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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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Conboy JG. Unannotated splicing regulatory elements in deep intron space. WILEY INTERDISCIPLINARY REVIEWS-RNA 2021; 12:e1656. [PMID: 33887804 DOI: 10.1002/wrna.1656] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 03/14/2021] [Accepted: 03/23/2021] [Indexed: 12/21/2022]
Abstract
Deep intron space harbors a diverse array of splicing regulatory elements that cooperate with better-known exon-proximal elements to enforce proper tissue-specific and development-specific pre-mRNA processing. Many deep intron elements have been highly conserved through vertebrate evolution, yet remain poorly annotated in the human genome. Recursive splicing exons (RS-exons) and intraexons promote noncanonical, multistep resplicing pathways in long introns, involving transient intermediate structures that are greatly underrepresented in RNA-seq datasets. Decoy splice sites and decoy exons act at a distance to inhibit splicing catalysis at annotated splice sites, with functional consequences such as exon skipping and intron retention. RNA:RNA bridges can juxtapose distant sequences within or across introns to activate deep intron splicing enhancers and silencers, to loop out exons to be skipped, or to select one member of a mutually exclusive set of exons. Similarly, protein bridges mediated by interactions among transcript-bound RNA binding proteins (RBPs) can modulate splicing outcomes. Experimental disruption of deep intron elements serving any of these functions can abrogate normal splicing, strongly suggesting that natural mutations of deep intron elements can do likewise to cause human disease. Understanding noncanonical splicing pathways and discovering deep intron regulatory signals, many of which map hundreds to many thousands of nucleotides from annotated splice junctions, is of great academic interest for basic scientists studying alternative splicing mechanisms. Hopefully, this knowledge coupled with increased analysis of deep intron sequences will also have important medical applications, as better interpretation of deep intron mutations may reveal new disease mechanisms and suggest new therapies. This article is categorized under: RNA Processing > Splicing Regulation/Alternative Splicing.
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Affiliation(s)
- John G Conboy
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, California, USA
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4
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SRSF9 Regulates Cassette Exon Splicing of Caspase-2 by Interacting with Its Downstream Exon. Cells 2021; 10:cells10030679. [PMID: 33808656 PMCID: PMC8003524 DOI: 10.3390/cells10030679] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/01/2021] [Accepted: 03/16/2021] [Indexed: 11/16/2022] Open
Abstract
Alternative splicing (AS) is an important posttranscriptional regulatory process. Damaged or unnecessary cells need to be removed though apoptosis to maintain physiological processes. Caspase-2 pre-mRNA produces pro-apoptotic long mRNA and anti-apoptotic short mRNA isoforms through AS. How AS of Caspase-2 is regulated remains unclear. In the present study, we identified a novel regulatory protein SRSF9 for AS of Caspase-2 cassette exon 9. Knock-down (KD) of SRSF9 increased inclusion of cassette exon and on the other hand, overexpression of SRSF9 decreased inclusion of this exon. Deletion mutagenesis demonstrated that exon 9, parts of intron 9, exon 8 and exon 10 were not required for the role of SRSF9 in Caspase-2 AS. However, deletion and substitution mutation analysis revealed that AGGAG sequence located at exon 10 provided functional target for SRSF9. In addition, RNA-pulldown mediated immunoblotting analysis showed that SRSF9 interacted with this sequence. Gene ontology analysis of RNA-seq from SRSF9 KD cells demonstrates that SRSF9 could regulate AS of a subset of apoptosis related genes. Collectively, our results reveal a basis for regulation of Caspase-2 AS.
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Li S, Shen L, Huang L, Lei S, Cai X, Breitzig M, Zhang B, Yang A, Ji W, Huang M, Zheng Q, Sun H, Wang F. PTBP1 enhances exon11a skipping in Mena pre-mRNA to promote migration and invasion in lung carcinoma cells. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2019; 1862:858-869. [PMID: 31075540 DOI: 10.1016/j.bbagrm.2019.04.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 04/16/2019] [Accepted: 04/18/2019] [Indexed: 12/13/2022]
Abstract
Alternative splicing (AS) events occur in the majority of human genes. AS in a single gene can give rise to different functions among multiple isoforms. Human ortholog of mammalian enabled (Mena) is a conserved regulator of actin dynamics that plays an important role in metastasis. Mena has been shown to have multiple splice variants in human tumor cells due to AS. However, the mechanism mediated Mena AS has not been elucidated. Here we showed that polypyrimidine tract-binding protein 1 (PTBP1) could modulate Mena AS. First, PTBP1 levels were elevated in metastatic lung cancer cells as well as during epithelial-mesenchymal transition (EMT) process. Then, knockdown of PTBP1 using shRNA inhibited migration and invasion of lung carcinoma cells and decreased the Mena exon11a skipping, whereas overexpression of PTBP1 had the opposite effects. The results of RNA pull-down assays and mutation analyses demonstrated that PTBP1 functionally targeted and physically interacted with polypyrimidine sequences on both upstream intron11 (TTTTCCCCTT) and downstream intron11a (TTTTTTTTTCTTT). In addition, the results of migration and invasion assays as well as detection of filopodia revealed that the effect of PTBP1 was reversed by knockdown of Mena but not Mena11a+. Overexpressed MenaΔ11a also rescued the PTBP1-induced migration and invasion. Taken together, our study provides a novel mechanism that PTBP1 modulates Mena exon11a skipping, and indicates that PTBP1 depends on the level of Mena11a- to promote lung cancer cells migration and invasion. The regulation of Mena AS may be a potential prognostic marker and a promising target for treatment of lung carcinoma.
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Affiliation(s)
- Shuaiguang Li
- Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou 510632, China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of pharmacy, Jinan University, Guangzhou 510632, China
| | - Lianghua Shen
- Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou 510632, China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of pharmacy, Jinan University, Guangzhou 510632, China
| | - Luyuan Huang
- Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Sijia Lei
- Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou 510632, China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of pharmacy, Jinan University, Guangzhou 510632, China
| | - Xingdong Cai
- Department of Respiratory, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Mason Breitzig
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, MDC 19, Tampa, FL 33612, USA
| | - Bin Zhang
- Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou 510632, China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of pharmacy, Jinan University, Guangzhou 510632, China
| | - Annan Yang
- Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou 510632, China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of pharmacy, Jinan University, Guangzhou 510632, China
| | - Wenzuo Ji
- Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou 510632, China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of pharmacy, Jinan University, Guangzhou 510632, China
| | - Meiyan Huang
- Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou 510632, China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of pharmacy, Jinan University, Guangzhou 510632, China
| | - Qing Zheng
- Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou 510632, China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of pharmacy, Jinan University, Guangzhou 510632, China
| | - Hanxiao Sun
- Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou 510632, China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of pharmacy, Jinan University, Guangzhou 510632, China
| | - Feng Wang
- Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou 510632, China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of pharmacy, Jinan University, Guangzhou 510632, China.
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6
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Wang X, Li Y, Fan Y, Yu X, Mao X, Jin F. PTBP1 promotes the growth of breast cancer cells through the PTEN/Akt pathway and autophagy. J Cell Physiol 2018; 233:8930-8939. [PMID: 29856478 PMCID: PMC6175200 DOI: 10.1002/jcp.26823] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Accepted: 04/30/2018] [Indexed: 12/22/2022]
Abstract
Invasion and migration is the hallmark of malignant tumors as well as the major cause for breast cancer death. The polypyrimidine tract binding, PTB, protein serves as an important model for understanding how RNA binding proteins affect proliferation and invasion and how changes in the expression of these proteins can control complex programs of tumorigenesis. We have investigated some roles of polypyrimidine tract binding protein 1 (PTBP1) in human breast cancer. We found that PTBP1 was upregulated in breast cancer tissues compared with normal tissues and the same result was confirmed in breast cancer cell lines. Knockdown of PTBP1 substantially inhibited tumor cell growth, migration, and invasion. These results suggest that PTBP1 is associated with breast tumorigenesis and appears to be required for tumor cell growth and maintenance of metastasis. We further analyzed the relationship between PTBP1 and clinicopathological parameters and found that PTBP1 was correlated with her‐2 expression, lymph node metastasis, and pathological stage. This will be a novel target for her‐2(+) breast cancer. PTBP1 exerts these effects, in part, by regulating the phosphatase and tensin homolog‐phosphatidylinositol‐4,5‐bisphosphate 3‐kinase/protein kinase B (PTEN‐PI3K/Akt) pathway and autophagy, and consequently alters cell growth and contributes to the invasion and metastasis.
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Affiliation(s)
- Xu Wang
- Department of Breast Surgery, The First Affiliated Hospital of China Medical University, Shenyang City, Liaoning, China
| | - Yang Li
- Department of Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, Shenyang, China
| | - Yan Fan
- Department of Pediatrics, The First Affiliated Hospital of China Medical University, Shenyang City, Liaoning, China
| | - Xinmiao Yu
- Department of Breast Surgery, The First Affiliated Hospital of China Medical University, Shenyang City, Liaoning, China
| | - Xiaoyun Mao
- Department of Breast Surgery, The First Affiliated Hospital of China Medical University, Shenyang City, Liaoning, China
| | - Feng Jin
- Department of Breast Surgery, The First Affiliated Hospital of China Medical University, Shenyang City, Liaoning, China
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7
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Wang ZN, Liu D, Yin B, Ju WY, Qiu HZ, Xiao Y, Chen YJ, Peng XZ, Lu CM. High expression of PTBP1 promote invasion of colorectal cancer by alternative splicing of cortactin. Oncotarget 2018; 8:36185-36202. [PMID: 28404950 PMCID: PMC5482648 DOI: 10.18632/oncotarget.15873] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 01/23/2017] [Indexed: 12/22/2022] Open
Abstract
Polypyrimidine tract-binding protein 1 (PTBP1) involving in almost all steps of mRNA regulation including alternative splicing metabolism during tumorigenesis due to its RNA-binding activity. Initially, we found that high expressed PTBP1 and poor prognosis was interrelated in colorectal cancer (CRC) patients with stages II and III CRC, which widely different in prognosis and treatment, by immunohistochemistry. PTBP1 was also upregulated in colon cancer cell lines. In our study, knockdown of PTBP1 by siRNA transfection decreased cell proliferation and invasion in vitro. Denovirus shRNA knockdown of PTBP1 inhibited colorectal cancer growth in vivo. Furthermore, PTBP1 regulates alternative splicing of many target genes involving in tumorgenesis in colon cancer cells. We confirmed that the splicing of cortactin exon 11 which was only contained in cortactin isoform-a, as a PTBP1 target. Knockdown of PTBP1 decreased the expression of cortactin isoform-a by exclusion of exon 11. Also the mRNA levels of PTBP1 and cortactin isoform-a were cooperatively expressed in colorectal cancer tissues. Knocking down cortactin isoform-a significantly decreased cell migration and invasion in colorectal cancer cells. Overexpression of cortactin isoform-a could rescue PTBP1-knockdown effect of cell motility. In summary the study revealed that PTBP1 facilitates colorectal cancer migration and invasion activities by inclusion of cortactin exon 11.
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Affiliation(s)
- Zhi-Na Wang
- Department of Gastroenteology and Hepatology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Dan Liu
- Department of Gastroenteology and Hepatology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China.,Department of Gastroenterology and Hepatology, The Second Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Bin Yin
- National Laboratory of Meidical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Wen-Yi Ju
- National Laboratory of Meidical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Hui-Zhong Qiu
- Department of General Surgery, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Yi Xiao
- Department of General Surgery, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Yuan-Jia Chen
- Department of Gastroenteology and Hepatology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Xiao-Zhong Peng
- National Laboratory of Meidical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Chong-Mei Lu
- Department of Gastroenteology and Hepatology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
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Kędzierska H, Piekiełko-Witkowska A. Splicing factors of SR and hnRNP families as regulators of apoptosis in cancer. Cancer Lett 2017; 396:53-65. [PMID: 28315432 DOI: 10.1016/j.canlet.2017.03.013] [Citation(s) in RCA: 146] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 03/08/2017] [Accepted: 03/08/2017] [Indexed: 12/19/2022]
Abstract
SR and hnRNP proteins were initially discovered as regulators of alternative splicing: the process of controlled removal of introns and selective joining of exons through which multiple transcripts and, subsequently, proteins can be expressed from a single gene. Alternative splicing affects genes involved in all crucial cellular processes, including apoptosis. During cancerogenesis impaired apoptotic control facilitates survival of cells bearing molecular aberrations, contributing to their unrestricted proliferation and chemoresistance. Apparently, SR and hnRNP proteins regulate all levels of expression of apoptotic genes, including transcription initiation and elongation, alternative splicing, mRNA stability, translation, and protein degradation. The frequently disturbed expressions of SR/hnRNP proteins in cancers lead to impaired functioning of target apoptotic genes, including regulators of the extrinsic (Fas, caspase-8, caspase-2, c-FLIP) and the intrinsic pathway (Apaf-1, caspase-9, ICAD), genes encoding Bcl-2 proteins, IAPs, and p53 tumor suppressor. Prototypical members of SR/hnRNP families, SRSF1 and hnRNP A1, promote synthesis of anti-apoptotic splice variants of Bcl-x and Mcl-1, which results in attenuation of programmed cell death in breast cancer and chronic myeloid leukemia. SR/hnRNP proteins significantly affect responses to chemotherapy, acting as mediators or modulators of drug-induced apoptosis. Aberrant expression of SRSF1 and hnRNP K can interfere with tumor responses to chemotherapy in pancreatic and liver cancers. Currently, a number of splicing factor inhibitors is being tested in pre-clinical and clinical trials. In this review we discuss recent findings on the role of SR and hnRNP proteins in apoptotic control in cancer cells as well as their significance in anticancer treatments.
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Affiliation(s)
- Hanna Kędzierska
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, ul. Marymoncka 99/103, 01-813 Warsaw, Poland
| | - Agnieszka Piekiełko-Witkowska
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, ul. Marymoncka 99/103, 01-813 Warsaw, Poland.
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9
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Silipo M, Gautrey H, Tyson-Capper A. Deregulation of splicing factors and breast cancer development. J Mol Cell Biol 2015; 7:388-401. [PMID: 25948865 DOI: 10.1093/jmcb/mjv027] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 02/24/2015] [Indexed: 11/13/2022] Open
Abstract
It is well known that many genes implicated in the development and progression of breast cancer undergo aberrant alternative splicing events to produce proteins with pro-cancer properties. These changes in alternative splicing can arise from mutations or single-nucleotide polymorphisms (SNPs) within the DNA sequences of cancer-related genes, which can strongly affect the activity of splicing factors and influence the splice site choice. However, it is important to note that absence of mutations is not sufficient to prevent misleading choices in splice site selection. There is now increasing evidence to demonstrate that the expression profile of ten splicing factors (including SRs and hnRNPs) and eight RNA-binding proteins changes in breast cancer cells compared with normal cells. These modifications strongly influence the alternative splicing pattern of many cancer-related genes despite the absence of any detrimental mutations within their DNA sequences. Thus, a comprehensive assessment of the splicing factor status in breast cancer is important to provide insights into the mechanisms that lead to breast cancer development and metastasis. Whilst most studies focus on mutations that affect alternative splicing in cancer-related genes, this review focuses on splicing factors and RNA-binding proteins that are themselves deregulated in breast cancer and implicated in cancer-related alternative splicing events.
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Affiliation(s)
- Marco Silipo
- Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Hannah Gautrey
- Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Alison Tyson-Capper
- Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
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10
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Jang HN, Lee M, Loh TJ, Choi SW, Oh HK, Moon H, Cho S, Hong SE, Kim DH, Sheng Z, Green MR, Park D, Zheng X, Shen H. Exon 9 skipping of apoptotic caspase-2 pre-mRNA is promoted by SRSF3 through interaction with exon 8. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1839:25-32. [PMID: 24321384 DOI: 10.1016/j.bbagrm.2013.11.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 11/14/2013] [Accepted: 11/26/2013] [Indexed: 01/24/2023]
Abstract
Alternative splicing plays an important role in gene expression by producing different proteins from a gene. Caspase-2 pre-mRNA produces anti-apoptotic Casp-2S and pro-apoptotic Casp-2L proteins through exon 9 inclusion or skipping. However, the molecular mechanisms of exon 9 splicing are not well understood. Here we show that knockdown of SRSF3 (also known as SRp20) with siRNA induced significant increase of endogenous exon 9 inclusion. In addition, overexpression of SRSF3 promoted exon 9 skipping. Thus we conclude that SRSF3 promotes exon 9 skipping. In order to understand the functional target of SRSF3 on caspase-2 pre-mRNA, we performed substitution and deletion mutagenesis on the potential SRSF3 binding sites that were predicted from previous reports. We demonstrate that substitution mutagenesis of the potential SRSF3 binding site on exon 8 severely disrupted the effects of SRSF3 on exon 9 skipping. Furthermore, with the approach of RNA pulldown and immunoblotting analysis we show that SRSF3 interacts with the potential SRSF3 binding RNA sequence on exon 8 but not with the mutant RNA sequence. In addition, we show that a deletion of 26nt RNA from 5' end of exon 8, a 33nt RNA from 3' end of exon 10 and a 2225nt RNA from intron 9 did not compromise the function of SRSF3 on exon 9 splicing. Therefore we conclude that SRSF3 promotes exon 9 skipping of caspase-2 pre-mRNA by interacting with exon 8. Our results reveal a novel mechanism of caspase-2 pre-mRNA splicing.
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Affiliation(s)
- Ha Na Jang
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Minho Lee
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Tiing Jen Loh
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Seung-Woo Choi
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Hyun Kyung Oh
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Heegyum Moon
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Sunghee Cho
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Seong-Eui Hong
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Do Han Kim
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Zhi Sheng
- Virginia Tech Carilion Research Institute, Roanoke, VA, 24016, USA; Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Michael R Green
- Howard Hughes Medical Institute and Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Daeho Park
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Xuexiu Zheng
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Haihong Shen
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
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11
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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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12
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Brynychová V, Hlaváč V, Ehrlichová M, Václavíková R, Pecha V, Trnková M, Wald M, Mrhalová M, Kubáčková K, Pikus T, Kodet R, Kovář J, Souček P. Importance of transcript levels of caspase-2 isoforms S and L for breast carcinoma progression. Future Oncol 2013; 9:427-38. [DOI: 10.2217/fon.12.200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aim: A role of caspase-2 in chemotherapy-induced apoptosis has been suggested. Our study aimed to evaluate the prognostic and predictive importance of caspase-2 isoforms in breast cancer patients. Materials & methods: Caspase-2L and -2S transcript levels were determined in paired tumor and non-malignant control tissues from 64 patients after neoadjuvant chemotherapy and 100 pretreatment patients (general set) by real-time PCR with absolute quantification. Results: Low but statistically significant upregulation of caspase-2L in tumor versus control tissues was observed in both sets. Significant associations of the levels of caspase-2L, -2S or S/L ratio with clinical prognostic factors were observed. However, none of these associations were confirmed in both sets. Levels of caspase-2 isoforms or the S/L ratio did not significantly associate with progression-free survival in the general set or with chemotherapy response in the neoadjuvant set. Conclusion: Our results suggest that the role of caspase-2 isoforms in the progression of breast cancer may considerably differ between pre- and post-chemotherapy patients.
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Affiliation(s)
- Veronika Brynychová
- Toxicogenomics Unit, Department of Toxicology & Safety, National Institute of Public Health, Srobarova 48, 100 42, Prague 10, Czech Republic
- Third Faculty of Medicine, Charles University, Prague 10, Czech Republic
| | - Viktor Hlaváč
- Toxicogenomics Unit, Department of Toxicology & Safety, National Institute of Public Health, Srobarova 48, 100 42, Prague 10, Czech Republic
- Third Faculty of Medicine, Charles University, Prague 10, Czech Republic
| | - Marie Ehrlichová
- Toxicogenomics Unit, Department of Toxicology & Safety, National Institute of Public Health, Srobarova 48, 100 42, Prague 10, Czech Republic
| | - Radka Václavíková
- Toxicogenomics Unit, Department of Toxicology & Safety, National Institute of Public Health, Srobarova 48, 100 42, Prague 10, Czech Republic
| | - Václav Pecha
- Department of Oncosurgery, MEDICON, Prague 4, Czech Republic
| | | | - Martin Wald
- Department of Surgery, 2nd Faculty of Medicine, Charles University in Prague & Motol University Hospital, Prague 5, Czech Republic
| | - Marcela Mrhalová
- Department of Pathology & Molecular Medicine, 2nd Faculty of Medicine, Charles University in Prague & Motol University Hospital, Prague 5, Czech Republic
| | - Kateřina Kubáčková
- Department of Oncology & Radiotherapy, 2nd Faculty of Medicine, Charles University in Prague & Motol University Hospital, Prague 5, Czech Republic
| | - Tomáš Pikus
- Department of Oncology & Radiotherapy, 2nd Faculty of Medicine, Charles University in Prague & Motol University Hospital, Prague 5, Czech Republic
| | - Roman Kodet
- Department of Pathology & Molecular Medicine, 2nd Faculty of Medicine, Charles University in Prague & Motol University Hospital, Prague 5, Czech Republic
| | - Jan Kovář
- Division of Cell & Molecular Biology, Third Faculty of Medicine, Charles University, Prague 10, Czech Republic
| | - Pavel Souček
- Toxicogenomics Unit, Department of Toxicology & Safety, National Institute of Public Health, Srobarova 48, 100 42, Prague 10, Czech Republic.
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13
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Ruirui K, Ray P, Yang M, Wen P, Zhu L, Liu J, Fushimi K, Kar A, Liu Y, He R, Kuo D, Wu JY. Alternative Pre-mRNA Splicing, Cell Death, and Cancer. Cancer Treat Res 2013; 158:181-212. [PMID: 24222359 DOI: 10.1007/978-3-642-31659-3_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Alternative splicing is one of the most powerful mechanisms for generating functionally distinct products from a single genetic loci and for fine-tuning gene activities at the post-transcriptional level. Alternative splicing plays important roles in regulating genes critical for cell death. These cell death genes encode death ligands, cell surface death receptors, intracellular death regulators, signal transduction molecules, and death executor enzymes such as caspases and nucleases. Alternative splicing of these genes often leads to the formation of functionally different products, some of which have antagonistic effects that are either cell death-promoting or cell death-preventing. Differential alternative splicing can affect expression, subcellular distribution, and functional activities of the gene products. Molecular defects in splicing regulation of cell death genes have been associated with cancer development and resistance to treatment. Studies using molecular, biochemical, and systems-based approaches have begun to reveal mechanisms underlying the regulation of alternative splicing of cell death genes. Systematic studies have begun to uncover the multi-level interconnected networks that regulate alternative splicing. A global picture of the complex mechanisms that regulate cell death genes at the pre-mRNA splicing level has thus begun to emerge.
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Affiliation(s)
- Kong Ruirui
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Science, Beijing, China
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14
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Wang Y, Xiao X, Zhang J, Choudhury R, Robertson A, Li K, Ma M, Burge CB, Wang Z. A complex network of factors with overlapping affinities represses splicing through intronic elements. Nat Struct Mol Biol 2012; 20:36-45. [PMID: 23241926 PMCID: PMC3537874 DOI: 10.1038/nsmb.2459] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Accepted: 11/05/2012] [Indexed: 12/11/2022]
Abstract
To better understand splicing regulation, we used a cell-based screen to identify ten diverse motifs that inhibit splicing from intron. Each motif was validated in another human cell type and gene context, and their presence correlated with in vivo splicing changes. All motifs exhibited exonic splicing enhancer or silencer activity, and grouping these motifs based on their distributions yielded clusters with distinct patterns of context-dependent activity. Candidate regulatory factors associated with each motif were identified, recovering 24 known and novel splicing regulators. Specific domains in selected factors were sufficient to confer ISS activity. Many factors bound multiple distinct motifs with similar affinity, and all motifs were recognized by multiple factors, revealing a complex, overlapping network of protein:RNA interactions. This arrangement enables individual cis-element to function differently in distinct cellular contexts depending on the spectrum of regulatory factors present.
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Affiliation(s)
- Yang Wang
- Department of Pharmacology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, USA
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15
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Lahijani MS, Farivar S, Amiri M, Sarhady M. Roles of Bax and Caspase2 genes in the apoptosis of fetal ovary germ cell induced by 4 (3H) quinazolinone-2-ethyl-2-phenyl ethyl. Mol Cell Toxicol 2012. [DOI: 10.1007/s13273-012-0037-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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16
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de Almagro MC, Mencia N, Noé V, Ciudad CJ. Coding polypurine hairpins cause target-induced cell death in breast cancer cells. Hum Gene Ther 2011; 22:451-63. [PMID: 20942657 DOI: 10.1089/hum.2010.102] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Polypurine reverse-Hoogsteen hairpins (PPRHs) are double-stranded DNA molecules formed by two polypurine stretches linked by a pentathymidine loop, with intramolecular reverse-Hoogsteen bonds that allow a hairpin structure. PPRHs bind to polypyrimidine targets by Watson-Crick bonds maintaining simultaneously a hairpin structure due to intramolecular Hoogsteen bonds. Previously, we described the ability of Template-PPRHs to decrease mRNA levels because these PPRHs target the template DNA strand interfering with the transcription process. Now, we designed Coding-PPRHs, a new type of PPRHs that directly target the pre-mRNA. The dihydrofolate reductase (dhfr) gene was selected as a target in breast cancer therapy. These PPRHs caused a high degree of cytotoxicity and a decrease in DHFR mRNA and protein levels, but by a different mechanism of action than Template-PPRHs. Coding-PPRHs interfere with the splicing process by competing with U2 auxiliary factor 65 for binding to the polypyrimidine target sequence, leading to a lower amount of mature mRNA. These new PPRHs showed high specificity as no off-target effects were found. The application of these molecules as therapeutic tools was tested in breast cancer cells resistant to methotrexate, obtaining a noticeable cytotoxicity even though the dhfr locus was amplified. Coding-PPRHs can be considered as new molecules to decrease gene expression at the mRNA level and an alternative to other antisense molecules.
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Affiliation(s)
- M Cristina de Almagro
- Department of Biochemistry and Molecular Biology, School of Pharmacy, University of Barcelona, E-08028 Barcelona, Spain
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17
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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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18
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Kitevska T, Spencer DMS, Hawkins CJ. Caspase-2: controversial killer or checkpoint controller? Apoptosis 2009; 14:829-48. [PMID: 19479377 DOI: 10.1007/s10495-009-0365-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The caspases are an evolutionarily conserved family of cysteine proteases, with essential roles in apoptosis or inflammation. Caspase-2 was the second caspase to be cloned and it resembles the prototypical nematode caspase CED-3 more closely than any other mammalian protein. An absence of caspase-2-specific reagents and the subtle phenotype of caspase-2-deficient mice have hampered definition of the physiological role of caspase-2 and identification of factors regulating its activity. Although some data implicate caspase-2 in apoptotic pathways, a link with apoptosis has been less firmly established for caspase-2 than for some other caspases. Emerging evidence suggests that caspase-2 regulates the cell cycle and may act as a tumour suppressor. This article critically reviews the current state of knowledge regarding the biochemistry and biology of this controversial caspase.
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Affiliation(s)
- Tanja Kitevska
- Department of Biochemistry, La Trobe University, Bundoora, VIC 3086, Australia
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19
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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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20
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Up-regulation of the proapoptotic caspase 2 splicing isoform by a candidate tumor suppressor, RBM5. Proc Natl Acad Sci U S A 2008; 105:15708-13. [PMID: 18840686 DOI: 10.1073/pnas.0805569105] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Similar to many genes involved in programmed cell death (PCD), the caspase 2 (casp-2) gene generates both proapoptotic and antiapoptotic isoforms by alternative splicing. Using a yeast RNA-protein interaction assay, we identified RBM5 (also known as LUCA-15) as a protein that binds to casp-2 pre-mRNA. In both transfected cells and in vitro splicing assay, RBM5 enhances the formation of proapoptotic Casp-2L. RBM5 binds to a U/C-rich sequence immediately upstream of the previously identified In100 splicing repressor element. Our mutagenesis experiments demonstrate that RBM5 binding to this intronic sequence regulates the ratio of proapoptotic/antiapoptotic casp-2 splicing isoforms, suggesting that casp-2 splicing regulation by RBM5 may contribute to its tumor suppressor activity. Our work has uncovered a player in casp-2 alternative splicing regulation and revealed a link between the alternative splicing regulator and the candidate tumor suppressor gene. Together with previous studies, our work suggests that splicing control of cell death genes may be an important aspect in tumorigenesis. Enhancing the expression or activities of splicing regulators that promote the production of proapoptotic splicing isoforms might provide a therapeutic approach to cancer.
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21
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Venables JP, Koh CS, Froehlich U, Lapointe E, Couture S, Inkel L, Bramard A, Paquet ER, Watier V, Durand M, Lucier JF, Gervais-Bird J, Tremblay K, Prinos P, Klinck R, Elela SA, Chabot B. Multiple and specific mRNA processing targets for the major human hnRNP proteins. Mol Cell Biol 2008; 28:6033-43. [PMID: 18644864 PMCID: PMC2547008 DOI: 10.1128/mcb.00726-08] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2008] [Revised: 05/30/2008] [Accepted: 07/11/2008] [Indexed: 12/22/2022] Open
Abstract
Alternative splicing is a key mechanism regulating gene expression, and it is often used to produce antagonistic activities particularly in apoptotic genes. Heterogeneous nuclear ribonucleoparticle (hnRNP) proteins form a family of RNA-binding proteins that coat nascent pre-mRNAs. Many but not all major hnRNP proteins have been shown to participate in splicing control. The range and specificity of hnRNP protein action remain poorly documented, even for those affecting splice site selection. We used RNA interference and a reverse transcription-PCR screening platform to examine the implications of 14 of the major hnRNP proteins in the splicing of 56 alternative splicing events in apoptotic genes. Out of this total of 784 alternative splicing reactions tested in three human cell lines, 31 responded similarly to a knockdown in at least two different cell lines. On the other hand, the impact of other hnRNP knockdowns was cell line specific. The broadest effects were obtained with hnRNP K and C, two proteins whose role in alternative splicing had not previously been firmly established. Different hnRNP proteins affected distinct sets of targets with little overlap even between closely related hnRNP proteins. Overall, our study highlights the potential contribution of all of these major hnRNP proteins in alternative splicing control and shows that the targets for individual hnRNP proteins can vary in different cellular contexts.
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Affiliation(s)
- Julian P Venables
- Département de Microbiologie et d'Infectiologie, Faculté de Médecine et des Sciences de la Santé, 3001, 12th Avenue Nord, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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22
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Wang C, Norton JT, Ghosh S, Kim J, Fushimi K, Wu JY, Stack MS, Huang S. Polypyrimidine tract-binding protein (PTB) differentially affects malignancy in a cell line-dependent manner. J Biol Chem 2008; 283:20277-87. [PMID: 18499661 DOI: 10.1074/jbc.m803682200] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RNA processing is altered during malignant transformation, and expression of the polypyrimidine tract-binding protein (PTB) is often increased in cancer cells. Although some data support that PTB promotes cancer, the functional contribution of PTB to the malignant phenotype remains to be clarified. Here we report that although PTB levels are generally increased in cancer cell lines from multiple origins and in endometrial adenocarcinoma tumors, there appears to be no correlation between PTB levels and disease severity or metastatic capacity. The three isoforms of PTB increase heterogeneously among different tumor cells. PTB knockdown in transformed cells by small interfering RNA decreases cellular growth in monolayer culture and to a greater extent in semi-solid media without inducing apoptosis. Down-regulation of PTB expression in a normal cell line reduces proliferation even more significantly. Reduction of PTB inhibits the invasive behavior of two cancer cell lines in Matrigel invasion assays but enhances the invasive behavior of another. At the molecular level, PTB in various cell lines differentially affects the alternative splicing pattern of the same substrates, such as caspase 2. Furthermore, overexpression of PTB does not enhance proliferation, anchorage-independent growth, or invasion in immortalized or normal cells. These data demonstrate that PTB is not oncogenic and can either promote or antagonize a malignant trait dependent upon the specific intra-cellular environment.
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Affiliation(s)
- Chen Wang
- Department of Cell and Molecular Biology, Feinberg School of Medicine of Northwestern University, Chicago, IL 60611, USA
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23
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Havlioglu N, Wang J, Fushimi K, Vibranovski MD, Kan Z, Gish W, Fedorov A, Long M, Wu JY. An intronic signal for alternative splicing in the human genome. PLoS One 2007; 2:e1246. [PMID: 18043753 PMCID: PMC2082412 DOI: 10.1371/journal.pone.0001246] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Accepted: 10/23/2007] [Indexed: 11/23/2022] Open
Abstract
An important level at which the expression of programmed cell death (PCD) genes is regulated is alternative splicing. Our previous work identified an intronic splicing regulatory element in caspase-2 (casp-2) gene. This 100-nucleotide intronic element, In100, consists of an upstream region containing a decoy 3' splice site and a downstream region containing binding sites for splicing repressor PTB. Based on the signal of In100 element in casp-2, we have detected the In100-like sequences as a family of sequence elements associated with alternative splicing in the human genome by using computational and experimental approaches. A survey of human genome reveals the presence of more than four thousand In100-like elements in 2757 genes. These In100-like elements tend to locate more frequent in intronic regions than exonic regions. EST analyses indicate that the presence of In100-like elements correlates with the skipping of their immediate upstream exons, with 526 genes showing exon skipping in such a manner. In addition, In100-like elements are found in several human caspase genes near exons encoding the caspase active domain. RT-PCR experiments show that these caspase genes indeed undergo alternative splicing in a pattern predicted to affect their functional activity. Together, these results suggest that the In100-like elements represent a family of intronic signals for alternative splicing in the human genome.
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Affiliation(s)
- Necat Havlioglu
- Department of Pathology, Saint Louis University, St. Louis, Missouri, United States of America
| | - Jun Wang
- Department of Ecology and Evolution, The University of Chicago, Chicago, Illinois, United States of America
| | - Kazuo Fushimi
- Department of Neurology, Lurie Comprehensive Cancer Center, Center for Genetic Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
| | - Maria D. Vibranovski
- Department of Ecology and Evolution, The University of Chicago, Chicago, Illinois, United States of America
| | - Zhengyan Kan
- Department of Genetics, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Warren Gish
- Department of Genetics, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Alexei Fedorov
- Department of Medicine and Program in Bioinformatics and Proteomics/Genomics, Medical University of Ohio, Toledo, Ohio, United States of America
| | - Manyuan Long
- Department of Ecology and Evolution, The University of Chicago, Chicago, Illinois, United States of America
| | - Jane Y. Wu
- Department of Neurology, Lurie Comprehensive Cancer Center, Center for Genetic Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
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24
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Saulière J, Sureau A, Expert-Bezançon A, Marie J. The polypyrimidine tract binding protein (PTB) represses splicing of exon 6B from the beta-tropomyosin pre-mRNA by directly interfering with the binding of the U2AF65 subunit. Mol Cell Biol 2006; 26:8755-69. [PMID: 16982681 PMCID: PMC1636812 DOI: 10.1128/mcb.00893-06] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Revised: 06/27/2006] [Accepted: 09/06/2006] [Indexed: 11/20/2022] Open
Abstract
Splicing of exon 6B from the beta-tropomyosin pre-mRNA is repressed in nonmuscle cells and myoblasts by a complex array of intronic elements surrounding the exon. In this study, we analyzed the proteins that mediate splicing repression of exon 6B through binding to the upstream element. We identified the polypyrimidine tract binding protein (PTB) as a component of complexes isolated from myoblasts that assemble onto the branch point region and the pyrimidine tract. In vitro splicing assays and PTB knockdown experiments by RNA interference demonstrated that PTB acts as a repressor of splicing of exon 6B. Using psoralen experiments, we showed that PTB acts at an early stage of spliceosome assembly by preventing the binding of U2 snRNA on the branch point. Using UV cross-linking and immunoprecipitation experiments with site-specific labeled RNA in PTB-depleted nuclear extracts, we found that the decrease in PTB was correlated with an increase in U2AF65. In addition, competition experiments showed that PTB is able to displace the binding of U2AF65 on the polypyrimidine tract. Our results strongly support a model whereby PTB competes with U2AF65 for binding to the polypyrimidine tract.
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Affiliation(s)
- Jérôme Saulière
- Centre de Génétique Moléculaire, UPR2167, CNRS, 1 avenue de la Terrasse, 91198 Gif sur Yvette, France
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25
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Cheung HC, Corley LJ, Fuller GN, McCutcheon IE, Cote GJ. Polypyrimidine tract binding protein and Notch1 are independently re-expressed in glioma. Mod Pathol 2006; 19:1034-41. [PMID: 16729017 DOI: 10.1038/modpathol.3800635] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Polypyrimidine tract binding protein (PTB) is expressed in developing mammalian astrocytes, absent in mature adult astrocytes, and aberrantly elevated in gliomas. It is unclear whether PTB is a coincidental marker of tumor progression or a significant mediator of tumorigenesis. In developing Drosophila, the absence of the PTB homolog, hephaestus, results in increased Notch activity. Since Notch is a well-known inducer of glial cell fate, we determined whether overexpression of PTB in glial cell tumors provides a selective growth advantage by inhibiting activated Notch (Notch1IC)-mediated differentiation. To do this, we performed an immunohistochemical analysis for expression of PTB, activated Notch1 (Notch1IC), Hes1 (a Notch target), and GFAP on an extensive human tissue microarray that included 246 gliomas, 10 gliosarcomas, and 10 normal brains. Statistically significant PTB overexpression was seen in all glioma grades, with the highest increase in grade IV tumors. Notch1IC was also abnormally expressed in gliomas except in a subset of grade IV tumors in which it was absent. This decrease in Notch1IC was not associated with increased PTB expression. We conclude that PTB, and Notch1 serve as independent and functionally unlinked markers of glioma progression.
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Affiliation(s)
- Hannah C Cheung
- Department of Endocrine Neoplasia and Hormonal Disorders, The University of Texas MD Anderson Cancer Center, Houston, 77030, USA
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26
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Scali C, Catteruccia F, Li Q, Crisanti A. Identification of sex-specific transcripts of the Anopheles gambiae doublesex gene. ACTA ACUST UNITED AC 2006; 208:3701-3709. [PMID: 16169947 PMCID: PMC1350936 DOI: 10.1242/jeb.01819] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The understanding of the molecular mechanisms of sex differentiation in the mosquito Anopheles gambiae could identify important candidate genes for inducing selective male sterility in transgenic lines or for sex-controlled expression of lethal genes. In many insects, doublesex (dsx) is the double-switch gene at the bottom of the somatic sex-determination cascade that determines the differentiation of sexually dimorphic traits. We report here on the identification of the dsx homologue in A. gambiae and on the characterization of its sex-specific transcripts. Agdsx consists of seven exons, distributed over an 85 kb region on chromosome 2R, which are sex-specifically spliced to produce the female and male AgdsxF and AgdsxM transcripts. AgdsxF contains a 795 bp ORF, coding for a protein of 265 amino acids, while AgdsxM comprises a much longer (1866 bp) ORF, coding for a 622 aa protein. Differences in the exon/intron organization suggest that Agdsx sex-specific splicing results from a different mechanism from Drosophila melanogaster dsx. These findings represent an important step towards the understanding of sex differentiation in Anopheles and will facilitate the use of gene transfer technologies to manipulate sex ratios for vector control programs based on the sterile insect technique.
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27
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Kwok JBJ, Hallupp M, Loy CT, Chan DKY, Woo J, Mellick GD, Buchanan DD, Silburn PA, Halliday GM, Schofield PR. GSK3B polymorphisms alter transcription and splicing in Parkinson's disease. Ann Neurol 2006; 58:829-39. [PMID: 16315267 DOI: 10.1002/ana.20691] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder characterized by a combination of motor symptoms. We identified two functional single nucleotide polymorphisms in the glycogen synthase kinase-3beta gene (GSK3B). A promoter single nucleotide polymorphism (rs334558) is associated with transcriptional strength in vitro in which the T allele has greater activity. An intronic single nucleotide polymorphism (rs6438552) regulates selection of splice acceptor sites in vitro. The T allele is associated with altered splicing in lymphocytes and increased levels of GSK3B transcripts that lack exons 9 and 11 (GSKDeltaexon9+11). Increased levels of GSKDeltaexon9+11 correlated with enhanced phosphorylation of its substrate, Tau. In a comparison of PD and control brains, there was increased in frequency of T allele (rs6438552) and corresponding increase in GSKDeltaexon9+11 and Tau phosphorylation in PD brains. Conditional logistic regression indicated gene-gene interaction between T/T genotype of rs334558 and H1/H1 haplotype of microtubule-associated protein Tau (MAPT) gene (p = 0.009). There was association between a haplotype (T alleles of both GSK3B polymorphisms) and disease risk after stratification by Tau haplotypes ((H1/H2+H2/H2 individuals: odds ratio, 1.64; p = 0.007; (H1/H1 individuals: odds ratio, 0.68; p < 0.001). Ours results suggest GSK3B polymorphisms alter transcription and splicing and interact with Tau haplotypes to modify disease risk in PD.
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Affiliation(s)
- John B J Kwok
- Garvan Institute of Medical Research, University of New South Wales, Barker Street, Randwick, Sydney NSW 2031, Australia
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Le Sommer C, Lesimple M, Mereau A, Menoret S, Allo MR, Hardy S. PTB regulates the processing of a 3'-terminal exon by repressing both splicing and polyadenylation. Mol Cell Biol 2005; 25:9595-607. [PMID: 16227608 PMCID: PMC1265821 DOI: 10.1128/mcb.25.21.9595-9607.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Revised: 07/05/2005] [Accepted: 08/01/2005] [Indexed: 11/20/2022] Open
Abstract
The polypyrimidine tract binding protein (PTB) has been described as a global repressor of regulated exons. To investigate PTB functions in a physiological context, we used a combination of morpholino-mediated knockdown and transgenic overexpression strategies in Xenopus laevis embryos. We show that embryonic endoderm and skin deficient in PTB displayed a switch of the alpha-tropomyosin pre-mRNA 3' end processing to the somite-specific pattern that results from the utilization of an upstream 3'-terminal exon designed exon 9A9'. Conversely, somitic targeted overexpression of PTB resulted in the repression of the somite-specific exon 9A9' and a switch towards the nonmuscle pattern. These results validate PTB as a key physiological regulator of the 3' end processing of the alpha-tropomyosin pre-mRNA. Moreover, using a minigene strategy in the Xenopus oocyte, we show that in addition to repressing the splicing of exon 9A9', PTB regulates the cleavage/polyadenylation of this 3'-terminal exon.
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Affiliation(s)
- Caroline Le Sommer
- UMR 6061 CNRS-Université de Rennes 1, IFR 140 Faculté de Médecine, CS 34317, 35043 Rennes Cedex, France
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29
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Matlin AJ, Clark F, Smith CWJ. Understanding alternative splicing: towards a cellular code. Nat Rev Mol Cell Biol 2005; 6:386-98. [PMID: 15956978 DOI: 10.1038/nrm1645] [Citation(s) in RCA: 930] [Impact Index Per Article: 48.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In violation of the 'one gene, one polypeptide' rule, alternative splicing allows individual genes to produce multiple protein isoforms - thereby playing a central part in generating complex proteomes. Alternative splicing also has a largely hidden function in quantitative gene control, by targeting RNAs for nonsense-mediated decay. Traditional gene-by-gene investigations of alternative splicing mechanisms are now being complemented by global approaches. These promise to reveal details of the nature and operation of cellular codes that are constituted by combinations of regulatory elements in pre-mRNA substrates and by cellular complements of splicing regulators, which together determine regulated splicing pathways.
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Affiliation(s)
- Arianne J Matlin
- Department of Biochemistry, 80 Tennis Court Road, University of Cambridge, CB2 1GA, UK
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30
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Schwerk C, Schulze-Osthoff K. Regulation of Apoptosis by Alternative Pre-mRNA Splicing. Mol Cell 2005; 19:1-13. [PMID: 15989960 DOI: 10.1016/j.molcel.2005.05.026] [Citation(s) in RCA: 417] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Revised: 02/22/2005] [Accepted: 05/05/2005] [Indexed: 12/15/2022]
Abstract
Apoptosis, a phenomenon that allows the regulated destruction and disposal of damaged or unwanted cells, is common to many cellular processes in multicellular organisms. In humans more than 200 proteins are involved in apoptosis, many of which are dysregulated or defective in human diseases including cancer. A large number of apoptotic factors are regulated via alternative splicing, a process that allows for the production of discrete protein isoforms with often distinct functions from a common mRNA precursor. The abundance of apoptosis genes that are alternatively spliced and the often antagonistic roles of the generated protein isoforms strongly imply that alternative splicing is a crucial mechanism for regulating life and death decisions. Importantly, modulation of isoform production of cell death proteins via pharmaceutical manipulation of alternative splicing may open up new therapeutic avenues for the treatment of disease.
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Affiliation(s)
- Christian Schwerk
- Institute of Molecular Medicine, University of Düsseldorf, Building 23.12, Universitätsstrasse 1, 40225 Düsseldorf, Germany
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31
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Jia Y, del Rio HS, Robbins AL, Louzada ES. Cloning and sequence analysis of a low temperature-induced gene from trifoliate orange with unusual pre-mRNA processing. PLANT CELL REPORTS 2004; 23:159-66. [PMID: 15138696 DOI: 10.1007/s00299-004-0805-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2003] [Revised: 04/12/2004] [Accepted: 04/12/2004] [Indexed: 05/23/2023]
Abstract
Exposure of cold-hardy Rubidoux trifoliate orange [Poncirus trifoliata (L) Raf.] plants to temperatures from 28 degrees C to -5 degrees C enabled us to isolate and characterize a novel citrus low-temperature gene (CLT) with two transcripts, called CLTa and CLTb, from leaves and stems. CLTa was produced when plants were subjected to low temperatures (starting at 10 degrees C), while CLTb was constitutively expressed. Both CLTa and CLTb have the same open reading frame (ORF) of 165 nucleotides and encode a small (54 deduced amino acid) protein. However, CLTa has an additional 98 nucleotides in the 3'-untranslated region (UTR) that are absent in CLTb. Expression analysis using relative quantitative RT-PCR demonstrated that CLTa is expressed exclusively at low temperatures, while CLTb is expressed constitutively (expression verified from 33 degrees C to -5 degrees C). A GenBank database search identified 61 nucleotides inside of the ORF that are highly similar to low-temperature-responsive genes from Arabidopsis thaliana and Solanum tuberosum. The deduced amino acid sequence revealed similarity with low-temperature-responsive proteins from A. thaliana, Oryza sativa, and S. tuberosum of 77%, 81%, and 73.9%, respectively. A genomic clone was isolated, and the genome organization revealed the presence of three exons and two introns, the second of which is in the 3' UTR and participates in alternative 3' splice site selection. One of the 3' splice sites of the second intron was located immediately before the additional 98-bp non-coding fragment of CLTa, and the second at the very end of the 98-bp fragment. Additionally, the presence of the tetranucleotides TCTT and TTCT, which are involved in the regulation of transcript processing in animals and possibly also active in peach, was found in this intron. Competition for splicing sites on the pre-mRNA in the spliceosome, which is induced by low temperature, may be involved in the production of the two transcripts of the CLT gene.
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MESH Headings
- Acclimatization/genetics
- Alternative Splicing/genetics
- Arabidopsis Proteins/genetics
- Arabidopsis Proteins/metabolism
- Cloning, Molecular
- Cold Temperature
- DNA, Complementary/analysis
- DNA, Complementary/genetics
- Exons/genetics
- Gene Expression Regulation, Plant/genetics
- Gene Expression Regulation, Plant/physiology
- Genes, Plant/genetics
- Genome, Plant
- Introns/genetics
- Molecular Sequence Data
- Molecular Weight
- Open Reading Frames/genetics
- Oryza/genetics
- Oryza/metabolism
- Plant Proteins/biosynthesis
- Plant Proteins/genetics
- Plant Proteins/isolation & purification
- Poncirus/genetics
- Poncirus/metabolism
- RNA Precursors/genetics
- RNA Precursors/metabolism
- RNA Processing, Post-Transcriptional
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
- Solanum tuberosum/genetics
- Solanum tuberosum/metabolism
- Spliceosomes/genetics
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Affiliation(s)
- Y Jia
- Citrus Center, Texas A&M University-Kingsville, 312 N International Blvd, 78596 Weslaco, TX 78596, USA
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He X, Ee PLR, Coon JS, Beck WT. Alternative Splicing of theMultidrug Resistance Protein 1/ATP Binding Cassette Transporter SubfamilyGene in Ovarian Cancer Creates Functional Splice Variants and Is Associated with Increased Expression of the Splicing Factors PTB and SRp20. Clin Cancer Res 2004; 10:4652-60. [PMID: 15269137 DOI: 10.1158/1078-0432.ccr-03-0439] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Overexpression of multidrug resistance protein 1 (MRP1) confers resistance to a range of chemotherapeutic agents in cell lines and could be involved in clinical drug resistance of some tumor types also. We examined MRP1 expression in a small series of untreated human ovarian tumors and matched normal tissues. EXPERIMENTAL DESIGN We analyzed ten pairs of snap-frozen ovarian tumor and matched normal total ovarian tissues from the same patients for expression of MRP1 by reverse transcription-PCR. Amplified PCR products were sequenced to reveal splicing events of MRP1. MRP1 splice variants were expressed as enhanced green fluorescent fusion proteins in HEK293T cells to demonstrate their localization in the cell and their activity in conferring resistance to doxorubicin. The expression of splicing factors PTB and SRp20 was examined by Western blot. RESULTS MRP1 was expressed in all 10 of the pairs of specimens. Multiple MRP1 cDNA fragments of various sizes were amplified between exons 10 and 19. Of interest, more MRP1 cDNA fragments were detected in ovarian tumors than in matched normal tissues in 9 of 10 pairs. We identified 10 splicing forms between exons 10 and 19 of the MRP1 gene with exon skipping ranging from 1 to 7. Amplification of the entire coding region of MRP1 from 1 ovarian tumor revealed >20 splice variants. We found whole and partial exon skipping and partial intron inclusion in these splice variants. We expressed 3 of these MRP1 splice variants in HEK293T cells and found that they appeared to localize to the plasma membrane and were functional in conferring resistance to doxorubicin. In addition, we identified a few nucleotide variations in this gene. To understand the basis for increased splice variants in the tumors, we examined splicing factor expression in these tissues. Western blot analysis revealed that two splicing factors, PTB and SRp20, were overexpressed in most ovarian tumors compared with their matched normal ovarian tissues. Importantly, overexpression of both of these splicing factors was associated with the increased number of MRP1 splicing forms in the ovarian tissues. CONCLUSION The MRP1 gene undergoes alternative splicing at a higher frequency in ovarian tumors than in matched normal tissues. Some of these splice variants confer resistance to doxorubicin. Expression of splicing factors PTB and SRp20 is strongly associated with the alternative splicing of the MRP1 gene.
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Affiliation(s)
- Xiaolong He
- Department of Biopharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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33
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Hamon S, Le Sommer C, Mereau A, Allo MR, Hardy S. Polypyrimidine tract-binding protein is involved in vivo in repression of a composite internal/3' -terminal exon of the Xenopus alpha-tropomyosin Pre-mRNA. J Biol Chem 2004; 279:22166-75. [PMID: 15010470 DOI: 10.1074/jbc.m313809200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The Xenopus alpha(fast)-tropomyosin gene contains, at its 3' -end, a composite internal/3' -terminal exon (exon 9A9'), which is subjected to three different patterns of splicing according to the cell type. Exon 9A9' is included as a terminal exon in the myotome and as an internal exon in adult striated muscles, whereas it is skipped in nonmuscle cells. We have developed an in vivo model based on transient expression of minigenes encompassing the regulated exon 9A9' in Xenopus oocytes and embryos. We first show that the different alpha-tropomyosin minigenes recapitulate the splicing pattern of the endogenous gene and constitute valuable tools to seek regulatory sequences involved in exon 9A9' usage. A mutational analysis led to the identification of an intronic element that is involved in the repression of exon 9A9' in nonmuscle cells. This element harbors four polypyrimidine track-binding protein (PTB) binding sites that are essential for the repression of exon 9A9'. We show using UV cross-linking and immunoprecipitation experiments that Xenopus PTB (XPTB) interacts with these PTB binding sites. Finally, we show that depletion of endogenous XPTB in Xenopus embryos using a morpholinobased translational inhibition strategy resulted in exon 9A9' inclusion in embryonic epidermal cells. These results demonstrate that XPTB is required in vivo to repress the terminal exon 9A9' and suggest that PTB could be a major actor in the repression of regulated 3' -terminal exon.
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Affiliation(s)
- Sandra Hamon
- UMR 6061 CNRS, Université de Rennes 1, Faculté de Médecine, 35043 Rennes cedex, France
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34
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Wang J, Gao QS, Wang Y, Lafyatis R, Stamm S, Andreadis A. Tau exon 10, whose missplicing causes frontotemporal dementia, is regulated by an intricate interplay of cis elements and trans factors. J Neurochem 2004; 88:1078-90. [PMID: 15009664 DOI: 10.1046/j.1471-4159.2003.02232.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Tau is a microtubule-associated protein whose transcript undergoes complex regulated splicing in the mammalian nervous system. In humans, exon 10 of the gene is an alternatively spliced cassette which is adult-specific and which codes for a microtubule binding domain. Mutations that affect splicing of exon 10 have been shown to cause inherited frontotemporal dementia (FTDP). In this study, we reconstituted naturally occurring exon 10 FTDP mutants and classified their effects on its splicing. We also carried out a comprehensive survey of the influence of splicing regulators on exon 10 inclusion and tentatively identified the site of action for several of these factors. Lastly, we identified the domains of regulators SWAP and hnRNPG, which are required for regulation of exon 10 splicing.
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Affiliation(s)
- Junning Wang
- Shriver Center at UMMS, Waltham, Massachusetts 02452, USA
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35
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McCutcheon IE, Hentschel SJ, Fuller GN, Jin W, Cote GJ. Expression of the splicing regulator polypyrimidine tract-binding protein in normal and neoplastic brain. Neuro Oncol 2004; 6:9-14. [PMID: 14769134 PMCID: PMC1871971 DOI: 10.1215/s1152851703000279] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Polypyrimidine tract-binding protein (PTB) is a nuclear factor that binds to the polypyrimidine tract of pre-mRNA introns, where it is associated with negative regulation of RNA splicing and with exon silencing. We have previously demonstrated that PTB expression is increased during glial cell transformation and that this increase correlates brain and in glial and neuronal tumors. Paraffin sections were stained by using a primary monoclonal antibody against PTB. Tissues that were analyzed included normal with changes in the RNA splicing of the fibroblast growth factor receptor 1. In this paper we examine the specific cellular distribution of PTB expression in normal brain (n = 2) and tumors of various types (low-grade astrocytoma, n = 2; anaplastic astrocytoma, n = 2; glioblastoma, n = 4; medulloblastoma, n = 4; central neurocytoma, n = 2; dysplastic gangliocytoma, n = 1; ganglioglioma, n = 1; paraganglioma, n = 1). In glial cell populations the majority of astrocytes and oligodendrocytes were negative, but occasional positively staining cells were observed. Strongly positive PTB staining was observed in ependymocytes, choroid plexus epithelium, microglia, arachnoid membrane, and adenohypophysis, and weak staining was found in the neurohypophysis. In all cases vascular endothelium and smooth muscle stained strongly. In tumor samples, intense positive nuclear staining was observed in transformed cells of low-grade astrocytoma, anaplastic astrocytoma, glioblastoma multiforme, medulloblastoma, paraganglioma, and the glial population of both ganglioglioma and dysplastic gangliocytoma (the neuronal cells of both were negative). In medulloblastoma, neoplastic neuronal cells were positive, as were other cell lineages. In normal brain, all neuron populations and pineocytes were negative for PTB. We conclude that although glial cells show derepression of PTB expression, a similar mechanism is absent in both nonneoplastic neurons and in most neuronally derived tumor cells. Strong upregulation of PTB expression in tumor cells of glial or primitive neuroectodermal origin suggests involvement of this protein in cellular transformation. Whether PTB affects splicing of RNAs critical to cellular transformation or proliferation is an important question for future research.
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Affiliation(s)
- Ian E McCutcheon
- Department of Neurosurgery, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
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36
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Banerjee H, Rahn A, Gawande B, Guth S, Valcarcel J, Singh R. The conserved RNA recognition motif 3 of U2 snRNA auxiliary factor (U2AF 65) is essential in vivo but dispensable for activity in vitro. RNA (NEW YORK, N.Y.) 2004; 10:240-53. [PMID: 14730023 PMCID: PMC1370536 DOI: 10.1261/rna.5153204] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Accepted: 10/13/2003] [Indexed: 05/09/2023]
Abstract
The general splicing factor U2AF(65) recognizes the polypyrimidine tract (Py tract) that precedes 3' splice sites and has three RNA recognition motifs (RRMs). The C-terminal RRM (RRM3), which is highly conserved, has been proposed to contribute to Py-tract binding and establish protein-protein contacts with splicing factors mBBP/SF1 and SAP155. Unexpectedly, we find that the human RRM3 domain is dispensable for U2AF(65) activity in vitro. However, it has an essential function in Schizosaccharomyces pombe distinct from binding to the Py tract or to mBBP/SF1 and SAP155. First, deletion of RRM3 from the human protein has no effect on Py-tract binding. Second, RRM123 and RRM12 select similar sequences from a random pool of RNA. Third, deletion of RRM3 has no effect on the splicing activity of U2AF(65) in vitro. However, deletion of the RRM3 domain of S. pombe U2AF(59) abolishes U2AF function in vivo. In addition, certain amino acid substitutions on the four-stranded beta-sheet surface of RRM3 compromise U2AF function in vivo without affecting binding to mBBP/SF1 or SAP155 in vitro. We propose that RRM3 has an unrecognized function that is possibly relevant for the splicing of only a subset of cellular introns. We discuss the implications of these observations on previous models of U2AF function.
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Affiliation(s)
- Hiren Banerjee
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, Boulder, Colorado 80309, USA
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37
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Solier S, Lansiaux A, Logette E, Wu J, Soret J, Tazi J, Bailly C, Desoche L, Solary E, Corcos L. Topoisomerase I and II Inhibitors Control Caspase-2 Pre-Messenger RNA Splicing in Human Cells. Mol Cancer Res 2004. [DOI: 10.1158/1541-7786.53.2.1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
We have recently shown that the topoisomerase II inhibitor, etoposide (VP16), could trigger caspase-2 pre-mRNA splicing in human leukemic cell lines. This leads to increased inclusion of exon 9, which is specifically inserted into the short caspase-2S isoform mRNA and absent from the long caspase-2L isoform mRNA. One of the consequences of this alternative splicing is a decrease in the total amount of the mature form of caspase-2L mRNA and protein. In this study, we analyzed the effects of several representative molecules of various classes of cytotoxic agents on caspase-2 pre-mRNA splicing in both U937 leukemic cells and in HeLa cervix carcinoma cells. Very strikingly, both topoisomerase I (camptothecin and homocamptothecin derivatives) and II (VP16, amsacrine, doxorubicin, mitoxantrone) inhibitors induced exon 9 inclusion. DNA intercalating glycosyl indolocarbazole derivatives as well as DNA alkylating agents, such as cisplatin and melphalan, antimetabolites like 5-fluorouracil, and mitotic spindle poisons like vinblastine had no effect. Therefore, both classes of DNA topoisomerases can control pre-mRNA splicing of the caspase-2 transcript. In addition, the splicing reaction brought about by camptothecin was hampered in human CEM/C2 and in murine P388-45R leukemic deficient in topoisomerase I activity. Conversely, VP16 did not trigger caspase-2 alternative splicing in human HL60/MX2 leukemic cells harboring a mutant topoisomerase II. Minigene transfection analysis revealed that topoisomerase inhibitors did not change the splicing profile when cis-acting elements in intron-9, reported to control exon 9 inclusion independently of drug treatment, were removed. Rather, our experiments suggest that exon 9 inclusion induced by topoisomerase inhibitors reflects the activity exerted by topoisomerase I or II on proteins that control splicing reactions, or their direct involvement in pre-mRNA splicing.
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Affiliation(s)
- Stéphanie Solier
- 1Inserm U517, Faculty of Medicine, Dijon, France
- 2Service d' Hématologie Clinique, CHRU le Bocage, Dijon, France
| | - Amélie Lansiaux
- 3Inserm U524, Institut de Recherches sur le Cancer de Lille, Lille Cedex, France
| | | | - Jane Wu
- 4Department of Pediatrics, Washington University School of Medicine, McDonnell Pediatric Research Building Rm 3107, St. Louis, MO; and
| | - Johann Soret
- 5Metazoan Messenger RNAs Metabolism, IGM, UMR 5535 CNRS, Montpellier, France
| | - Jamal Tazi
- 5Metazoan Messenger RNAs Metabolism, IGM, UMR 5535 CNRS, Montpellier, France
| | - Christian Bailly
- 3Inserm U524, Institut de Recherches sur le Cancer de Lille, Lille Cedex, France
| | | | - Eric Solary
- 1Inserm U517, Faculty of Medicine, Dijon, France
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38
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Villemaire J, Dion I, Elela SA, Chabot B. Reprogramming alternative pre-messenger RNA splicing through the use of protein-binding antisense oligonucleotides. J Biol Chem 2003; 278:50031-9. [PMID: 14522969 DOI: 10.1074/jbc.m308897200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alternative pre-messenger RNA splicing is a major contributor to proteomic diversity in higher eukaryotes and represents a key step in the control of protein function in a large variety of biological systems. As a means of artificially altering splice site choice, we have investigated the impact of positioning proteins in the vicinity of 5' splice sites. We find that a recombinant GST-MS2 protein interferes with 5' splice site use, most efficiently when it binds upstream of that site. To broaden the use of proteins as steric inhibitors of splicing, we have tested the activity of antisense oligonucleotides carrying binding sites for the heterogeneous nuclear ribonucleoprotein A1/A2 proteins. In a HeLa cell extract, tailed oligonucleotides complementary to exonic sequences elicit strong shifts in 5' splice site selection. In four different human cell lines, an interfering oligonucleotide carrying A1/A2 binding sites also shifted the alternative splicing of the Bcl-x pre-mRNA more efficiently than oligonucleotides acting through duplex formation only. The use of protein-binding oligonucleotides that interfere with U1 small nuclear ribonucleoprotein binding therefore represents a novel and powerful approach to control splice site selection in cells.
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Affiliation(s)
- Jonathan Villemaire
- Département de microbiologie et d'infectiologie, RNA/RNP Group, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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Li K, Arikan MC, Andreadis A. Modulation of the membrane-binding domain of tau protein: splicing regulation of exon 2. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2003; 116:94-105. [PMID: 12941465 DOI: 10.1016/s0169-328x(03)00259-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Tau is a microtubule-associated protein whose transcript undergoes complex regulated splicing in the mammalian nervous system. The N-terminal domain of the protein interacts with the axonal membrane, and is modulated by regulated inclusion of exons 2 and 3. These two tau exons are alternatively spliced cassettes, in which exon 3 never appears independently of exon 2. Previous work with tau minigene constructs indicated that exon 2 resembles a constitutive exon. In this study, we show that exon 2 is regulated by a combination of exonic and intronic enhancers and silencers. Furthermore, we demonstrate that known splicing regulators affect the ratio of exon 2 isoforms. Lastly, we tentatively pinpoint the site of action of several splicing factors which regulate tau exon 2.
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Affiliation(s)
- Karen Li
- Division of Neurobiology of Developmental Disorders, Shriver Center for Mental Retardation at UMMS, Waltham, MA 02452, USA
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40
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Lu A, Tang Y, Ran R, Clark JF, Aronow BJ, Sharp FR. Genomics of the periinfarction cortex after focal cerebral ischemia. J Cereb Blood Flow Metab 2003; 23:786-810. [PMID: 12843783 DOI: 10.1097/01.wcb.0000062340.80057.06] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Understanding transcriptional changes in brain after ischemia may provide therapeutic targets for treating stroke and promoting recovery. To study these changes on a genomic scale, oligonucleotide arrays were used to assess RNA samples from periinfarction cortex of adult Sprague-Dawley rats 24 h after permanent middle cerebral artery occlusions. Of the 328 regulated transcripts in ischemia compared with sham-operated animals, 264 were upregulated, 64 were downregulated, and 163 (49.7%) had not been reported in stroke. Of the functional groups modulated by ischemia: G-protein-related genes were the least reported; and cytokines, chemokines, stress proteins, and cell adhesion and immune molecules were the most highly expressed. Quantitative reverse transcription polymerase chain reaction of 20 selected genes at 2, 4, and 24 h after ischemia showed early upregulated genes (2 h) including Narp, Rad, G33A, HYCP2, Pim-3, Cpg21, JAK2, CELF, Tenascin, and DAF. Late upregulated genes (24 h) included Cathepsin C, Cip-26, Cystatin B, PHAS-I, TBFII, Spr, PRG1, and LPS-binding protein. Glycerol 3-phosphate dehydrogenase, which is involved in mitochondrial reoxidation of glycolysis derived NADH, was regulated more than 60-fold. Plasticity-related transcripts were regulated, including Narp, agrin, and Cpg21. A newly reported lung pathway was also regulated in ischemic brain: C/EBP induction of Egr-1 (NGFI-A) with downstream induction of PAI-1, VEGF, ICAM, IL1, and MIP1. Genes regulated acutely after stroke may modulate cell survival and death; also, late regulated genes may be related to tissue repair and functional recovery.
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Affiliation(s)
- Aigang Lu
- Department of Neurology, University of Cincinnati, Cincinnati, Ohio 45267, USA
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Wu JY, Tang H, Havlioglu N. Alternative pre-mRNA splicing and regulation of programmed cell death. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2003; 31:153-85. [PMID: 12494766 DOI: 10.1007/978-3-662-09728-1_6] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- J Y Wu
- Department of Pediatrics and Department of Molecular Biology and Pharmacology, MPRB Rm3107, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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42
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Miriami E, Margalit H, Sperling R. Conserved sequence elements associated with exon skipping. Nucleic Acids Res 2003; 31:1974-83. [PMID: 12655015 PMCID: PMC152795 DOI: 10.1093/nar/gkg279] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2002] [Revised: 01/28/2003] [Accepted: 01/28/2003] [Indexed: 11/12/2022] Open
Abstract
One of the major forms of alternative splicing, which generates multiple mRNA isoforms differing in the precise combinations of their exon sequences, is exon skipping. While in constitutive splicing all exons are included, in the skipped pattern(s) one or more exons are skipped. The regulation of this process is still not well understood; so far, cis- regulatory elements (such as exonic splicing enhancers) were identified in individual cases. We therefore set to investigate the possibility that exon skipping is controlled by sequences in the adjacent introns. We employed a computer analysis on 54 sequences documented as undergoing exon skipping, and identified two motifs both in the upstream and downstream introns of the skipped exons. One motif is highly enriched in pyrimidines (mostly C residues), and the other motif is highly enriched in purines (mostly G residues). The two motifs differ from the known cis-elements present at the 5' and 3' splice site. Interestingly, the two motifs are complementary, and their relative positional order is conserved in the flanking introns. These suggest that base pairing interactions can underlie a mechanism that involves secondary structure to regulate exon skipping. Remarkably, the two motifs are conserved in mouse orthologous genes that undergo exon skipping.
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Affiliation(s)
- Elana Miriami
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, The Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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43
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Martinet W, Knaapen MWM, De Meyer GRY, Herman AG, Kockx MM. Overexpression of the anti-apoptotic caspase-2 short isoform in macrophage-derived foam cells of human atherosclerotic plaques. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 162:731-6. [PMID: 12598307 PMCID: PMC1868102 DOI: 10.1016/s0002-9440(10)63869-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Apoptosis or programmed cell death is a cellular suicide mechanism that frequently occurs in advanced human atherosclerotic plaques. Caspases, a family of cysteine proteases, have been identified as important effectors of the death machinery. In this study, we report strong caspase-2 immunoreactivity in foam cells of macrophage-origin around the necrotic core of advanced human atherosclerotic plaques. In contrast, smooth muscle cells (SMCs) and macrophages in the fibrous cap as well as endothelial cells, medial SMCs, and SMCs from mammary arteries are negative for caspase-2. Caspase-2-positive macrophages were isolated from human plaques by laser capture microdissection and were then analyzed by Western blotting. A single band of approximately 35 kd corresponding with the precursor of the short, anti-apoptotic isoform of caspase-2 (caspase-2S) could be identified. Treatment of human U937 macrophages with the DNA strand-breaking agents etoposide or camptothecin stimulated caspase-2S expression. Since atherosclerotic plaques contain a high number of DNA strand breaks, our results provide evidence for a survival factor in macrophage-derived foam cells of human atherosclerotic plaques that might be up-regulated in response to DNA damage.
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Affiliation(s)
- Wim Martinet
- Division of Pharmacology, University of Antwerp, Wilrijk, Belgium
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Logette E, Wotawa A, Solier S, Desoche L, Solary E, Corcos L. The human caspase-2 gene: alternative promoters, pre-mRNA splicing and AUG usage direct isoform-specific expression. Oncogene 2003; 22:935-46. [PMID: 12584573 DOI: 10.1038/sj.onc.1206172] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Caspases have been shown to play important roles in apoptotic cell death, cytokine maturation and cell differentiation. However, the transcriptional regulation of the corresponding CASP genes remains poorly known. We describe a 5.1 kb fragment located upstream of the first translated exon in the human CASP-2 gene, which is known to encode caspase-2L and -2S protein isoforms. Transient transfection experiments, together with transcription start site mapping and transcript analysis, demonstrate that each caspase mRNA is initiated from separate promoter regions, and produced from alternative splicing events in these regions. The CASP-2L promoter is much stronger than the CASP-2S promoter, in good agreement with the respective transcript levels of the two caspases. In addition, several in-frame translational start sites can be identified for each isoform, one of which is common to both, present in the second common exon, and used efficiently. Surprisingly, the short isoform may also be initiated at a downstream AUG codon within the same exon. Thus, promoter strength, alternative transcriptional initiation and 5'-splicing events regulate the expression of the main caspase-2 isoforms that may be translated from alternative translation initiation codons.
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45
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Dansereau DA, Lunke MD, Finkielsztein A, Russell MA, Brook WJ. Hephaestus encodes a polypyrimidine tract binding protein that regulates Notch signalling during wing development in Drosophila melanogaster. Development 2002; 129:5553-66. [PMID: 12421697 DOI: 10.1242/dev.00153] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We describe the role of the Drosophila melanogaster hephaestus gene in wing development. We have identified several hephaestus mutations that map to a gene encoding a predicted RNA-binding protein highly related to human polypyrimidine tract binding protein and Xenopus laevis 60 kDa Vg1 mRNA-binding protein. Polypyrimidine tract binding proteins play diverse roles in RNA processing including the subcellular localization of mRNAs, translational control, internal ribosome entry site use, and the regulation of alternate exon selection. The analysis of gene expression in imaginal discs and adult cuticle of genetic mosaic animals supports a role for hephaestus in Notch signalling. Somatic clones lacking hephaestus express the Notch target genes wingless and cut, induce ectopic wing margin in adjacent wild-type tissue, inhibit wing-vein formation and have increased levels of Notch intracellular domain immunoreactivity. Clones mutant for both Delta and hephaestus have the characteristic loss-of-function thick vein phenotype of DELTA: These results lead to the hypothesis that hephaestus is required to attenuate Notch activity following its activation by Delta. This is the first genetic analysis of polypyrimidine tract binding protein function in any organism and the first evidence that such proteins may be involved in the Notch signalling pathway.
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Affiliation(s)
- David A Dansereau
- Genes and Development Research Group, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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46
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Wotawa A, Solier S, Logette E, Solary E, Corcos L. Differential influence of etoposide on two caspase-2 mRNA isoforms in leukemic cells. Cancer Lett 2002; 185:181-9. [PMID: 12169392 DOI: 10.1016/s0304-3835(02)00287-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Etoposide (VP-16) is an anticancer agent that induces apoptosis in human leukemic cell lines such as U937 and HL60. We performed RNase protection assays, with two distinct cRNA panels covering most of caspase and BCL-2-related genes, using total RNA from cell lines exposed to various concentrations of the drug. Our results show that VP-16 down-regulates expression of most surveyed genes with the noticeable exception of casp-2S mRNA that is up regulated whereas casp-2L mRNA is decreased. Since these mRNAs are produced by the alternative splicing of exon 9, we devised a reverse transcriptase-polymerase chain reaction method using primers from exons 8 and 10 to demonstrate that VP-16 stimulates the production of exon 9-containing sequences, irrespective of active transcription. However, this effect is specific of the 3'-end of the CASP-2 gene since no difference in the relative amounts of the 5'-end of the mRNA species is detected. Nevertheless, the level of full-length casp-2L mRNA together with that of procaspase-2L protein, which is pro-apoptotic, are decreased under VP-16 treatment, suggesting that an early cell response to treatment by cytotoxic agents is to down-regulate expression of selected pro-apoptotic proteins.
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MESH Headings
- Alternative Splicing/drug effects
- Apoptosis/drug effects
- Apoptosis Regulatory Proteins
- Caspase 2
- Caspases/biosynthesis
- Caspases/genetics
- Cysteine Endopeptidases/biosynthesis
- Cysteine Endopeptidases/genetics
- Dactinomycin/pharmacology
- Enzyme Induction/drug effects
- Enzyme Precursors/biosynthesis
- Enzyme Precursors/genetics
- Etoposide/pharmacology
- Exons/genetics
- Gene Expression Regulation, Leukemic/drug effects
- Genes, bcl-2
- HL-60 Cells/drug effects
- HL-60 Cells/enzymology
- Humans
- Leukemia, Monocytic, Acute/enzymology
- Leukemia, Monocytic, Acute/pathology
- Leukemia, Promyelocytic, Acute/enzymology
- Leukemia, Promyelocytic, Acute/pathology
- Myeloid Cell Leukemia Sequence 1 Protein
- Neoplasm Proteins/biosynthesis
- Neoplasm Proteins/genetics
- Protein Biosynthesis
- Proteins/genetics
- Proto-Oncogene Proteins/biosynthesis
- Proto-Oncogene Proteins c-bcl-2/biosynthesis
- Proto-Oncogenes
- RNA, Messenger/biosynthesis
- RNA, Neoplasm/biosynthesis
- Reverse Transcriptase Polymerase Chain Reaction
- U937 Cells/drug effects
- U937 Cells/enzymology
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Affiliation(s)
- Anne Wotawa
- INSERM U517, IFR 100, Faculty of Medicine, 7 boulevard Jeanne d'Arc, 21000, Dijon, France
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Abstract
Mutually exclusive use of exons IIIb or IIIc in FGF-R2 transcripts requires the silencing of exon IIIb. This repression is mediated by silencer elements upstream and downstream of the exon. Both silencers bind the polypyrimidine tract binding protein (PTB) and PTB binding sites within these elements are required for efficient silencing of exon IIIb. Recruitment of MS2-PTB fusion proteins upstream or downstream of exon IIIb causes repression of this exon. Depletion of endogenous PTB using RNAi increases exon IIIb inclusion in transcripts derived from minigenes and from the endogenous FGF-R2 gene. These data demonstrate that PTB is a negative regulator of exon definition in vivo.
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Affiliation(s)
- Eric J Wagner
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
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Ray BK, Murphy R, Ray P, Ray A. SAF-2, a splice variant of SAF-1, acts as a negative regulator of transcription. J Biol Chem 2002; 277:46822-30. [PMID: 12270922 DOI: 10.1074/jbc.m206299200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Serum amyloid A-activating factor-1 (SAF-1), a Cys(2)His(2)-type zinc finger transcription factor, regulates inflammation-induced expression of serum amyloid A protein that is linked to the pathogenesis of reactive amyloidosis, rheumatoid arthritis, and atherosclerosis. Here we report the identification of a novel splice variant, SAF-2, of the SAF family bearing strong sequence similarity to SAF-1. The N-terminal 426 amino acids of both SAF-1 and SAF-2 are identical containing two polyalanine tracts, one proline-rich domain, and six zinc fingers. However, the C terminus of SAF-2 containing two additional zinc fingers is different from SAF-1, which indicates the capability of different biochemical function. We show that SAF-2 interacts more avidly with the SAF-binding element, but its transactivation potential is much lower than SAF-1. Furthermore, co-expression of SAF-2 markedly suppresses SAF-1-regulated promoter function. Finally, we show that the level of SAF-2 protein is reduced during many inflammatory conditions, whereas the SAF-1 protein level remains unchanged. Together, these data suggest that the relative abundance of SAF-2 plays a critical role in the fine tuned regulation of inflammation-responsive genes that are controlled by SAF-1.
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Affiliation(s)
- Bimal K Ray
- Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri 65211.
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Expert-Bezançon A, Le Caer JP, Marie J. Heterogeneous nuclear ribonucleoprotein (hnRNP) K is a component of an intronic splicing enhancer complex that activates the splicing of the alternative exon 6A from chicken beta-tropomyosin pre-mRNA. J Biol Chem 2002; 277:16614-23. [PMID: 11867641 DOI: 10.1074/jbc.m201083200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Splicing of the chicken beta-tropomyosin exon 6A is stimulated, both in vivo and in vitro, by an intronic pyrimidine-rich element (S4) located 37 nucleotides downstream of exon 6A. Several pyrimidine-rich sequences are able to substitute for the natural S4 enhancer with various stimulatory effects. We show that the different enhancer sequences recruit U1 small nuclear ribonucleoprotein (SnRNP) to the exon 6A 5' splice site, with an efficiency that correlates with the splicing activation. By using RNA affinity and two-dimensional gel electrophoresis, we characterized several proteins that bind to the different enhancer sequences. Heterogeneous nuclear ribonucleoprotein (hnRNP) K and hnRNP I (polypyrimidine track-binding protein, PTB) exhibit a higher level of interaction with the strong enhancer sequences (S4) than with the weakest enhancers. Functional analysis shows that hnRNP K is a component of the enhancer complex that promotes exon 6A splicing through the wild-type S4 sequence. The addition of recombinant hnRNP K to nuclear extracts preincubated with poly(rC) RNA competitor completely restores splicing efficiency to the original level. hnRNP I (PTB) was also found associated with the strong enhancer sequences. Its function in the splicing of exon 6A is discussed.
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50
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Van Loo G, Demol H, van Gurp M, Hoorelbeke B, Schotte P, Beyaert R, Zhivotovsky B, Gevaert K, Declercq W, Vandekerckhove J, Vandenabeele P. A matrix-assisted laser desorption ionization post-source decay (MALDI-PSD) analysis of proteins released from isolated liver mitochondria treated with recombinant truncated Bid. Cell Death Differ 2002; 9:301-8. [PMID: 11859412 DOI: 10.1038/sj.cdd.4400966] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2001] [Revised: 09/18/2001] [Accepted: 09/26/2001] [Indexed: 01/18/2023] Open
Abstract
A crucial event in the process of apoptosis is caspase-dependent generation of truncated Bid (tBid), inducing release of cytochrome c. In an in vitro reconstitution system we combined purified recombinant tBid with isolated liver mitochondria and identified the released proteins using a proteomic matrix-assisted laser desorption ionization post-source decay (MALDI-PSD) approach. In order to meet physiological conditions, the concentration of tBid was chosen such that it was unable to induce cytochrome c release in mitochondria derived from liver-specific Bcl-2-transgenic mice. Several mitochondrial proteins were identified to be released in a tBid-dependent way, among which cytochrome c, DIABLO/Smac, adenylate kinase 2, acyl-CoA-binding protein, endonuclease G, polypyrimidine tract-binding protein, a type-I RNA helicase, a WD-40 repeat-containing protein and the serine protease Omi. Western blotting confirmed the absence of adenylate kinase 3, a matrix mitochondrial protein. These results demonstrate that a physiologically relevant concentration of tBid is sufficient to induce release of particular intermembrane mitochondrial proteins belonging to a broad molecular-mass range.
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Affiliation(s)
- G Van Loo
- Flanders Interuniversity Institute for Biotechnology and Ghent University, Department of Molecular Biology, Unit of Molecular Signaling and Cell Death, KL Ledeganckstraat 35, B-9000 Gent, Belgium
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