra, Barcelona, Spain
- * E-mail: (JA); (NFK)
| | - Norbert F. Käufer
- Institute of Genetics, Technische Universität Braunschweig, Braunschweig, Germany
- * E-mail: (JA); (NFK)
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9
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Blanco MR, Martin JS, Kahlscheuer ML, Krishnan R, Abelson J, Laederach A, Walter NG. Single Molecule Cluster Analysis dissects splicing pathway conformational dynamics. Nat Methods 2015; 12:1077-84. [PMID: 26414013 DOI: 10.1038/nmeth.3602] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 08/10/2015] [Indexed: 02/01/2023]
Abstract
We report Single Molecule Cluster Analysis (SiMCAn), which utilizes hierarchical clustering of hidden Markov modeling-fitted single-molecule fluorescence resonance energy transfer (smFRET) trajectories to dissect the complex conformational dynamics of biomolecular machines. We used this method to study the conformational dynamics of a precursor mRNA during the splicing cycle as carried out by the spliceosome. By clustering common dynamic behaviors derived from selectively blocked splicing reactions, SiMCAn was able to identify the signature conformations and dynamic behaviors of multiple ATP-dependent intermediates. In addition, it identified an open conformation adopted late in splicing by a 3' splice-site mutant, invoking a mechanism for substrate proofreading. SiMCAn enables rapid interpretation of complex single-molecule behaviors and should prove useful for the comprehensive analysis of a plethora of dynamic cellular machines.
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Affiliation(s)
- Mario R Blanco
- Department of Chemistry, Single Molecule Analysis Group, University of Michigan, Ann Arbor, Michigan, USA.,Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Joshua S Martin
- Biology Department, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Matthew L Kahlscheuer
- Department of Chemistry, Single Molecule Analysis Group, University of Michigan, Ann Arbor, Michigan, USA
| | - Ramya Krishnan
- Department of Chemistry, Single Molecule Analysis Group, University of Michigan, Ann Arbor, Michigan, USA
| | - John Abelson
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, USA
| | - Alain Laederach
- Biology Department, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Nils G Walter
- Department of Chemistry, Single Molecule Analysis Group, University of Michigan, Ann Arbor, Michigan, USA
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10
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Shi M, Wang S, Yao Y, Li Y, Zhang H, Han F, Nie H, Su J, Wang Z, Yue L, Cao J, Li Y. Biological and clinical significance of epigenetic silencing of MARVELD1 gene in lung cancer. Sci Rep 2014; 4:7545. [PMID: 25520033 PMCID: PMC4269892 DOI: 10.1038/srep07545] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 12/01/2014] [Indexed: 01/20/2023] Open
Abstract
Epigenetic silence in cancer frequently altered signal-transduction pathways during the early stages of tumor development. Recent progress in the field of cancer epigenetics has led to new opportunities for diagnosis and treatment of cancer. We previously demonstrated that novel identified nuclear factor MARVELD1 was widely expressed in human tissues, but down-regulated by promoter methylation in multiple cancers. This study was carried out to determine the biological and clinical significance of MARVELD1 gene silencing in lung cancer. Here, we found the reduced MARVELD1 expression significantly correlated with diagnostic histopathology and malignant degree of lung cancers. DNA hypermethylation and histone deacetylation synergistically inactivated MARVELD1 gene in lung cancer cells. Moreover, MARVELD1 modulated the efficiency of nonsense-mediated mRNA decay (NMD) through interaction with NMD core factor SMG1. The decreased MARVELD1 level in lung cancer reduces NMD efficiency through diminishing the association between NMD complex component UPF1/SMG1 and premature termination codons containing mRNA (PTC-mRNA). The results suggested that MARVELD1 silencing is an appealing diagnostic biomarker for lung cancer and epigenetic silencing of MARVELD1 gene links with the regulatory mechanism of NMD pathway in lung cancer, which may be required for tumorigenesis.
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Affiliation(s)
- Ming Shi
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Shan Wang
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Yuanfei Yao
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Yiqun Li
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Hao Zhang
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Fang Han
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Huan Nie
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Jie Su
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Zeyu Wang
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Lei Yue
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Jingyan Cao
- Department of Medical Oncology, Harbin Medical University Cancer Hospital, Harbin, China
| | - Yu Li
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
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11
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Heyn P, Kalinka AT, Tomancak P, Neugebauer KM. Introns and gene expression: cellular constraints, transcriptional regulation, and evolutionary consequences. Bioessays 2014; 37:148-54. [PMID: 25400101 PMCID: PMC4654234 DOI: 10.1002/bies.201400138] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A gene's “expression profile” denotes the number of transcripts present relative to all other transcripts. The overall rate of transcript production is determined by transcription and RNA processing rates. While the speed of elongating RNA polymerase II has been characterized for many different genes and organisms, gene-architectural features – primarily the number and length of exons and introns – have recently emerged as important regulatory players. Several new studies indicate that rapidly cycling cells constrain gene-architecture toward short genes with a few introns, allowing efficient expression during short cell cycles. In contrast, longer genes with long introns exhibit delayed expression, which can serve as timing mechanisms for patterning processes. These findings indicate that cell cycle constraints drive the evolution of gene-architecture and shape the transcriptome of a given cell type. Furthermore, a tendency for short genes to be evolutionarily young hints at links between cellular constraints and the evolution of animal ontogeny.
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Affiliation(s)
- Patricia Heyn
- MRC Human Genetics Unit, IGMM, University of Edinburgh, Edinburgh, UK
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12
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Kinz-Thompson CD, Gonzalez RL. smFRET studies of the 'encounter' complexes and subsequent intermediate states that regulate the selectivity of ligand binding. FEBS Lett 2014; 588:3526-38. [PMID: 25066296 PMCID: PMC4779314 DOI: 10.1016/j.febslet.2014.07.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 07/14/2014] [Accepted: 07/15/2014] [Indexed: 10/25/2022]
Abstract
The selectivity with which a biomolecule can bind its cognate ligand when confronted by the vast array of structurally similar, competing ligands that are present in the cell underlies the fidelity of some of the most fundamental processes in biology. Because they collectively comprise one of only a few methods that can sensitively detect the 'encounter' complexes and subsequent intermediate states that regulate the selectivity of ligand binding, single-molecule fluorescence, and particularly single-molecule fluorescence resonance energy transfer (smFRET), approaches have revolutionized studies of ligand-binding reactions. Here, we describe a widely used smFRET strategy that enables investigations of a large variety of ligand-binding reactions, and discuss two such reactions, aminoacyl-tRNA selection during translation elongation and splice site selection during spliceosome assembly, that highlight both the successes and challenges of smFRET studies of ligand-binding reactions. We conclude by reviewing a number of emerging experimental and computational approaches that are expanding the capabilities of smFRET approaches for studies of ligand-binding reactions and that promise to reveal the mechanisms that control the selectivity of ligand binding with unprecedented resolution.
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Affiliation(s)
| | - Ruben L Gonzalez
- Department of Chemistry, Columbia University, New York, NY 10027, United States.
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13
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Valdés J, Nozaki T, Sato E, Chiba Y, Nakada-Tsukui K, Villegas-Sepúlveda N, Winkler R, Azuara-Liceaga E, Mendoza-Figueroa MS, Watanabe N, Santos HJ, Saito-Nakano Y, Galindo-Rosales JM. Proteomic analysis of Entamoeba histolytica in vivo assembled pre-mRNA splicing complexes. J Proteomics 2014; 111:30-45. [PMID: 25109466 DOI: 10.1016/j.jprot.2014.07.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 06/27/2014] [Accepted: 07/23/2014] [Indexed: 10/24/2022]
Abstract
UNLABELLED The genome of the human intestinal parasite Entamoeba histolytica contains nearly 3000 introns and bioinformatic predictions indicate that major and minor spliceosomes occur in Entamoeba. However, except for the U2-, U4-, U5- and U6 snRNAs, no other splicing factor has been cloned and characterized. Here, we HA-tagged cloned the snRNP component U1A and assessed its expression and nuclear localization. Because the snRNP-free U1A form interacts with polyadenylate-binding protein, HA-U1A immunoprecipitates could identify early and late splicing complexes. Avoiding Entamoeba's endonucleases and ensuring the precipitation of RNA-binding proteins, parasite cultures were UV cross-linked prior to nuclear fraction immunoprecipitations with HA antibodies, and precipitates were subjected to tandem mass spectrometry (MS/MS) analyses. To discriminate their nuclear roles (chromatin-, co-transcriptional-, splicing-related), MS/MS analyses were carried out with proteins eluted with MS2-GST-sepharose from nuclear extracts of an MS2 aptamer-tagged Rabx13 intron amoeba transformant. Thus, we probed thirty-six Entamoeba proteins corresponding to 32 cognate splicing-specific factors, including 13 DExH/D helicases required for all stages of splicing, and 12 different splicing-related helicases were identified also. Furthermore 50 additional proteins, possibly involved in co-transcriptional processes were identified, revealing the complexity of co-transcriptional splicing in Entamoeba. Some of these later factors were not previously found in splicing complex analyses. BIOLOGICAL SIGNIFICANCE Numerous facts about the splicing of the nearly 3000 introns of the Entamoeba genome have not been unraveled, particularly the splicing factors and their activities. Considering that many of such introns are located in metabolic genes, the knowledge of the splicing cues has the potential to be used to attack or control the parasite. We have found numerous new splicing-related factors which could have therapeutic benefit. We also detected all the DExH/A RNA helicases involved in splicing and splicing proofreading control. Still, Entamoeba is very inefficient in splicing fidelity, thus we may have found a possible model system to study these processes.
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Affiliation(s)
- Jesús Valdés
- Departament of Biochemistry, CINVESTAV, México D.F., Mexico.
| | - Tomoyoshi Nozaki
- Department of Parasitology, National Institute of Infectious Diseases, Tokyo, Japan
| | - Emi Sato
- Department of Parasitology, National Institute of Infectious Diseases, Tokyo, Japan
| | - Yoko Chiba
- University of Tsukuba, Graduate School of Life and Environmental Sciences, Tsukuba, Japan
| | - Kumiko Nakada-Tsukui
- Department of Parasitology, National Institute of Infectious Diseases, Tokyo, Japan
| | | | - Robert Winkler
- Department of Biotechnology and Biochemistry, CINVESTAV Unidad Irapuato, Irapuato, Guanajuato, Mexico
| | | | | | - Natsuki Watanabe
- University of Tsukuba, Graduate School of Life and Environmental Sciences, Tsukuba, Japan
| | - Herbert J Santos
- Department of Parasitology, National Institute of Infectious Diseases, Tokyo, Japan; University of Tsukuba, Graduate School of Life and Environmental Sciences, Tsukuba, Japan; Institute of Biology, College of Science, University of the Philippines Diliman, Quezon City, Philippines
| | - Yumiko Saito-Nakano
- Department of Parasitology, National Institute of Infectious Diseases, Tokyo, Japan
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14
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Björk P, Wieslander L. Mechanisms of mRNA export. Semin Cell Dev Biol 2014; 32:47-54. [PMID: 24813364 DOI: 10.1016/j.semcdb.2014.04.027] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 04/17/2014] [Indexed: 02/02/2023]
Abstract
Release of properly processed and assembled mRNPs from the actively transcribing genes, movement of the mRNPs through the interchromatin and interaction with the Nuclear Pore Complexes, leading to cytoplasmic export, are essential steps of eukaryotic gene expression. Here, we review these intranuclear gene expression steps.
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Affiliation(s)
- Petra Björk
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden.
| | - Lars Wieslander
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden.
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15
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Cvačková Z, Matějů D, Staněk D. Retinitis Pigmentosa Mutations ofSNRNP200Enhance Cryptic Splice-Site Recognition. Hum Mutat 2013; 35:308-17. [DOI: 10.1002/humu.22481] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 11/05/2013] [Indexed: 12/16/2022]
Affiliation(s)
- Zuzana Cvačková
- Laboratory of RNA Biology; Institute of Molecular Genetics ASCR; Prague 142 20 Czech Republic
| | - Daniel Matějů
- Laboratory of RNA Biology; Institute of Molecular Genetics ASCR; Prague 142 20 Czech Republic
| | - David Staněk
- Laboratory of RNA Biology; Institute of Molecular Genetics ASCR; Prague 142 20 Czech Republic
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16
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Volanakis A, Passoni M, Hector RD, Shah S, Kilchert C, Granneman S, Vasiljeva L. Spliceosome-mediated decay (SMD) regulates expression of nonintronic genes in budding yeast. Genes Dev 2013; 27:2025-38. [PMID: 24065768 PMCID: PMC3792478 DOI: 10.1101/gad.221960.113] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We uncovered a novel role for the spliceosome in regulating mRNA expression levels that involves splicing coupled to RNA decay, which we refer to as spliceosome-mediated decay (SMD). Our transcriptome-wide studies identified numerous transcripts that are not known to have introns but are spliced by the spliceosome at canonical splice sites in Saccharomyces cerevisiae. Products of SMD are primarily degraded by the nuclear RNA surveillance machinery. We demonstrate that SMD can significantly down-regulate mRNA levels; splicing at canonical splice sites in the bromodomain factor 2 (BDF2) transcript reduced transcript levels roughly threefold by generating unstable products that are rapidly degraded by the nuclear surveillance machinery. Regulation of BDF2 mRNA levels by SMD requires Bdf1, a functionally redundant Bdf2 paralog that plays a role in recruiting the spliceosome to the BDF2 mRNA. Interestingly, mutating BDF2 5' splice site and branch point consensus sequences partially suppresses the bdf1Δ temperature-sensitive phenotype, suggesting that maintaining proper levels of Bdf2 via SMD is biologically important. We propose that the spliceosome can also repress protein-coding gene expression by promoting nuclear turnover of spliced RNA products and provide an insight for coordinated regulation of Bdf1 and Bdf2 levels in the cell.
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Affiliation(s)
- Adam Volanakis
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
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17
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Gonzàlez-Porta M, Frankish A, Rung J, Harrow J, Brazma A. Transcriptome analysis of human tissues and cell lines reveals one dominant transcript per gene. Genome Biol 2013; 14:R70. [PMID: 23815980 PMCID: PMC4053754 DOI: 10.1186/gb-2013-14-7-r70] [Citation(s) in RCA: 183] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 07/01/2013] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND RNA sequencing has opened new avenues for the study of transcriptome composition. Significant evidence has accumulated showing that the human transcriptome contains in excess of a hundred thousand different transcripts. However, it is still not clear to what extent this diversity prevails when considering the relative abundances of different transcripts from the same gene. RESULTS Here we show that, in a given condition, most protein coding genes have one major transcript expressed at significantly higher level than others, that in human tissues the major transcripts contribute almost 85 percent to the total mRNA from protein coding loci, and that often the same major transcript is expressed in many tissues. We detect a high degree of overlap between the set of major transcripts and a recently published set of alternatively spliced transcripts that are predicted to be translated utilizing proteomic data. Thus, we hypothesize that although some minor transcripts may play a functional role, the major ones are likely to be the main contributors to the proteome. However, we still detect a non-negligible fraction of protein coding genes for which the major transcript does not code a protein. CONCLUSIONS Overall, our findings suggest that the transcriptome from protein coding loci is dominated by one transcript per gene and that not all the transcripts that contribute to transcriptome diversity are equally likely to contribute to protein diversity. This observation can help to prioritize candidate targets in proteomics research and to predict the functional impact of the detected changes in variation studies.
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18
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Yang F, Wang XY, Zhang ZM, Pu J, Fan YJ, Zhou J, Query CC, Xu YZ. Splicing proofreading at 5' splice sites by ATPase Prp28p. Nucleic Acids Res 2013; 41:4660-70. [PMID: 23462954 PMCID: PMC3632134 DOI: 10.1093/nar/gkt149] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Fidelity and efficiency of pre-mRNA splicing are critical for generating functional mRNAs, but how such accuracy in 5′ splice site (SS) selection is attained is not fully clear. Through a series of yeast genetic screens, we isolated alleles of prp28 that improve splicing of suboptimal 5′SS substrates, demonstrating that WT-Prp28p proofreads, and consequently rejects, poor 5′SS. Prp28p is thought to facilitate the disruption of 5′SS–U1 snRNA pairing to allow for 5′SS–U6 snRNA pairing in the catalytic spliceosome; unexpectedly, 5′SS proofreading by Prp28p is dependent on competition with the stability of the 5′SS:U6 duplex, but not the 5′SS:U1 duplex. E404K, the strongest prp28 allele containing a mutation located in the linker region between adenosine triphosphatase (ATPase) subdomains, exhibited lower RNA-binding activity and enhanced splicing of suboptimal substrates before first-step catalysis, suggesting that decreased Prp28p activity allows longer time for suboptimal 5′SS substrates to pair with U6 snRNA and thereby reduces splicing fidelity. Residue E404 is critical for providing high splicing activity, demonstrated here in both yeast and Drosophila cells. Thus, the subdomain linker in Prp28p plays important roles both in splicing efficiency across species and in proofreading of 5′SS.
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Affiliation(s)
- Fei Yang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
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19
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Yap K, Makeyev EV. Regulation of gene expression in mammalian nervous system through alternative pre-mRNA splicing coupled with RNA quality control mechanisms. Mol Cell Neurosci 2013; 56:420-8. [PMID: 23357783 DOI: 10.1016/j.mcn.2013.01.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 01/15/2013] [Accepted: 01/17/2013] [Indexed: 12/12/2022] Open
Abstract
Eukaryotic gene expression is orchestrated on a genome-wide scale through several post-transcriptional mechanisms. Of these, alternative pre-mRNA splicing expands the proteome diversity and modulates mRNA stability through downstream RNA quality control (QC) pathways including nonsense-mediated decay (NMD) of mRNAs containing premature termination codons and nuclear retention and elimination (NRE) of intron-containing transcripts. Although originally identified as mechanisms for eliminating aberrant transcripts, a growing body of evidence suggests that NMD and NRE coupled with deliberate changes in pre-mRNA splicing patterns are also used in a number of biological contexts for deterministic control of gene expression. Here we review recent studies elucidating molecular mechanisms and biological significance of these gene regulation strategies with a specific focus on their roles in nervous system development and physiology. This article is part of a Special Issue entitled 'RNA and splicing regulation in neurodegeneration'.
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Affiliation(s)
- Karen Yap
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
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20
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Abstract
Several bacterial fermentation products and their synthetic derivatives display antitumour activities and bind tightly to components of the spliceosome, which is the complex molecular machinery involved in the removal of introns from mRNA precursors in eukaryotic cells. The drugs alter gene expression, including alternative splicing, of genes that are important for cancer progression. A flurry of recent reports has revealed that genes encoding splicing factors, including the drug target splicing factor 3B subunit 1 (SF3B1), are among the most highly mutated in various haematological malignancies such as chronic lymphocytic leukaemia and myelodysplastic syndromes. These observations highlight the role of splicing factors in cancer and suggest that an understanding of the molecular effects of drugs targeting these proteins could open new perspectives for studies of the spliceosome and its role in cancer progression, and for the development of novel antitumour therapies.
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21
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Abstract
In eukaryotic cells, introns are spliced from pre-mRNAs by the spliceosome. Both the composition and the structure of the spliceosome are highly dynamic, and eight DExD/H RNA helicases play essential roles in controlling conformational rearrangements. There is evidence that the various helicases are functionally and physically connected with each other and with many other factors in the spliceosome. Understanding the dynamics of those interactions is essential to comprehend the mechanism and regulation of normal as well as of pathological splicing. This review focuses on recent advances in the characterization of the splicing helicases and their interactions, and highlights the deep integration of splicing helicases in global mRNP biogenesis pathways.
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Affiliation(s)
- Olivier Cordin
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
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22
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Webb TR, Joyner AS, Potter PM. The development and application of small molecule modulators of SF3b as therapeutic agents for cancer. Drug Discov Today 2012; 18:43-9. [PMID: 22885522 DOI: 10.1016/j.drudis.2012.07.013] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 06/29/2012] [Accepted: 07/26/2012] [Indexed: 01/05/2023]
Abstract
The identification of potent spliceosome modulators that demonstrate antitumor activity indicates that this complex may be a target for drug development. Several natural products have been demonstrated to bind to the SF3b1 subunit of this macromolecule and these agents modulate alternative RNA splicing. In this article we describe their biological properties, discuss the validity of the spliceosome as a therapeutic target, and propose that alteration of alternative splicing represents a viable approach for inducing tumor-selective cytotoxicity.
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Affiliation(s)
- Thomas R Webb
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
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23
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Yap K, Lim ZQ, Khandelia P, Friedman B, Makeyev EV. Coordinated regulation of neuronal mRNA steady-state levels through developmentally controlled intron retention. Genes Dev 2012; 26:1209-23. [PMID: 22661231 DOI: 10.1101/gad.188037.112] [Citation(s) in RCA: 205] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Differentiated cells acquire unique structural and functional traits through coordinated expression of lineage-specific genes. An extensive battery of genes encoding components of the synaptic transmission machinery and specialized cytoskeletal proteins is activated during neurogenesis, but the underlying regulation is not well understood. Here we show that genes encoding critical presynaptic proteins are transcribed at a detectable level in both neurons and nonneuronal cells. However, in nonneuronal cells, the splicing of 3'-terminal introns within these genes is repressed by the polypyrimidine tract-binding protein (Ptbp1). This inhibits the export of incompletely spliced mRNAs to the cytoplasm and triggers their nuclear degradation. Clearance of these intron-containing transcripts occurs independently of the nonsense-mediated decay (NMD) pathway but requires components of the nuclear RNA surveillance machinery, including the nuclear pore-associated protein Tpr and the exosome complex. When Ptbp1 expression decreases during neuronal differentiation, the regulated introns are spliced out, thus allowing the accumulation of translation-competent mRNAs in the cytoplasm. We propose that this mechanism counters ectopic and precocious expression of functionally linked neuron-specific genes and ensures their coherent activation in the appropriate developmental context.
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Affiliation(s)
- Karen Yap
- School of Biological Sciences, Nanyang Technological University, Singapore
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24
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Pérez-Valle J, Vilardell J. Intronic features that determine the selection of the 3' splice site. WILEY INTERDISCIPLINARY REVIEWS-RNA 2012; 3:707-17. [PMID: 22807288 DOI: 10.1002/wrna.1131] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Most eukaryotic primary transcripts include segments, or introns, that will be accurately removed during RNA biogenesis. This process, known as pre-messenger RNA splicing, is catalyzed by the spliceosome, accurately selecting a set of intronic marks from others apparently equivalent. This identification is critical, as incorrectly spliced RNAs can be toxic for the organism. One of these marks, the dinucleotide AG, signals the intronic 3' end, or 3' splice site (ss). In this review we will focus on those intronic features that have an impact on 3' ss selection. These include the location and type of neighboring sequences, and their distance to the 3' end. We will see that their interplay is needed to select the right intronic end, and that this can be modulated by additional intronic elements that contribute to alternative splicing, whereby diverse RNAs can be generated from identical precursors. This complexity, still poorly understood, is fundamental for the accuracy of gene expression. In addition, a clear knowledge of 3' ss selection is needed to fully decipher the coding potential of genomes.
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Affiliation(s)
- Jorge Pérez-Valle
- Department of Molecular Genòmics, Institute of Molecular Biology of Barcelona (IBMB), Barcelona, Spain
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25
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Abstract
All RNA species in yeast cells are subject to turnover. Work over the past 20 years has defined degradation mechanisms for messenger RNAs, transfer RNAs, ribosomal RNAs, and noncoding RNAs. In addition, numerous quality control mechanisms that target aberrant RNAs have been identified. Generally, each decay mechanism contains factors that funnel RNA substrates to abundant exo- and/or endonucleases. Key issues for future work include determining the mechanisms that control the specificity of RNA degradation and how RNA degradation processes interact with translation, RNA transport, and other cellular processes.
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Affiliation(s)
- Roy Parker
- Department of Molecular and Cellular Biology, University of Arizona and Howard Hughes Medical Institute, Tucson, AZ 85721, USA.
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26
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Semlow DR, Staley JP. Staying on message: ensuring fidelity in pre-mRNA splicing. Trends Biochem Sci 2012; 37:263-73. [PMID: 22564363 DOI: 10.1016/j.tibs.2012.04.001] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 02/23/2012] [Accepted: 04/03/2012] [Indexed: 12/28/2022]
Abstract
The faithful expression of genes requires that cellular machinery select substrates with high specificity at each step in gene expression. High specificity is particularly important at the stage of nuclear pre-mRNA splicing, during which the spliceosome selects splice sites and excises intervening introns. With low specificity, the usage of alternative sites would yield insertions, deletions and frame shifts in mRNA. Recently, biochemical, genetic and genome-wide approaches have significantly advanced our understanding of splicing fidelity. In particular, we have learned that DExD/H-box ATPases play a general role in rejecting and discarding suboptimal substrates and that these factors serve as a paradigm for proofreading NTPases in other systems. Recent advances have also defined fundamental questions for future investigations.
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Affiliation(s)
- Daniel R Semlow
- Graduate Program in Cell and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
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27
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St Laurent G, Savva YA, Kapranov P. Dark matter RNA: an intelligent scaffold for the dynamic regulation of the nuclear information landscape. Front Genet 2012; 3:57. [PMID: 22539933 PMCID: PMC3336093 DOI: 10.3389/fgene.2012.00057] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Accepted: 03/28/2012] [Indexed: 01/15/2023] Open
Abstract
Perhaps no other topic in contemporary genomics has inspired such diverse viewpoints as the 95+% of the genome, previously known as “junk DNA,” that does not code for proteins. Here, we present a theory in which dark matter RNA plays a role in the generation of a landscape of spatial micro-domains coupled to the information signaling matrix of the nuclear landscape. Within and between these micro-domains, dark matter RNAs additionally function to tether RNA interacting proteins and complexes of many different types, and by doing so, allow for a higher performance of the various processes requiring them at ultra-fast rates. This improves signal to noise characteristics of RNA processing, trafficking, and epigenetic signaling, where competition and differential RNA binding among proteins drives the computational decisions inherent in regulatory events.
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Affiliation(s)
- Georges St Laurent
- Immunovirology - Biogenesis Group, University of Antioquia, Medellin, Colombia
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28
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Tavanez JP, Madl T, Kooshapur H, Sattler M, Valcárcel J. hnRNP A1 proofreads 3' splice site recognition by U2AF. Mol Cell 2012; 45:314-29. [PMID: 22325350 DOI: 10.1016/j.molcel.2011.11.033] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 08/01/2011] [Accepted: 11/23/2011] [Indexed: 01/03/2023]
Abstract
One of the earliest steps in metazoan pre-mRNA splicing involves binding of U2 snRNP auxiliary factor (U2AF) 65 KDa subunit to the polypyrimidine (Py) tract and of the 35 KDa subunit to the invariant AG dinucleotide at the intron 3' end. Here we use in vitro and in vivo depletion, as well as reconstitution assays using purified components, to identify hnRNP A1 as an RNA binding protein that allows U2AF to discriminate between pyrimidine-rich RNA sequences followed or not by a 3' splice site AG. Biochemical and NMR data indicate that hnRNP A1 forms a ternary complex with the U2AF heterodimer on AG-containing/uridine-rich RNAs, while it displaces U2AF from non-AG-containing/uridine-rich RNAs, an activity that requires the glycine-rich domain of hnRNP A1. Consistent with the functional relevance of this activity for splicing, proofreading assays reveal a role for hnRNP A1 in U2AF-mediated recruitment of U2 snRNP to the pre-mRNA.
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Affiliation(s)
- Joao Paulo Tavanez
- Centre de Regulació Genòmica, Dr. Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra, Dr. Aiguader 88, 08003 Barcelona, Spain
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29
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Burke JE, Sashital DG, Zuo X, Wang YX, Butcher SE. Structure of the yeast U2/U6 snRNA complex. RNA (NEW YORK, N.Y.) 2012; 18:673-83. [PMID: 22328579 PMCID: PMC3312555 DOI: 10.1261/rna.031138.111] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The U2/U6 snRNA complex is a conserved and essential component of the active spliceosome that interacts with the pre-mRNA substrate and essential protein splicing factors to promote splicing catalysis. Here we have elucidated the solution structure of a 111-nucleotide U2/U6 complex using an approach that integrates SAXS, NMR, and molecular modeling. The U2/U6 structure contains a three-helix junction that forms an extended "Y" shape. The U6 internal stem-loop (ISL) forms a continuous stack with U2/U6 Helices Ib, Ia, and III. The coaxial stacking of Helix Ib on the U6 ISL is a configuration that is similar to the Domain V structure in group II introns. Interestingly, essential features of the complex--including the U80 metal binding site, AGC triad, and pre-mRNA recognition sites--localize to one face of the molecule. This observation suggests that the U2/U6 structure is well-suited for orienting substrate and cofactors during splicing catalysis.
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Affiliation(s)
- Jordan E. Burke
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - Dipali G. Sashital
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - Xiaobing Zuo
- Advanced Photon Source, Argonne National Laboratory, Chicago, Illinois 60437, USA
| | - Yun-Xing Wang
- National Cancer Institute, National Institutes of Health, Frederick, Maryland 21702, USA
| | - Samuel E. Butcher
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
- Corresponding author.E-mail .
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30
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Cordin O, Hahn D, Beggs JD. Structure, function and regulation of spliceosomal RNA helicases. Curr Opin Cell Biol 2012; 24:431-8. [PMID: 22464735 DOI: 10.1016/j.ceb.2012.03.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 02/12/2012] [Accepted: 03/08/2012] [Indexed: 01/24/2023]
Abstract
Pre-mRNA splicing requires the activities of several ATPases from the DEAH-box, DEAD-box and Ski2-like helicase families to control conformational rearrangements within the spliceosome. Recent findings indicate that several spliceosomal helicases can act at multiple stages of the splicing reaction, and information on how those multiple actions are controlled are emerging. The recently solved crystal structure of the DEAH-box helicase Prp43 provides novel insights into the similarities and differences between the three helicase families. Here we discuss the potential family-specific mechanisms of spliceosomal RNA helicases and their regulation.
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Affiliation(s)
- Olivier Cordin
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh, EH9 3JR, UK
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31
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Allende-Vega N, Dayal S, Agarwala U, Sparks A, Bourdon JC, Saville MK. p53 is activated in response to disruption of the pre-mRNA splicing machinery. Oncogene 2012; 32:1-14. [PMID: 22349816 DOI: 10.1038/onc.2012.38] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In this study, we show that interfering with the splicing machinery results in activation of the tumour-suppressor p53. The spliceosome was targeted by small interfering RNA-mediated knockdown of proteins associated with different small nuclear ribonucleoprotein complexes and by using the small-molecule splicing modulator TG003. These interventions cause: the accumulation of p53, an increase in p53 transcriptional activity and can result in p53-dependent G(1) cell cycle arrest. Mdm2 and MdmX are two key repressors of p53. We show that a decrease in MdmX protein level contributes to p53 activation in response to targeting the spliceosome. Interfering with the spliceosome also causes an increase in the rate of degradation of Mdm2. Alterations in splicing are linked with tumour development. There are frequently global changes in splicing in cancer. Our study suggests that p53 activation could participate in protection against potential tumour-promoting defects in the spliceosome. A number of known p53-activating agents affect the splicing machinery and this could contribute to their ability to upregulate p53. Preclinical studies indicate that tumours can be more sensitive than normal cells to small-molecule spliceosome inhibitors. Activation of p53 could influence the selective anti-tumour activity of this therapeutic approach.
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Affiliation(s)
- N Allende-Vega
- Division of Cancer Research, Medical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Angus, UK
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32
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Wiludda C, Schulze S, Gowik U, Engelmann S, Koczor M, Streubel M, Bauwe H, Westhoff P. Regulation of the photorespiratory GLDPA gene in C(4) flaveria: an intricate interplay of transcriptional and posttranscriptional processes. THE PLANT CELL 2012; 24:137-51. [PMID: 22294620 PMCID: PMC3289567 DOI: 10.1105/tpc.111.093872] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 12/23/2011] [Accepted: 01/12/2012] [Indexed: 05/05/2023]
Abstract
The mitochondrial Gly decarboxylase complex (GDC) is a key component of the photorespiratory pathway that occurs in all photosynthetically active tissues of C(3) plants but is restricted to bundle sheath cells in C(4) species. GDC is also required for general cellular C(1) metabolism. In the Asteracean C(4) species Flaveria trinervia, a single functional GLDP gene, GLDPA, encodes the P-subunit of GDC, a decarboxylating Gly dehydrogenase. GLDPA promoter reporter gene fusion studies revealed that this promoter is active in bundle sheath cells and the vasculature of transgenic Flaveria bidentis (C(4)) and the Brassicacean C(3) species Arabidopsis thaliana, suggesting the existence of an evolutionarily conserved gene regulatory system in the bundle sheath. Here, we demonstrate that GLDPA gene regulation is achieved by an intricate interplay of transcriptional and posttranscriptional mechanisms. The GLDPA promoter is composed of two tandem promoters, P(R2) and P(R7), that together ensure a strong bundle sheath expression. While the proximal promoter (P(R7)) is active in the bundle sheath and vasculature, the distal promoter (P(R2)) drives uniform expression in all leaf chlorenchyma cells and the vasculature. An intron in the 5' untranslated leader of P(R2)-derived transcripts is inefficiently spliced and apparently suppresses the output of P(R2) by eliciting RNA decay.
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Affiliation(s)
- Christian Wiludda
- Heinrich-Heine-Universität Düsseldorf, Institut für Entwicklungs- und Molekularbiologie der Pflanzen, 40225 Duesseldorf, Germany
| | - Stefanie Schulze
- Heinrich-Heine-Universität Düsseldorf, Institut für Entwicklungs- und Molekularbiologie der Pflanzen, 40225 Duesseldorf, Germany
| | - Udo Gowik
- Heinrich-Heine-Universität Düsseldorf, Institut für Entwicklungs- und Molekularbiologie der Pflanzen, 40225 Duesseldorf, Germany
| | - Sascha Engelmann
- Heinrich-Heine-Universität Düsseldorf, Institut für Entwicklungs- und Molekularbiologie der Pflanzen, 40225 Duesseldorf, Germany
| | - Maria Koczor
- Heinrich-Heine-Universität Düsseldorf, Institut für Entwicklungs- und Molekularbiologie der Pflanzen, 40225 Duesseldorf, Germany
| | - Monika Streubel
- Heinrich-Heine-Universität Düsseldorf, Institut für Entwicklungs- und Molekularbiologie der Pflanzen, 40225 Duesseldorf, Germany
| | - Hermann Bauwe
- Universität Rostock, Abteilung Pflanzenphysiologie, 18059 Rostock, Germany
| | - Peter Westhoff
- Heinrich-Heine-Universität Düsseldorf, Institut für Entwicklungs- und Molekularbiologie der Pflanzen, 40225 Duesseldorf, Germany
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33
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Boehr DD. Promiscuity in protein-RNA interactions: conformational ensembles facilitate molecular recognition in the spliceosome: conformational diversity in U2AF⁶⁵ facilitates binding to diverse RNA sequences. Bioessays 2011; 34:174-80. [PMID: 22144099 DOI: 10.1002/bies.201100152] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Here I discuss findings that suggest a universal mechanism for proteins (and RNA) to recognize and interact with various binding partners by selectively binding to different conformations that pre-exist in the free protein's conformational ensemble. The tandem RNA recognition motif domains of splicing factor U2AF⁶⁵ fluctuate in solution between a predominately closed conformation in which the RNA binding site of one of the domains is blocked, and a lowly populated open conformation in which both RNA binding pockets are accessible. RNA binding to U2AF⁶⁵ may thus occur through the weakly populated open conformation, and the binding interaction stabilizes the open conformation. The conformational diversity observed in U2AF⁶⁵ might also facilitate binding to diverse RNA sequences as found in the polypyrimidine tracts that help define 3' splice sites. Similar binding pathways in other systems have important consequences in biological regulation, molecular evolution, and information storage.
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Affiliation(s)
- David D Boehr
- Department of Chemistry, The Pennsylvania State University, 240 Chemistry Building, University Park, PA, USA.
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