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Kumar K, Sinha SK, Maity U, Kirti PB, Kumar KRR. Insights into established and emerging roles of SR protein family in plants and animals. WILEY INTERDISCIPLINARY REVIEWS. RNA 2023; 14:e1763. [PMID: 36131558 DOI: 10.1002/wrna.1763] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 08/11/2022] [Accepted: 08/22/2022] [Indexed: 05/13/2023]
Abstract
Splicing of pre-mRNA is an essential part of eukaryotic gene expression. Serine-/arginine-rich (SR) proteins are highly conserved RNA-binding proteins present in all metazoans and plants. SR proteins are involved in constitutive and alternative splicing, thereby regulating the transcriptome and proteome diversity in the organism. In addition to their role in splicing, SR proteins are also involved in mRNA export, nonsense-mediated mRNA decay, mRNA stability, and translation. Due to their pivotal roles in mRNA metabolism, SR proteins play essential roles in normal growth and development. Hence, any misregulation of this set of proteins causes developmental defects in both plants and animals. SR proteins from the animal kingdom are extensively studied for their canonical and noncanonical functions. Compared with the animal kingdom, plant genomes harbor more SR protein-encoding genes and greater diversity of SR proteins, which are probably evolved for plant-specific functions. Evidence from both plants and animals confirms the essential role of SR proteins as regulators of gene expression influencing cellular processes, developmental stages, and disease conditions. This article is categorized under: RNA Processing > Splicing Mechanisms RNA Processing > Splicing Regulation/Alternative Splicing.
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Affiliation(s)
- Kundan Kumar
- Department of Biotechnology, Indira Gandhi National Tribal University (IGNTU), Amarkantak, India
| | - Shubham Kumar Sinha
- Department of Biotechnology, Indira Gandhi National Tribal University (IGNTU), Amarkantak, India
| | - Upasana Maity
- Department of Biotechnology, Indira Gandhi National Tribal University (IGNTU), Amarkantak, India
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2
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Das R, Jakubowski MA, Spildener J, Cheng YW. Identification of Novel MET Exon 14 Skipping Variants in Non-Small Cell Lung Cancer Patients: A Prototype Workflow Involving in Silico Prediction and RT-PCR. Cancers (Basel) 2022; 14:cancers14194814. [PMID: 36230737 PMCID: PMC9563401 DOI: 10.3390/cancers14194814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 09/11/2022] [Accepted: 09/22/2022] [Indexed: 11/16/2022] Open
Abstract
Background and aims: The MET exon 14 skipping (METex14) is an oncogenic driver mutation that provides a therapeutic opportunity in non-small cell lung cancer (NSCLCs) patients. This event often results from sequence changes at the MET canonical splicing sites. We characterize two novel non-canonical splicing site variants of MET that produce METex14. Materials and Methods: Two variants were identified in three advanced-stage NSCLC patients in a next-generation sequencing panel. The potential impact on splicing was predicted using in silico tools. METex14 mutation was confirmed using reverse transcription (RT)-PCR and a Sanger sequencing analysis on RNA extracted from stained cytology smears. Results: The interrogated MET (RefSeq ID NM_000245.3) variants include a single nucleotide substitution, c.3028+3A>T, in intron 14 and a deletion mutation, c.3012_3028del, in exon 14. The in silico prediction analysis exhibited reduced splicing strength in both variants compared with the MET normal transcript. The RT-PCR and subsequent Sanger sequencing analyses confirmed METex14 skipping in all three patients carrying these variants. Conclusion: This study reveals two non-canonical MET splice variants that cause exon 14 skipping, concurrently also proposes a clinical workflow for the classification of such non-canonical splicing site variants detected by routine DNA-based NGS test. It shows the usefulness of in silico prediction to identify potential METex14 driver mutation and exemplifies the opportunity of routine cytology slides for RNA-based testing.
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Affiliation(s)
| | | | | | - Yu-Wei Cheng
- Correspondence: ; Tel.: +1-216-445-0757; Fax: +1-216-445-0681
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3
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Srivastava S, Abraham PR, Mukhopadhyay S. Aptamers: An Emerging Tool for Diagnosis and Therapeutics in Tuberculosis. Front Cell Infect Microbiol 2021; 11:656421. [PMID: 34277465 PMCID: PMC8280756 DOI: 10.3389/fcimb.2021.656421] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 06/09/2021] [Indexed: 11/13/2022] Open
Abstract
Tuberculosis (TB) has been plaguing human civilization for centuries, and currently around one-third of the global population is affected with TB. Development of novel intervention tools for early diagnosis and therapeutics against Mycobacterium tuberculosis (M.tb) is the main thrust area in today's scenario. In this direction global efforts were made to use aptamers, the chemical antibodies as tool for TB diagnostics and therapeutics. This review describes the various aptamers introduced for targeting M.tb and highlights the need for development of novel aptamers to selectively target virulent proteins of M.tb for vaccine and anti-TB drugs. The objective of this review is to highlight the diagnostic and therapeutic application of aptamers used for tuberculosis. The discovery of aptamers, SELEX technology, different types of SELEX development processes, DNA and RNA aptamers reported for diseases and pathogenic agents as well have also been described in detail. But the emphasis of this review is on the development of aptamers which can block the function of virulent mycobacterial components for developing newer TB vaccine candidates and/or drug targets. Aptamers designed to target M.tb cell wall proteins, virulent factors, secretory proteins, or combination could orchestrate advanced diagnosis and therapeutic measures for tuberculosis.
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Affiliation(s)
- Shruti Srivastava
- Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD), Hyderabad, India
| | - Philip Raj Abraham
- Unit of OMICS, ICMR-Vector Control Research Centre (VCRC), Puducherry, India
| | - Sangita Mukhopadhyay
- Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD), Hyderabad, India
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4
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Allemailem KS, Almatroudi A, Alsahli MA, Basfar GT, Alrumaihi F, Rahmani AH, Khan AA. Recent advances in understanding oligonucleotide aptamers and their applications as therapeutic agents. 3 Biotech 2020; 10:551. [PMID: 33269185 PMCID: PMC7686427 DOI: 10.1007/s13205-020-02546-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Accepted: 11/06/2020] [Indexed: 12/12/2022] Open
Abstract
The innovative discovery of aptamers was based on target-specific treatment in clinical diagnostics and therapeutics. Aptamers are synthetic, single-stranded oligonucleotides, simply described as chemical antibodies, which can bind to diverse targets with high specificity and affinity. Aptamers are synthesized by the SELEX technique, and possess distinctive properties as small size (10-50 kDa), higher stability, easy manufacture and less immunogenicity. These oligonucleotides are easily degraded by nucleases, so require some important modifications like capping and incorporation of modified nucleotides. RNA aptamers can be modified chemically on 2' positions using -NH3, -F, -deoxy, or -OMe groups to enhance their nuclease resistance. Aptamers have been employed for multiple purposes, as direct drugs or aptamer-drug conjugates targeted against different diseased cells. Different aptamer-conjugated nanovehicles (e.g., micelles, liposomes, silica nano-shells) have been designed to transport diverse anticancer-drugs like doxorubicin and cisplatin in bulk to minimize systemic cytotoxicity. Some drug-loaded nanovehicles (up to 97% loading capacity) and conjugated with specific aptamer resulted in more than 60% tumor inhibition as compared to unconjugated drug-loaded nanovehicles which showed only 31% cancer inhibition. In addition, aptamers have been widely used in basic research, food safety, environmental monitoring, clinical diagnostics and therapeutics. Different FDA-approved RNA and DNA aptamers are now available in the market, used for the treatment of diverse diseases, especially cancer. These aptamers include Macugen, Pegaptanib, etc. Despite a good progress in aptamer use, the present-day chemotherapeutics and drug targeting systems still face great challenges. Here in this review article, we are discussing nucleic acid aptamers, preparation, role in the transportation of different nanoparticle vehicles and their applications as therapeutic agents.
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Affiliation(s)
- Khaled S. Allemailem
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
- Department of Basic Health Sciences, College of Applied Medical Sciences, Qassim University, P.O. Box 6699, Buraydah, 51452 Saudi Arabia
| | - Ahmad Almatroudi
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
| | - Mohammed A. Alsahli
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
| | - Ghaiyda Talal Basfar
- Department of Laboratory Medicine, Faculty of Applied Medical Sciences, Umm Al-Qura University, Makkah, Saudi Arabia
| | - Faris Alrumaihi
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
| | - Arshad Husain Rahmani
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
| | - Amjad Ali Khan
- Department of Basic Health Sciences, College of Applied Medical Sciences, Qassim University, P.O. Box 6699, Buraydah, 51452 Saudi Arabia
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5
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Rong S, Buerer L, Rhine CL, Wang J, Cygan KJ, Fairbrother WG. Mutational bias and the protein code shape the evolution of splicing enhancers. Nat Commun 2020; 11:2845. [PMID: 32504065 PMCID: PMC7275064 DOI: 10.1038/s41467-020-16673-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 04/28/2020] [Indexed: 02/06/2023] Open
Abstract
Exonic splicing enhancers (ESEs) are enriched in exons relative to introns and bind splicing activators. This study considers a fundamental question of co-evolution: How did ESE motifs become enriched in exons prior to the evolution of ESE recognition? We hypothesize that the high exon to intron motif ratios necessary for ESE function were created by mutational bias coupled with purifying selection on the protein code. These two forces retain certain coding motifs in exons while passively depleting them from introns. Through the use of simulations, genomic analyses, and high throughput splicing assays, we confirm the key predictions of this hypothesis, including an overlap between protein and splicing information in ESEs. We discuss the implications of mutational bias as an evolutionary driver in other cis-regulatory systems. Splicing is regulated by cis-acting elements in pre-mRNAs such as exonic or intronic splicing enhancers and silencers. Here the authors show that exonic splicing enhancers are enriched in exons compared to introns due to mutational bias coupled with purifying selection on the protein code.
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Affiliation(s)
- Stephen Rong
- Center for Computational Molecular Biology, Brown University, Providence, RI, 02912, USA.,Ecology and Evolutionary Biology, Brown University, Providence, RI, 02912, USA
| | - Luke Buerer
- Center for Computational Molecular Biology, Brown University, Providence, RI, 02912, USA
| | - Christy L Rhine
- Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, 02912, USA
| | - Jing Wang
- Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, 02912, USA
| | - Kamil J Cygan
- Center for Computational Molecular Biology, Brown University, Providence, RI, 02912, USA.,Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, 02912, USA
| | - William G Fairbrother
- Center for Computational Molecular Biology, Brown University, Providence, RI, 02912, USA. .,Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, 02912, USA. .,Hassenfeld Child Health Innovation Institute of Brown University, Providence, RI, 02912, USA.
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6
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7
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Sinha K, Mukhopadhyay CDAS. Quantitative detection of neurotransmitter using aptamer: From diagnosis to therapeutics. J Biosci 2020; 45:44. [PMID: 32098923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Neurotransmitters, the small molecule chemical messenger responsible for nervous system regulation and can control joy, fear, depression, insomnia, craving for carbohydrates, drugs, and alcohols. Variation in neurotransmitter levels is a characteristic manifestation of several neurological diseases. Accurate diagnosis of these diseases caused due to an imbalance in neurotransmitter level followed by impaired transmission of signals between neurons and other body parts remains a great challenge for the clinicians. Recent evidences reveal, artificial single-stranded nucleotides called 'aptamer' are widely used as biosensors, antibody substitutes, diagnostic agents, and for targeted therapy. These aptamers are superior candidate both for early detection and diagnosis of many neurological disorders caused due to suboptimal level of neurotransmitters. Presently, noninvasive neurotransmitter detection by aptamer has been found to be an easy, fast, and cost-effective choice. In addition, increased specificity, stability, affinity, and reproducibility of aptamers, high throughput screening of aptamer-based sensing platforms have been observed. Moreover, clinical applicability of aptamer has also proved to be efficacious, though still at a preliminary stage. Herein, we review salient features of aptamerbased sensing technology used for neurotransmitter detection particularly their chemical modifications, selection, assay development, immobilization, therapeutic efficiency, and stability for early diagnosis of diseases caused due to neurotransmitter imbalance.
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Affiliation(s)
- Koel Sinha
- Centre for Healthcare Science and Technology, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711 103, India
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8
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Ptok J, Müller L, Theiss S, Schaal H. Context matters: Regulation of splice donor usage. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2019; 1862:194391. [PMID: 31202784 DOI: 10.1016/j.bbagrm.2019.06.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 06/07/2019] [Accepted: 06/09/2019] [Indexed: 11/16/2022]
Abstract
Elaborate research on splicing, starting in the late seventies, evolved from the discovery that 5' splice sites are recognized by their complementarity to U1 snRNA towards the realization that RNA duplex formation cannot be the sole basis for 5'ss selection. Rather, their recognition is highly influenced by a number of context factors including transcript architecture as well as splicing regulatory elements (SREs) in the splice site neighborhood. In particular, proximal binding of splicing regulatory proteins highly influences splicing outcome. The importance of SRE integrity especially becomes evident in the light of human pathogenic mutations where single nucleotide changes in SREs can severely affect the resulting transcripts. Bioinformatics tools nowadays greatly assist in the computational evaluation of 5'ss, their neighborhood and the impact of pathogenic mutations. Although predictions are already quite robust, computational evaluation of the splicing regulatory landscape still faces challenges to increase future reliability. This article is part of a Special Issue entitled: RNA structure and splicing regulation edited by Francisco Baralle, Ravindra Singh and Stefan Stamm.
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Affiliation(s)
- Johannes Ptok
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Lisa Müller
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Stephan Theiss
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Heiner Schaal
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany.
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9
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Ali MH, Elsherbiny ME, Emara M. Updates on Aptamer Research. Int J Mol Sci 2019; 20:E2511. [PMID: 31117311 PMCID: PMC6566374 DOI: 10.3390/ijms20102511] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 04/26/2019] [Accepted: 04/30/2019] [Indexed: 02/07/2023] Open
Abstract
For many years, different probing techniques have mainly relied on antibodies for molecular recognition. However, with the discovery of aptamers, this has changed. The science community is currently considering using aptamers in molecular targeting studies because of the many potential advantages they have over traditional antibodies. Some of these possible advantages are their specificity, higher binding affinity, better target discrimination, minimized batch-to-batch variation, and reduced side effects. Overall, these characteristics of aptamers have attracted scholars to use them as molecular probes in place of antibodies, with some aptamer-based targeting products being now available in the market. The present review is aimed at discussing the potential of aptamers as probes in molecular biology and in super-resolution microscopy.
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Affiliation(s)
- Mohamed H Ali
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza 12578, Egypt.
- current address: Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA.
| | - Marwa E Elsherbiny
- Department of Pharmacology and Toxicology, Ahram Canadian University, 6th of October City, Giza 12566, Egypt.
| | - Marwan Emara
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza 12578, Egypt.
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10
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Kinghorn AB, Fraser LA, Liang S, Shiu SCC, Tanner JA. Aptamer Bioinformatics. Int J Mol Sci 2017; 18:E2516. [PMID: 29186809 PMCID: PMC5751119 DOI: 10.3390/ijms18122516] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 11/17/2017] [Accepted: 11/20/2017] [Indexed: 02/07/2023] Open
Abstract
Aptamers are short nucleic acid sequences capable of specific, high-affinity molecular binding. They are isolated via SELEX (Systematic Evolution of Ligands by Exponential Enrichment), an evolutionary process that involves iterative rounds of selection and amplification before sequencing and aptamer characterization. As aptamers are genetic in nature, bioinformatic approaches have been used to improve both aptamers and their selection. This review will discuss the advancements made in several enclaves of aptamer bioinformatics, including simulation of aptamer selection, fragment-based aptamer design, patterning of libraries, identification of lead aptamers from high-throughput sequencing (HTS) data and in silico aptamer optimization.
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Affiliation(s)
| | | | | | | | - Julian A. Tanner
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR China; (A.B.K.); (L.A.F.); (S.L.); (S.C.-C.S.)
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11
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Liu J, Bhadra M, Sinnakannu JR, Yue WL, Tan CW, Rigo F, Ong ST, Roca X. Overcoming imatinib resistance conferred by the BIM deletion polymorphism in chronic myeloid leukemia with splice-switching antisense oligonucleotides. Oncotarget 2017; 8:77567-77585. [PMID: 29100409 PMCID: PMC5652800 DOI: 10.18632/oncotarget.20658] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 07/25/2017] [Indexed: 11/25/2022] Open
Abstract
Many tyrosine kinase-driven cancers, including chronic myeloid leukemia (CML), are characterized by high response rates to specific tyrosine kinase inhibitors (TKIs) like imatinib. In East Asians, primary imatinib resistance is caused by a deletion polymorphism in Intron 2 of the BIM gene, whose product is required for TKI-induced apoptosis. The deletion biases BIM splicing from exon 4 to exon 3, generating splice isoforms lacking the exon 4-encoded pro-apoptotic BH3 domain, which impairs the ability of TKIs to induce apoptosis. We sought to identify splice-switching antisense oligonucleotides (ASOs) that block exon 3 but enhance exon 4 splicing, and thereby resensitize BIM deletion-containing cancers to imatinib. First, we mapped multiple cis-acting splicing elements around BIM exon 3 by minigene mutations, and found an exonic splicing enhancer acting via SRSF1. Second, by a systematic ASO walk, we isolated ASOs that corrected the aberrant BIM splicing. Eight of 67 ASOs increased exon 4 levels in BIM deletion-containing cells, and restored imatinib-induced apoptosis and TKI sensitivity. This proof-of-principle study proves that resistant CML cells by BIM deletion polymorphism can be resensitized to imatinib via splice-switching BIM ASOs. Future optimizations might yield a therapeutic ASO as precision-medicine adjuvant treatment for BIM-polymorphism-associated TKI-resistant CML and other cancers.
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Affiliation(s)
- Jun Liu
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Malini Bhadra
- School of Biological Sciences, Nanyang Technological University, Singapore
| | | | - Wan Lin Yue
- School of Biological Sciences, Nanyang Technological University, Singapore.,CN Yang Scholars Programme, Nanyang Technological University, Singapore
| | - Cheryl Weiqi Tan
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Frank Rigo
- Ionis Pharmaceuticals, Carlsbad, California, USA
| | - S Tiong Ong
- Cancer and Stem Cell Biology Signature Research Programme, Duke-NUS Medical School, Singapore.,Department of Haematology, Singapore General Hospital, Singapore.,Department of Medical Oncology, National Cancer Centre Singapore, Singapore.,Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
| | - Xavier Roca
- School of Biological Sciences, Nanyang Technological University, Singapore
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12
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Sharma TK, Bruno JG, Dhiman A. ABCs of DNA aptamer and related assay development. Biotechnol Adv 2017; 35:275-301. [PMID: 28108354 DOI: 10.1016/j.biotechadv.2017.01.003] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 11/19/2016] [Accepted: 01/17/2017] [Indexed: 12/14/2022]
Abstract
This review is intended to guide the novice in aptamer research and development to understand virtually all of the aptamer development options and currently available assay modalities. Aptamer development topics range from discussions of basic and advanced versions of Systematic Evolution of Ligands by EXponential Enrichment (SELEX) and SELEX variations involving incorporation of exotic unnatural nucleotides to expand library diversity for even greater aptamer affinity and specificity to improved next generation methods of DNA sequencing, screening and tracking aptamer development throughout the SELEX process and characterization of lead aptamer candidates. Aptamer assay development topics include descriptions of various colorimetric and fluorescent assays in microplates or on membranes including homogeneous beacon and multiplexed Fluorescence Resonance Energy Transfer (FRET) assays. Finally, a discussion of the potential for marketing successful aptamer-based assays or test kits is included.
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Affiliation(s)
- Tarun Kumar Sharma
- Center for Biodesign and Diagnostics, Translational Health Science and Technology Institute, Faridabad, Haryana 121001, India; AptaBharat Innovation Private Limited, Translational Health Science and Technology Institute Incubator, Haryana 121001, India.
| | - John G Bruno
- Operational Technologies Corporation, 4100 NW Loop 410, Suite, 230, San Antonio, TX 78229, USA..
| | - Abhijeet Dhiman
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi 110029, India.; Faculty of Pharmacy, Uttarakhand Technical University, Dehradun 248007, Uttarakhand, India
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13
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Abstract
Serine and arginine-rich (SR) proteins are RNA-binding proteins (RBPs) known as constitutive and alternative splicing regulators. As splicing is linked to transcriptional and post-transcriptional steps, SR proteins are implicated in the regulation of multiple aspects of the gene expression program. Recent global analyses of SR-RNA interaction maps have advanced our understanding of SR-regulated gene expression. Diverse SR proteins play partially overlapping but distinct roles in transcription-coupled splicing and mRNA processing in the nucleus. In addition, shuttling SR proteins act as adaptors for mRNA export and as regulators for translation in the cytoplasm. This mini-review will summarize the roles of SR proteins as RNA binders, regulators, and connectors from transcription in the nucleus to translation in the cytoplasm.
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Affiliation(s)
- Sunjoo Jeong
- Department of Bioconvergent Science and Technology, Dankook University, Yongin 16890,
Korea
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14
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Hartung AM, Swensen J, Uriz IE, Lapin M, Kristjansdottir K, Petersen USS, Bang JMV, Guerra B, Andersen HS, Dobrowolski SF, Carey JC, Yu P, Vaughn C, Calhoun A, Larsen MR, Dyrskjøt L, Stevenson DA, Andresen BS. The Splicing Efficiency of Activating HRAS Mutations Can Determine Costello Syndrome Phenotype and Frequency in Cancer. PLoS Genet 2016; 12:e1006039. [PMID: 27195699 PMCID: PMC4873146 DOI: 10.1371/journal.pgen.1006039] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 04/18/2016] [Indexed: 12/25/2022] Open
Abstract
Costello syndrome (CS) may be caused by activating mutations in codon 12/13 of the HRAS proto-oncogene. HRAS p.Gly12Val mutations have the highest transforming activity, are very frequent in cancers, but very rare in CS, where they are reported to cause a severe, early lethal, phenotype. We identified an unusual, new germline p.Gly12Val mutation, c.35_36GC>TG, in a 12-year-old boy with attenuated CS. Analysis of his HRAS cDNA showed high levels of exon 2 skipping. Using wild type and mutant HRAS minigenes, we confirmed that c.35_36GC>TG results in exon 2 skipping by simultaneously disrupting the function of a critical Exonic Splicing Enhancer (ESE) and creation of an Exonic Splicing Silencer (ESS). We show that this vulnerability of HRAS exon 2 is caused by a weak 3' splice site, which makes exon 2 inclusion dependent on binding of splicing stimulatory proteins, like SRSF2, to the critical ESE. Because the majority of cancer- and CS- causing mutations are located here, they affect splicing differently. Therefore, our results also demonstrate that the phenotype in CS and somatic cancers is not only determined by the different transforming potentials of mutant HRAS proteins, but also by the efficiency of exon 2 inclusion resulting from the different HRAS mutations. Finally, we show that a splice switching oligonucleotide (SSO) that blocks access to the critical ESE causes exon 2 skipping and halts proliferation of cancer cells. This unravels a potential for development of new anti-cancer therapies based on SSO-mediated HRAS exon 2 skipping.
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Affiliation(s)
- Anne-Mette Hartung
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Jeff Swensen
- Caris Life Sciences, Phoenix, Arizona, United States of America
- Department of Pathology, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- ARUP Laboratories, Salt Lake City, Utah, United States of America
| | - Inaki E. Uriz
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Morten Lapin
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Karen Kristjansdottir
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Ulrika S. S. Petersen
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Jeanne Mari V. Bang
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Barbara Guerra
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Henriette Skovgaard Andersen
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Steven F. Dobrowolski
- Department of Pathology, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - John C. Carey
- Department of Pediatrics, University of Utah, Salt Lake City, Utah, United States of America
| | - Ping Yu
- ARUP Laboratories, Salt Lake City, Utah, United States of America
| | - Cecily Vaughn
- ARUP Laboratories, Salt Lake City, Utah, United States of America
| | - Amy Calhoun
- Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Martin R. Larsen
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Lars Dyrskjøt
- Department of Molecular Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - David A. Stevenson
- Division of Medical Genetics, Stanford University, Stanford, California, United States of America
| | - Brage S. Andresen
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
- * E-mail:
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Tang SJ, Luo S, Ho JXJ, Ly PT, Goh E, Roca X. Characterization of the Regulation of CD46 RNA Alternative Splicing. J Biol Chem 2016; 291:14311-14323. [PMID: 27226545 DOI: 10.1074/jbc.m115.710350] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Indexed: 11/06/2022] Open
Abstract
Here we present a detailed analysis of the alternative splicing regulation of human CD46, which generates different isoforms with distinct functions. CD46 is a ubiquitous membrane protein that protects host cells from complement and plays other roles in immunity, autophagy, and cell adhesion. CD46 deficiency causes an autoimmune disorder, and this protein is also involved in pathogen infection and cancer. Before this study, the mechanisms of CD46 alternative splicing remained unexplored even though dysregulation of this process has been associated with autoimmune diseases. We proved that the 5' splice sites of CD46 cassette exons 7 and 8 encoding extracellular domains are defined by noncanonical mechanisms of base pairing to U1 small nuclear RNA. Next we characterized the regulation of CD46 cassette exon 13, whose inclusion or skipping generates different cytoplasmic tails with distinct functions. Using splicing minigenes, we identified multiple exonic and intronic splicing enhancers and silencers that regulate exon 13 inclusion via trans-acting splicing factors like PTBP1 and TIAL1. Interestingly, a common splicing activator such as SRSF1 appears to repress CD46 exon 13 inclusion. We also report that expression of CD46 mRNA isoforms is further regulated by non-sense-mediated mRNA decay and transcription speed. Finally, we successfully manipulated CD46 exon 13 inclusion using antisense oligonucleotides, opening up opportunities for functional studies of the isoforms as well as for therapeutics for autoimmune diseases. This study provides insight into CD46 alternative splicing regulation with implications for its function in the immune system and for genetic disease.
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Affiliation(s)
- Sze Jing Tang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Shufang Luo
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Jia Xin Jessie Ho
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Phuong Thao Ly
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Eling Goh
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Xavier Roca
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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Tan SY, Acquah C, Sidhu A, Ongkudon CM, Yon LS, Danquah MK. SELEX Modifications and Bioanalytical Techniques for Aptamer-Target Binding Characterization. Crit Rev Anal Chem 2016; 46:521-37. [PMID: 26980177 DOI: 10.1080/10408347.2016.1157014] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The quest to improve the detection of biomolecules and cells in health and life sciences has led to the discovery and characterization of various affinity bioprobes. Libraries of synthetic oligonucleotides (ssDNA/ssRNA) with randomized sequences are employed during Systematic Evolution of Ligands by Exponential Enrichment (SELEX) to select highly specific affinity probes called aptamers. With much focus on the generation of aptamers for a variety of target molecules, conventional SELEX protocols have been modified to develop new and improved SELEX protocols yielding highly specific and stable aptamers. Various techniques have been used to analyze the binding interactions between aptamers and their cognate molecules with associated merits and limitations. This article comprehensively reviews research advancements in the generation of aptamers, analyses physicochemical conditions affecting their binding characteristics to cellular and biomolecular targets, and discusses various field applications of aptameric binding. Biophysical techniques employed in the characterization of the molecular and binding features of aptamers to their cognate targets are also discussed.
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Affiliation(s)
- Sze Y Tan
- a Department of Chemical Engineering , Curtin University , Sarawak , Malaysia.,b Curtin Sarawak Research Institute , Curtin University , Sarawak , Malaysia
| | - Caleb Acquah
- a Department of Chemical Engineering , Curtin University , Sarawak , Malaysia.,b Curtin Sarawak Research Institute , Curtin University , Sarawak , Malaysia
| | - Amandeep Sidhu
- b Curtin Sarawak Research Institute , Curtin University , Sarawak , Malaysia.,c Faculty of Health Sciences , Curtin University , Perth , Australia
| | - Clarence M Ongkudon
- d Biotechnology Research Institute , University Malaysia Sabah , Kota Kinabalu , Sabah , Malaysia
| | - L S Yon
- a Department of Chemical Engineering , Curtin University , Sarawak , Malaysia
| | - Michael K Danquah
- a Department of Chemical Engineering , Curtin University , Sarawak , Malaysia.,b Curtin Sarawak Research Institute , Curtin University , Sarawak , Malaysia
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Farrokh S, Brillen AL, Haendeler J, Altschmied J, Schaal H. Critical regulators of endothelial cell functions: for a change being alternative. Antioxid Redox Signal 2015; 22:1212-29. [PMID: 25203279 DOI: 10.1089/ars.2014.6023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
SIGNIFICANCE The endothelium regulates vessel dilation and constriction, balances hemostasis, and inhibits thrombosis. In addition, pro- and anti-angiogenic molecules orchestrate proliferation, survival, and migration of endothelial cells. Regulation of all these processes requires fine-tuning of signaling pathways, which can easily be tricked into running the opposite direction when exogenous or endogenous signals get out of hand. Surprisingly, some critical regulators of physiological endothelial functions can turn malicious by mere alternative splicing, leading to the expression of protein isoforms with opposite functions. RECENT ADVANCES While reviewing the evidence of alternative splicing on cellular physiology, it became evident that expression of splice factors and their activities are regulated by externally triggered signaling cascades. Furthermore, genome-wide identification of RNA-binding sites of splicing regulatory proteins now offer a glimpse into the splicing code responsible for alternative splicing of molecules regulating endothelial functions. CRITICAL ISSUES Due to the constantly growing number of transcript and protein isoforms, it will become more and more important to identify and characterize all transcripts and proteins regulating endothelial cell functions. One critical issue will be a non-ambiguous nomenclature to keep consistency throughout different laboratories. FUTURE DIRECTIONS RNA-deep sequencing focusing on exon-exon junction needs to more reliably identify alternative splicing events combined with functional analyses that will uncover more splice variants contributing to or inhibiting proper endothelial functions. In addition, understanding the signals mediating alternative splicing and its regulation might allow us to derive new strategies to preserve endothelial function by suppressing or upregulating specific protein isoforms. Antioxid. Redox Signal. 22, 1212-1229.
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Affiliation(s)
- Sabrina Farrokh
- 1 Heisenberg-Group-Environmentally-Induced Cardiovascular Degeneration, IUF-Leibniz Research Institute for Environmental Medicine , Düsseldorf, Germany
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18
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Sestili F, Palombieri S, Botticella E, Mantovani P, Bovina R, Lafiandra D. TILLING mutants of durum wheat result in a high amylose phenotype and provide information on alternative splicing mechanisms. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2015; 233:127-133. [PMID: 25711820 DOI: 10.1016/j.plantsci.2015.01.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 01/15/2015] [Accepted: 01/18/2015] [Indexed: 05/20/2023]
Abstract
The amylose/amylopectin ratio has a major influence over the properties of starch and determines its optimal end use. Here, high amylose durum wheat has been bred by combining knock down alleles at the two homoelogous genes encoding starch branching enzyme IIa (SBEIIa-A and SBEIIa-B). The complete silencing of these genes had a number of pleiotropic effects on starch synthesis: it affected the transcriptional activity of SBEIIb, ISA1 (starch debranching enzyme) and all of the genes encoding starch synthases (SSI, SSIIa, SSIII and GBSSI). The starch produced by grain of the double SBEIIa mutants was high in amylose (up to ∼1.95 fold that of the wild type) and contained up to about eight fold more resistant starch. A single nucleotide polymorphism adjacent to the splice site at the end of exon 10 of the G364E mutant copies of both SBEIIa-A and SBEIIa-B resulted in the loss of a conserved exonic splicing silencer element. Its starch was similar to that of the SBEIIa double mutant. G364E SBEIIa pre-mRNA was incorrectly processed, resulting in the formation of alternative, but non-functional splicing products.
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Affiliation(s)
- Francesco Sestili
- Department of Agriculture, Forestry, Nature & Energy, University of Tuscia, Via S Camillo de Lellis SNC, 01100 Viterbo, Italy.
| | - Samuela Palombieri
- Department of Agriculture, Forestry, Nature & Energy, University of Tuscia, Via S Camillo de Lellis SNC, 01100 Viterbo, Italy.
| | - Ermelinda Botticella
- Department of Agriculture, Forestry, Nature & Energy, University of Tuscia, Via S Camillo de Lellis SNC, 01100 Viterbo, Italy.
| | - Paola Mantovani
- Società Produttori Sementi Spa, Via Macero 1, 40050 Argelato, Bologna, Italy.
| | - Riccardo Bovina
- Società Produttori Sementi Spa, Via Macero 1, 40050 Argelato, Bologna, Italy; Department of Agricultural Science (DipSA), University of Bologna, Viale Fanin 44, 40127 Bologna, Italy.
| | - Domenico Lafiandra
- Department of Agriculture, Forestry, Nature & Energy, University of Tuscia, Via S Camillo de Lellis SNC, 01100 Viterbo, Italy.
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Soemedi R, Vega H, Belmont JM, Ramachandran S, Fairbrother WG. Genetic variation and RNA binding proteins: tools and techniques to detect functional polymorphisms. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 825:227-66. [PMID: 25201108 DOI: 10.1007/978-1-4939-1221-6_7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
At its most fundamental level the goal of genetics is to connect genotype to phenotype. This question is asked at a basic level evaluating the role of genes and pathways in genetic model organism. Increasingly, this question is being asked in the clinic. Genomes of individuals and populations are being sequenced and compared. The challenge often comes at the stage of analysis. The variant positions are analyzed with the hope of understanding human disease. However after a genome or exome has been sequenced, the researcher is often deluged with hundreds of potentially relevant variations. Traditionally, amino-acid changing mutations were considered the tractable class of disease-causing mutations; however, mutations that disrupt noncoding elements are the subject of growing interest. These noncoding changes are a major avenue of disease (e.g., one in three hereditary disease alleles are predicted to affect splicing). Here, we review some current practices of medical genetics, the basic theory behind biochemical binding and functional assays, and then explore technical advances in how variations that alter RNA protein recognition events are detected and studied. These advances are advances in scale-high-throughput implementations of traditional biochemical assays that are feasible to perform in any molecular biology laboratory. This chapter utilizes a case study approach to illustrate some methods for analyzing polymorphisms. The first characterizes a functional intronic SNP that deletes a high affinity PTB site using traditional low-throughput biochemical and functional assays. From here we demonstrate the utility of high-throughput splicing and spliceosome assembly assays for screening large sets of SNPs and disease alleles for allelic differences in gene expression. Finally we perform three pilot drug screens with small molecules (G418, tetracycline, and valproic acid) that illustrate how compounds that rescue specific instances of differential pre-mRNA processing can be discovered.
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Affiliation(s)
- Rachel Soemedi
- Center for Computational Molecular Biology, Brown University, Providence, RI, USA
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20
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Santillan BA, Moye C, Mittelman D, Wilson JH. GFP-based fluorescence assay for CAG repeat instability in cultured human cells. PLoS One 2014; 9:e113952. [PMID: 25423602 PMCID: PMC4244167 DOI: 10.1371/journal.pone.0113952] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 11/03/2014] [Indexed: 12/13/2022] Open
Abstract
Trinucleotide repeats can be highly unstable, mutating far more frequently than point mutations. Repeats typically mutate by addition or loss of units of the repeat. CAG repeat expansions in humans trigger neurological diseases that include myotonic dystrophy, Huntington disease, and several spinocerebellar ataxias. In human cells, diverse mechanisms promote CAG repeat instability, and in mice, the mechanisms of instability are varied and tissue-dependent. Dissection of mechanistic complexity and discovery of potential therapeutics necessitates quantitative and scalable screens for repeat mutation. We describe a GFP-based assay for screening modifiers of CAG repeat instability in human cells. The assay exploits an engineered intronic CAG repeat tract that interferes with expression of an inducible GFP minigene. Like the phenotypes of many trinucleotide repeat disorders, we find that GFP function is impaired by repeat expansion, in a length-dependent manner. The intensity of fluorescence varies inversely with repeat length, allowing estimates of repeat tract changes in live cells. We validate the assay using transcription through the repeat and engineered CAG-specific nucleases, which have previously been reported to induce CAG repeat instability. The assay is relatively fast and should be adaptable to large-scale screens of chemical and shRNA libraries.
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Affiliation(s)
- Beatriz A. Santillan
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Christopher Moye
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - David Mittelman
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - John H. Wilson
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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21
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Abstract
Sequence-specific RNA-binding proteins (RBPs) bind to pre-mRNA to control alternative splicing, but it is not yet possible to read the 'splicing code' that dictates splicing regulation on the basis of genome sequence. Each alternative splicing event is controlled by multiple RBPs, the combined action of which creates a distribution of alternatively spliced products in a given cell type. As each cell type expresses a distinct array of RBPs, the interpretation of regulatory information on a given RNA target is exceedingly dependent on the cell type. RBPs also control each other's functions at many levels, including by mutual modulation of their binding activities on specific regulatory RNA elements. In this Review, we describe some of the emerging rules that govern the highly context-dependent and combinatorial nature of alternative splicing regulation.
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Affiliation(s)
- Xiang-Dong Fu
- Department of Cellular and Molecular Medicine and Institute for Genomic, Medicine, University of California San Diego, La Jolla, California 92093–0651, USA
| | - Manuel Ares
- Center for Molecular Biology of RNA, and Department of Molecular, Cell, and Developmental Biology, University of California at Santa Cruz, Santa Cruz, California 95064, USA
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22
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Absence of an intron splicing silencer in porcine Smn1 intron 7 confers immunity to the exon skipping mutation in human SMN2. PLoS One 2014; 9:e98841. [PMID: 24892836 PMCID: PMC4043917 DOI: 10.1371/journal.pone.0098841] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 05/08/2014] [Indexed: 11/19/2022] Open
Abstract
Spinal Muscular Atrophy is caused by homozygous loss of SMN1. All patients retain at least one copy of SMN2 which produces an identical protein but at lower levels due to a silent mutation in exon 7 which results in predominant exclusion of the exon. Therapies targeting the splicing of SMN2 exon 7 have been in development for several years, and their efficacy has been measured using either in vitro cellular assays or in vivo small animal models such as mice. In this study we evaluated the potential for constructing a mini-pig animal model by introducing minimal changes in the endogenous porcine Smn1 gene to maintain the native genomic structure and regulation. We found that while a Smn2-like mutation can be introduced in the porcine Smn1 gene and can diminish the function of the ESE, it would not recapitulate the splicing pattern seen in human SMN2 due to absence of a functional ISS immediately downstream of exon 7. We investigated the ISS region and show here that the porcine ISS is inactive due to disruption of a proximal hnRNP A1 binding site, while a distal hnRNP A1 binding site remains functional but is unable to maintain the functionality of the ISS as a whole.
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23
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Qian W, Liu F. Regulation of alternative splicing of tau exon 10. Neurosci Bull 2014; 30:367-77. [PMID: 24627328 DOI: 10.1007/s12264-013-1411-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Accepted: 01/03/2014] [Indexed: 12/22/2022] Open
Abstract
The neuronal microtubule-associated protein tau is abnormally hyperphosphorylated and aggregated into neurofibrillary tangles in the brains of individuals with Alzheimer's disease and related neurodegenerative disorders. The adult human brain expresses six isoforms of tau generated by alternative splicing of exons 2, 3, and 10 of its pre-mRNA. Exon 10 encodes the second microtubule-binding repeat of tau. Its alternative splicing produces tau isoforms with either three or four microtubule-binding repeats, termed 3R-tau and 4Rtau. In the normal adult human brain, the level of 3R-tau is approximately equal to that of 4R-tau. Several silent and intronic mutations of the tau gene associated with FTDP-17T (frontotemporal dementia with Parkinsonism linked to chromosome 17 and specifically characterized by tau pathology) only disrupt exon 10 splicing, but do not influence the primary sequence of the tau protein. Thus, abnormal exon 10 splicing is sufficient to cause neurodegeneration and dementia. Here, we review the regulation of tau exon 10 splicing by cis-elements and trans-factors and summarize all the mutations associated with FTDP-17T and related tauopathies. The findings suggest that correction of exon 10 splicing may be a potential target for tau exon 10 splicing-related tauopathies.
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Affiliation(s)
- Wei Qian
- Department of Biochemistry and Molecular Biology, School of Medicine, Nantong University, Nantong, 226001, China
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24
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Chen J, Weiss WA. Alternative splicing in cancer: implications for biology and therapy. Oncogene 2014; 34:1-14. [PMID: 24441040 DOI: 10.1038/onc.2013.570] [Citation(s) in RCA: 194] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 11/26/2013] [Accepted: 11/26/2013] [Indexed: 12/11/2022]
Abstract
Alternative splicing has critical roles in normal development and can promote growth and survival in cancer. Aberrant splicing, the production of noncanonical and cancer-specific mRNA transcripts, can lead to loss-of-function in tumor suppressors or activation of oncogenes and cancer pathways. Emerging data suggest that aberrant splicing products and loss of canonically spliced variants correlate with stage and progression in malignancy. Here, we review the splicing landscape of TP53, BARD1 and AR to illuminate roles for alternative splicing in cancer. We also examine the intersection between alternative splicing pathways and novel therapeutic approaches.
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Affiliation(s)
- J Chen
- 1] Biomedical Sciences Graduate Program, University of California, San Francisco, CA, USA [2] Department of Neurology, University of California, San Francisco, CA, USA
| | - W A Weiss
- 1] Department of Neurology, University of California, San Francisco, CA, USA [2] Department of Neurological Surgery and Pediatrics, University of California, San Francisco, CA, USA
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25
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Cáceres EF, Hurst LD. The evolution, impact and properties of exonic splice enhancers. Genome Biol 2013; 14:R143. [PMID: 24359918 PMCID: PMC4054783 DOI: 10.1186/gb-2013-14-12-r143] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Accepted: 12/20/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In humans, much of the information specifying splice sites is not at the splice site. Exonic splice enhancers are one of the principle non-splice site motifs. Four high-throughput studies have provided a compendium of motifs that function as exonic splice enhancers, but only one, RESCUE-ESE, has been generally employed to examine the properties of enhancers. Here we consider these four datasets to ask whether there is any consensus on the properties and impacts of exonic splice enhancers. RESULTS While only about 1% of all the identified hexamer motifs are common to all analyses we can define reasonably sized sets that are found in most datasets. These consensus intersection datasets we presume reflect the true properties of exonic splice enhancers. Given prior evidence for the properties of enhancers and splice-associated mutations, we ask for all datasets whether the exonic splice enhancers considered are purine enriched; enriched near exon boundaries; able to predict trends in relative codon usage; slow evolving at synonymous sites; rare in SNPs; associated with weak splice sites; and enriched near longer introns. While the intersect datasets match expectations, only one original dataset, RESCUE-ESE, does. Unexpectedly, a fully experimental dataset identifies motifs that commonly behave opposite to the consensus, for example, being enriched in exon cores where splice-associated mutations are rare. CONCLUSIONS Prior analyses that used the RESCUE-ESE set of hexamers captured the properties of consensus exonic splice enhancers. We estimate that at least 4% of synonymous mutations are deleterious owing to an effect on enhancer functioning.
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26
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Reddy AS, Marquez Y, Kalyna M, Barta A. Complexity of the alternative splicing landscape in plants. THE PLANT CELL 2013; 25:3657-83. [PMID: 24179125 PMCID: PMC3877793 DOI: 10.1105/tpc.113.117523] [Citation(s) in RCA: 516] [Impact Index Per Article: 46.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Revised: 09/27/2013] [Accepted: 10/08/2013] [Indexed: 05/18/2023]
Abstract
Alternative splicing (AS) of precursor mRNAs (pre-mRNAs) from multiexon genes allows organisms to increase their coding potential and regulate gene expression through multiple mechanisms. Recent transcriptome-wide analysis of AS using RNA sequencing has revealed that AS is highly pervasive in plants. Pre-mRNAs from over 60% of intron-containing genes undergo AS to produce a vast repertoire of mRNA isoforms. The functions of most splice variants are unknown. However, emerging evidence indicates that splice variants increase the functional diversity of proteins. Furthermore, AS is coupled to transcript stability and translation through nonsense-mediated decay and microRNA-mediated gene regulation. Widespread changes in AS in response to developmental cues and stresses suggest a role for regulated splicing in plant development and stress responses. Here, we review recent progress in uncovering the extent and complexity of the AS landscape in plants, its regulation, and the roles of AS in gene regulation. The prevalence of AS in plants has raised many new questions that require additional studies. New tools based on recent technological advances are allowing genome-wide analysis of RNA elements in transcripts and of chromatin modifications that regulate AS. Application of these tools in plants will provide significant new insights into AS regulation and crosstalk between AS and other layers of gene regulation.
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Affiliation(s)
- Anireddy S.N. Reddy
- Department of Biology, Program in Molecular Plant Biology, Program in Cell and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
- Address correspondence to
| | - Yamile Marquez
- Max F. Perutz Laboratories, Medical University of Vienna, Vienna A-1030, Austria
| | - Maria Kalyna
- Max F. Perutz Laboratories, Medical University of Vienna, Vienna A-1030, Austria
| | - Andrea Barta
- Max F. Perutz Laboratories, Medical University of Vienna, Vienna A-1030, Austria
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27
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Puisac B, Teresa-Rodrigo ME, Arnedo M, Gil-Rodríguez MC, Pérez-Cerdá C, Ribes A, Pié A, Bueno G, Gómez-Puertas P, Pié J. Analysis of aberrant splicing and nonsense-mediated decay of the stop codon mutations c.109G>T and c.504_505delCT in 7 patients with HMG-CoA lyase deficiency. Mol Genet Metab 2013; 108:232-40. [PMID: 23465862 DOI: 10.1016/j.ymgme.2013.01.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 01/25/2013] [Indexed: 12/13/2022]
Abstract
Eukaryotic cells can be protected against mutations that generate stop codons by nonsense-mediated mRNA decay (NMD) and/or nonsense-associated altered splicing (NAS). However, the processes are only partially understood and do not always occur. In this work, we study these phenomena in the stop codon mutations c.109G>T (p.Glu37*) and c.504_505delCT; the second and third most frequent mutations in HMG-CoA lyase deficiency (MIM #246450). The deficiency affects the synthesis of ketone bodies and produces severe disorders during early childhood. We used a minigene approach, real-time quantitative PCR and the inhibition of NMD by puromycin treatment, to study the effect of stop codons on splicing (NAS) and NMD in seven patients. Surprisingly, none of the stop codons studied appears to be the direct cause of aberrant splicing. In the mutation c.109G>T, the splicing is due to the base change G>T at position 109, which is critical and cannot be explained by disruption of exonic splicing enhancer (ESE) elements, by the appearance of exonic splicing silencer (ESS) elements which were predicted by bioinformatic tools or by the stop codons. Moreover, the mutation c.504_505delCT produces two mRNA transcripts both with stop codons that generate simultaneous NMD phenomena. The effects of the mutations studied on splicing seemed to be similar in all the patients. Furthermore, we report a Spanish patient with 3-hydroxy-3-methylglutaric aciduria and a novel missense mutation: c.825C>G (p.Asn275Lys).
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Affiliation(s)
- Beatriz Puisac
- Unit of Clinical Genetics and Functional Genomics, Department of Pharmacology-Physiology, School of Medicine, University of Zaragoza, E-50009 Zaragoza, Spain
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28
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Challenges and opportunities for small molecule aptamer development. J Nucleic Acids 2012; 2012:748913. [PMID: 23150810 PMCID: PMC3488411 DOI: 10.1155/2012/748913] [Citation(s) in RCA: 286] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 09/08/2012] [Indexed: 12/14/2022] Open
Abstract
Aptamers are single-stranded oligonucleotides that bind to targets with high affinity and selectivity. Their use as molecular recognition elements has emerged as a viable approach for biosensing, diagnostics, and therapeutics. Despite this potential, relatively few aptamers exist that bind to small molecules. Small molecules are important targets for investigation due to their diverse biological functions as well as their clinical and commercial uses. Novel, effective molecular recognition probes for these compounds are therefore of great interest. This paper will highlight the technical challenges of aptamer development for small molecule targets, as well as the opportunities that exist for their application in biosensing and chemical biology.
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29
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Abstract
Aptamers are single-stranded oligonucleotides that bind to targets with high affinity and selectivity. Their use as molecular recognition elements has emerged as a viable approach for biosensing, diagnostics, and therapeutics. Despite this potential, relatively few aptamers exist that bind to small molecules. Small molecules are important targets for investigation due to their diverse biological functions as well as their clinical and commercial uses. Novel, effective molecular recognition probes for these compounds are therefore of great interest. This paper will highlight the technical challenges of aptamer development for small molecule targets, as well as the opportunities that exist for their application in biosensing and chemical biology.
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30
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Kamath U, Compton J, Islamaj-Doğan R, De Jong KA, Shehu A. An evolutionary algorithm approach for feature generation from sequence data and its application to DNA splice site prediction. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2012; 9:1387-1398. [PMID: 22508909 DOI: 10.1109/tcbb.2012.53] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Associating functional information with biological sequences remains a challenge for machine learning methods. The performance of these methods often depends on deriving predictive features from the sequences sought to be classified. Feature generation is a difficult problem, as the connection between the sequence features and the sought property is not known a priori. It is often the task of domain experts or exhaustive feature enumeration techniques to generate a few features whose predictive power is then tested in the context of classification. This paper proposes an evolutionary algorithm to effectively explore a large feature space and generate predictive features from sequence data. The effectiveness of the algorithm is demonstrated on an important component of the gene-finding problem, DNA splice site prediction. This application is chosen due to the complexity of the features needed to obtain high classification accuracy and precision. Our results test the effectiveness of the obtained features in the context of classification by Support Vector Machines and show significant improvement in accuracy and precision over state-of-the-art approaches.
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Affiliation(s)
- Uday Kamath
- Department of Computer Science, George Mason University, Ashburn, VA 20147, USA.
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31
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Wei WJ, Mu SR, Heiner M, Fu X, Cao LJ, Gong XF, Bindereif A, Hui J. YB-1 binds to CAUC motifs and stimulates exon inclusion by enhancing the recruitment of U2AF to weak polypyrimidine tracts. Nucleic Acids Res 2012; 40:8622-36. [PMID: 22730292 PMCID: PMC3458536 DOI: 10.1093/nar/gks579] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The human Y box-binding protein-1 (YB-1) is a deoxyribonucleic acid (DNA)/ribonucleic acid (RNA)-binding protein with pleiotropic functions. Besides its roles in the regulation of transcription and translation, several recent studies indicate that YB-1 is a spliceosome-associated protein and is involved in alternative splicing, but the underlying mechanism has remained elusive. Here, we define both CAUC and CACC as high-affinity binding motifs for YB-1 by systematic evolution of ligands by exponential enrichment (SELEX) and demonstrate that these newly defined motifs function as splicing enhancers. Interestingly, on the endogenous CD44 gene, YB-1 appears to mediate a network interaction to activate exon v5 inclusion via multiple CAUC motifs in both the alternative exon and its upstream polypyrimidine tract. We provide evidence that YB-1 activates splicing by facilitating the recruitment of U2AF65 to weak polypyrimidine tracts through direct protein–protein interactions. Together, these findings suggest a vital role of YB-1 in activating a subset of weak 3′ splice sites in mammalian cells.
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Affiliation(s)
- Wen-Juan Wei
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 200031 Shanghai, China
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32
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Challenges and opportunities for small molecule aptamer development. J Nucleic Acids 2012; 2012:748913. [PMID: 23150810 PMCID: PMC3488411 DOI: 10.1155/2012/748913;+10.1155/2012/748913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
Aptamers are single-stranded oligonucleotides that bind to targets with high affinity and selectivity. Their use as molecular recognition elements has emerged as a viable approach for biosensing, diagnostics, and therapeutics. Despite this potential, relatively few aptamers exist that bind to small molecules. Small molecules are important targets for investigation due to their diverse biological functions as well as their clinical and commercial uses. Novel, effective molecular recognition probes for these compounds are therefore of great interest. This paper will highlight the technical challenges of aptamer development for small molecule targets, as well as the opportunities that exist for their application in biosensing and chemical biology.
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33
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Aquino-Jarquin G, Toscano-Garibay JD. RNA aptamer evolution: two decades of SELEction. Int J Mol Sci 2011; 12:9155-71. [PMID: 22272125 PMCID: PMC3257122 DOI: 10.3390/ijms12129155] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 11/24/2011] [Accepted: 11/28/2011] [Indexed: 11/16/2022] Open
Abstract
Aptamers are small non-coding RNAs capable of recognizing, with high specificity and affinity, a wide variety of molecules in a manner that resembles antibodies. This class of nucleic acids is the resulting product of applying a well-established screening method known as SELEX. First developed in 1990, the SELEX process has become a powerful tool to select structured oligonucleotides for the recognition of targets, starting with small molecules, going through protein complexes until whole cells. SELEX has also evolved along with new technologies positioning itself as an alternative in the design of a new class of therapeutic agents in modern molecular medicine. This review is an historical follow-up of SELEX method over the two decades since its first appearance.
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Affiliation(s)
- Guillermo Aquino-Jarquin
- Unit of Research on Oncological Disease, Children’s Hospital of Mexico Federico Gomez, Mexico City 06720, Mexico; E-Mail:
| | - Julia D. Toscano-Garibay
- Regenerative Medicine Laboratory. Research Direction, Mexico’s Juarez Hospital, Mexico City 07760, Mexico
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +52-55-57477560 ext.7476
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34
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Changes in exon-intron structure during vertebrate evolution affect the splicing pattern of exons. Genome Res 2011; 22:35-50. [PMID: 21974994 DOI: 10.1101/gr.119834.110] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Exon-intron architecture is one of the major features directing the splicing machinery to the short exons that are located within long flanking introns. However, the evolutionary dynamics of exon-intron architecture and its impact on splicing is largely unknown. Using a comparative genomic approach, we analyzed 17 vertebrate genomes and reconstructed the ancestral motifs of both 3' and 5' splice sites, as also the ancestral length of exons and introns. Our analyses suggest that vertebrate introns increased in length from the shortest ancestral introns to the longest primate introns. An evolutionary analysis of splice sites revealed that weak splice sites act as a restrictive force keeping introns short. In contrast, strong splice sites allow recognition of exons flanked by long introns. Reconstruction of the ancestral state suggests these phenomena were not prevalent in the vertebrate ancestor, but appeared during vertebrate evolution. By calculating evolutionary rate shifts in exons, we identified cis-acting regulatory sequences that became fixed during the transition from early vertebrates to mammals. Experimental validations performed on a selection of these hexamers confirmed their regulatory function. We additionally revealed many features of exons that can discriminate alternative from constitutive exons. These features were integrated into a machine-learning approach to predict whether an exon is alternative. Our algorithm obtains very high predictive power (AUC of 0.91), and using these predictions we have identified and successfully validated novel alternatively spliced exons. Overall, we provide novel insights regarding the evolutionary constraints acting upon exons and their recognition by the splicing machinery.
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35
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Ke S, Shang S, Kalachikov SM, Morozova I, Yu L, Russo JJ, Ju J, Chasin LA. Quantitative evaluation of all hexamers as exonic splicing elements. Genome Res 2011; 21:1360-74. [PMID: 21659425 DOI: 10.1101/gr.119628.110] [Citation(s) in RCA: 170] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We describe a comprehensive quantitative measure of the splicing impact of a complete set of RNA 6-mer sequences by deep sequencing successfully spliced transcripts. All 4096 6-mers were substituted at five positions within two different internal exons in a 3-exon minigene, and millions of successfully spliced transcripts were sequenced after transfection of human cells. The results allowed the assignment of a relative splicing strength score to each mutant molecule. The effect of 6-mers on splicing often depended on their location; much of this context effect could be ascribed to the creation of different overlapping sequences at each site. Taking these overlaps into account, the splicing effect of each 6-mer could be quantified, and 6-mers could be designated as enhancers (ESEseqs) and silencers (ESSseqs), with an ESRseq score indicating their strength. Some 6-mers exhibited positional bias relative to the two splice sites. The distribution and conservation of these ESRseqs in and around human exons supported their classification. Predicted RNA secondary structure effects were also seen: Effective enhancers, silencers and 3' splice sites tend to be single stranded, and effective 5' splice sites tend to be double stranded. 6-mers that may form positive or negative synergy with another were also identified. Chromatin structure may also influence the splicing enhancement observed, as a good correspondence was found between splicing performance and the predicted nucleosome occupancy scores of 6-mers. This approach may prove of general use in defining nucleic acid regulatory motifs, substitute for functional SELEX in most cases, and provide insights about splicing mechanisms.
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Affiliation(s)
- Shengdong Ke
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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36
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Kralovicova J, Hwang G, Asplund AC, Churbanov A, Smith CIE, Vorechovsky I. Compensatory signals associated with the activation of human GC 5' splice sites. Nucleic Acids Res 2011; 39:7077-91. [PMID: 21609956 PMCID: PMC3167603 DOI: 10.1093/nar/gkr306] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
GC 5′ splice sites (5′ss) are present in ∼1% of human introns, but factors promoting their efficient selection are poorly understood. Here, we describe a case of X-linked agammaglobulinemia resulting from a GC 5′ss activated by a mutation in BTK intron 3. This GC 5′ss was intrinsically weak, yet it was selected in >90% primary transcripts in the presence of a strong and intact natural GT counterpart. We show that efficient selection of this GC 5′ss required a high density of GAA/CAA-containing splicing enhancers in the exonized segment and was promoted by SR proteins 9G8, Tra2β and SC35. The GC 5′ss was efficiently inhibited by splice-switching oligonucleotides targeting either the GC 5′ss itself or the enhancer. Comprehensive analysis of natural GC-AG introns and previously reported pathogenic GC 5′ss showed that their efficient activation was facilitated by higher densities of splicing enhancers and lower densities of silencers than their GT 5′ss equivalents. Removal of the GC-AG introns was promoted to a minor extent by the splice-site strength of adjacent exons and inhibited by flanking Alu repeats, with the first downstream Alus located on average at a longer distance from the GC 5′ss than other transposable elements. These results provide new insights into the splicing code that governs selection of noncanonical splice sites.
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Affiliation(s)
- Jana Kralovicova
- University of Southampton School of Medicine, Division of Human Genetics, Southampton SO16 6YD, UK
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37
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Doktor TK, Schroeder LD, Vested A, Palmfeldt J, Andersen HS, Gregersen N, Andresen BS. SMN2 exon 7 splicing is inhibited by binding of hnRNP A1 to a common ESS motif that spans the 3' splice site. Hum Mutat 2011; 32:220-30. [PMID: 21120954 DOI: 10.1002/humu.21419] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 11/02/2010] [Indexed: 11/05/2022]
Abstract
Spinal Muscular Atrophy is caused by homozygous loss of SMN1 with phenotypic modulation by SMN2. SMN2 expresses only limited amounts of full-length transcript due to skipping of exon 7 caused by disruption of an SF2/ASF binding ESE. Additionally, hnRNP A1 has been reported to inhibit inclusion of SMN2 exon 7. We previously reported high similarity between the sequence spanning the 3' ss of SMN1 and SMN2 exon 7 and an hnRNP A1 binding ESS, which regulates MCAD exon 5 splicing. We show here that this 3' ss motif indeed functions as a crucial hnRNP A1 binding ESS, which inhibits inclusion of SMN1/2 exon 7 and is antagonized by the SMN1 ESE, but not by the inactive SMN2 sequence. Pull-down experiments revealed a specific interaction between hnRNP A1 and the 3' ss AG-dinucleotide, which could be disrupted by mutations shown to improve splicing in reporter minigenes. Genomic analyses revealed that in the human genome, 3' ss matching the SMN1/2 ESS motif region are much less abundant than 3' ss with a disrupted ESS motif. This indicates that this ESS may be a general splicing inhibitory motif, which binds hnRNP A1 and inhibits exon inclusion by binding to 3' ss harboring this ESS motif.
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Affiliation(s)
- Thomas Koed Doktor
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
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38
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Xiao X, Lee JH. Systems analysis of alternative splicing and its regulation. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2011; 2:550-565. [PMID: 20836047 DOI: 10.1002/wsbm.84] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Alternative splicing (AS) has emerged as a key mechanism that accounts for gene expression diversity in metazoan organisms. Splicing is tightly regulated by a repertoire of RNA and protein factors and RNA sequence elements that function in a cooperative manner. Systems-level experimental and computational approaches have been instrumental in establishing comprehensive profiles of transcript variants generated by AS. In addition, systems biology approaches are starting to define how combinatorial splicing regulation shapes the complex splicing phenotypes observed in different tissue types and developmental stages and under different conditions. Here, we review recent progress in these areas.
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Affiliation(s)
- Xinshu Xiao
- Department of Physiological Science, University of California, Los Angeles, CA 90095, USA.,Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Jae-Hyung Lee
- Department of Physiological Science, University of California, Los Angeles, CA 90095, USA.,Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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39
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Shukla JN, Nagaraju J. Doublesex: a conserved downstream gene controlled by diverse upstream regulators. J Genet 2010; 89:341-56. [DOI: 10.1007/s12041-010-0046-6] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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40
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Dobrowolski SF, Andersen HS, Doktor TK, Andresen BS. The phenylalanine hydroxylase c.30C>G synonymous variation (p.G10G) creates a common exonic splicing silencer. Mol Genet Metab 2010; 100:316-23. [PMID: 20457534 DOI: 10.1016/j.ymgme.2010.04.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Accepted: 04/07/2010] [Indexed: 11/30/2022]
Abstract
PKU is caused by mutations in PAH. A c.30C>G synonymous variation in exon 1, previously reported as neutral, was observed in two patients. The variation creates a GGG triplet, which is part of several exonic splicing silencer (ESS) motifs. Because the 5'-splice site of PAH exon 1 is intrinsically weak and therefore could be responsive to a new flanking ESS, we hypothesized that c.30C>G could cause aberrant mRNA splicing. We demonstrate that c.30C>G causes aberrant mRNA splicing in two different reporter minigenes, and that this is abolished if a preexisting flanking GGG triplet is disrupted. GGG triplets are part of the consensus motif bound by splicing-inhibitory hnRNPH proteins and we observed a dramatic increase in hnRNPH binding to c.30C>G PAH RNA. We conclude that c.30C>G creates a hnRNPH-binding ESS, which can disrupt mRNA splicing. A disease-causing mutation in HEXB, which has previously been associated with exon skipping in patients also creates a GGG triplet. We show that the mutant HEXB motif causes exon skipping of a reporter minigene and that this is also influenced by a flanking GGG triplet. We suggest that aberrant splicing caused by creation/abolishment of GGG triplets located together with a preexisting flanking GGG triplet, may be an underreported cause of human disease. It is important to recognize that exonic sequence changes may disrupt mRNA splicing. This is particularly important in PAH, since PKU patients harboring such mutations are unlikely to respond to therapy with 6R-tetrahydrobiopterin (BH(4)), despite the fact that the genetic code indicates otherwise.
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Affiliation(s)
- Steven F Dobrowolski
- Department of Pathology, School of Medicine, University of Utah, Salt Lake City, UT, USA
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41
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Cherny D, Gooding C, Eperon GE, Coelho MB, Bagshaw CR, Smith CWJ, Eperon IC. Stoichiometry of a regulatory splicing complex revealed by single-molecule analyses. EMBO J 2010; 29:2161-72. [PMID: 20502437 PMCID: PMC2905242 DOI: 10.1038/emboj.2010.103] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Accepted: 05/05/2010] [Indexed: 12/17/2022] Open
Abstract
Splicing is regulated by complex interactions of numerous RNA-binding proteins. The molecular mechanisms involved remain elusive, in large part because of ignorance regarding the numbers of proteins in regulatory complexes. Polypyrimidine tract-binding protein (PTB), which regulates tissue-specific splicing, represses exon 3 of alpha-tropomyosin through distant pyrimidine-rich tracts in the flanking introns. Current models for repression involve either PTB-mediated looping or the propagation of complexes between tracts. To test these models, we used single-molecule approaches to count the number of bound PTB molecules both by counting the number of bleaching steps of GFP molecules linked to PTB within complexes and by analysing their total emissions. Both approaches showed that five or six PTB molecules assemble. Given the domain structures, this suggests that the molecules occupy primarily multiple overlapping potential sites in the polypyrimidine tracts, excluding propagation models. As an alternative to direct looping, we propose that repression involves a multistep process in which PTB binding forms small local loops, creating a platform for recruitment of other proteins that bring these loops into close proximity.
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Affiliation(s)
- Dmitry Cherny
- Department of Biochemistry, University of Leicester, Leicester, UK
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42
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Culler SJ, Hoff KG, Voelker RB, Berglund JA, Smolke CD. Functional selection and systematic analysis of intronic splicing elements identify active sequence motifs and associated splicing factors. Nucleic Acids Res 2010; 38:5152-65. [PMID: 20385591 PMCID: PMC2926609 DOI: 10.1093/nar/gkq248] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Despite the critical role of pre-mRNA splicing in generating proteomic diversity and regulating gene expression, the sequence composition and function of intronic splicing regulatory elements (ISREs) have not been well elucidated. Here, we employed a high-throughput in vivo Screening PLatform for Intronic Control Elements (SPLICE) to identify 125 unique ISRE sequences from a random nucleotide library in human cells. Bioinformatic analyses reveal consensus motifs that resemble splicing regulatory elements and binding sites for characterized splicing factors and that are enriched in the introns of naturally occurring spliced genes, supporting their biological relevance. In vivo characterization, including an RNAi silencing study, demonstrate that ISRE sequences can exhibit combinatorial regulatory activity and that multiple trans-acting factors are involved in the regulatory effect of a single ISRE. Our work provides an initial examination into the sequence characteristics and function of ISREs, providing an important contribution to the splicing code.
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Affiliation(s)
- Stephanie J Culler
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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43
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Zhang Z, Theler D, Kaminska KH, Hiller M, de la Grange P, Pudimat R, Rafalska I, Heinrich B, Bujnicki JM, Allain FHT, Stamm S. The YTH domain is a novel RNA binding domain. J Biol Chem 2010; 285:14701-10. [PMID: 20167602 DOI: 10.1074/jbc.m110.104711] [Citation(s) in RCA: 212] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The YTH (YT521-B homology) domain was identified by sequence comparison and is found in 174 different proteins expressed in eukaryotes. It is characterized by 14 invariant residues within an alpha-helix/beta-sheet structure. Here we show that the YTH domain is a novel RNA binding domain that binds to a short, degenerated, single-stranded RNA sequence motif. The presence of the binding motif in alternative exons is necessary for YT521-B to directly influence splice site selection in vivo. Array analyses demonstrate that YT521-B predominantly regulates vertebrate-specific exons. An NMR titration experiment identified the binding surface for single-stranded RNA on the YTH domain. Structural analyses indicate that the YTH domain is related to the pseudouridine synthase and archaeosine transglycosylase (PUA) domain. Our data show that the YTH domain conveys RNA binding ability to a new class of proteins that are found in all eukaryotic organisms.
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Affiliation(s)
- Zhaiyi Zhang
- Institute for Biochemistry, Universität Erlangen-Nuremberg, Fahrstrasse 17, 91054 Erlangen, Germany
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44
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Goren A, Kim E, Amit M, Vaknin K, Kfir N, Ram O, Ast G. Overlapping splicing regulatory motifs--combinatorial effects on splicing. Nucleic Acids Res 2010; 38:3318-27. [PMID: 20110253 PMCID: PMC2879502 DOI: 10.1093/nar/gkq005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Regulation of splicing in eukaryotes occurs through the coordinated action of multiple splicing factors. Exons and introns contain numerous putative binding sites for splicing regulatory proteins. Regulation of splicing is presumably achieved by the combinatorial output of the binding of splicing factors to the corresponding binding sites. Although putative regulatory sites often overlap, no extensive study has examined whether overlapping regulatory sequences provide yet another dimension to splicing regulation. Here we analyzed experimentally-identified splicing regulatory sequences using a computational method based on the natural distribution of nucleotides and splicing regulatory sequences. We uncovered positive and negative interplay between overlapping regulatory sequences. Examination of these overlapping motifs revealed a unique spatial distribution, especially near splice donor sites of exons with weak splice donor sites. The positively selected overlapping splicing regulatory motifs were highly conserved among different species, implying functionality. Overall, these results suggest that overlap of two splicing regulatory binding sites is an evolutionary conserved widespread mechanism of splicing regulation. Finally, over-abundant motif overlaps were experimentally tested in a reporting minigene revealing that overlaps may facilitate a mode of splicing that did not occur in the presence of only one of the two regulatory sequences that comprise it.
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Affiliation(s)
- Amir Goren
- Department of Human Genetics and Molecular Medicine, Sackler Faculty of Medicine, Tel-Aviv University, Ramat Aviv 69978, Israel
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45
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Chen X, Denison L, Levy M, Ellington AD. Direct selection for ribozyme cleavage activity in cells. RNA (NEW YORK, N.Y.) 2009; 15:2035-45. [PMID: 19776159 PMCID: PMC2764470 DOI: 10.1261/rna.1635209] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Selection may prove to be a powerful tool for the generation of functional RNAs for in vivo genetic regulation. However, traditional in vitro selection schemes do not mimic physiological conditions, and in vivo selection schemes frequently use small pool sizes. Here we describe a hybrid in vitro/in vivo selection scheme that overcomes both of these disadvantages. In this new method, PCR-amplified expression templates are transfected into mammalian cells, transcribed hammerhead RNAs self-cleave, and the extracted, functional hammerhead ribozyme species are specifically amplified for the next round of selection. Using this method we have selected a number of cis-cleaving hammerhead ribozyme variants that are functional in vivo and lead to the inhibition of gene expression. More importantly, these results have led us to develop a quantitative, kinetic model that can be used to assess the stringency of the hybrid selection scheme and to direct future experiments.
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Affiliation(s)
- Xi Chen
- Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA
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46
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Vorechovsky I. Transposable elements in disease-associated cryptic exons. Hum Genet 2009; 127:135-54. [PMID: 19823873 DOI: 10.1007/s00439-009-0752-4] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Accepted: 09/27/2009] [Indexed: 11/28/2022]
Abstract
Transposable elements (TEs) make up a half of the human genome, but the extent of their contribution to cryptic exon activation that results in genetic disease is unknown. Here, a comprehensive survey of 78 mutation-induced cryptic exons previously identified in 51 disease genes revealed the presence of TEs in 40 cases (51%). Most TE-containing exons were derived from short interspersed nuclear elements (SINEs), with Alus and mammalian interspersed repeats (MIRs) covering >18 and >16% of the exonized sequences, respectively. The majority of SINE-derived cryptic exons had splice sites at the same positions of the Alu/MIR consensus as existing SINE exons and their inclusion in the mRNA was facilitated by phylogenetically conserved changes that improved both traditional and auxiliary splicing signals, thus marking intronic TEs amenable for pathogenic exonization. The overrepresentation of MIRs among TE exons is likely to result from their high average exon inclusion levels, which reflect their strong splice sites, a lack of splicing silencers and a high density of enhancers, particularly (G)AA(G) motifs. These elements were markedly depleted in antisense Alu exons, had the most prominent position on the exon-intron gradient scale and are proposed to promote exon definition through enhanced tertiary RNA interactions involving unpaired (di)adenosines. The identification of common mechanisms by which the most dynamic parts of the genome contribute both to new exon creation and genetic disease will facilitate detection of intronic mutations and the development of computational tools that predict TE hot-spots of cryptic exon activation.
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Affiliation(s)
- Igor Vorechovsky
- Division of Human Genetics, University of Southampton School of Medicine, MP808, Tremona Road, Southampton SO16 6YD, UK.
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47
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Venables JP, Klinck R, Koh C, Gervais-Bird J, Bramard A, Inkel L, Durand M, Couture S, Froehlich U, Lapointe E, Lucier JF, Thibault P, Rancourt C, Tremblay K, Prinos P, Chabot B, Elela SA. Cancer-associated regulation of alternative splicing. Nat Struct Mol Biol 2009; 16:670-6. [PMID: 19448617 DOI: 10.1038/nsmb.1608] [Citation(s) in RCA: 275] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Accepted: 04/21/2009] [Indexed: 02/06/2023]
Abstract
Alternative splicing of pre-mRNA increases the diversity of protein functions. Here we show that about half of all active alternative splicing events in ovarian and breast tissues are changed in tumors, and many seem to be regulated by a single factor; sequence analysis revealed binding sites for the RNA binding protein FOX2 downstream of one-third of the exons skipped in cancer. High-resolution analysis of FOX2 binding sites defined the precise positions relative to alternative exons at which the protein may function as either a silencer or an enhancer. Most of the identified targets were shifted in the same direction by FOX2 depletion in cell lines as they were in breast and ovarian cancer tissues. Notably, we found expression of FOX2 itself is downregulated in ovarian cancer and its splicing is altered in breast cancer samples. These results suggest that the decreased expression of FOX2 in cancer tissues modulates splicing and controls proliferation.
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Affiliation(s)
- Julian P Venables
- Laboratoire de génomique fonctionnelle de l'Université de Sherbrooke, Sherbrooke, Québec, Canada
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48
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Li H, Liu G, Yu J, Cao W, Lobo VG, Xie J. In vivo selection of kinase-responsive RNA elements controlling alternative splicing. J Biol Chem 2009; 284:16191-16201. [PMID: 19386606 DOI: 10.1074/jbc.m900393200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Alternative pre-mRNA splicing is often controlled by cell signals, for example, those activating the cAMP-dependent protein kinase (PKA) or the Ca2+/calmodulin-dependent protein kinase IV (CaMKIV). We have shown that CaMKIV regulates alternative splicing through short CA repeats and hnRNP L. Here we use a splicing reporter that shows PKA/CaMKIV promotion of exon inclusion to select from exons containing random 13-nt sequences for RNA elements responsive to the kinases in cultured cells. This selection not only identified both PKA- and CaMKIV-responsive elements that are similar to the CaMKIV-responsive RNA element 1 (CaRRE1) or CA repeats, but also A-rich elements not previously known to respond to these kinases. Consistently, hnRNP L is identified as a factor binding the CA-rich elements. Analyses of the motifs in the highly responsive elements indicate that they are indeed critical for the kinase effect and are enriched in alternative exons. Interestingly, a CAAAAAA motif is sufficient for the PKA/CaMKIV-regulated splicing of the exon 16 of the CaMK kinase beta1 (CaMKK2) transcripts, implying a role of this motif in signaling cross-talk or feedback regulation between these kinases through alternative splicing. Therefore, these experiments identified a group of RNA elements responsive to PKA and CaMKIV from in vivo selection. This also provides an approach for selecting RNA elements similarly responsive to other cell signals controlling alternative splicing.
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Affiliation(s)
- Hongzhao Li
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Guodong Liu
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Jiankun Yu
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Wenguang Cao
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Vincent G Lobo
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Jiuyong Xie
- From the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada.
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Hui J. Regulation of mammalian pre-mRNA splicing. ACTA ACUST UNITED AC 2009; 52:253-60. [DOI: 10.1007/s11427-009-0037-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Accepted: 12/01/2008] [Indexed: 12/22/2022]
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Abstract
The SR protein family comprises a number of phylogenetically conserved and structurally related proteins with a characteristic domain rich in arginine and serine residues, known as the RS domain. They play significant roles in constitutive pre-mRNA splicing and are also important regulators of alternative splicing. In addition they participate in post-splicing activities, such as mRNA nuclear export, nonsense-mediated mRNA decay and mRNA translation. These wide-ranging roles of SR proteins highlight their importance as pivotal regulators of mRNA metabolism, and if these functions are disrupted, developmental defects or disease may result. Furthermore, animal models have shown a highly specific, non-redundant role for individual SR proteins in the regulation of developmental processes. Here, we will review the current literature to demonstrate how SR proteins are emerging as one of the master regulators of gene expression.
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