1
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Burgardt R, Lambert D, Heuwieser C, Sack M, Wagner G, Weinberg Z, Wachter A. Positioning of pyrimidine motifs around cassette exons defines their PTB-dependent splicing in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2024; 118:2202-2218. [PMID: 38578875 DOI: 10.1111/tpj.16739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Accepted: 03/14/2024] [Indexed: 04/07/2024]
Abstract
Alternative splicing (AS) is a complex process that generates transcript variants from a single pre-mRNA and is involved in numerous biological functions. Many RNA-binding proteins are known to regulate AS; however, little is known about the underlying mechanisms, especially outside the mammalian clade. Here, we show that polypyrimidine tract binding proteins (PTBs) from Arabidopsis thaliana regulate AS of cassette exons via pyrimidine (Py)-rich motifs close to the alternative splice sites. Mutational studies on three PTB-dependent cassette exon events revealed that only some of the Py motifs in this region are critical for AS. Moreover, in vitro binding of PTBs did not reflect a motif's impact on AS in vivo. Our mutational studies and bioinformatic investigation of all known PTB-regulated cassette exons from A. thaliana and human suggested that the binding position of PTBs relative to a cassette exon defines whether its inclusion or skipping is induced. Accordingly, exon skipping is associated with a higher frequency of Py stretches within the cassette exon, and in human also upstream of it, whereas exon inclusion is characterized by increased Py motif occurrence downstream of said exon. Enrichment of Py motifs downstream of PTB-activated 5' splice sites is also seen for PTB-dependent intron removal and alternative 5' splice site events from A. thaliana, suggesting this is a common step of exon definition. In conclusion, the position-dependent AS regulatory mechanism by PTB homologs has been conserved during the separate evolution of plants and mammals, while other critical features, in particular intron length, have considerably changed.
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Affiliation(s)
- Rica Burgardt
- Institute for Molecular Physiology (imP), University of Mainz, Hanns-Dieter-Hüsch-Weg 17, 55128, Mainz, Germany
| | - Dorothee Lambert
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
| | - Christina Heuwieser
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
| | - Maximilian Sack
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107, Leipzig, Germany
| | - Gabriele Wagner
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
| | - Zasha Weinberg
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107, Leipzig, Germany
| | - Andreas Wachter
- Institute for Molecular Physiology (imP), University of Mainz, Hanns-Dieter-Hüsch-Weg 17, 55128, Mainz, Germany
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
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2
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Zhang YE, Stuelten CH. Alternative splicing in EMT and TGF-β signaling during cancer progression. Semin Cancer Biol 2024; 101:1-11. [PMID: 38614376 PMCID: PMC11180579 DOI: 10.1016/j.semcancer.2024.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 11/20/2023] [Accepted: 04/04/2024] [Indexed: 04/15/2024]
Abstract
Epithelial to mesenchymal transition (EMT) is a physiological process during development where epithelial cells transform to acquire mesenchymal characteristics, which allows them to migrate and colonize secondary tissues. Many cellular signaling pathways and master transcriptional factors exert a myriad of controls to fine tune this vital process to meet various developmental and physiological needs. Adding to the complexity of this network are post-transcriptional and post-translational regulations. Among them, alternative splicing has been shown to play important roles to drive EMT-associated phenotypic changes, including actin cytoskeleton remodeling, cell-cell junction changes, cell motility and invasiveness. In advanced cancers, transforming growth factor-β (TGF-β) is a major inducer of EMT and is associated with tumor cell metastasis, cancer stem cell self-renewal, and drug resistance. This review aims to provide an overview of recent discoveries regarding alternative splicing events and the involvement of splicing factors in the EMT and TGF-β signaling. It will emphasize the importance of various splicing factors involved in EMT and explore their regulatory mechanisms.
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Affiliation(s)
- Ying E Zhang
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.
| | - Christina H Stuelten
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
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3
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Nazim M, Lin CH, Feng AC, Xiao W, Yeom KH, Li M, Daly AE, Tan X, Vu H, Ernst J, Carey MF, Smale ST, Black DL. Alternative splicing of a chromatin modifier alters the transcriptional regulatory programs of stem cell maintenance and neuronal differentiation. Cell Stem Cell 2024; 31:754-771.e6. [PMID: 38701759 PMCID: PMC11126784 DOI: 10.1016/j.stem.2024.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 01/24/2024] [Accepted: 04/01/2024] [Indexed: 05/05/2024]
Abstract
Development of embryonic stem cells (ESCs) into neurons requires intricate regulation of transcription, splicing, and translation, but how these processes interconnect is not understood. We found that polypyrimidine tract binding protein 1 (PTBP1) controls splicing of DPF2, a subunit of BRG1/BRM-associated factor (BAF) chromatin remodeling complexes. Dpf2 exon 7 splicing is inhibited by PTBP1 to produce the DPF2-S isoform early in development. During neuronal differentiation, loss of PTBP1 allows exon 7 inclusion and DPF2-L expression. Different cellular phenotypes and gene expression programs were induced by these alternative DPF2 isoforms. We identified chromatin binding sites enriched for each DPF2 isoform, as well as sites bound by both. In ESC, DPF2-S preferential sites were bound by pluripotency factors. In neuronal progenitors, DPF2-S sites were bound by nuclear factor I (NFI), while DPF2-L sites were bound by CCCTC-binding factor (CTCF). DPF2-S sites exhibited enhancer modifications, while DPF2-L sites showed promoter modifications. Thus, alternative splicing redirects BAF complex targeting to impact chromatin organization during neuronal development.
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Affiliation(s)
- Mohammad Nazim
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Chia-Ho Lin
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - An-Chieh Feng
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Wen Xiao
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Kyu-Hyeon Yeom
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Mulin Li
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Allison E Daly
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Xianglong Tan
- Department of Biological Chemistry, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Ha Vu
- Department of Biological Chemistry, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Jason Ernst
- Department of Biological Chemistry, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Michael F Carey
- Department of Biological Chemistry, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Stephen T Smale
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Douglas L Black
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA.
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4
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Zavileyskiy LG, Pervouchine DD. Post-transcriptional Regulation of Gene Expression via Unproductive Splicing. Acta Naturae 2024; 16:4-13. [PMID: 38698955 PMCID: PMC11062102 DOI: 10.32607/actanaturae.27337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Accepted: 03/01/2024] [Indexed: 05/05/2024] Open
Abstract
Unproductive splicing is a mechanism of post-transcriptional gene expression control in which premature stop codons are inserted into protein-coding transcripts as a result of regulated alternative splicing, leading to their degradation via the nonsense-mediated decay pathway. This mechanism is especially characteristic of RNA-binding proteins, which regulate each other's expression levels and those of other genes in multiple auto- and cross-regulatory loops. Deregulation of unproductive splicing is a cause of serious human diseases, including cancers, and is increasingly being considered as a prominent therapeutic target. This review discusses the types of unproductive splicing events, the mechanisms of auto- and cross-regulation, nonsense-mediated decay escape, and problems in identifying unproductive splice isoforms. It also provides examples of deregulation of unproductive splicing in human diseases and discusses therapeutic strategies for its correction using antisense oligonucleotides and small molecules.
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Affiliation(s)
- L. G. Zavileyskiy
- Lomonosov Moscow State University, Moscow, 119192 Russian Federation
- Skolkovo Institute of Science and Technology, Moscow, 121205 Russian Federation
| | - D. D. Pervouchine
- Skolkovo Institute of Science and Technology, Moscow, 121205 Russian Federation
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5
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Lee S, Aubee JI, Lai EC. Regulation of alternative splicing and polyadenylation in neurons. Life Sci Alliance 2023; 6:e202302000. [PMID: 37793776 PMCID: PMC10551640 DOI: 10.26508/lsa.202302000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 09/22/2023] [Accepted: 09/25/2023] [Indexed: 10/06/2023] Open
Abstract
Cell-type-specific gene expression is a fundamental feature of multicellular organisms and is achieved by combinations of regulatory strategies. Although cell-restricted transcription is perhaps the most widely studied mechanism, co-transcriptional and post-transcriptional processes are also central to the spatiotemporal control of gene functions. One general category of expression control involves the generation of multiple transcript isoforms from an individual gene, whose balance and cell specificity are frequently tightly regulated via diverse strategies. The nervous system makes particularly extensive use of cell-specific isoforms, specializing the neural function of genes that are expressed more broadly. Here, we review regulatory strategies and RNA-binding proteins that direct neural-specific isoform processing. These include various classes of alternative splicing and alternative polyadenylation events, both of which broadly diversify the neural transcriptome. Importantly, global alterations of splicing and alternative polyadenylation are characteristic of many neural pathologies, and recent genetic studies demonstrate how misregulation of individual neural isoforms can directly cause mutant phenotypes.
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Affiliation(s)
- Seungjae Lee
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA
| | - Joseph I Aubee
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA
| | - Eric C Lai
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA
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6
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Xie JQ, Zhou X, Jia ZC, Su CF, Zhang Y, Fernie AR, Zhang J, Du ZY, Chen MX. Alternative Splicing, An Overlooked Defense Frontier of Plants with Respect to Bacterial Infection. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023. [PMID: 37916838 DOI: 10.1021/acs.jafc.3c04163] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
Disease represents a major problem in sustainable agricultural development. Plants interact closely with various microorganisms during their development and in response to the prevailing environment. In particular, pathogenic microorganisms can cause plant diseases, affecting the fertility, yield, and longevity of plants. During the long coevolution of plants and their pathogens, plants have evolved both molecular pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) signaling networks in order to regulate host cells in response to pathogen infestation. Additionally, in the postgenomic era, alternative splicing (AS) has become uncovered as one of the major drivers of proteome diversity, and abnormal RNA splicing is closely associated with bacterial infections. Currently, the complexity of host-bacteria interactions is a much studied area of research that has shown steady progress over the past decade. Although the development of high-throughput sequencing technologies and their application in transcriptomes have revolutionized our understanding of AS, many mechanisms related to host-bacteria interactions remain still unclear. To this end, this review summarizes the changes observed in AS during host-bacteria interactions and outlines potential therapeutics for bacterial diseases based on existing studies. In doing so, we hope to provide guidelines for plant disease management in agriculture.
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Affiliation(s)
- Ji-Qin Xie
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Sciences/Institute of Agro-bioengineering, Guizhou University, Guiyang, Guizhou 550025, China
| | - Xiang Zhou
- National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Center for R&D of Fine Chemicals of Guizhou University, Guiyang 550025, China
| | - Zi-Chang Jia
- National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Center for R&D of Fine Chemicals of Guizhou University, Guiyang 550025, China
| | - Chang-Feng Su
- Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Sciences/Institute of Agro-bioengineering, Guizhou University, Guiyang, Guizhou 550025, China
| | - Youjun Zhang
- Center of Plant System Biology and Biotechnology, 4000 Plovdiv, Bulgaria
- Max-Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Golm, Germany
| | - Alisdair R Fernie
- Center of Plant System Biology and Biotechnology, 4000 Plovdiv, Bulgaria
- Max-Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Golm, Germany
| | - Jianhua Zhang
- Department of Biology, Hong Kong Baptist University, and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Zhi-Yan Du
- Department of Molecular Biosciences & Bioengineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Mo-Xian Chen
- National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Center for R&D of Fine Chemicals of Guizhou University, Guiyang 550025, China
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7
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Bushra S, Lin YN, Joudaki A, Ito M, Ohkawara B, Ohno K, Masuda A. Neural Isoforms of Agrin Are Generated by Reduced PTBP1-RNA Interaction Network Spanning the Neuron-Specific Splicing Regions in AGRN. Int J Mol Sci 2023; 24:ijms24087420. [PMID: 37108583 PMCID: PMC10139058 DOI: 10.3390/ijms24087420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 04/12/2023] [Accepted: 04/14/2023] [Indexed: 04/29/2023] Open
Abstract
Agrin is a heparan sulfate proteoglycan essential for the clustering of acetylcholine receptors at the neuromuscular junction. Neuron-specific isoforms of agrin are generated by alternative inclusion of three exons, called Y, Z8, and Z11 exons, although their processing mechanisms remain elusive. We found, by inspection of splicing cis-elements into the human AGRN gene, that binding sites for polypyrimidine tract binding protein 1 (PTBP1) were extensively enriched around Y and Z exons. PTBP1-silencing enhanced the coordinated inclusion of Y and Z exons in human SH-SY5Y neuronal cells, even though three constitutive exons are flanked by these alternative exons. Deletion analysis using minigenes identified five PTBP1-binding sites with remarkable splicing repression activities around Y and Z exons. Furthermore, artificial tethering experiments indicated that binding of a single PTBP1 molecule to any of these sites represses nearby Y or Z exons as well as the other distal exons. The RRM4 domain of PTBP1, which is required for looping out a target RNA segment, was likely to play a crucial role in the repression. Neuronal differentiation downregulates PTBP1 expression and promotes the coordinated inclusion of Y and Z exons. We propose that the reduction in the PTPB1-RNA network spanning these alternative exons is essential for the generation of the neuron-specific agrin isoforms.
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Affiliation(s)
- Samira Bushra
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Aichi, Japan
| | - Ying-Ni Lin
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Aichi, Japan
| | - Atefeh Joudaki
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Aichi, Japan
| | - Mikako Ito
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Aichi, Japan
| | - Bisei Ohkawara
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Aichi, Japan
| | - Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Aichi, Japan
| | - Akio Masuda
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Aichi, Japan
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8
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Ye R, Hu N, Cao C, Su R, Xu S, Yang C, Zhou X, Xue Y. Capture RIC-seq reveals positional rules of PTBP1-associated RNA loops in splicing regulation. Mol Cell 2023; 83:1311-1327.e7. [PMID: 36958328 DOI: 10.1016/j.molcel.2023.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 01/10/2023] [Accepted: 02/27/2023] [Indexed: 03/25/2023]
Abstract
RNA-binding proteins (RBPs) bind at different positions of the pre-mRNA molecules to promote or reduce the usage of a particular exon. Seeking to understand the working principle of these positional effects, we develop a capture RIC-seq (CRIC-seq) method to enrich specific RBP-associated in situ proximal RNA-RNA fragments for deep sequencing. We determine hnRNPA1-, SRSF1-, and PTBP1-associated proximal RNA-RNA contacts and regulatory mechanisms in HeLa cells. Unexpectedly, the 3D RNA map analysis shows that PTBP1-associated loops in individual introns preferentially promote cassette exon splicing by accelerating asymmetric intron removal, whereas the loops spanning across cassette exon primarily repress splicing. These "positional rules" can faithfully predict PTBP1-regulated splicing outcomes. We further demonstrate that cancer-related splicing quantitative trait loci can disrupt RNA loops by reducing PTBP1 binding on pre-mRNAs to cause aberrant splicing in tumors. Our study presents a powerful method for exploring the functions of RBP-associated RNA-RNA proximal contacts in gene regulation and disease.
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Affiliation(s)
- Rong Ye
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Naijing Hu
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Changchang Cao
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Ruibao Su
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shihan Xu
- State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou, Zhejiang 325003, China
| | - Chen Yang
- State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou, Zhejiang 325003, China
| | - Xiangtian Zhou
- State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou, Zhejiang 325003, China
| | - Yuanchao Xue
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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9
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Iannone C, Kainov Y, Zhuravskaya A, Hamid F, Nojima T, Makeyev EV. PTBP1-activated co-transcriptional splicing controls epigenetic status of pluripotent stem cells. Mol Cell 2023; 83:203-218.e9. [PMID: 36626906 DOI: 10.1016/j.molcel.2022.12.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 11/15/2022] [Accepted: 12/12/2022] [Indexed: 01/11/2023]
Abstract
Many spliceosomal introns are excised from nascent transcripts emerging from RNA polymerase II (RNA Pol II). The extent of cell-type-specific regulation and possible functions of such co-transcriptional events remain poorly understood. We examined the role of the RNA-binding protein PTBP1 in this process using an acute depletion approach followed by the analysis of chromatin- and RNA Pol II-associated transcripts. We show that PTBP1 activates the co-transcriptional excision of hundreds of introns, a surprising effect given that this protein is known to promote intron retention. Importantly, some co-transcriptionally activated introns fail to complete their splicing without PTBP1. In a striking example, retention of a PTBP1-dependent intron triggers nonsense-mediated decay of transcripts encoding DNA methyltransferase DNMT3B. We provide evidence that this regulation facilitates the natural decline in DNMT3B levels in developing neurons and protects differentiation-specific genes from ectopic methylation. Thus, PTBP1-activated co-transcriptional splicing is a widespread phenomenon mediating epigenetic control of cellular identity.
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Affiliation(s)
- Camilla Iannone
- Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK
| | - Yaroslav Kainov
- Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK
| | - Anna Zhuravskaya
- Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK
| | - Fursham Hamid
- Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK
| | - Takayuki Nojima
- Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Eugene V Makeyev
- Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK.
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10
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Qiu J, Qu R, Lin M, Xu J, Zhu Q, Zhang Z, Sun J. Position-dependent effects of hnRNP A1/A2 in SMN1/2 exon7 splicing. BIOCHIMICA ET BIOPHYSICA ACTA (BBA) - GENE REGULATORY MECHANISMS 2022; 1865:194875. [DOI: 10.1016/j.bbagrm.2022.194875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 09/08/2022] [Accepted: 09/28/2022] [Indexed: 11/07/2022]
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11
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Dai S, Wang C, Zhang C, Feng L, Zhang W, Zhou X, He Y, Xia X, Chen B, Song W. PTB: Not just a polypyrimidine tract-binding protein. J Cell Physiol 2022; 237:2357-2373. [PMID: 35288937 DOI: 10.1002/jcp.30716] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 02/19/2022] [Accepted: 02/22/2022] [Indexed: 01/21/2023]
Abstract
Polypyrimidine tract-binding protein (PTB), as a member of the heterogeneous nuclear ribonucleoprotein family, functions by rapidly shuttling between the nucleus and the cytoplasm. PTB is involved in the alternative splicing of pre-messenger RNA (mRNA) and almost all steps of mRNA metabolism. PTB regulation is organ-specific; brain- or muscle-specific microRNAs and long noncoding RNAs partially contribute to regulating PTB, thereby modulating many physiological and pathological processes, such as embryonic development, cell development, spermatogenesis, and neuron growth and differentiation. Previous studies have shown that PTB knockout can inhibit tumorigenesis and development. The knockout of PTB in glial cells can be reprogrammed into functional neurons, which shows great promise in the field of nerve regeneration but is controversial.
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Affiliation(s)
- Shirui Dai
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China.,Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, P. R. China
| | - Chao Wang
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Cheng Zhang
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Lemeng Feng
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Wulong Zhang
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Xuezhi Zhou
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Ye He
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Xiaobo Xia
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Baihua Chen
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, P. R. China
| | - Weitao Song
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
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12
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Zheng X, Zhu J, Liu J, Wang H, Qin Y, Jiang P, Xiao L, Gong T, Li Y, Peng X, Xu X, Cheng L, Huang L, Chen Q, Zhou X, Margolskee RF. Sweet taste perception in mice is blunted by PTBP1-regulated skipping of Tas1r2 exon 4. Chem Senses 2022; 47:6884719. [PMID: 36484118 DOI: 10.1093/chemse/bjac034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Taste perception, initiated by activation of taste receptors in taste bud cells, is crucial for regulating nutrient intake. Genetic polymorphisms in taste receptor genes cannot fully explain the wide individual variations of taste sensitivity. Alternative splicing (AS) is a ubiquitous posttranscriptional mode of gene regulation that enriches the functional diversity of proteins. Here, we report the identification of a novel splicing variant of sweet taste receptor gene Tas1r2 (Tas1r2_∆e4) in mouse taste buds and the mechanism by which it diminishes sweet taste responses in vitro and in vivo. Skipping of Tas1r2 exon 4 in Tas1r2_∆e4 led to loss of amino acids in the extracellular Venus flytrap domain, and the truncated isoform reduced the response of sweet taste receptors (STRs) to all sweet compounds tested by generating nonfunctional T1R2/T1R3 STR heterodimers. The splicing factor PTBP1 (polypyrimidine tract-binding protein 1) promoted Tas1r2_∆e4 generation through binding to a polypyrimidine-rich splicing silencer in Tas1r2 exon 4, thus decreasing STR function and sweet taste perception in mice. Taken together, these data reveal the existence of a regulated AS event in Tas1r2 expression and its effect on sweet taste perception, providing a novel mechanism for modulating taste sensitivity at the posttranscriptional level.
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Affiliation(s)
- Xin Zheng
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Jianhui Zhu
- Stomatology Hospital, School of Stomatology, Zhejiang University School of Medicine, Zhejiang Provincial Clinical Research Center for Oral Diseases, Key Laboratory of Oral Biomedical Research of Zhejiang Province, Cancer Center of Zhejiang University, Hangzhou 310006, P. R. China
| | - Jiaxin Liu
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Hong Wang
- Monell Chemical Senses Center, Philadelphia, PA 19104, USA
| | - Yumei Qin
- School of Food Science and Bioengineering, Zhejiang Gongshang University, Hangzhou 310006, P. R. China
| | - Peihua Jiang
- Monell Chemical Senses Center, Philadelphia, PA 19104, USA
| | - Li Xiao
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Tao Gong
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Yuqing Li
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Xian Peng
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Xin Xu
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Lei Cheng
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
| | - Liquan Huang
- College of Life Sciences, Zhejiang University, Hangzhou 310058, P. R. China
| | - Qianming Chen
- Stomatology Hospital, School of Stomatology, Zhejiang University School of Medicine, Zhejiang Provincial Clinical Research Center for Oral Diseases, Key Laboratory of Oral Biomedical Research of Zhejiang Province, Cancer Center of Zhejiang University, Hangzhou 310006, P. R. China
| | - Xuedong Zhou
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China
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13
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Shu B, Zhou YX, Li H, Zhang RZ, He C, Yang X. The METTL3/MALAT1/PTBP1/USP8/TAK1 axis promotes pyroptosis and M1 polarization of macrophages and contributes to liver fibrosis. Cell Death Discov 2021; 7:368. [PMID: 34839365 PMCID: PMC8627510 DOI: 10.1038/s41420-021-00756-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 10/27/2021] [Accepted: 11/02/2021] [Indexed: 12/24/2022] Open
Abstract
Pro-inflammatory M1 macrophages, via activating hepatic stellate cells, contribute to liver fibrosis. In this study, we examined the mechanism and the significance of a signaling axis, METTL3/MALAT1/PTBP1/USP8/TAK1, in regulating pyroptosis and M1 polarization of hepatic macrophages. Liver fibrosis model was established in vivo by CCl4 treatment; M1 polarization was induced in vitro by treating macrophages with lipopolysaccharide or interferon γ. Expressions of METTL3, MALAT1, PTBP1, USP8, and TAK1 were measured by RT-PCR and/or Western blot in Kupffer cells (KCs) isolated from in vivo model or in vitro activated macrophages. Macrophage phenotypes including inflammation (RT-qPCR analysis of a panel of proinflammatory cytokines and ELISA on productions of interleukin (IL)−1β and IL-18) and pyroptosis (Western blot of NLRP3, Caspase-1, and GSDMD) were investigated. The impact of METTL3 on m6A methylation of MALAT1 was examined by methylated RNA immunoprecipitation (RIP), the interaction between PTBP1 and MALAT1 or USP8 mRNA by combining RNA pull-down, RIP, and RNA stability assays, and the crosstalk between USP8 and TAK1 by co-immunoprecipitation and protein degradation assays. Functional significance of individual component of METTL3/MALAT1/PTBP1/USP8/TAK1 axis was assessed by combining gain-of-function and loss-of-function approaches. In KCs isolated from in vivo liver fibrosis model or in vitro M1-polarized macrophages, METTL3 was up-regulated, and sequentially, it increased MALAT1 level via m6A methylation, which promoted USP8 mRNA degradation through the interaction with PTBP1. Reduced USP8 expression regulated the ubiquitination and protein stability of TAK1, which promoted pyroptosis and inflammation of macrophages. The signaling cascade METTL3/MALAT1/PTBP1/USP8/TAK1, by essentially stimulating pyroptosis and inflammation of macrophages, aggravates liver fibrosis. Therefore, targeting individual components of this axis may benefit the treatment of liver fibrosis.
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Affiliation(s)
- Bo Shu
- Department of General Surgery, The Second Xiangya Hospital, Central South University, 410011, Changsha, Hunan Province, China
| | - Ying-Xia Zhou
- Department of Surgical Operation, The Second Xiangya Hospital, Central South University, 410011, Changsha, Hunan Province, China
| | - Hao Li
- Department of General Surgery, The Second Xiangya Hospital, Central South University, 410011, Changsha, Hunan Province, China
| | - Rui-Zhi Zhang
- Department of General Surgery, The Second Xiangya Hospital, Central South University, 410011, Changsha, Hunan Province, China
| | - Chao He
- Department of General Surgery, The Second Xiangya Hospital, Central South University, 410011, Changsha, Hunan Province, China
| | - Xin Yang
- Department of General Surgery, The Second Xiangya Hospital, Central South University, 410011, Changsha, Hunan Province, China.
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14
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Wong J, Martelly W, Sharma S. A Reporter Based Cellular Assay for Monitoring Splicing Efficiency. J Vis Exp 2021. [PMID: 34605821 DOI: 10.3791/63014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
During gene expression, the vital step of pre-mRNA splicing involves accurate recognition of splice sites and efficient assembly of spliceosomal complexes to join exons and remove introns prior to cytoplasmic export of the mature mRNA. Splicing efficiency can be altered by the presence of mutations at splice sites, the influence of trans-acting splicing factors, or the activity of therapeutics. Here, we describe the protocol for a cellular assay that can be applied for monitoring the splicing efficiency of any given exon. The assay uses an adaptable plasmid encoded 3-exon/2-intron minigene reporter, which can be expressed in mammalian cells by transient transfection. Post-transfection, total cellular RNA is isolated, and the efficiency of exon splicing in the reporter mRNA is determined by either primer extension or semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). We describe how the impact of disease associated 5' splice-site mutations can be determined by introducing them in the reporter; and how the suppression of these mutations can be achieved by co-transfection with U1 small nuclear RNA (snRNA) construct carrying compensatory mutations in its 5' region that basepairs with the 5'-splice sites at exon-intron junctions in pre-mRNAs. Thus, the reporter can be used for the design of therapeutic U1 particles to improve recognition of mutant 5' splice-sites. Insertion of cis-acting regulatory sites, such as splicing enhancer or silencer sequences, into the reporter can also be used to examine the role of U1 snRNP in regulation mediated by a specific alternative splicing factor. Finally, reporter expressing cells can be incubated with small molecules to determine the effect of potential therapeutics on constitutive pre-mRNA splicing or on exons carrying mutant 5' splice sites. Overall, the reporter assay can be applied to monitor splicing efficiency in a variety of conditions to study fundamental splicing mechanisms and splicing-associated diseases.
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Affiliation(s)
- Jason Wong
- Department of Basic Medical Sciences, College of Medicine-Phoenix, University of Arizona
| | - William Martelly
- Department of Basic Medical Sciences, College of Medicine-Phoenix, University of Arizona
| | - Shalini Sharma
- Department of Basic Medical Sciences, College of Medicine-Phoenix, University of Arizona;
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15
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Campagne S, de Vries T, Malard F, Afanasyev P, Dorn G, Dedic E, Kohlbrecher J, Boehringer D, Cléry A, Allain FHT. An in vitro reconstituted U1 snRNP allows the study of the disordered regions of the particle and the interactions with proteins and ligands. Nucleic Acids Res 2021; 49:e63. [PMID: 33677607 PMCID: PMC8216277 DOI: 10.1093/nar/gkab135] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 02/11/2021] [Accepted: 02/17/2021] [Indexed: 11/17/2022] Open
Abstract
U1 small nuclear ribonucleoparticle (U1 snRNP) plays a central role during RNA processing. Previous structures of U1 snRNP revealed how the ribonucleoparticle is organized and recognizes the pre-mRNA substrate at the exon–intron junction. As with many other ribonucleoparticles involved in RNA metabolism, U1 snRNP contains extensions made of low complexity sequences. Here, we developed a protocol to reconstitute U1 snRNP in vitro using mostly full-length components in order to perform liquid-state NMR spectroscopy. The accuracy of the reconstitution was validated by probing the shape and structure of the particle by SANS and cryo-EM. Using an NMR spectroscopy-based approach, we probed, for the first time, the U1 snRNP tails at atomic detail and our results confirm their high degree of flexibility. We also monitored the labile interaction between the splicing factor PTBP1 and U1 snRNP and validated the U1 snRNA stem loop 4 as a binding site for the splicing regulator on the ribonucleoparticle. Altogether, we developed a method to probe the intrinsically disordered regions of U1 snRNP and map the interactions controlling splicing regulation. This approach could be used to get insights into the molecular mechanisms of alternative splicing and screen for potential RNA therapeutics.
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Affiliation(s)
- Sébastien Campagne
- Institute of Biochemistry, Department of Biology, ETH Zurich, Hönggerbergring 64, CH-8093 Zürich, Switzerland
| | - Tebbe de Vries
- Institute of Biochemistry, Department of Biology, ETH Zurich, Hönggerbergring 64, CH-8093 Zürich, Switzerland
| | - Florian Malard
- Institute of Biochemistry, Department of Biology, ETH Zurich, Hönggerbergring 64, CH-8093 Zürich, Switzerland
| | - Pavel Afanasyev
- Cryo-EM Knowledge Hub (CEMK), ETH Zurich, Hönggerbergring 64, CH-8093 Zürich, Switzerland
| | - Georg Dorn
- Institute of Biochemistry, Department of Biology, ETH Zurich, Hönggerbergring 64, CH-8093 Zürich, Switzerland
| | - Emil Dedic
- Institute of Biochemistry, Department of Biology, ETH Zurich, Hönggerbergring 64, CH-8093 Zürich, Switzerland
| | | | - Daniel Boehringer
- Cryo-EM Knowledge Hub (CEMK), ETH Zurich, Hönggerbergring 64, CH-8093 Zürich, Switzerland
| | - Antoine Cléry
- Institute of Biochemistry, Department of Biology, ETH Zurich, Hönggerbergring 64, CH-8093 Zürich, Switzerland
| | - Frédéric H-T Allain
- Institute of Biochemistry, Department of Biology, ETH Zurich, Hönggerbergring 64, CH-8093 Zürich, Switzerland
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16
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Artemyeva-Isman OV, Porter ACG. U5 snRNA Interactions With Exons Ensure Splicing Precision. Front Genet 2021; 12:676971. [PMID: 34276781 PMCID: PMC8283771 DOI: 10.3389/fgene.2021.676971] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Accepted: 05/12/2021] [Indexed: 11/13/2022] Open
Abstract
Imperfect conservation of human pre-mRNA splice sites is necessary to produce alternative isoforms. This flexibility is combined with the precision of the message reading frame. Apart from intron-termini GU_AG and the branchpoint A, the most conserved are the exon-end guanine and +5G of the intron start. Association between these guanines cannot be explained solely by base-pairing with U1 snRNA in the early spliceosome complex. U6 succeeds U1 and pairs +5G in the pre-catalytic spliceosome, while U5 binds the exon end. Current U5 snRNA reconstructions by CryoEM cannot explain the conservation of the exon-end G. Conversely, human mutation analyses show that guanines of both exon termini can suppress splicing mutations. Our U5 hypothesis explains the mechanism of splicing precision and the role of these conserved guanines in the pre-catalytic spliceosome. We propose: (1) optimal binding register for human exons and U5-the exon junction positioned at U5Loop1 C39|C38; (2) common mechanism for base-pairing of human U5 snRNA with diverse exons and bacterial Ll.LtrB intron with new loci in retrotransposition-guided by base pair geometry; and (3) U5 plays a significant role in specific exon recognition in the pre-catalytic spliceosome. Statistical analyses showed increased U5 Watson-Crick pairs with the 5'exon in the absence of +5G at the intron start. In 5'exon positions -3 and -5, this effect is specific to U5 snRNA rather than U1 snRNA of the early spliceosome. Increased U5 Watson-Crick pairs with 3'exon position +1 coincide with substitutions of the conserved -3C at the intron 3'end. Based on mutation and X-ray evidence, we propose that -3C pairs with U2 G31 juxtaposing the branchpoint and the 3'intron end. The intron-termini pair, formed in the pre-catalytic spliceosome to be ready for transition after branching, and the early involvement of the 3'intron end ensure that the 3'exon contacts U5 in the pre-catalytic complex. We suggest that splicing precision is safeguarded cooperatively by U5, U6, and U2 snRNAs that stabilize the pre-catalytic complex by Watson-Crick base pairing. In addition, our new U5 model explains the splicing effect of exon-start +1G mutations: U5 Watson-Crick pairs with exon +2C/+3G strongly promote exon inclusion. We discuss potential applications for snRNA therapeutics and gene repair by reverse splicing.
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Affiliation(s)
- Olga V Artemyeva-Isman
- Gene Targeting Group, Centre for Haematology, Department of Immunology and Inflammation, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Andrew C G Porter
- Gene Targeting Group, Centre for Haematology, Department of Immunology and Inflammation, Faculty of Medicine, Imperial College London, London, United Kingdom
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17
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Martelly W, Fellows B, Kang P, Vashisht A, Wohlschlegel JA, Sharma S. Synergistic roles for human U1 snRNA stem-loops in pre-mRNA splicing. RNA Biol 2021; 18:2576-2593. [PMID: 34105434 DOI: 10.1080/15476286.2021.1932360] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
During spliceosome assembly, interactions that bring the 5' and 3' ends of an intron in proximity are critical for the production of mature mRNA. Here, we report synergistic roles for the stem-loops 3 (SL3) and 4 (SL4) of the human U1 small nuclear RNA (snRNA) in maintaining the optimal U1 snRNP function, and formation of cross-intron contact with the U2 snRNP. We find that SL3 and SL4 bind distinct spliceosomal proteins and combining a U1 snRNA activity assay with siRNA-mediated knockdown, we demonstrate that SL3 and SL4 act through the RNA helicase UAP56 and the U2 protein SF3A1, respectively. In vitro analysis using UV crosslinking and splicing assays indicated that SL3 likely promotes the SL4-SF3A1 interaction leading to enhancement of A complex formation and pre-mRNA splicing. Overall, these results highlight the vital role of the distinct contacts of SL3 and SL4 in bridging the pre-mRNA bound U1 and U2 snRNPs during the early steps of human spliceosome assembly.
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Affiliation(s)
- William Martelly
- Department of Basic Medical Sciences, College of Medicine-Phoenix, University of Arizona, Phoenix, AZ, USA.,School of Life Sciences, Arizona State University, Tempe, AZ, USA
| | - Bernice Fellows
- Department of Basic Medical Sciences, College of Medicine-Phoenix, University of Arizona, Phoenix, AZ, USA
| | - Paul Kang
- Department of Epidemiology and Biostatistics, Mel and Enid Zuckerman College of Public Health-Phoenix, University of Arizona, Phoenix, AZ, USA
| | - Ajay Vashisht
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA, USA
| | - James A Wohlschlegel
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA, USA
| | - Shalini Sharma
- Department of Basic Medical Sciences, College of Medicine-Phoenix, University of Arizona, Phoenix, AZ, USA
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18
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Weskamp K, Olwin BB, Parker R. Post-Transcriptional Regulation in Skeletal Muscle Development, Repair, and Disease. Trends Mol Med 2020; 27:469-481. [PMID: 33384234 DOI: 10.1016/j.molmed.2020.12.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/30/2020] [Accepted: 12/02/2020] [Indexed: 12/14/2022]
Abstract
Skeletal muscle formation is a complex process that requires tight spatiotemporal control of key myogenic factors. Emerging evidence suggests that RNA processing is crucial for the regulation of these factors, and that multiple post-transcriptional regulatory pathways work dependently and independently of one another to enable precise control of transcripts throughout muscle development and repair. Moreover, disruption of these pathways is implicated in neuromuscular disease, and the recent development of RNA-mediated therapies shows enormous promise in the treatment of these disorders. We discuss the overlapping post-transcriptional regulatory pathways that mediate muscle development, how these pathways are disrupted in neuromuscular disorders, and advances in RNA-mediated therapies that present a novel approach to the treatment of these diseases.
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Affiliation(s)
- Kaitlin Weskamp
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA.
| | - Bradley B Olwin
- Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
| | - Roy Parker
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA; Howard Hughes Medical Institute, Chevy Chase, MD, USA.
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19
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Ontiveros RJ, Hernandez L, Nguyen H, Hernandez Lopez AL, Shankar A, Kim E, Keppetipola NM. Identification and Characterization of a Minimal Functional Splicing Regulatory Protein, PTBP1. Biochemistry 2020; 59:4766-4774. [PMID: 33284593 DOI: 10.1021/acs.biochem.0c00664] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polypyrimidine tract binding protein 1 (PTBP1) is a well-studied RNA binding protein that serves as an important model for understanding molecular mechanisms underlying alternative splicing regulation. PTBP1 has four RNA binding domains (RBDs) connected via linker regions. Additionally, PTBP1 has an N-terminal unstructured region that contains nuclear import and export sequences. Each RBD can bind to pyrimidine rich elements with high affinity to mediate splicing activity. Studies support a variety of models for how PTBP1 can mediate splicing regulation on target exons. Obtaining a detailed atomic view hinges on determining a crystal structure of PTBP1 bound to a target RNA transcript. Here, we created a minimal functional PTBP1 with deletions in both linker 1 and linker 2 regions and assayed for activity on certain regulated exons, including the c-Src N1 exon. We show that for a subset of PTBP1-regulated exons the linker regions are not necessary for splicing repression activity. Gel mobility shift assays reveal the linker deletion mutant binds with 12-fold higher affinity to a target RNA sequence compared to wild-type PTBP1. A minimal PTBP1 that also contains an N-terminal region deletion binds to a target RNA with an affinity higher than that of wild-type PTBP1. Moreover, this minimal protein oligomerizes readily to form a distinct higher-order complex previously shown to be required for mediating splicing repression. This minimal functional PTBP1 protein can serve as a candidate for future structure studies to understand the mechanism of splicing repression for certain regulated exons.
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Affiliation(s)
- Robert J Ontiveros
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Luis Hernandez
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Haylena Nguyen
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California 92831, United States
| | - Adrian Lino Hernandez Lopez
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90035, United States
| | - Archana Shankar
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Enoch Kim
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Niroshika M Keppetipola
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California 92831, United States
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20
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Abstract
High-throughput sequencing-based methods and their applications in the study of transcriptomes have revolutionized our understanding of alternative splicing. Networks of functionally coordinated and biologically important alternative splicing events continue to be discovered in an ever-increasing diversity of cell types in the context of physiologically normal and disease states. These studies have been complemented by efforts directed at defining sequence codes governing splicing and their cognate trans-acting factors, which have illuminated important combinatorial principles of regulation. Additional studies have revealed critical roles of position-dependent, multivalent protein-RNA interactions that direct splicing outcomes. Investigations of evolutionary changes in RNA binding proteins, splice variants, and associated cis elements have further shed light on the emergence, mechanisms, and functions of splicing networks. Progress in these areas has emphasized the need for a coordinated, community-based effort to systematically address the functions of individual splice variants associated with normal and disease biology.
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21
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Zhu W, Zhou BL, Rong LJ, Ye L, Xu HJ, Zhou Y, Yan XJ, Liu WD, Zhu B, Wang L, Jiang XJ, Ren CP. Roles of PTBP1 in alternative splicing, glycolysis, and oncogensis. J Zhejiang Univ Sci B 2020; 21:122-136. [PMID: 32115910 DOI: 10.1631/jzus.b1900422] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Polypyrimidine tract-binding protein 1 (PTBP1) plays an essential role in splicing and is expressed in almost all cell types in humans, unlike the other proteins of the PTBP family. PTBP1 mediates several cellular processes in certain types of cells, including the growth and differentiation of neuronal cells and activation of immune cells. Its function is regulated by various molecules, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and RNA-binding proteins. PTBP1 plays roles in various diseases, particularly in some cancers, including colorectal cancer, renal cell cancer, breast cancer, and glioma. In cancers, it acts mainly as a regulator of glycolysis, apoptosis, proliferation, tumorigenesis, invasion, and migration. The role of PTBP1 in cancer has become a popular research topic in recent years, and this research has contributed greatly to the formulation of a useful therapeutic strategy for cancer. In this review, we summarize recent findings related to PTBP1 and discuss how it regulates the development of cancer cells.
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Affiliation(s)
- Wei Zhu
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Bo-Lun Zhou
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Li-Juan Rong
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Li Ye
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Hong-Juan Xu
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Yao Zhou
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Xue-Jun Yan
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Wei-Dong Liu
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Bin Zhu
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Lei Wang
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Xing-Jun Jiang
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Cai-Ping Ren
- NHC Key Laboratory of Carcinogenesis (Central South University) and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha 410008, China
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22
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Li L, Cao Y, Zhao F, Mao B, Ren X, Wang Y, Guan Y, You Y, Li S, Yang T, Zhao X. Validation and Classification of Atypical Splicing Variants Associated With Osteogenesis Imperfecta. Front Genet 2019; 10:979. [PMID: 31737030 PMCID: PMC6832110 DOI: 10.3389/fgene.2019.00979] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 09/13/2019] [Indexed: 01/17/2023] Open
Abstract
Osteogenesis Imperfecta (OI) is a rare inherited bone dysplasia, which is mainly caused by mutations in genes encoding type I collagen including COL1A1 and COL1A2. It has been well established to identify the classical variants as well as consensus splicing-site-variants in these genes in our previous studies. However, how atypical variants affect splicing in OI patients remains unclear. From a cohort of 867 OI patients, we collected blood samples from 34 probands which contain 29 variants that are located close to splice donor/acceptor sites in either COL1A1 or COL1A2. By conducting minigene assay and sequencing analysis, we found that 17 out of 29 variants led to aberrant splicing effects, while no remarkable aberrant splicing effect was observed in the remaining 12 variants. Among the 17 variants that affect splicing, 14 variants led to single splicing influence: 9 led to exon skipping, 2 resulted in truncated exon, and 3 caused intron retention. There were three complicated cases showing more than one mutant transcript caused by recognition of several different splice sites. This functional study expands our knowledge of atypical splicing variants, and emphasizes the importance of clarifying the splicing effect for variants near exon/intron boundaries in OI.
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Affiliation(s)
- Lulu Li
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Yixuan Cao
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Feiyue Zhao
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Bin Mao
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Xiuzhi Ren
- Department of Orthopaedics, The People's Hospital of Wuqing District, Tianjin, China
| | - Yanzhou Wang
- Department of Pediatric Orthopaedics, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, United States
| | - Yi You
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Shan Li
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Tao Yang
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Xiuli Zhao
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
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