1
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Choi S, Cho N, Kim EM, Kim KK. The role of alternative pre-mRNA splicing in cancer progression. Cancer Cell Int 2023; 23:249. [PMID: 37875914 PMCID: PMC10594706 DOI: 10.1186/s12935-023-03094-3] [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: 09/06/2023] [Accepted: 10/06/2023] [Indexed: 10/26/2023] Open
Abstract
Alternative pre-mRNA splicing is a critical mechanism that generates multiple mRNA from a single gene, thereby increasing the diversity of the proteome. Recent research has highlighted the significance of specific splicing isoforms in cellular processes, particularly in regulating cell numbers. In this review, we examine the current understanding of the role of alternative splicing in controlling cancer cell growth and discuss specific splicing factors and isoforms and their molecular mechanisms in cancer progression. These isoforms have been found to intricately control signaling pathways crucial for cell cycle progression, proliferation, and apoptosis. Furthermore, studies have elucidated the characteristics and functional importance of splicing factors that influence cell numbers. Abnormal expression of oncogenic splicing isoforms and splicing factors, as well as disruptions in splicing caused by genetic mutations, have been implicated in the development and progression of tumors. Collectively, these findings provide valuable insights into the complex interplay between alternative splicing and cell proliferation, thereby suggesting the potential of alternative splicing as a therapeutic target for cancer.
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Affiliation(s)
- Sunkyung Choi
- Department of Biochemistry, College of Natural Sciences, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Namjoon Cho
- Department of Biochemistry, College of Natural Sciences, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Eun-Mi Kim
- Department of Predictive Toxicology, Korea Institute of Toxicology, Daejeon, 34114, Republic of Korea.
| | - Kee K Kim
- Department of Biochemistry, College of Natural Sciences, Chungnam National University, Daejeon, 34134, Republic of Korea.
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2
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Chen XD, Liu HL, Li S, Hu KB, Wu QY, Liao P, Wang HY, Long ZY, Lu XM, Wang YT. The latest role of nerve-specific splicing factor PTBP1 in the transdifferentiation of glial cells into neurons. WILEY INTERDISCIPLINARY REVIEWS. RNA 2023; 14:e1740. [PMID: 35574699 DOI: 10.1002/wrna.1740] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 04/16/2022] [Accepted: 04/21/2022] [Indexed: 11/07/2022]
Abstract
Central nervous system injury diseases can cause the loss of many neurons, and it is difficult to regenerate. The field of regenerative medicine believes that supplementing the missing neurons may be an ideal method for nerve injury repair. Recent studies have found that down-regulation of polypyrimidine tract binding protein 1 (PTBP1) expression can make glial cells transdifferentiate into different types of neurons, which is expected to be an alternative therapy to restore neuronal function. This article summarized the research progress on the structure and biological function of the PTBP family, the mutual regulation of PTBP1 and PTBP2, their role in neurogenesis, and the latest research progress in targeting PTBP1 to mediate the transdifferentiation of glial cells into neurons, which may provide some new strategies and new ideas for the future treatment of central nervous system injury and neurodegenerative diseases. This article is categorized under: RNA Processing > Splicing Regulation/Alternative Splicing.
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Affiliation(s)
- Xing-Dong Chen
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China.,State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
| | - Hui-Lin Liu
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
| | - Sen Li
- State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
| | - Kai-Bin Hu
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
| | - Qing-Yun Wu
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
| | - Ping Liao
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
| | - Hai-Yan Wang
- State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
| | - Zai-Yun Long
- State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
| | - Xiu-Min Lu
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
| | - Yong-Tang Wang
- State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
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3
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Pan YJ, Liu BW, Pei DS. The Role of Alternative Splicing in Cancer: Regulatory Mechanism, Therapeutic Strategy, and Bioinformatics Application. DNA Cell Biol 2022; 41:790-809. [PMID: 35947859 DOI: 10.1089/dna.2022.0322] [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: 11/12/2022] Open
Abstract
[Formula: see text] Alternative splicing (AS) can generate distinct transcripts and subsequent isoforms that play differential functions from the same pre-mRNA. Recently, increasing numbers of studies have emerged, unmasking the association between AS and cancer. In this review, we arranged AS events that are closely related to cancer progression and presented promising treatments based on AS for cancer therapy. Obtaining proliferative capacity, acquiring invasive properties, gaining angiogenic features, shifting metabolic ability, and getting immune escape inclination are all splicing events involved in biological processes. Spliceosome-targeted and antisense oligonucleotide technologies are two novel strategies that are hopeful in tumor therapy. In addition, bioinformatics applications based on AS were summarized for better prediction and elucidation of regulatory routines mingled in. Together, we aimed to provide a better understanding of complicated AS events associated with cancer biology and reveal AS a promising target of cancer treatment in the future.
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Affiliation(s)
- Yao-Jie Pan
- Department of Pathology, Laboratory of Clinical and Experimental Pathology, Xuzhou Medical University, Xuzhou, China
| | - Bo-Wen Liu
- Department of General Surgery, Xuzhou Medical University, Xuzhou, China
| | - Dong-Sheng Pei
- Department of Pathology, Laboratory of Clinical and Experimental Pathology, Xuzhou Medical University, Xuzhou, China
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4
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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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5
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Liu S, Kang WJ, Abrimian A, Xu J, Cartegni L, Majumdar S, Hesketh P, Bekker A, Pan YX. Alternative Pre-mRNA Splicing of the Mu Opioid Receptor Gene, OPRM1: Insight into Complex Mu Opioid Actions. Biomolecules 2021; 11:biom11101525. [PMID: 34680158 PMCID: PMC8534031 DOI: 10.3390/biom11101525] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 10/11/2021] [Accepted: 10/11/2021] [Indexed: 12/03/2022] Open
Abstract
Most opioid analgesics used clinically, including morphine and fentanyl, as well as the recreational drug heroin, act primarily through the mu opioid receptor, a class A Rhodopsin-like G protein-coupled receptor (GPCR). The single-copy mu opioid receptor gene, OPRM1, undergoes extensive alternative splicing, creating multiple splice variants or isoforms via a variety of alternative splicing events. These OPRM1 splice variants can be categorized into three major types based on the receptor structure: (1) full-length 7 transmembrane (TM) C-terminal variants; (2) truncated 6TM variants; and (3) single TM variants. Increasing evidence suggests that these OPRM1 splice variants are pharmacologically important in mediating the distinct actions of various mu opioids. More importantly, the OPRM1 variants can be targeted for development of novel opioid analgesics that are potent against multiple types of pain, but devoid of many side-effects associated with traditional opiates. In this review, we provide an overview of OPRM1 alternative splicing and its functional relevance in opioid pharmacology.
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Affiliation(s)
- Shan Liu
- Department of Anesthesiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; (S.L.); (W.-J.K.); (A.A.); (J.X.); (P.H.); (A.B.)
| | - Wen-Jia Kang
- Department of Anesthesiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; (S.L.); (W.-J.K.); (A.A.); (J.X.); (P.H.); (A.B.)
| | - Anna Abrimian
- Department of Anesthesiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; (S.L.); (W.-J.K.); (A.A.); (J.X.); (P.H.); (A.B.)
| | - Jin Xu
- Department of Anesthesiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; (S.L.); (W.-J.K.); (A.A.); (J.X.); (P.H.); (A.B.)
| | - Luca Cartegni
- Department of Chemical Biology, Ernest Mario School of Pharmacy Rutgers University, Piscataway, NJ 08854, USA;
| | - Susruta Majumdar
- Center for Clinical Pharmacology, University of Health Sciences & Pharmacy and Washington University School of Medicine, St. Louis, MO 63110, USA;
| | - Patrick Hesketh
- Department of Anesthesiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; (S.L.); (W.-J.K.); (A.A.); (J.X.); (P.H.); (A.B.)
| | - Alex Bekker
- Department of Anesthesiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; (S.L.); (W.-J.K.); (A.A.); (J.X.); (P.H.); (A.B.)
| | - Ying-Xian Pan
- Department of Anesthesiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; (S.L.); (W.-J.K.); (A.A.); (J.X.); (P.H.); (A.B.)
- Correspondence: ; Tel.: +1-973-972-3213
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6
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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: 3] [Impact Index Per Article: 0.8] [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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7
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Ji Y, Mishra RK, Davuluri RV. In silico analysis of alternative splicing on drug-target gene interactions. Sci Rep 2020; 10:134. [PMID: 31924844 PMCID: PMC6954184 DOI: 10.1038/s41598-019-56894-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 12/18/2019] [Indexed: 12/24/2022] Open
Abstract
Identifying and evaluating the right target are the most important factors in early drug discovery phase. Most studies focus on one protein ignoring the multiple splice-variant or protein-isoforms, which might contribute to unexpected therapeutic activity or adverse side effects. Here, we present computational analysis of cancer drug-target interactions affected by alternative splicing. By integrating information from publicly available databases, we curated 883 FDA approved or investigational stage small molecule cancer drugs that target 1,434 different genes, with an average of 5.22 protein isoforms per gene. Of these, 618 genes have ≥5 annotated protein-isoforms. By analyzing the interactions with binding pocket information, we found that 76% of drugs either miss a potential target isoform or target other isoforms with varied expression in multiple normal tissues. We present sequence and structure level alignments at isoform-level and make this information publicly available for all the curated drugs. Structure-level analysis showed ligand binding pocket architectures differences in size, shape and electrostatic parameters between isoforms. Our results emphasize how potentially important isoform-level interactions could be missed by solely focusing on the canonical isoform, and suggest that on- and off-target effects at isoform-level should be investigated to enhance the productivity of drug-discovery research.
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Affiliation(s)
- Yanrong Ji
- Division of Health and Biomedical Informatics, Department of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Rama K Mishra
- The Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, IL, USA.,Department of Biochemistry and Molecular Genetics, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Ramana V Davuluri
- Division of Health and Biomedical Informatics, Department of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
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8
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Belanger K, Nutter CA, Li J, Yu P, Kuyumcu-Martinez MN. A developmentally regulated spliced variant of PTBP1 is upregulated in type 1 diabetic hearts. Biochem Biophys Res Commun 2018; 509:384-389. [PMID: 30594394 DOI: 10.1016/j.bbrc.2018.12.150] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 12/20/2018] [Indexed: 01/09/2023]
Abstract
Alternative splicing (AS) is dysregulated in Type 1 diabetic (T1D) hearts but mechanisms responsible are unclear. Here, we provide evidence that the RNA binding protein (RBP) PTBP1 is modulated in adult T1D hearts contributing to AS changes. We show that a spliced variant of PTBP1 that is highly expressed in normal newborn mouse hearts is aberrantly expressed in adult T1D mouse hearts. Comparing known PTBP1-target datasets to our T1D mouse transcriptome datasets, we discovered a group of genes with PTBP1 binding sites in their pre-mRNAs that are differentially spliced in T1D mouse hearts. We demonstrated that inducible expression of diabetes-induced PTBP1 spliced variant has less repressive splicing function. Notably, PTBP1 regulates AS of some of its targets antagonistically to RBFOX2. In sum, our results indicate that diabetic conditions disrupt developmental regulation of PTBP1 leading to differential AS of PTBP1 target genes. Identification of PTBP1 and PTBP1-regulated RNA networks can provide RNA-based therapies for the treatment of diabetes cardiac complications.
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Affiliation(s)
- KarryAnne Belanger
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Curtis A Nutter
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA
| | - Jin Li
- Department of Electrical and Computer Engineering & TEES-AgriLife Center for Bioinformatics and Genomic Systems Engineering, Texas A&M University, College Station, TX, 77843, USA
| | - Peng Yu
- Department of Electrical and Computer Engineering & TEES-AgriLife Center for Bioinformatics and Genomic Systems Engineering, Texas A&M University, College Station, TX, 77843, USA
| | - Muge N Kuyumcu-Martinez
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, 77555, USA; Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, 77555, USA; Institute for Translational Sciences, University of Texas Medical Branch, Galveston, TX, 77555, USA.
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9
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RBM4a modulates the impact of PRDM16 on development of brown adipocytes through an alternative splicing mechanism. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1865:1515-1525. [PMID: 30327195 DOI: 10.1016/j.bbamcr.2018.08.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 08/02/2018] [Accepted: 08/03/2018] [Indexed: 12/15/2022]
Abstract
Brown adipocytes (BAs) exhibit an energy-expending signature that is important in balancing metabolic homeostasis. In this study, results of transcriptome analyses revealed the reprogrammed splicing profile of the PR domain containing 16 (PRDM16) gene, a key transcription factor involved in brown adipogenesis, throughout development of wild-type brown adipose tissues (BATs). Moreover, discriminative splicing patterns of PRDM16 transcripts were noted in embryonic and postnatal RBM4a-/- BATs. Overexpression of RBM4a enhanced the relative levels of PRDM16-ex 16 transcripts by simultaneously interacting with exonic and intronic CU elements, which encoded the PRDM16S isoform containing a distinct C-terminus. The presence of the overexpressed PRDM16S isoform showed a stronger effect than the overexpressed PRDM16L isoform on enhancing transcriptional activity of the RBM4a and the PGC-1α promoter. Overexpression of the PRDM16S isoform exerted more-prominent effects on enhancing the BAT-related gene program and energy expenditure compared to those of PRDM16L-overexpressing cells. Our studies demonstrated that RBM4a-regulated alternative splicing constituted another regulatory mechanism for strengthening the influence of PRDM16 on the development of brown adipocytes.
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10
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Singh R. RNA-protein interactions that regulate pre-mRNA splicing. Gene Expr 2018; 10:79-92. [PMID: 11868989 PMCID: PMC5977533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Splicing of nuclear precursor messenger RNAs is an important and ubiquitous type of gene regulation in metazoans. Splicing joins the coding sequences called exons by removing the intervening noncoding sequences, introns, from primary transcripts. Alternative splicing generates an enormous repertoire of functional diversity by producing multiple RNAs and proteins from a single gene. In fact, recent genome sequences from several organisms suggest that splicing regulation is likely to provide an important source of functional diversity in more complex organisms. Because splice sites are short sequences at the ends of introns, the functional splice sites have to be distinguished from an excessively large number of sequences in the primary transcripts that resemble a splice site. Furthermore, alternative splice sites have to be correctly chosen at appropriate times. Thus, selection of proper splice sites remains a daunting biological problem. This review focuses on a few examples in which the molecular and biochemical basis for splice site selection is better understood.
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Affiliation(s)
- Ravinder Singh
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, 80309, USA.
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11
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Yin J, Wang X, Zhang L, Wang X, Liu H, Hu Y, Yan X, Tang Y, Wang J, Li Z, Yu Z, Cao Y, Han S. Peptidome analysis of lung tissues from a hyperoxia‐induced bronchopulmonary dysplasia mouse model: Insights into the pathophysiological process of bronchopulmonary dysplasia. J Cell Physiol 2018; 233:7101-7112. [PMID: 29741761 DOI: 10.1002/jcp.26633] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 03/30/2018] [Indexed: 12/30/2022]
Affiliation(s)
- Jing Yin
- Department of Pediatrics, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
| | - Xingyun Wang
- Department of Pediatrics, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
- Nanjing Maternity and Child Health Care Institute, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
| | - Le Zhang
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Xing Wang
- Nanjing Maternity and Child Health Care Institute, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
| | - Heng Liu
- Department of Pediatrics, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
| | - Yin Hu
- Department of Pediatrics, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
| | - Xiangyun Yan
- Department of Pediatrics, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
| | - Yongfeng Tang
- Department of Pediatrics, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
| | - Juan Wang
- Department of Pediatrics, The First People's Hospital of Lianyungang City, Lianyungang, Jiangsu, China
| | - Zhengyin Li
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Zhangbin Yu
- Department of Pediatrics, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
| | - Yan Cao
- Nanjing Maternity and Child Health Care Institute, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
| | - Shuping Han
- Department of Pediatrics, The Affiliated Obsterics and Gynecology Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, Jiangsu, China
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12
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Suess B, Kemmerer K, Weigand JE. Splicing and Alternative Splicing Impact on Gene Design. Synth Biol (Oxf) 2018. [DOI: 10.1002/9783527688104.ch7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Beatrix Suess
- Department of Biology; Technische Universität Darmstadt; Schnittspahnstraße 10 64287 Darmstadt Germany
| | - Katrin Kemmerer
- Department of Biology; Technische Universität Darmstadt; Schnittspahnstraße 10 64287 Darmstadt Germany
| | - Julia E. Weigand
- Department of Biology; Technische Universität Darmstadt; Schnittspahnstraße 10 64287 Darmstadt Germany
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13
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EMT and stemness: flexible processes tuned by alternative splicing in development and cancer progression. Mol Cancer 2017; 16:8. [PMID: 28137272 PMCID: PMC5282733 DOI: 10.1186/s12943-016-0579-2] [Citation(s) in RCA: 193] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 12/25/2016] [Indexed: 12/17/2022] Open
Abstract
Epithelial-to-mesenchymal transition (EMT) is associated with metastasis formation as well as with generation and maintenance of cancer stem cells. In this way, EMT contributes to tumor invasion, heterogeneity and chemoresistance. Morphological and functional changes involved in these processes require robust reprogramming of gene expression, which is only partially accomplished at the transcriptional level. Alternative splicing is another essential layer of gene expression regulation that expands the cell proteome. This step in post-transcriptional regulation of gene expression tightly controls cell identity between epithelial and mesenchymal states and during stem cell differentiation. Importantly, dysregulation of splicing factor function and cancer-specific splicing isoform expression frequently occurs in human tumors, suggesting the importance of alternative splicing regulation for cancer biology. In this review, we briefly discuss the role of EMT programs in development, stem cell differentiation and cancer progression. Next, we focus on selected examples of key factors involved in EMT and stem cell differentiation that are regulated post-transcriptionally through alternative splicing mechanisms. Lastly, we describe relevant oncogenic splice-variants that directly orchestrate cancer stem cell biology and tumor EMT, which may be envisioned as novel targets for therapeutic intervention.
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14
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The impact of RNA binding motif protein 4-regulated splicing cascade on the progression and metabolism of colorectal cancer cells. Oncotarget 2016; 6:38046-60. [PMID: 26506517 PMCID: PMC4741983 DOI: 10.18632/oncotarget.5710] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 10/06/2015] [Indexed: 01/17/2023] Open
Abstract
Dysregulated splicing of pre-messenger (m)RNA is considered a molecular occasion of carcinogenesis. However, the underlying mechanism is complex and remains to be investigated. Herein, we report that the upregulated miR-92a reduced the RNA-binding motif 4 (RBM4) protein expression, leading to the imbalanced expression of the neuronal polypyrimidine tract-binding (nPTB) protein through alternative splicing-coupled nonsense mediated decay (NMD) mechanism. Increase in nPTB protein enhances the relative level of fibroblast growth factor receptor 2 IIIc (FGFR2) and pyruvate kinase M2 (PKM2) transcripts which contribute to the progression and metabolic signature of CRC cells. Expression profiles of RBM4 and downstream alternative splicing events are consistently observed in cancerous tissues compared to adjacent normal tissues. These results constitute a mechanistic understanding of RBM4 on repressing the carcinogenesis of colorectal cells.
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15
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Wu Y, Davison J, Qu X, Morrissey C, Storer B, Brown L, Vessella R, Nelson P, Fang M. Methylation profiling identified novel differentially methylated markers including OPCML and FLRT2 in prostate cancer. Epigenetics 2016; 11:247-58. [PMID: 26890304 DOI: 10.1080/15592294.2016.1148867] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
To develop new methods to distinguish indolent from aggressive prostate cancers (PCa), we utilized comprehensive high-throughput array-based relative methylation (CHARM) assay to identify differentially methylated regions (DMRs) throughout the genome, including both CpG island (CGI) and non-CGI regions in PCa patients based on Gleason grade. Initially, 26 samples, including 8 each of low [Gleason score (GS) 6] and high (GS ≥7) grade PCa samples and 10 matched normal prostate tissues, were analyzed as a discovery cohort. We identified 3,567 DMRs between normal and cancer tissues, and 913 DMRs distinguishing low from high-grade cancers. Most of these DMRs were located at CGI shores. The top 5 candidate DMRs from the low vs. high Gleason comparison, including OPCML, ELAVL2, EXT1, IRX5, and FLRT2, were validated by pyrosequencing using the discovery cohort. OPCML and FLRT2 were further validated in an independent cohort consisting of 20 low-Gleason and 33 high-Gleason tissues. We then compared patients with biochemical recurrence (n=70) vs. those without (n=86) in a third cohort, and they showed no difference in methylation at these DMR loci. When GS 3+4 cases and GS 4+3 cases were compared, OPCML-DMR methylation showed a trend of lower methylation in the recurrence group (n=30) than in the no-recurrence (n=52) group. We conclude that whole-genome methylation profiling with CHARM revealed distinct patterns of differential DNA methylation between normal prostate and PCa tissues, as well as between different risk groups of PCa as defined by Gleason scores. A panel of selected DMRs may serve as novel surrogate biomarkers for Gleason score in PCa.
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Affiliation(s)
- Yu Wu
- a Fred Hutchinson Cancer Research Center , Seattle , WA
| | - Jerry Davison
- a Fred Hutchinson Cancer Research Center , Seattle , WA
| | - Xiaoyu Qu
- a Fred Hutchinson Cancer Research Center , Seattle , WA
| | | | - Barry Storer
- a Fred Hutchinson Cancer Research Center , Seattle , WA
| | | | - Robert Vessella
- b University of Washington , Seattle , WA.,c Puget Sound VA Health Care System , Seattle , WA
| | - Peter Nelson
- a Fred Hutchinson Cancer Research Center , Seattle , WA.,b University of Washington , Seattle , WA
| | - Min Fang
- a Fred Hutchinson Cancer Research Center , Seattle , WA.,b University of Washington , Seattle , WA
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16
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Lin JC, Lu YH, Liu YR, Lin YJ. RBM4a-regulated splicing cascade modulates the differentiation and metabolic activities of brown adipocytes. Sci Rep 2016; 6:20665. [PMID: 26857472 PMCID: PMC4746625 DOI: 10.1038/srep20665] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 01/11/2016] [Indexed: 12/11/2022] Open
Abstract
RNA-binding motif protein 4a (RBM4a) reportedly reprograms splicing profiles of the insulin receptor (IR) and myocyte enhancer factor 2C (MEF2C) genes, facilitating the differentiation of brown adipocytes. Using an RNA-sequencing analysis, we first compared the gene expressing profiles between wild-type and RBM4a−/− brown adipocytes. The ablation of RBM4a led to increases in the PTBP1, PTBP2 (nPTB), and Nova1 proteins, whereas elevated RBM4a reduced the expression of PTBP1 and PTBP2 proteins in brown adipocytes through an alternative splicing-coupled nonsense-mediated decay mechanism. Subsequently, RBM4a indirectly shortened the half-life of the Nova1 transcript which was comparatively stable in the presence of PTBP2. RBM4a diminished the influence of PTBP2 in adipogenic development by reprogramming the splicing profiles of the FGFR2 and PKM genes. These results constitute a mechanistic understanding of the RBM4a-modulated splicing cascade during the brown adipogenesis.
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Affiliation(s)
- Jung-Chun Lin
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Yi-Han Lu
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Yun-Ru Liu
- Joint Biobank, Office of Human Research, Taipei Medical University, Taipei, Taiwan
| | - Ying-Ju Lin
- School of Chinese Medicine, China Medical University, Taichung, Taiwan
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17
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Bebee TW, Park JW, Sheridan KI, Warzecha CC, Cieply BW, Rohacek AM, Xing Y, Carstens RP. The splicing regulators Esrp1 and Esrp2 direct an epithelial splicing program essential for mammalian development. eLife 2015; 4. [PMID: 26371508 PMCID: PMC4566030 DOI: 10.7554/elife.08954] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 08/18/2015] [Indexed: 12/13/2022] Open
Abstract
Tissue- and cell-type-specific regulators of alternative splicing (AS) are essential components of posttranscriptional gene regulation, necessary for normal cellular function, patterning, and development. Mice with ablation of Epithelial splicing regulatory protein (Esrp1) develop cleft lip and palate. Loss of both Esrp1 and its paralog Esrp2 results in widespread developmental defects with broad implications to human disease. Deletion of the Esrps in the epidermis revealed their requirement for establishing a proper skin barrier, a primary function of epithelial cells comprising the epidermis. We profiled the global Esrp-mediated splicing regulatory program in epidermis, which revealed large-scale programs of epithelial cell-type-specific splicing required for epithelial cell functions. These mice represent a valuable model for evaluating the essential role for AS in development and function of epithelial cells, which play essential roles in tissue homeostasis in numerous organs, and provide a genetic tool to evaluate important functional properties of epithelial-specific splice variants in vivo. DOI:http://dx.doi.org/10.7554/eLife.08954.001 Genes are turned into their protein products via two steps. The first, transcription, produces an intermediate RNA molecule or ‘transcript’; the second step, translation, turns the transcript into a protein. Most genes in mammals contain stretches of DNA called exons, which code for protein, interspersed with sequences called introns that do not. Therefore, a transcript must be ‘spliced’ before translation—the introns are removed and the exons joined. In some genes, certain exons can be optionally included or excluded from a transcript to produce different versions of the same protein that can often have very different functions. This is known as alternative splicing, and is essential for normal development. A large number of regulatory proteins control this process, many of which are only made in specific types of cells or tissues. Esrp1 and Esrp2 are two proteins that regulate alternative splicing in epithelial cells. These specialized cells form sheets that line most organs in the body and are found in the epidermis, the outermost layer of the skin. Although Esrp1 and Esrp2 have previously been studied in the laboratory using cultured cell lines, their roles have not been investigated in living animals. Bebee, Park et al. have now examined mice that are unable to produce one or both of these proteins. Mice that only lacked Esrp1 developed a cleft lip and palate. In mice that lacked both proteins, many organs failed to develop correctly and in some cases did not form at all. In the epidermis, the loss of Esrp1 and Esrp2 disrupted the splicing of the transcripts from genes that give epithelial cells many of their specialized characteristics, such as the ability to form sheets of cells with well formed junctions between them. This meant that epidermis that lacked Esrp1 and Esrp2 could not form a proper barrier layer, which is a crucial role of epithelia in skin as well as in other organs. In future, the mutant mice will be valuable for exploring how alternative splicing affects the development of epithelial cells and their properties. DOI:http://dx.doi.org/10.7554/eLife.08954.002
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Affiliation(s)
- Thomas W Bebee
- Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Juw Won Park
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, United States
| | - Katherine I Sheridan
- Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Claude C Warzecha
- Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Benjamin W Cieply
- Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Alex M Rohacek
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Yi Xing
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, United States
| | - Russ P Carstens
- Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
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18
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Calabretta S, Bielli P, Passacantilli I, Pilozzi E, Fendrich V, Capurso G, Fave GD, Sette C. Modulation of PKM alternative splicing by PTBP1 promotes gemcitabine resistance in pancreatic cancer cells. Oncogene 2015; 35:2031-9. [PMID: 26234680 PMCID: PMC4650269 DOI: 10.1038/onc.2015.270] [Citation(s) in RCA: 159] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 05/11/2015] [Accepted: 06/05/2015] [Indexed: 02/07/2023]
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is an aggressive and incurable disease. Poor prognosis is due to multiple reasons, including acquisition of resistance to gemcitabine, the first line chemotherapeutic approach. Thus, there is a strong need for novel therapies, targeting more directly the molecular aberrations of this disease. We found that chronic exposure of PDAC cells to gemcitabine selected a subpopulation of cells that are drug-resistant (DR-PDAC cells). Importantly, alternative splicing of the pyruvate kinase gene (PKM) was differentially modulated in DR-PDAC cells, resulting in promotion of the cancer-related PKM2 isoform, whose high expression also correlated with shorter recurrence free survival in PDAC patients. Switching PKM splicing by antisense oligonucleotides to favour the alternative PKM1 variant rescued sensitivity of DR-PDAC cells to gemcitabine and cisplatin, suggesting that PKM2 expression is required to withstand drug-induced genotoxic stress. Mechanistically, up-regulation of the polypyrimidine-tract binding protein (PTBP1), a key modulator of PKM splicing, correlated with PKM2 expression in DR-PDAC cell lines. PTBP1 was recruited more efficiently to PKM pre-mRNA in DR- than in parental PDAC cells. Accordingly, knockdown of PTBP1 in DR-PDAC cells reduced its recruitment to the PKM pre-mRNA, promoted splicing of the PKM1 variant and abolished drug resistance. Thus, chronic exposure to gemcitabine leads to up-regulation of PTBP1 and modulation of PKM alternative splicing in PDAC cells, conferring resistance to the drug. These findings point to PKM2 and PTBP1 as new potential therapeutic targets to improve response of PDAC to chemotherapy.
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Affiliation(s)
- S Calabretta
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy.,Department of Science Medical/Chirurgic and Translational Medicine, University of Rome La Sapienza, Rome, Italy
| | - P Bielli
- Laboratory of Neuroembryology, Fondazione Santa Lucia, Rome, Italy
| | - I Passacantilli
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy.,Department of Science Medical/Chirurgic and Translational Medicine, University of Rome La Sapienza, Rome, Italy
| | - E Pilozzi
- Department of Clinic and Molecular Medicine, University of Rome La Sapienza, Rome, Italy
| | - V Fendrich
- Department of Surgery, Philipps-University Marburg, Marburg, Germany
| | - G Capurso
- Department of Science Medical/Chirurgic and Translational Medicine, University of Rome La Sapienza, Rome, Italy
| | - G Delle Fave
- Department of Science Medical/Chirurgic and Translational Medicine, University of Rome La Sapienza, Rome, Italy
| | - C Sette
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy.,Laboratory of Neuroembryology, Fondazione Santa Lucia, Rome, Italy
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19
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A posttranscriptional mechanism that controls Ptbp1 abundance in the Xenopus epidermis. Mol Cell Biol 2014; 35:758-68. [PMID: 25512611 DOI: 10.1128/mcb.01040-14] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The output of alternative splicing depends on the cooperative or antagonistic activities of several RNA-binding proteins (RBPs), like Ptbp1 and Esrp1 in Xenopus. Fine-tuning of the RBP abundance is therefore of prime importance to achieve tissue- or cell-specific splicing patterns. Here, we addressed the mechanisms leading to the high expression of the ptbp1 gene, which encodes Ptbp1, in Xenopus epidermis. Two splice isoforms of ptbp1 mRNA differ by the presence of an alternative exon 11, and only the isoform including exon 11 can be translated to a full-length protein. In vivo minigene assays revealed that the nonproductive isoform was predominantly produced. Knockdown experiments demonstrated that Esrp1, which is specific to the epidermis, strongly stimulated the expression of ptbp1 by favoring the productive isoform. Consequently, knocking down esrp1 phenocopied ptbp1 inactivation. Conversely, Ptbp1 repressed the expression of its own gene by favoring the nonproductive isoform. Hence, a complex posttranscriptional mechanism controls Ptbp1 abundance in Xenopus epidermis: skipping of exon 11 is the default splicing pattern, but Esrp1 stimulates ptbp1 expression by favoring the inclusion of exon 11 up to a level that is limited by Ptbp1 itself. These results decipher a posttranscriptional mechanism that achieves various abundances of the ubiquitous RBP Ptbp1 in different tissues.
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20
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Bitting RL, Schaeffer D, Somarelli JA, Garcia-Blanco MA, Armstrong AJ. The role of epithelial plasticity in prostate cancer dissemination and treatment resistance. Cancer Metastasis Rev 2014; 33:441-68. [PMID: 24414193 PMCID: PMC4230790 DOI: 10.1007/s10555-013-9483-z] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Nearly 30,000 men die annually in the USA of prostate cancer, nearly uniformly from metastatic dissemination. Despite recent advances in hormonal, immunologic, bone-targeted, and cytotoxic chemotherapies, treatment resistance and further dissemination are inevitable in men with metastatic disease. Emerging data suggests that the phenomenon of epithelial plasticity, encompassing both reversible mesenchymal transitions and acquisition of stemness traits, may underlie this lethal biology of dissemination and treatment resistance. Understanding the molecular underpinnings of this cellular plasticity from preclinical models of prostate cancer and from biomarker studies of human metastatic prostate cancer has provided clues to novel therapeutic approaches that may delay or prevent metastatic disease and lethality over time. This review will discuss the preclinical and clinical evidence for epithelial plasticity in this rapidly changing field and relate this to clinical phenotype and resistance in prostate cancer while suggesting novel therapeutic approaches.
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Affiliation(s)
- Rhonda L. Bitting
- Division of Medical Oncology, Duke Cancer Institute, Duke University, DUMC Box 102002, Durham, NC 27710, USA. Department of Medicine, Duke University, Durham, NC, USA. Center for RNA Biology, Duke University, Durham, NC, USA
| | - Daneen Schaeffer
- Center for RNA Biology, Duke University, Durham, NC, USA. Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
| | - Jason A. Somarelli
- Center for RNA Biology, Duke University, Durham, NC, USA. Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
| | - Mariano A. Garcia-Blanco
- Department of Medicine, Duke University, Durham, NC, USA. Center for RNA Biology, Duke University, Durham, NC, USA. Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
| | - Andrew J. Armstrong
- Division of Medical Oncology, Duke Cancer Institute, Duke University, DUMC Box 102002, Durham, NC 27710, USA. Department of Medicine, Duke University, Durham, NC, USA. Center for RNA Biology, Duke University, Durham, NC, USA. Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
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21
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Finch PW, Mark Cross LJ, McAuley DF, Farrell CL. Palifermin for the protection and regeneration of epithelial tissues following injury: new findings in basic research and pre-clinical models. J Cell Mol Med 2014; 17:1065-87. [PMID: 24151975 PMCID: PMC4118166 DOI: 10.1111/jcmm.12091] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 05/06/2013] [Accepted: 05/15/2013] [Indexed: 02/06/2023] Open
Abstract
Keratinocyte growth factor (KGF) is a paracrine-acting epithelial mitogen produced by cells of mesenchymal origin, that plays an important role in protecting and repairing epithelial tissues. Pre-clinical data initially demonstrated that a recombinant truncated KGF (palifermin) could reduce gastrointestinal injury and mortality resulting from a variety of toxic exposures. Furthermore, the use of palifermin in patients with hematological malignancies reduced the incidence and duration of severe oral mucositis experienced after intensive chemoradiotherapy. Based upon these findings, as well as the observation that KGF receptors are expressed in many, if not all, epithelial tissues, pre-clinical studies have been conducted to determine the efficacy of palifermin in protecting different epithelial tissues from toxic injury in an attempt to model various clinical situations in which it might prove to be of benefit in limiting tissue damage. In this article, we review these studies to provide the pre-clinical background for clinical trials that are described in the accompanying article and the rationale for additional clinical applications of palifermin.
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22
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Juan WC, Roca X, Ong ST. Identification of cis-acting elements and splicing factors involved in the regulation of BIM Pre-mRNA splicing. PLoS One 2014; 9:e95210. [PMID: 24743263 PMCID: PMC3990581 DOI: 10.1371/journal.pone.0095210] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 03/25/2014] [Indexed: 11/25/2022] Open
Abstract
Aberrant changes in the expression of the pro-apoptotic protein, BCL-2-like 11 (BIM), can result in either impaired or excessive apoptosis, which can contribute to tumorigenesis and degenerative disorders, respectively. Altering BIM pre-mRNA splicing is an attractive approach to modulate apoptosis because BIM activity is partly determined by the alternative splicing of exons 3 or 4, whereby exon 3-containing transcripts are not apoptotic. Here we identified several cis-acting elements and splicing factors involved in BIM alternative splicing, as a step to better understand the regulation of BIM expression. We analyzed a recently discovered 2,903-bp deletion polymorphism within BIM intron 2 that biased splicing towards exon 3, and which also impaired BIM-dependent apoptosis. We found that this region harbors multiple redundant cis-acting elements that repress exon 3 inclusion. Furthermore, we have isolated a 23-nt intronic splicing silencer at the 3′ end of the deletion that is important for excluding exon 3. We also show that PTBP1 and hnRNP C repress exon 3 inclusion, and that downregulation of PTBP1 inhibited BIM-mediated apoptosis. Collectively, these findings start building our understanding of the cis-acting elements and splicing factors that regulate BIM alternative splicing, and also suggest potential approaches to alter BIM splicing for therapeutic purposes.
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Affiliation(s)
- Wen Chun Juan
- Cancer and Stem Cell Biology Signature Research Programme, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Xavier Roca
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- * E-mail: (XR); (STO)
| | - S. Tiong Ong
- Cancer and Stem Cell Biology Signature Research Programme, Duke-NUS Graduate Medical School, Singapore, Singapore
- Department of Haematology, Singapore General Hospital, Singapore, Singapore
- Department of Medical Oncology, National Cancer Centre, Singapore, Singapore
- Division of Medical Oncology, Department of Medicine, Duke University Medical Center, Chapel Hill, North Carolina, United States of America
- * E-mail: (XR); (STO)
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23
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Han A, Stoilov P, Linares AJ, Zhou Y, Fu XD, Black DL. De novo prediction of PTBP1 binding and splicing targets reveals unexpected features of its RNA recognition and function. PLoS Comput Biol 2014; 10:e1003442. [PMID: 24499931 PMCID: PMC3907290 DOI: 10.1371/journal.pcbi.1003442] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 11/23/2013] [Indexed: 11/28/2022] Open
Abstract
The splicing regulator Polypyrimidine Tract Binding Protein (PTBP1) has four RNA binding domains that each binds a short pyrimidine element, allowing recognition of diverse pyrimidine-rich sequences. This variation makes it difficult to evaluate PTBP1 binding to particular sites based on sequence alone and thus to identify target RNAs. Conversely, transcriptome-wide binding assays such as CLIP identify many in vivo targets, but do not provide a quantitative assessment of binding and are informative only for the cells where the analysis is performed. A general method of predicting PTBP1 binding and possible targets in any cell type is needed. We developed computational models that predict the binding and splicing targets of PTBP1. A Hidden Markov Model (HMM), trained on CLIP-seq data, was used to score probable PTBP1 binding sites. Scores from this model are highly correlated (ρ = −0.9) with experimentally determined dissociation constants. Notably, we find that the protein is not strictly pyrimidine specific, as interspersed Guanosine residues are well tolerated within PTBP1 binding sites. This model identifies many previously unrecognized PTBP1 binding sites, and can score PTBP1 binding across the transcriptome in the absence of CLIP data. Using this model to examine the placement of PTBP1 binding sites in controlling splicing, we trained a multinomial logistic model on sets of PTBP1 regulated and unregulated exons. Applying this model to rank exons across the mouse transcriptome identifies known PTBP1 targets and many new exons that were confirmed as PTBP1-repressed by RT-PCR and RNA-seq after PTBP1 depletion. We find that PTBP1 dependent exons are diverse in structure and do not all fit previous descriptions of the placement of PTBP1 binding sites. Our study uncovers new features of RNA recognition and splicing regulation by PTBP1. This approach can be applied to other multi-RRM domain proteins to assess binding site degeneracy and multifactorial splicing regulation. A key step in the regulation of mammalian genes is the splicing of the messenger RNA precursor to produce a mature mRNA that can be translated into a particular protein needed by the cell. Through the process of alternative splicing, mRNAs encoding different proteins can be derived from the same primary gene transcript. The regulation of this process plays essential roles in the development of differentiated tissues and is mediated by special pre-mRNA binding proteins. To understand how these proteins control gene expression, one must characterize what they recognize in RNA and identify these binding sites across the genome in order to predict their targets. Models that allow this prediction are essential to understanding developmental regulatory programs and their perturbation by disease causing mutations. In this study, we use statistical methods to build models of RNA recognition by the important splicing regulator PTBP1 and then apply these models to predict PTBP1 regulation of new gene transcripts. We show that PTBP1 has different specificity for RNA than was previously recognized and that its target exons are more diverse than was known before. There are many similar splicing regulators in mammalian cells, and these analyses provide a general framework for the computational analysis of their RNA binding and target identification.
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Affiliation(s)
- Areum Han
- Department of Bioengineering, University of California at Los Angeles, Los Angeles, California, United States of America
| | - Peter Stoilov
- Department of Biochemistry, School of Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Anthony J. Linares
- Molecular Biology Interdepartmental Graduate Program, University of California at Los Angeles, Los Angeles, California, United States of America
- Medical Scientist Training Program, University of California at Los Angeles, Los Angeles, California, United States of America
| | - Yu Zhou
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, United States of America
| | - Xiang-Dong Fu
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, United States of America
| | - Douglas L. Black
- Department of Bioengineering, University of California at Los Angeles, Los Angeles, California, United States of America
- Department of Microbiology, Immunology and Molecular Genetics, University of California at Los Angeles, Los Angeles, California, United States of America
- Howard Hughes Medical Institute, University of California at Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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24
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Sanidas I, Polytarchou C, Hatziapostolou M, Ezell SA, Kottakis F, Hu L, Guo A, Xie J, Comb MJ, Iliopoulos D, Tsichlis PN. Phosphoproteomics screen reveals akt isoform-specific signals linking RNA processing to lung cancer. Mol Cell 2014; 53:577-90. [PMID: 24462114 DOI: 10.1016/j.molcel.2013.12.018] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 11/02/2013] [Accepted: 12/18/2013] [Indexed: 01/09/2023]
Abstract
The three Akt isoforms are functionally distinct. Here we show that their phosphoproteomes also differ, suggesting that their functional differences are due to differences in target specificity. One of the top cellular functions differentially regulated by Akt isoforms is RNA processing. IWS1, an RNA processing regulator, is phosphorylated by Akt3 and Akt1 at Ser720/Thr721. The latter is required for the recruitment of SETD2 to the RNA Pol II complex. SETD2 trimethylates histone H3 at K36 during transcription, creating a docking site for MRG15 and PTB. H3K36me3-bound MRG15 and PTB regulate FGFR-2 splicing, which controls tumor growth and invasiveness downstream of IWS1 phosphorylation. Twenty-one of the twenty-four non-small-cell-lung carcinomas we analyzed express IWS1. More importantly, the stoichiometry of IWS1 phosphorylation in these tumors correlates with the FGFR-2 splicing pattern and with Akt phosphorylation and Akt3 expression. These data identify an Akt isoform-dependent regulatory mechanism for RNA processing and demonstrate its role in lung cancer.
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Affiliation(s)
- Ioannis Sanidas
- Molecular Oncology Research Institute, Tufts Medical Center, Boston, MA 02111, USA
| | - Christos Polytarchou
- Molecular Oncology Research Institute, Tufts Medical Center, Boston, MA 02111, USA; Division of Digestive Diseases, Center for Systems Biomedicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Maria Hatziapostolou
- Molecular Oncology Research Institute, Tufts Medical Center, Boston, MA 02111, USA; Division of Digestive Diseases, Center for Systems Biomedicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Scott A Ezell
- Molecular Oncology Research Institute, Tufts Medical Center, Boston, MA 02111, USA
| | - Filippos Kottakis
- Molecular Oncology Research Institute, Tufts Medical Center, Boston, MA 02111, USA
| | - Lan Hu
- Department of Biostatistics and Computational Biology, Center for Cancer Computational Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Ailan Guo
- Cell Signaling Technology, Danvers, MA 01923, USA
| | - Jianxin Xie
- Cell Signaling Technology, Danvers, MA 01923, USA
| | | | - Dimitrios Iliopoulos
- Division of Digestive Diseases, Center for Systems Biomedicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Philip N Tsichlis
- Molecular Oncology Research Institute, Tufts Medical Center, Boston, MA 02111, USA.
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25
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26
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Oltean S, Bates DO. Hallmarks of alternative splicing in cancer. Oncogene 2013; 33:5311-8. [PMID: 24336324 DOI: 10.1038/onc.2013.533] [Citation(s) in RCA: 451] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Revised: 11/04/2013] [Accepted: 11/04/2013] [Indexed: 12/17/2022]
Abstract
The immense majority of genes are alternatively spliced and there are many isoforms specifically associated with cancer progression and metastasis. The splicing pattern of specific isoforms of numerous genes is altered as cells move through the oncogenic process of gaining proliferative capacity, acquiring angiogenic, invasive, antiapoptotic and survival properties, becoming free from growth factor dependence and growth suppression, altering their metabolism to cope with hypoxia, enabling them to acquire mechanisms of immune escape, and as they move through the epithelial-mesenchymal and mesenchymal-epithelial transitions and metastasis. Each of the 'hallmarks of cancer' is associated with a switch in splicing, towards a more aggressive invasive cancer phenotype. The choice of isoforms is regulated by several factors (signaling molecules, kinases, splicing factors) currently being identified systematically by a number of high-throughput, independent and unbiased methodologies. Splicing factors are de-regulated in cancer, and in some cases are themselves oncogenes or pseudo-oncogenes and can contribute to positive feedback loops driving cancer progression. Tumour progression may therefore be associated with a coordinated splicing control, meaning that there is the potential for a relatively small number of splice factors or their regulators to drive multiple oncogenic processes. The understanding of how splicing contributes to the various phenotypic traits acquired by tumours as they progress and metastasise, and in particular how alternative splicing is coordinated, can and is leading to the development of a new class of anticancer therapeutics-the alternative-splicing inhibitors.
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Affiliation(s)
- S Oltean
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - D O Bates
- Division of Pre-clinical Oncology, School of Clinical Sciences, University of Nottingham, Queen's Medical Center, Nottingham, UK
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New insights into functional roles of the polypyrimidine tract-binding protein. Int J Mol Sci 2013; 14:22906-32. [PMID: 24264039 PMCID: PMC3856098 DOI: 10.3390/ijms141122906] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Revised: 11/13/2013] [Accepted: 11/13/2013] [Indexed: 12/20/2022] Open
Abstract
Polypyrimidine Tract Binding Protein (PTB) is an intensely studied RNA binding protein involved in several post-transcriptional regulatory events of gene expression. Initially described as a pre-mRNA splicing regulator, PTB is now widely accepted as a multifunctional protein shuttling between nucleus and cytoplasm. Accordingly, PTB can interact with selected RNA targets, structural elements and proteins. There is increasing evidence that PTB and its paralog PTBP2 play a major role as repressors of alternatively spliced exons, whose transcription is tissue-regulated. In addition to alternative splicing, PTB is involved in almost all steps of mRNA metabolism, including polyadenylation, mRNA stability and initiation of protein translation. Furthermore, it is well established that PTB recruitment in internal ribosome entry site (IRES) activates the translation of picornaviral and cellular proteins. Detailed studies of the structural properties of PTB have contributed to our understanding of the mechanism of RNA binding by RNA Recognition Motif (RRM) domains. In the present review, we will describe the structural properties of PTB, its paralogs and co-factors, the role in post-transcriptional regulation and actions in cell differentiation and pathogenesis. Defining the multifunctional roles of PTB will contribute to the understanding of key regulatory events in gene expression.
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28
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Kuroyanagi H, Watanabe Y, Hagiwara M. CELF family RNA-binding protein UNC-75 regulates two sets of mutually exclusive exons of the unc-32 gene in neuron-specific manners in Caenorhabditis elegans. PLoS Genet 2013; 9:e1003337. [PMID: 23468662 PMCID: PMC3585155 DOI: 10.1371/journal.pgen.1003337] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Accepted: 01/07/2013] [Indexed: 12/19/2022] Open
Abstract
An enormous number of alternative pre–mRNA splicing patterns in multicellular organisms are coordinately defined by a limited number of regulatory proteins and cis elements. Mutually exclusive alternative splicing should be strictly regulated and is a challenging model for elucidating regulation mechanisms. Here we provide models of the regulation of two sets of mutually exclusive exons, 4a–4c and 7a–7b, of the Caenorhabditis elegans uncoordinated (unc)-32 gene, encoding the a subunit of V0 complex of vacuolar-type H+-ATPases. We visualize selection patterns of exon 4 and exon 7 in vivo by utilizing a trio and a pair of symmetric fluorescence splicing reporter minigenes, respectively, to demonstrate that they are regulated in tissue-specific manners. Genetic analyses reveal that RBFOX family RNA–binding proteins ASD-1 and FOX-1 and a UGCAUG stretch in intron 7b are involved in the neuron-specific selection of exon 7a. Through further forward genetic screening, we identify UNC-75, a neuron-specific CELF family RNA–binding protein of unknown function, as an essential regulator for the exon 7a selection. Electrophoretic mobility shift assays specify a short fragment in intron 7a as the recognition site for UNC-75 and demonstrate that UNC-75 specifically binds via its three RNA recognition motifs to the element including a UUGUUGUGUUGU stretch. The UUGUUGUGUUGU stretch in the reporter minigenes is actually required for the selection of exon 7a in the nervous system. We compare the amounts of partially spliced RNAs in the wild-type and unc-75 mutant backgrounds and raise a model for the mutually exclusive selection of unc-32 exon 7 by the RBFOX family and UNC-75. The neuron-specific selection of unc-32 exon 4b is also regulated by UNC-75 and the unc-75 mutation suppresses the Unc phenotype of the exon-4b-specific allele of unc-32 mutants. Taken together, UNC-75 is the neuron-specific splicing factor and regulates both sets of the mutually exclusive exons of the unc-32 gene. Tissue-specific and mutually exclusive alternative pre–mRNA splicing is a challenging model for elucidating regulation mechanisms. We previously demonstrated that evolutionarily conserved RBFOX family RNA–binding proteins ASD-1 and FOX-1 and a muscle-specific RNA–binding protein SUP-12 cooperatively direct muscle-specific selection of exon 5B of the C. elegans egl-15 gene. Here we demonstrate that two sets of mutually exclusive exons, 4a–4c and 7a–7b, of the unc-32 gene are regulated in tissue-specific manners and that ASD-1 and FOX-1, expressed in a variety of tissues, can regulate the neuron-specific selection of unc-32 exon 7a in combination with the neuron-specific CELF family RNA–binding protein UNC-75. We determine the cis-elements for the RBFOX family and UNC-75, which separately reside in intron 7b and intron 7a, respectively. By analyzing the partially spliced RNA species, we propose the orders of intron removal and the sites of action for the RBFOX family and UNC-75 in the mutually exclusive selection of exon 7a and exon 7b. We also demonstrate that UNC-75 regulates the neuron-specific selection of exon 4b and propose the models of the mutually exclusive selection of exons 4a, 4b, and 4c. These studies thus provide novel modes of regulation for tissue-specific and mutually exclusive alternative splicing in vivo.
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Affiliation(s)
- Hidehito Kuroyanagi
- Graduate School of Biomedical Science, Tokyo Medical and Dental University, Tokyo, Japan.
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29
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Lee KM, Tarn WY. Coupling pre-mRNA processing to transcription on the RNA factory assembly line. RNA Biol 2013; 10:380-90. [PMID: 23392244 DOI: 10.4161/rna.23697] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
It has been well-documented that nuclear processing of primary transcripts of RNA polymerase II occurs co-transcriptionally and is functionally coupled to transcription. Moreover, increasing evidence indicates that transcription influences pre-mRNA splicing and even several post-splicing RNA processing events. In this review, we discuss the issues of how RNA polymerase II modulates co-transcriptional RNA processing events via its carboxyl terminal domain, and the protein domains involved in coupling of transcription and RNA processing events. In addition, we describe how transcription influences the expression or stability of mRNAs through the formation of distinct mRNP complexes. Finally, we delineate emerging findings that chromatin modifications function in the regulation of RNA processing steps, especially splicing, in addition to transcription. Overall, we provide a comprehensive view that transcription could integrate different control systems, from epigenetic to post-transcriptional control, for efficient gene expression.
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Affiliation(s)
- Kuo-Ming Lee
- Institute of Biomedical Sciences; Academia Sinica; Taipei, Taiwan
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30
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RBFOX2 is an important regulator of mesenchymal tissue-specific splicing in both normal and cancer tissues. Mol Cell Biol 2012; 33:396-405. [PMID: 23149937 DOI: 10.1128/mcb.01174-12] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Alternative splicing provides a critical and flexible layer of regulation intervening in many biological processes to regulate the diversity of proteins and impact cell phenotype. To identify alternative splicing differences that distinguish epithelial from mesenchymal tissues, we have investigated hundreds of cassette exons using a high-throughput reverse transcription-PCR (RT-PCR) platform. Extensive changes in splicing were noted between epithelial and mesenchymal tissues in both human colon and ovarian tissues, with many changes from mostly one splice variant to predominantly the other. Remarkably, many of the splicing differences that distinguish normal mesenchymal from normal epithelial tissues matched those that differentiate normal ovarian tissues from ovarian cancer. Furthermore, because splicing profiling could classify cancer cell lines according to their epithelial/mesenchymal characteristics, we used these cancer cell lines to identify regulators for these specific splicing signatures. By knocking down 78 potential splicing factors in five cell lines, we provide an extensive view of the complex regulatory landscape associated with the epithelial and mesenchymal states, thus revealing that RBFOX2 is an important driver of mesenchymal tissue-specific splicing.
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Lu J, Li C, Shi C, Balducci J, Huang H, Ji HL, Chang Y, Huang Y. Identification of novel splice variants and exons of human endothelial cell-specific chemotaxic regulator (ECSCR) by bioinformatics analysis. Comput Biol Chem 2012; 41:41-50. [PMID: 23147565 DOI: 10.1016/j.compbiolchem.2012.10.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 10/10/2012] [Accepted: 10/11/2012] [Indexed: 01/01/2023]
Abstract
Recent discovery of biological function of endothelial cell-specific chemotaxic regulator (ECSCR), previously known as endothelial cell-specific molecule 2 (ECSM2), in modulating endothelial cell migration, apoptosis, and angiogenesis, has made it an attractive molecule in vascular research. Thus, identification of splice variants of ECSCR could provide new strategies for better understanding its roles in health and disease. In this study, we performed a series of blast searches on the human EST database with known ECSCR cDNA sequence (Variant 1), and identified additional three splice variants (Variants 2-4). When examining the ECSCR gene in the human genome assemblies, we found a large unknown region between Exons 9 and 11. By PCR amplification and sequencing, we partially mapped Exon 10 within this previously unknown region of the ECSCR gene. Taken together, in addition to previously reported human ECSCR, we identified three novel full-length splice variants potentially encoding different protein isoforms. We further defined a total of twelve exons and nearly all exon-intron boundaries of the gene, of which only eight are annotated in current public databases. Our work provides new information on gene structure and alternative splicing of the human ECSCR, which may imply its functional complexity. This undoubtedly opens new opportunities for future investigation of the biological and pathological significance of these ECSCR splice variants.
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Affiliation(s)
- Jia Lu
- Department of Obstetrics and Gynecology, Barrow Neurological Institute, St Joseph's Hospital and Medical Center, Phoenix, AZ 85013, USA
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32
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Biamonti G, Bonomi S, Gallo S, Ghigna C. Making alternative splicing decisions during epithelial-to-mesenchymal transition (EMT). Cell Mol Life Sci 2012; 69:2515-26. [PMID: 22349259 PMCID: PMC11115103 DOI: 10.1007/s00018-012-0931-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Revised: 01/22/2012] [Accepted: 01/24/2012] [Indexed: 12/22/2022]
Abstract
Alternative splicing generates multiple mRNAs from a single transcript and is a major contributor to proteomic diversity and to the control of gene expression in complex organisms. Not surprisingly, this post-transcriptional event is tightly regulated in different tissues and developmental stages. An increasing body of evidences supports a causative role of aberrant alternative splicing in cancer. However, very little is known about its impact on cellular processes crucially involved in tumor progression. The aim of this review is to discuss the link between alternative splicing and the epithelial-to-mesenchymal transition (EMT), one of the major routes by which cancer cells acquire invasive capabilities and become metastatic. We begin with a brief overview of alternative splicing. Next, we discuss alternative splicing factors that regulate EMT. Finally, we provide examples of target genes presenting alternative splicing changes that contribute to the morphological conversions in the EMT process.
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Affiliation(s)
- Giuseppe Biamonti
- Istituto di Genetica Molecolare – Consiglio Nazionale delle Ricerche, via Abbiategrasso 207, 27100 Pavia, Italy
| | - Serena Bonomi
- Istituto di Genetica Molecolare – Consiglio Nazionale delle Ricerche, via Abbiategrasso 207, 27100 Pavia, Italy
| | - Stefania Gallo
- Istituto di Genetica Molecolare – Consiglio Nazionale delle Ricerche, via Abbiategrasso 207, 27100 Pavia, Italy
| | - Claudia Ghigna
- Istituto di Genetica Molecolare – Consiglio Nazionale delle Ricerche, via Abbiategrasso 207, 27100 Pavia, Italy
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33
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Keppetipola N, Sharma S, Li Q, Black DL. Neuronal regulation of pre-mRNA splicing by polypyrimidine tract binding proteins, PTBP1 and PTBP2. Crit Rev Biochem Mol Biol 2012; 47:360-78. [PMID: 22655688 DOI: 10.3109/10409238.2012.691456] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Alternative splicing patterns are regulated by RNA binding proteins that assemble onto each pre-mRNA to form a complex RNP structure. The polypyrimidine tract binding protein, PTB, has served as an informative model for understanding how RNA binding proteins affect spliceosome assembly and how changes in the expression of these proteins can control complex programs of splicing in tissues. In this review, we describe the mechanisms of splicing regulation by PTB and its function, along with its paralog PTBP2, in neuronal development.
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Affiliation(s)
- Niroshika Keppetipola
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA, USA
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34
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Montes M, Becerra S, Sánchez-Álvarez M, Suñé C. Functional coupling of transcription and splicing. Gene 2012; 501:104-17. [DOI: 10.1016/j.gene.2012.04.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 04/02/2012] [Accepted: 04/05/2012] [Indexed: 01/13/2023]
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35
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Huang C, Xie MH, Liu W, Yang B, Yang F, Huang J, Huang J, Wu Q, Fu XD, Zhang Y. A structured RNA in hepatitis B virus post-transcriptional regulatory element represses alternative splicing in a sequence-independent and position-dependent manner. FEBS J 2011; 278:1533-46. [PMID: 21371260 DOI: 10.1111/j.1742-4658.2011.08077.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Hepatitis B virus (HBV) transcripts are subjected to multiple splicing decisions, but the mechanism of splicing regulation remains poorly understood. In this study, we used a well-investigated alternative splicing reporter to dissect splicing regulatory elements residing in the post-transcriptional regulatory element (PRE) of HBV. A strong intronic splicing silencer (ISS) with a minimal functional element of 105 nucleotides (referred to as PRE-ISS) was identified and, interestingly, both the sense and antisense strands of the element were found to strongly suppress alternative splicing in multiple human cell lines. PRE-ISS folds into a double-hairpin structure, in which substitution mutations disrupting the double-hairpin structure abolish the splicing silencer activity. Although it harbors two previously identified binding sites for polypyrimidine tract binding protein, PRE-ISS represses splicing independent of this protein. The silencing function of PRE-ISS exhibited a strong position dependence, decreasing with the distance from affected splice sites. PRE-ISS does not belong to the intronic region of any HBV splicing variants identified thus far, preventing the testing of this intronic silencer function in the regulation of HBV splicing. These findings, together with the identification of multiple sense-antisense ISSs in the HBV genome, support the hypothesis that a sequence-independent and structure-dependent regulatory mechanism may have evolved to repress cryptic splice sites in HBV transcripts, thereby preventing their aberrant splicing during viral replication in the host.
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Affiliation(s)
- Chen Huang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China
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36
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David CJ, Manley JL. Alternative pre-mRNA splicing regulation in cancer: pathways and programs unhinged. Genes Dev 2011; 24:2343-64. [PMID: 21041405 DOI: 10.1101/gad.1973010] [Citation(s) in RCA: 621] [Impact Index Per Article: 47.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Alternative splicing of mRNA precursors is a nearly ubiquitous and extremely flexible point of gene control in humans. It provides cells with the opportunity to create protein isoforms of differing, even opposing, functions from a single gene. Cancer cells often take advantage of this flexibility to produce proteins that promote growth and survival. Many of the isoforms produced in this manner are developmentally regulated and are preferentially re-expressed in tumors. Emerging insights into this process indicate that pathways that are frequently deregulated in cancer often play important roles in promoting aberrant splicing, which in turn contributes to all aspects of tumor biology.
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Affiliation(s)
- Charles J David
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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37
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Tang ZZ, Sharma S, Zheng S, Chawla G, Nikolic J, Black DL. Regulation of the mutually exclusive exons 8a and 8 in the CaV1.2 calcium channel transcript by polypyrimidine tract-binding protein. J Biol Chem 2011; 286:10007-16. [PMID: 21282112 PMCID: PMC3060452 DOI: 10.1074/jbc.m110.208116] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
CaV1.2 calcium channels play roles in diverse cellular processes such as gene regulation, muscle contraction, and membrane excitation and are diversified in their activity through extensive alternative splicing of the CaV1.2 mRNA. The mutually exclusive exons 8a and 8 encode alternate forms of transmembrane segment 6 (IS6) in channel domain 1. The human genetic disorder Timothy syndrome is caused by mutations in either of these two CaV1.2 exons, resulting in disrupted Ca2+ homeostasis and severe pleiotropic disease phenotypes. The tissue-specific pattern of exon 8/8a splicing leads to differences in symptoms between patients with exon 8 or 8a mutations. Elucidating the mechanisms controlling the exon 8/8a splicing choice will be important in understanding the spectrum of defects associated with the disease. We found that the polypyrimidine tract-binding protein (PTB) mediates a switch from exon 8 to 8a splicing. PTB and its neuronal homolog, nPTB, are widely studied splicing regulators controlling large sets of alternative exons. During neuronal development, PTB expression is down-regulated with a concurrent increase in nPTB expression. Exon 8a is largely repressed in embryonic mouse brain but is progressively induced during neuronal differentiation as PTB is depleted. This splicing repression is mediated by the direct binding of PTB to sequence elements upstream of exon 8a. The nPTB protein is a weaker repressor of exon 8a, resulting in a shift in exon choice when nPTB replaces PTB in cells. These results provide mechanistic understanding of how these two exons, important for human disease, are controlled.
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Affiliation(s)
- Zhen Zhi Tang
- Howard Hughes Medical Institute, UCLA, Los Angeles, California 90095, USA
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38
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Takeuchi A, Hosokawa M, Nojima T, Hagiwara M. Splicing reporter mice revealed the evolutionally conserved switching mechanism of tissue-specific alternative exon selection. PLoS One 2010; 5:e10946. [PMID: 20532173 PMCID: PMC2880598 DOI: 10.1371/journal.pone.0010946] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Accepted: 05/10/2010] [Indexed: 12/16/2022] Open
Abstract
Since alternative splicing of pre-mRNAs is essential for generating tissue-specific diversity in proteome, elucidating its regulatory mechanism is indispensable to understand developmental process or tissue-specific functions. We have been focusing on tissue-specific regulation of mutually exclusive selection of alternative exons because this implies the typical molecular mechanism of alternative splicing regulation and also can be good examples to elicit general rule of “splice code”. So far, mutually exclusive splicing regulation has been explained by the outcome from the balance of multiple regulators that enhance or repress either of alternative exons discretely. However, this “balance” model is open to questions of how to ensure the selection of only one appropriate exon out of several candidates and how to switch them. To answer these questions, we generated an original bichromatic fluorescent splicing reporter system for mammals using fibroblast growth factor-receptor 2 (FGFR2) gene as model. By using this splicing reporter, we demonstrated that FGFR2 gene is regulated by the “switch-like” mechanism, in which key regulators modify the ordered splice-site recognition of two mutually exclusive exons, eventually ensure single exon selection and their distinct switching. Also this finding elucidated the evolutionally conserved “splice code,” in which combination of tissue-specific and broadly expressed RNA binding proteins regulate alternative splicing of specific gene in a tissue-specific manner. These findings provide the significant cue to understand how a number of spliced genes are regulated in various tissue-specific manners by a limited number of regulators, eventually to understand developmental process or tissue-specific functions.
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Affiliation(s)
- Akihide Takeuchi
- Department of Functional Genomics, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
- Department of Anatomy and Developmental Biology, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan
| | - Motoyasu Hosokawa
- Laboratory of Gene Expression, School of Biomedical Science, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
| | - Takayuki Nojima
- Department of Functional Genomics, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
- Laboratory of Gene Expression, School of Biomedical Science, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
| | - Masatoshi Hagiwara
- Department of Functional Genomics, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
- Laboratory of Gene Expression, School of Biomedical Science, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
- Department of Anatomy and Developmental Biology, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan
- * E-mail:
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39
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Luco RF, Pan Q, Tominaga K, Blencowe BJ, Pereira-Smith OM, Misteli T. Regulation of alternative splicing by histone modifications. Science 2010; 327:996-1000. [PMID: 20133523 DOI: 10.1126/science.1184208] [Citation(s) in RCA: 781] [Impact Index Per Article: 55.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Alternative splicing of pre-mRNA is a prominent mechanism to generate protein diversity, yet its regulation is poorly understood. We demonstrated a direct role for histone modifications in alternative splicing. We found distinctive histone modification signatures that correlate with the splicing outcome in a set of human genes, and modulation of histone modifications causes splice site switching. Histone marks affect splicing outcome by influencing the recruitment of splicing regulators via a chromatin-binding protein. These results outline an adaptor system for the reading of histone marks by the pre-mRNA splicing machinery.
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Affiliation(s)
- Reini F Luco
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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40
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Rajan P, Elliott DJ, Robson CN, Leung HY. Alternative splicing and biological heterogeneity in prostate cancer. Nat Rev Urol 2009; 6:454-60. [DOI: 10.1038/nrurol.2009.125] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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41
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Ohe K, Tamai KT, Parvinen M, Sassone-Corsi P. DAX-1 and SOX6 molecular interplay results in an antagonistic effect in pre-mRNA splicing. Dev Dyn 2009; 238:1595-604. [DOI: 10.1002/dvdy.21957] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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42
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Stern MZ, Gupta SK, Salmon-Divon M, Haham T, Barda O, Levi S, Wachtel C, Nilsen TW, Michaeli S. Multiple roles for polypyrimidine tract binding (PTB) proteins in trypanosome RNA metabolism. RNA (NEW YORK, N.Y.) 2009; 15:648-65. [PMID: 19218552 PMCID: PMC2661826 DOI: 10.1261/rna.1230209] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Trypanosomatid genomes encode for numerous proteins containing an RNA recognition motif (RRM), but the function of most of these proteins in mRNA metabolism is currently unknown. Here, we report the function of two such proteins that we have named PTB1 and PTB2, which resemble the mammalian polypyrimidine tract binding proteins (PTB). RNAi silencing of these factors indicates that both are essential for life. PTB1 and PTB2 reside mostly in the nucleus, but are found in the cytoplasm, as well. Microarray analysis performed on PTB1 and PTB2 RNAi silenced cells indicates that each of these factors differentially affects the transcriptome, thus regulating a different subset of mRNAs. PTB1 and PTB2 substrates were categorized bioinformatically, based on the presence of PTB binding sites in their 5' and 3' flanking sequences. Both proteins were shown to regulate mRNA stability. Interestingly, PTB proteins are essential for trans-splicing of genes containing C-rich polypyrimidine tracts. PTB1, but not PTB2, also affects cis-splicing. The specificity of binding of PTB1 was established in vivo and in vitro using a model substrate. This study demonstrates for the first time that trans-splicing of only certain substrates requires specific factors such as PTB proteins for their splicing. The trypanosome PTB proteins, like their mammalian homologs, represent multivalent RNA binding proteins that regulate mRNAs from their synthesis to degradation.
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43
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Baughan TD, Dickson A, Osman EY, Lorson CL. Delivery of bifunctional RNAs that target an intronic repressor and increase SMN levels in an animal model of spinal muscular atrophy. Hum Mol Genet 2009; 18:1600-11. [PMID: 19228773 DOI: 10.1093/hmg/ddp076] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Spinal muscular atrophy (SMA) is a motor neuron disease caused by the loss of survival motor neuron-1 (SMN1). A nearly identical copy gene, SMN2, is present in all SMA patients, which produces low levels of functional protein. Although the SMN2 coding sequence has the potential to produce normal, full-length SMN, approximately 90% of SMN2-derived transcripts are alternatively spliced and encode a truncated protein lacking the final coding exon (exon 7). SMN2, however, is an excellent therapeutic target. Previously, we developed bifunctional RNAs that bound SMN exon 7 and modulated SMN2 splicing. To optimize the efficiency of the bifunctional RNAs, a different antisense target was required. To this end, we genetically verified the identity of a putative intronic repressor and developed bifunctional RNAs that target this sequence. Consequently, there is a 2-fold mechanism of SMN induction: inhibition of the intronic repressor and recruitment of SR proteins via the SR recruitment sequence of the bifunctional RNA. The bifunctional RNAs effectively increased SMN in human primary SMA fibroblasts. Lead candidates were synthesized as 2'-O-methyl RNAs and were directly injected in the central nervous system of SMA mice. Single-RNA injections were able to illicit a robust induction of SMN protein in the brain and throughout the spinal column of neonatal SMA mice. In a severe model of SMA, mean life span was extended following the delivery of bifunctional RNAs. This technology has direct implications for the development of an SMA therapy, but also lends itself to a multitude of diseases caused by aberrant pre-mRNA splicing.
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Affiliation(s)
- Travis D Baughan
- Department of Molecular Microbiology and Immunology, Bond Life Sciences Center, University of Missouri, Columbia, 65211, USA
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TIA nuclear proteins regulate the alternate splicing of lysyl hydroxylase 2. J Invest Dermatol 2008; 129:1402-11. [PMID: 19110540 DOI: 10.1038/jid.2008.386] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Synthesis of collagen, a major component of the extracellular matrix, is increased dramatically in fibrotic conditions such as scleroderma. This overaccumulation of collagen is associated with increased pyridinoline cross-links. These cross-links are derived by the action of the alternatively spliced long form of lysyl hydroxylase 2 (LH2), a collagen telopeptide LH. As LH2 (long) is reported to be overexpressed in scleroderma fibroblasts, the regulation of LH2 splicing suggests an important step in controlling fibrosis. Using an LH2 minigene, we have compared the regulation of the alternative splicing pattern of LH2, both endogenously and in the minigene, by the RNA-binding splicing proteins TIA-1 and TIAL1 (T-cell-restricted intracellular antigens). A decrease in the ratio of LH2 (long) to LH2 (short) was observed in fibroblasts from TIAL1 knockout mice, and in HEK293 cells knocked down for TIA-1 and TIAL1. As a corollary, overexpression of TIA-1/TIAL1 in HEK293 cells resulted in an increase in LH2 (long) minigene transcripts, accompanied by a decrease in LH2 (short). In scleroderma fibroblasts, a double TIA-1/TIAL1 knockdown reduced the ratio of LH2 (long) to LH2 (short) by over fivefold compared to controls. Identification of these TIA regulatory factors therefore suggests a tool to manipulate cellular LH2 levels in scleroderma so that potential intervention therapies may be identified.
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hnRNP H and hnRNP F complex with Fox2 to silence fibroblast growth factor receptor 2 exon IIIc. Mol Cell Biol 2008; 28:5403-19. [PMID: 18573884 DOI: 10.1128/mcb.00739-08] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The heterogeneous nuclear ribonucleoprotein H (hnRNP) family of proteins has been shown to activate exon inclusion by binding intronic G triplets. Much less is known, however, about how hnRNP H and hnRNP F silence exons. In this study, we identify hnRNP H and hnRNP F proteins as being novel silencers of fibroblast growth factor receptor 2 exon IIIc. In cells that normally include this exon, we show that the overexpression of either hnRNP H1 or hnRNP F resulted in the dramatic silencing of exon IIIc. In cells that normally skip exon IIIc, skipping was disrupted when RNA interference was used to knock down both hnRNP H and hnRNP F. We show that an exonic GGG motif overlapped a critical exonic splicing enhancer, which was predicted to bind the SR protein ASF/SF2. Furthermore, the expression of ASF/SF2 reversed the silencing of exon IIIc caused by the expression of hnRNP H1. We show that hnRNP H and hnRNP F proteins are present in a complex with Fox2 and that the presence of Fox allows hnRNP H1 to better compete with ASF/SF2 for binding to exon IIIc. These results establish hnRNP H and hnRNP F as being repressors of exon inclusion and suggest that Fox proteins enhance their ability to antagonize ASF/SF2.
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Cheung HC, Baggerly KA, Tsavachidis S, Bachinski LL, Neubauer VL, Nixon TJ, Aldape KD, Cote GJ, Krahe R. Global analysis of aberrant pre-mRNA splicing in glioblastoma using exon expression arrays. BMC Genomics 2008; 9:216. [PMID: 18474104 PMCID: PMC2410136 DOI: 10.1186/1471-2164-9-216] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2007] [Accepted: 05/12/2008] [Indexed: 12/22/2022] Open
Abstract
Background Tumor-predominant splice isoforms were identified during comparative in silico sequence analysis of EST clones, suggesting that global aberrant alternative pre-mRNA splicing may be an epigenetic phenomenon in cancer. We used an exon expression array to perform an objective, genome-wide survey of glioma-specific splicing in 24 GBM and 12 nontumor brain samples. Validation studies were performed using RT-PCR on glioma cell lines, patient tumor and nontumor brain samples. Results In total, we confirmed 14 genes with glioma-specific splicing; seven were novel events identified by the exon expression array (A2BP1, BCAS1, CACNA1G, CLTA, KCNC2, SNCB, and TPD52L2). Our data indicate that large changes (> 5-fold) in alternative splicing are infrequent in gliomagenesis (< 3% of interrogated RefSeq entries). The lack of splicing changes may derive from the small number of splicing factors observed to be aberrantly expressed. Conclusion While we observed some tumor-specific alternative splicing, the number of genes showing exclusive tumor-specific isoforms was on the order of tens, rather than the hundreds suggested previously by in silico mining. Given the important role of alternative splicing in neural differentiation, there may be selective pressure to maintain a majority of splicing events in order to retain glial-like characteristics of the tumor cells.
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Affiliation(s)
- Hannah C Cheung
- Department of Endocrine Neoplasia and Hormonal Disorders, University of Texas M, D, Anderson Cancer Center, Houston, TX 77030, USA.
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Piergentili R, Mencarelli C. Drosophila melanogaster kl-3 and kl-5 Y-loops harbor triple-stranded nucleic acids. J Cell Sci 2008; 121:1605-12. [PMID: 18430782 DOI: 10.1242/jcs.025320] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Primary spermatocyte nuclei of Drosophila melanogaster contain three prominent lampbrush-like loops. The development of these structures has been associated with the transcription of three fertility factors located on the Y chromosome, named kl-5, kl-3 and ks-1. These loci have huge physical dimensions and contain extremely long introns. In addition, kl-3 and kl-5 were shown to encode two putative dynein subunits required for the correct assembly of the sperm axoneme. Here, we show that both the kl-5 and kl-3 loops are intensely decorated by monoclonal antibodies recognizing triple-stranded nucleic acids, and that each loop presents a peculiar molecular organization of triplex structures. Moreover, immunostaining of Drosophila hydei primary spermatocytes revealed that also in this species - which diverged from D. melanogaster 58 million years ago - Y-loops are decorated by anti-triplex antibodies, strongly suggesting a conserved role of loop-associated triplexes. Finally, we showed that in D. melanogaster wild-type lines that are raised at the non-permissive temperature of 31+/-0.5 degrees C (which is known to induce male sterility in flies) both the triplex immunostaining and the axonemal dynein heavy chains encoded by kl-3 and kl-5 are no longer detectable, which suggests a functional correlation between loop-associated triplexes, the presence of axonemal proteins and male fertility in fly.
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Affiliation(s)
- Roberto Piergentili
- Department of Genetics and Molecular Biology - Sapienza Università di Roma, 00185 Rome, Italy.
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Seth P, Miller HB, Lasda EL, Pearson JL, Garcia-Blanco MA. Identification of an intronic splicing enhancer essential for the inclusion of FGFR2 exon IIIc. J Biol Chem 2008; 283:10058-67. [PMID: 18256031 DOI: 10.1074/jbc.m800087200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The ligand specificity of fibroblast growth factor receptor 2 (FGFR2) is determined by the alternative splicing of exons 8 (IIIb) or 9 (IIIc). Exon IIIb is included in epithelial cells, whereas exon IIIc is included in mesenchymal cells. Although a number of cis elements and trans factors have been identified that play a role in exon IIIb inclusion in epithelium, little is known about the activation of exon IIIc in mesenchyme. We report here the identification of a splicing enhancer required for IIIc inclusion. This 24-nucleotide (nt) downstream intronic splicing enhancer (DISE) is located within intron 9 immediately downstream of exon IIIc. DISE was able to activate the inclusion of heterologous exons rat FGFR2 IIIb and human beta-globin exon 2 in cell lines from different tissues and species and also in HeLa cell nuclear extracts in vitro. DISE was capable of replacing the intronic activator sequence 1 (IAS1), a known IIIb splicing enhancer and vice versa. This fact, together with the requirement for DISE to be close to the 5'-splice site and the ability of DISE to promote binding of U1 snRNP, suggested that IAS1 and DISE belong to the same class of cis-acting elements.
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Affiliation(s)
- Puneet Seth
- Department of Molecular Genetics and Microbiology, and Center for RNA Biology, Duke University Medical Center, Durham, NC 27710, USA
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Abstract
The sequencing of the human genome and ensuing wave of data generation have brought new light upon the extent and importance of alternative splicing as an RNA regulatory mechanism. Alternative splicing could potentially explain the complexity of protein repertoire during evolution, and defects in the splicing mechanism are responsible for diseases as complex as cancer. Among the challenges that rise in light of these discoveries are cataloguing splice variation in the human and other eukaryotic genomes, and identifying and characterizing the splicing regulatory elements that control their expression. Bioinformatics efforts tackling these two questions are just at the beginning. This article is a survey of these methods.
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Affiliation(s)
- Liliana Florea
- Department of Computer Science, George Washington University, Academic Center-Rm 714, Washington DC 20052, USA.
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Villanueva S, Cespedes C, Gonzalez AA, Roessler E, Vio CP. Inhibition of bFGF-receptor type 2 increases kidney damage and suppresses nephrogenic protein expression after ischemic acute renal failure. Am J Physiol Regul Integr Comp Physiol 2008; 294:R819-28. [PMID: 18184769 DOI: 10.1152/ajpregu.00273.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recovery from acute renal failure (ARF) requires the replacement of injured cells by new cells that are able to restore tubule epithelial integrity. We have recently described the expression of nephrogenic proteins [Vimentin, neural cell adhesion molecule, basic fibroblast growth factor (bFGF), Pax-2, bone morphogen protein-7, Noggin, Smad 1-5-8, p-Smad, hypoxia-inducible factor-1alpha, vascular endothelial growth factor], in a time frame similar to that observed in kidney development, after ischemic ARF induced in an ischemia-reperfusion (I/R) model. Furthermore, we show that bFGF, a morphogen involved in mesenchyme/epithelial transition in kidney development, induces a reexpression of morphogenic proteins in an earlier time frame and accelerates the recovery process after renal damage. Herein, we confirm that renal morphogenes are modulated by bFGF and hypothesized that a decrease in bFGF receptor 2 (bFGFR2) levels by the use of antisense oligonucleotides diminishes the expression of morphogenes. Male Sprague-Dawley rats submitted to ischemic injury were injected with 112 microg/kg bFGFR2 antisense oligonucleotide (bFGFR2-ASO) followed by reperfusion. Rats were killed, and the expression of nephrogenic proteins and renal marker damage was analyzed by immunohistochemistry and immunoblot. Animals subjected to I/R treated with bFGFR2-ASO showed a significant reduction in morphogen levels (P < 0.05). In addition, we observed an increase in markers of renal damage: macrophages (ED-1) and interstitial alpha-smooth muscle actin. These results confirm that bFGF participates in the recovery process and that treatment with bFGFR2-ASO induces an altered expression of morphogen proteins.
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Affiliation(s)
- Sandra Villanueva
- Laboratorio de Fisiologia Integrativa y Molecular, Universidad de Los Andes, San Carlos Apoquindo 2200, Santiago, Chile.
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