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Shen J, Wang Q, Mao Y, Gao W, Duan S. Targeting the p53 signaling pathway in cancers: Molecular mechanisms and clinical studies. MedComm (Beijing) 2023; 4:e288. [PMID: 37256211 PMCID: PMC10225743 DOI: 10.1002/mco2.288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 04/25/2023] [Accepted: 05/08/2023] [Indexed: 06/01/2023] Open
Abstract
Tumor suppressor p53 can transcriptionally activate downstream genes in response to stress, and then regulate the cell cycle, DNA repair, metabolism, angiogenesis, apoptosis, and other biological responses. p53 has seven functional domains and 12 splice isoforms, and different domains and subtypes play different roles. The activation and inactivation of p53 are finely regulated and are associated with phosphorylation/acetylation modification and ubiquitination modification, respectively. Abnormal activation of p53 is closely related to the occurrence and development of cancer. While targeted therapy of the p53 signaling pathway is still in its early stages and only a few drugs or treatments have entered clinical trials, the development of new drugs and ongoing clinical trials are expected to lead to the widespread use of p53 signaling-targeted therapy in cancer treatment in the future. TRIAP1 is a novel p53 downstream inhibitor of apoptosis. TRIAP1 is the homolog of yeast mitochondrial intermembrane protein MDM35, which can play a tumor-promoting role by blocking the mitochondria-dependent apoptosis pathway. This work provides a systematic overview of recent basic research and clinical progress in the p53 signaling pathway and proposes that TRIAP1 is an important therapeutic target downstream of p53 signaling.
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Affiliation(s)
- Jinze Shen
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang ProvinceSchool of MedicineHangzhou City UniversityHangzhouZhejiangChina
| | - Qurui Wang
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang ProvinceSchool of MedicineHangzhou City UniversityHangzhouZhejiangChina
| | - Yunan Mao
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang ProvinceSchool of MedicineHangzhou City UniversityHangzhouZhejiangChina
| | - Wei Gao
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang ProvinceSchool of MedicineHangzhou City UniversityHangzhouZhejiangChina
| | - Shiwei Duan
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang ProvinceSchool of MedicineHangzhou City UniversityHangzhouZhejiangChina
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2
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Ramond F, Dalgliesh C, Grimmel M, Wechsberg O, Vetro A, Guerrini R, FitzPatrick D, Poole RL, Lebrun M, Bayat A, Grasshoff U, Bertrand M, Witt D, Turnpenny PD, Faundes V, Santa María L, Mendoza Fuentes C, Mabe P, Hussain SA, Mullegama SV, Torti E, Oehl-Jaschkowitz B, Salmon LB, Orenstein N, Shahar NR, Hagari O, Bazak L, Hoffjan S, Prada CE, Haack T, Elliott DJ. Clustered variants in the 5' coding region of TRA2B cause a distinctive neurodevelopmental syndrome. Genet Med 2022; 25:100003. [PMID: 36549593 DOI: 10.1016/j.gim.2022.100003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 12/14/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
PURPOSE Transformer2 proteins (Tra2α and Tra2β) control splicing patterns in human cells, and no human phenotypes have been associated with germline variants in these genes. The aim of this work was to associate germline variants in the TRA2B gene to a novel neurodevelopmental disorder. METHODS A total of 12 individuals from 11 unrelated families who harbored predicted loss-of-function monoallelic variants, mostly de novo, were recruited. RNA sequencing and western blot analyses of Tra2β-1 and Tra2β-3 isoforms from patient-derived cells were performed. Tra2β1-GFP, Tra2β3-GFP and CHEK1 exon 3 plasmids were transfected into HEK-293 cells. RESULTS All variants clustered in the 5' part of TRA2B, upstream of an alternative translation start site responsible for the expression of the noncanonical Tra2β-3 isoform. All affected individuals presented intellectual disability and/or developmental delay, frequently associated with infantile spasms, microcephaly, brain anomalies, autism spectrum disorder, feeding difficulties, and short stature. Experimental studies showed that these variants decreased the expression of the canonical Tra2β-1 isoform, whereas they increased the expression of the Tra2β-3 isoform, which is shorter and lacks the N-terminal RS1 domain. Increased expression of Tra2β-3-GFP were shown to interfere with the incorporation of CHEK1 exon 3 into its mature transcript, normally incorporated by Tra2β-1. CONCLUSION Predicted loss-of-function variants clustered in the 5' portion of TRA2B cause a new neurodevelopmental syndrome through an apparently dominant negative disease mechanism involving the use of an alternative translation start site and the overexpression of a shorter, repressive Tra2β protein.
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Affiliation(s)
- Francis Ramond
- Service de Génétique, Hôpital Nord, CHU Saint-Etienne, Saint-Etienne, France.
| | - Caroline Dalgliesh
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Mona Grimmel
- Institute of Medical Genetics and Applied Genomics, University of Tuebingen, Tübingen, Germany
| | - Oded Wechsberg
- Pediatric Genetics Unit, Schneider Children's Medical Center of Israel, Petach Tikva, Israel; Maccabi Healthcare Services, Tel Aviv, Israel
| | - Annalisa Vetro
- Neuroscience Department, Meyer Children's Hospital and University of Florence, Florence, Italy
| | - Renzo Guerrini
- Neuroscience Department, Meyer Children's Hospital and University of Florence, Florence, Italy
| | - David FitzPatrick
- MRC Human Genetics Unit, The University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Rebecca L Poole
- NHS Education for Scotland South East Region, South East of Scotland Clinical Genetics Service, Edinburgh, United Kingdom
| | - Marine Lebrun
- Service de Génétique, Hôpital Nord, CHU Saint-Etienne, Saint-Etienne, France
| | - Allan Bayat
- Institute for Regional Health Services, University of Southern Denmark, Odense, Denmark; Department of Epilepsy Genetics and Personalized Medicine, The Danish Epilepsy Center, Dianalund, Denmark
| | - Ute Grasshoff
- Institute of Medical Genetics and Applied Genomics, University of Tuebingen, Tübingen, Germany
| | - Miriam Bertrand
- Institute of Medical Genetics and Applied Genomics, University of Tuebingen, Tübingen, Germany
| | - Dennis Witt
- Institute of Medical Genetics and Applied Genomics, University of Tuebingen, Tübingen, Germany
| | - Peter D Turnpenny
- Clinical Genetics, Royal Devon University Healthcare NHS Foundation Trust, Exeter, United Kingdom
| | - Víctor Faundes
- Laboratorio de Genética y Enfermedades Metabólicas, Instituto de Nutrición y Tecnología de los Alimentos, Universidad de Chile, Santiago, Chile
| | - Lorena Santa María
- Laboratorio de Genética y Enfermedades Metabólicas, Instituto de Nutrición y Tecnología de los Alimentos, Universidad de Chile, Santiago, Chile
| | - Carolina Mendoza Fuentes
- Unidad de Endocrinología, División de Pediatría, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Paulina Mabe
- Unidad de Neurología, Hospital de Niños Dr. Exequiel González Cortés, Santiago, Chile
| | - Shaun A Hussain
- Division of Pediatric Neurology, University of California, Los Angeles, Los Angeles, CA
| | | | | | | | - Lina Basel Salmon
- Pediatric Genetics Unit, Schneider Children's Medical Center of Israel, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; The Raphael Recanati Genetic Institute, Rabin Medical Center, Beilinson Hospital, Petach Tikva, Israel; Pediatric Immunogenetics, Felsenstein Medical Research Center, Petach Tikva, Israel
| | - Naama Orenstein
- Pediatric Genetics Unit, Schneider Children's Medical Center of Israel, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Noa Ruhrman Shahar
- The Raphael Recanati Genetic Institute, Rabin Medical Center, Beilinson Hospital, Petach Tikva, Israel
| | - Ofir Hagari
- The Raphael Recanati Genetic Institute, Rabin Medical Center, Beilinson Hospital, Petach Tikva, Israel
| | - Lily Bazak
- The Raphael Recanati Genetic Institute, Rabin Medical Center, Beilinson Hospital, Petach Tikva, Israel
| | - Sabine Hoffjan
- Abteilung für Humangenetik, Ruhr-Universitat Bochum, Bochum, Germany
| | - Carlos E Prada
- Division of Genetics, Birth Defects and Metabolism, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL; Department of Pediatrics, Feinberg School of Medicine of Northwestern University, Chicago, IL
| | - Tobias Haack
- Institute of Medical Genetics and Applied Genomics, University of Tuebingen, Tübingen, Germany; Centre for Rare Diseases, University of Tuebingen, Tuebingen, Germany
| | - David J Elliott
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom.
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3
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Zeber-Lubecka N, Hennig EE. Genetic Susceptibility to Joint Occurrence of Polycystic Ovary Syndrome and Hashimoto's Thyroiditis: How Far Is Our Understanding? Front Immunol 2021; 12:606620. [PMID: 33746952 PMCID: PMC7968419 DOI: 10.3389/fimmu.2021.606620] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 01/07/2021] [Indexed: 12/15/2022] Open
Abstract
Polycystic ovary syndrome (PCOS) and Hashimoto’s thyroiditis (HT) are endocrine disorders that commonly occur among young women. A higher prevalence of HT in women with PCOS, relative to healthy individuals, is observed consistently. Combined occurrence of both diseases is associated with a higher risk of severe metabolic and reproductive complications. Genetic factors strongly impact the pathogenesis of both PCOS and HT and several susceptibility loci associated with a higher risk of both disorders have been identified. Furthermore, some candidate gene polymorphisms are thought to be functionally relevant; however, few genetic variants are proposed to be causally associated with the incidence of both disorders together.
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Affiliation(s)
- Natalia Zeber-Lubecka
- Department of Gastroenterology, Hepatology and Clinical Oncology, Centre of Postgraduate Medical Education, Warsaw, Poland
| | - Ewa E Hennig
- Department of Gastroenterology, Hepatology and Clinical Oncology, Centre of Postgraduate Medical Education, Warsaw, Poland.,Department of Genetics, Maria Skłodowska-Curie National Research Institute of Oncology, Warsaw, Poland
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4
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Pankivskyi S, Pastré D, Steiner E, Joshi V, Rynditch A, Hamon L. ITSN1 regulates SAM68 solubility through SH3 domain interactions with SAM68 proline-rich motifs. Cell Mol Life Sci 2020; 78:1745-1763. [PMID: 32780150 PMCID: PMC7904728 DOI: 10.1007/s00018-020-03610-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 06/03/2020] [Accepted: 07/22/2020] [Indexed: 02/06/2023]
Abstract
SAM68 is an mRNA-binding protein involved in mRNA processing in the nucleus that forms membraneless compartments called SAM68 Nuclear Bodies (SNBs). We found that intersectin 1 (ITSN1), a multidomain scaffold protein harboring five soluble SH3 domains, interacts with SAM68 proline-rich motifs (PRMs) surrounded by self-adhesive low complexity domains. While SAM68 is poorly soluble in vitro, the interaction of ITSN1 SH3 domains and mRNA with SAM68 enhances its solubility. In HeLa cells, the interaction between the first ITSN1 SH3 domain (SH3A) and P0, the N-terminal PRM of SAM68, induces the dissociation of SNBs. In addition, we reveal the ability of another SH3 domain (SH3D) of ITSN1 to bind to mRNAs. ITSN1 and mRNA may thus act in concert to promote SAM68 solubilization, consistent with the absence of mRNA in SNBs in cells. Together, these results support the notion of a specific chaperoning of PRM-rich SAM68 within nuclear ribonucleoprotein complexes by ITSN1 that may regulate the processing of a fraction of nuclear mRNAs, notably SAM68-controlled splicing events related to higher neuronal functions or cancer progression. This observation may also serve as a putative model of the interaction between other PRM-rich RBPs and signaling proteins harboring SH3 domains.
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Affiliation(s)
- S Pankivskyi
- SABNP, Univ Evry, INSERM U1204, Université Paris-Saclay, 91025, Evry, France.,Institute of Molecular Biology and Genetics, The National Academy of Sciences, 150 Zabolotnogo Street, Kyiv, 03680, Ukraine
| | - D Pastré
- SABNP, Univ Evry, INSERM U1204, Université Paris-Saclay, 91025, Evry, France
| | - E Steiner
- SABNP, Univ Evry, INSERM U1204, Université Paris-Saclay, 91025, Evry, France
| | - V Joshi
- SABNP, Univ Evry, INSERM U1204, Université Paris-Saclay, 91025, Evry, France
| | - A Rynditch
- Institute of Molecular Biology and Genetics, The National Academy of Sciences, 150 Zabolotnogo Street, Kyiv, 03680, Ukraine.
| | - L Hamon
- SABNP, Univ Evry, INSERM U1204, Université Paris-Saclay, 91025, Evry, France.
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5
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Ren H, Mi X, Zhao P, Zhao X, Wei N, Huang H, Meng Z, Kou J, Sun M, Liu Y, Zhang H, Yang J, Li W, Li H. TRAF4, a new substrate of SIAH1, participates in chemotherapy resistance of breast cancer cell by counteracting SIAH1-mediated downregulation of β-catenin. Breast Cancer Res Treat 2020; 183:275-289. [PMID: 32671611 DOI: 10.1007/s10549-020-05789-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Accepted: 07/04/2020] [Indexed: 12/22/2022]
Abstract
PURPOSE TRAF4 plays an important role in the development and progression of breast cancer, but its impact on chemotherapy resistance is as yet, however, poorly understood. METHODS Western blotting, immunoprecipitation, and immunofluorescence staining were used to identify and verify that TRAF4 was a novel substrate of SIAH1 and prevented SIAH1-mediated β-catenin degradation. Cell proliferation analysis and Flow cytometry analysis were utilized to detect TRAF4's function on the growth-inhibitory effect of etoposide. Immunohistochemistry was used to detect the expression of TRAF4, SIAH1, and β-catenin. Statistical analysis was used to analyze the relationships between them with clinical parameters and curative effect of chemotherapy pathologically. RESULTS Our results suggested that TRAF4 prevents SIAH1-mediated β-catenin degradation. TRAF4 was a novel substrate of SIAH1 and the TRAF domain of TRAF4 was critical for binding to SIAH1. TRAF4 reduced the growth-inhibitory effect of etoposide via reducing the number of S-phase cells and suppressing cell apoptosis. Concordantly, we found that breast cancer patients with a low-TRAF4 expression benefited most from chemotherapy, who had higher tumor volume reduction rate and better pathological response, while, the high-TRAF4 expression group had lower tumor volume reduction rate and poor pathological response. CONCLUSIONS TRAF4 was a novel substrate of SIAH1 and prevented SIAH1-mediated β-catenin degradation, which explains the protective effect of TRAF4 on β-catenin during cell stress and links TRAF4 to chemotherapy resistance in tumors. These findings implicated a novel pathway for the oncogenic function of TRAF4.
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Affiliation(s)
- Huayan Ren
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Xiaoyi Mi
- Department of Pathology, College of Basic Medical Sciences and First Affiliated Hospital, China Medical University, Shenyang, China
| | - Pengyuan Zhao
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Xueyan Zhao
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Na Wei
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Huifen Huang
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Zhongqin Meng
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Junna Kou
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Mingfang Sun
- Department of Pathology, College of Basic Medical Sciences and First Affiliated Hospital, China Medical University, Shenyang, China
| | - Yuqiong Liu
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Hongyan Zhang
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Jianping Yang
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Wencai Li
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China
| | - Huixiang Li
- Department of Pathology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China. .,College of Basic Medical Sciences, Zhengzhou University, Jianshe Road 1, Erqi Ward, Zhengzhou, 450052, P.R. China.
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6
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Gallego-Paez LM, Bordone MC, Leote AC, Saraiva-Agostinho N, Ascensão-Ferreira M, Barbosa-Morais NL. Alternative splicing: the pledge, the turn, and the prestige : The key role of alternative splicing in human biological systems. Hum Genet 2017; 136:1015-1042. [PMID: 28374191 PMCID: PMC5602094 DOI: 10.1007/s00439-017-1790-y] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 03/25/2017] [Indexed: 02/06/2023]
Abstract
Alternative pre-mRNA splicing is a tightly controlled process conducted by the spliceosome, with the assistance of several regulators, resulting in the expression of different transcript isoforms from the same gene and increasing both transcriptome and proteome complexity. The differences between alternative isoforms may be subtle but enough to change the function or localization of the translated proteins. A fine control of the isoform balance is, therefore, needed throughout developmental stages and adult tissues or physiological conditions and it does not come as a surprise that several diseases are caused by its deregulation. In this review, we aim to bring the splicing machinery on stage and raise the curtain on its mechanisms and regulation throughout several systems and tissues of the human body, from neurodevelopment to the interactions with the human microbiome. We discuss, on one hand, the essential role of alternative splicing in assuring tissue function, diversity, and swiftness of response in these systems or tissues, and on the other hand, what goes wrong when its regulatory mechanisms fail. We also focus on the possibilities that splicing modulation therapies open for the future of personalized medicine, along with the leading techniques in this field. The final act of the spliceosome, however, is yet to be fully revealed, as more knowledge is needed regarding the complex regulatory network that coordinates alternative splicing and how its dysfunction leads to disease.
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Affiliation(s)
- L M Gallego-Paez
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - M C Bordone
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - A C Leote
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - N Saraiva-Agostinho
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - M Ascensão-Ferreira
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - N L Barbosa-Morais
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal.
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7
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Human NDE1 splicing and mammalian brain development. Sci Rep 2017; 7:43504. [PMID: 28266585 PMCID: PMC5339911 DOI: 10.1038/srep43504] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 01/27/2017] [Indexed: 11/09/2022] Open
Abstract
Exploring genetic and molecular differences between humans and other close species may be the key to explain the uniqueness of our brain and the selective pressures under which it evolves. Recent discoveries unveiled the involvement of Nuclear distribution factor E-homolog 1 (NDE1) in human cerebral cortical neurogenesis and suggested a role in brain evolution; however the evolutionary changes involved have not been investigated. NDE1 has a different gene structure in human and mouse resulting in the production of diverse splicing isoforms. In particular, mouse uses the terminal exon 8 T, while Human uses terminal exon 9, which is absent in rodents. Through chimeric minigenes splicing assay we investigated the unique elements regulating NDE1 terminal exon choice. We found that selection of the terminal exon is regulated in a cell dependent manner and relies on gain/loss of splicing regulatory sequences across the exons. Our results show how evolutionary changes in cis as well as trans acting signals have played a fundamental role in determining NDE1 species specific splicing isoforms supporting the notion that alternative splicing plays a central role in human genome evolution, and possibly human cognitive predominance.
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8
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Wang Y, Liu Y, Nie H, Ma X, Xu Z. Alternative splicing of inner-ear-expressed genes. Front Med 2016; 10:250-7. [PMID: 27376950 DOI: 10.1007/s11684-016-0454-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 05/11/2016] [Indexed: 11/26/2022]
Abstract
Alternative splicing plays a fundamental role in the development and physiological function of the inner ear. Inner-ear-specific gene splicing is necessary to establish the identity and maintain the function of the inner ear. For example, exon 68 of Cadherin 23 (Cdh23) gene is subject to inner-ear-specific alternative splicing, and as a result, Cdh23(+ 68) is only expressed in inner ear hair cells. Alternative splicing along the tonotopic axis of the cochlea contributes to frequency tuning, particularly in lower vertebrates, such as chickens and turtles. Differential splicing of Kcnma1, which encodes for the α subunit of the Ca(2+)-activated K(+) channel (BK channel), has been suggested to affect the channel gating properties and is important for frequency tuning. Consequently, deficits in alternative splicing have been shown to cause hearing loss, as we can observe in Bronx Waltzer (bv) mice and Sfswap mutant mice. Despite the advances in this field, the regulation of alternative splicing in the inner ear remains elusive. Further investigation is also needed to clarify the mechanism of hearing loss caused by alternative splicing deficits.
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Affiliation(s)
- Yanfei Wang
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Yueyue Liu
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Hongyun Nie
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Xin Ma
- School of Control Science and Engineering, Shandong University, Jinan, 250061, China
| | - Zhigang Xu
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, 250100, China.
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9
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Yuan F, Chen X, Liu J, Feng W, Wu X, Chen SY. Up-regulation of Siah1 by ethanol triggers apoptosis in neural crest cells through p38 MAPK-mediated activation of p53 signaling pathway. Arch Toxicol 2016; 91:775-784. [PMID: 27270636 DOI: 10.1007/s00204-016-1746-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 06/01/2016] [Indexed: 01/22/2023]
Abstract
Seven in absentia homolog 1 (Siah1) is one of the E3 ubiquitin ligases and plays a key role in regulating target protein degradation. This study was designed to test the hypothesis that Siah1 mediates ethanol-induced apoptosis in NCCs through p38 MAPK-mediated activation of the p53 signaling pathway. We found that exposure of NCCs to ethanol resulted in the increases in the total protein levels of p53 and the phosphorylation of p53 at serine 15. Ethanol exposure also resulted in a significant increase in the phosphorylation of p38 MAPK. Knock-down of Siah1 dramatically reduced the ethanol-induced increase in the phosphorylation of p38 MAPK. Knock-down of Siah1 by siRNA or down-regulation of p38 MAPK by either siRNA or inhibitor significantly diminished ethanol-induced accumulations of p53 and the phosphorylation of p53. In addition, ethanol exposure resulted in a significant increase in the expression of p53 downstream targets and apoptosis in NCCs, which can be significantly diminished by down-regulation of Siah1 with siRNA. Knock-down of p38 MAPK by siRNA also dramatically reduced the ethanol-induced apoptosis. These results demonstrate that Siah1 plays a crucial role in ethanol-induced apoptosis in NCCs, and that the up-regulation of Siah1 by ethanol can trigger apoptosis through p38 MAPK-mediated activation of the p53 signaling pathway.
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Affiliation(s)
- Fuqiang Yuan
- Department of Pharmacology and Toxicology, University of Louisville Health Sciences Center, Louisville, KY, 40292, USA.,University of Louisville Alcohol Research Center, Louisville, KY, 40292, USA
| | - Xiaopan Chen
- Department of Pharmacology and Toxicology, University of Louisville Health Sciences Center, Louisville, KY, 40292, USA.,University of Louisville Alcohol Research Center, Louisville, KY, 40292, USA
| | - Jie Liu
- Department of Pharmacology and Toxicology, University of Louisville Health Sciences Center, Louisville, KY, 40292, USA.,University of Louisville Alcohol Research Center, Louisville, KY, 40292, USA
| | - Wenke Feng
- Department of Pharmacology and Toxicology, University of Louisville Health Sciences Center, Louisville, KY, 40292, USA.,University of Louisville Alcohol Research Center, Louisville, KY, 40292, USA.,Department of Medicine, University of Louisville, Louisville, KY, 40292, USA
| | - Xiaoyang Wu
- Ben May Department for Cancer Research, University of Chicago, Chicago, IL, 60637, USA
| | - Shao-Yu Chen
- Department of Pharmacology and Toxicology, University of Louisville Health Sciences Center, Louisville, KY, 40292, USA. .,University of Louisville Alcohol Research Center, Louisville, KY, 40292, USA.
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10
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Knauer SK, Mahendrarajah N, Roos WP, Krämer OH. The inducible E3 ubiquitin ligases SIAH1 and SIAH2 perform critical roles in breast and prostate cancers. Cytokine Growth Factor Rev 2015; 26:405-13. [DOI: 10.1016/j.cytogfr.2015.04.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2015] [Accepted: 04/27/2015] [Indexed: 12/15/2022]
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11
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Alternative splicing coupled nonsense-mediated decay generates neuronal cell type-specific expression of SLM proteins. J Neurosci 2015; 34:16755-61. [PMID: 25505328 DOI: 10.1523/jneurosci.3395-14.2014] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The unique physiological and morphological properties of neuronal populations are crucial for the appropriate functioning of neuronal circuits. Alternative splicing represents an attractive mechanism for generating cell type-specific molecular repertoires that steer neuronal development and function. However, the mechanisms that link neuronal identity to alternative splicing programs are poorly understood. We report that cell type-specific, mutually exclusive expression of two alternative splicing regulators, SLM1 and SLM2, in the mouse hippocampus is achieved by a cross-repression mechanism. Deletion of SLM2 in vivo modifies alternative splicing of its paralog Slm1 and stabilizes its mRNA, resulting in expression of SLM1 in previously SLM2-expressing cells. Despite this ectopic upregulation of SLM1, loss of SLM2 severely disrupts the alternative splicing regulation of Nrxn1, Nrxn2, and Nrxn3, highlighting that the two SLM paralogs have partially divergent functions. Our study uncovers a hierarchical, SLM2-dependent mechanism for establishing cell type-specific expression of neuronal splicing regulators in vivo.
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Lee H, Oh JY, Sung YA, Chung H, Kim HL, Kim GS, Cho YS, Kim JT. Genome-wide association study identified new susceptibility loci for polycystic ovary syndrome. Hum Reprod 2015; 30:723-31. [PMID: 25574032 DOI: 10.1093/humrep/deu352] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
STUDY QUESTION Are there any novel genetic markers of susceptibility to polycystic ovary syndrome (PCOS)? SUMMARY ANSWER We identified a novel susceptibility locus on chromosome 8q24.2 and several moderately associated loci for PCOS in Korean women. WHAT IS KNOWN ALREADY PCOS is a highly complex disorder with significant contributions from both genetic and environmental factors. Previous genome-wide association studies (GWAS) in the Han Chinese population identified several risk loci for PCOS. However, GWAS studies on PCOS remain very few. The aim of this study was to identify novel markers of susceptibility to PCOS through GWAS. STUDY DESIGN, SIZE, DURATION A two-stage GWAS was conducted. The initial discovery set for GWAS consisted of 976 PCOS cases and 946 controls. The second stage (replication study) included 249 PCOS cases and 778 controls. PARTICIPANTS/MATERIALS, SETTING, METHODS Patients were diagnosed according to the Rotterdam criteria. Genomic DNAs were genotyped using the HumanOmni1-Quad v1 array. In the replication stage, the 21 most promising signals selected from the discovery stage were tested for their association with PCOS. MAIN RESULTS AND THE ROLE OF CHANCE One novel locus with genome-wide significance and seven moderately associated loci for PCOS were identified. The strongest association was on chromosome 8q24.2 (rs10505648, OR = 0.52, P = 5.46 × 10(-8)), and other association signals were located at 4q35.2, 16p13.3, 4p12, 3q26.33, 9q21.32, 11p13 and 1p22 (P = 5.72 × 10(-6)-6.43 × 10(-5)). The strongest signal was located upstream of KHDRBS3, which is associated with telomerase activity, and could drive PCOS and related phenotypes. LIMITATIONS, REASONS FOR CAUTION The limitation of our study is the modest sample size used in the replication cohort. The limited sample size may contribute to a lack of statistical power to detect an association or show a trend in severity. WIDER IMPLICATIONS OF THE FINDINGS Our findings provide new insight into the genetics and biological pathways of PCOS and could contribute to the early diagnosis and prevention of metabolic and reproductive morbidities. STUDY FUNDING/COMPETING INTERESTS This work was supported in part by the grant from the Korea Centers for Disease Control and Prevention (2009-E00591-00). The work was also supported by the Ewha Global Top5 Grant 2013 of Ewha Womans University. None of the authors has any conflict of interest to declare.
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Affiliation(s)
- Hyejin Lee
- Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea
| | - Jee-Young Oh
- Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea
| | - Yeon-Ah Sung
- Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea
| | - Hyewon Chung
- Department of Obstetrics and Gynecology, Ewha Womans University School of Medicine, Seoul, Korea
| | - Hyung-Lae Kim
- Department of Biochemistry, Ewha Womans University School of Medicine, Seoul, Korea
| | - Gwang Sub Kim
- Department of Biomedical Science, Hallym University, Gangwon-do, Korea
| | - Yoon Shin Cho
- Department of Biomedical Science, Hallym University, Gangwon-do, Korea
| | - Jin Taek Kim
- Department of Internal Medicine, Eulji University College of Medicine, Seoul, Korea
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Schmid R, Grellscheid SN, Ehrmann I, Dalgliesh C, Danilenko M, Paronetto MP, Pedrotti S, Grellscheid D, Dixon RJ, Sette C, Eperon IC, Elliott DJ. The splicing landscape is globally reprogrammed during male meiosis. Nucleic Acids Res 2013; 41:10170-84. [PMID: 24038356 PMCID: PMC3905889 DOI: 10.1093/nar/gkt811] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Meiosis requires conserved transcriptional changes, but it is not known whether there is a corresponding set of RNA splicing switches. Here, we used RNAseq of mouse testis to identify changes associated with the progression from mitotic spermatogonia to meiotic spermatocytes. We identified ∼150 splicing switches, most of which affect conserved protein-coding exons. The expression of many key splicing regulators changed in the course of meiosis, including downregulation of polypyrimidine tract binding protein (PTBP1) and heterogeneous nuclear RNP A1, and upregulation of nPTB, Tra2β, muscleblind, CELF proteins, Sam68 and T-STAR. The sequences near the regulated exons were significantly enriched in target sites for PTB, Tra2β and STAR proteins. Reporter minigene experiments investigating representative exons in transfected cells showed that PTB binding sites were critical for splicing of a cassette exon in the Ralgps2 mRNA and a shift in alternative 5′ splice site usage in the Bptf mRNA. We speculate that nPTB might functionally replace PTBP1 during meiosis for some target exons, with changes in the expression of other splicing factors helping to establish meiotic splicing patterns. Our data suggest that there are substantial changes in the determinants and patterns of alternative splicing in the mitotic-to-meiotic transition of the germ cell cycle.
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Affiliation(s)
- Ralf Schmid
- Department of Biochemistry, University of Leicester, Leicester, LE1 9HN, UK, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, UK, School of Biological and Biomedical Sciences, Durham University, Durham, DH1 3LE, UK, Department of Health Sciences, University of 00135 Rome 'Foro Italico', Rome, Italy, Laboratories of Neuroembryology and of Cellular and Molecular Neurobiology, Fondazione Santa Lucia IRCCS, 00143 Rome, Italy, Department of Public Health and Cell Biology, University of Rome Tor Vergata, 00133 Rome, Italy, Institute of Particle Physics Phenomenology, Durham University, Durham, DH1 3LE, UK and Life Technologies Ltd., Paisley PA4 9RF, UK
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Zhou L, Chen B, Hua X, Zhou P, Guo L, Peng Y, Qiu K. Effect of newly identified hTERT-interacting proteins on telomerase activity. Acta Biochim Biophys Sin (Shanghai) 2013; 45:674-82. [PMID: 23709204 DOI: 10.1093/abbs/gmt056] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
There is a close relationship between telomeres-telomerase and age-related disease. Human telomerase reverse transcriptase (hTERT) is both the catalytic component of human telomerase and the rate-limiting determinant of telomerase activity. Its transcriptional regulation is the primary mode of control of telomerase activity. It is critical to find the proteins interacting with hTERT for exploring the regulatory mechanisms of the hTERT expression and the telomerase activity. In this study, the yeast two-hybrid system was used to screen the potential interactive proteins of hTERT. Six proteins were obtained, among which T-STAR, LOXL3, HKR3, and Par-4 were further confirmed as the interacting proteins of hTERT by co-immunoprecipitation. Then the sense and antisense gene eukaryotic expression vectors containing these four genes were constructed and transfected into tumor cell lines. The correlations among the expression levels of these four proteins, the expression level of hTERT, and the telomerase activity were analyzed. Results showed that the up-regulation of T-STAR expression and down-regulation of HKR3 expression led to the increase of hTERT expression and telomerase activity, while the up- and down-regulation of LOXL3 and Par-4 expressions had no obvious effect. Our results suggested that T-STAR has a positive correlation with the telomerase activity while HKR3 may be a negative regulator. This conclusion is important to further explore the influencing factors or regulation pathways of human telomerase activity, which may be of great importance for the potential clinical application.
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Affiliation(s)
- Lina Zhou
- Department of Endocrinology, Southwest Hospital, Third Military Medical University, Chongqing 400038, China
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15
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Ehrmann I, Dalgliesh C, Liu Y, Danilenko M, Crosier M, Overman L, Arthur HM, Lindsay S, Clowry GJ, Venables JP, Fort P, Elliott DJ. The tissue-specific RNA binding protein T-STAR controls regional splicing patterns of neurexin pre-mRNAs in the brain. PLoS Genet 2013; 9:e1003474. [PMID: 23637638 PMCID: PMC3636136 DOI: 10.1371/journal.pgen.1003474] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 03/07/2013] [Indexed: 11/18/2022] Open
Abstract
The RNA binding protein T-STAR was created following a gene triplication 520-610 million years ago, which also produced its two parologs Sam68 and SLM-1. Here we have created a T-STAR null mouse to identify the endogenous functions of this RNA binding protein. Mice null for T-STAR developed normally and were fertile, surprisingly, given the high expression of T-STAR in the testis and the brain, and the known infertility and pleiotropic defects of Sam68 null mice. Using a transcriptome-wide search for splicing targets in the adult brain, we identified T-STAR protein as a potent splicing repressor of the alternatively spliced segment 4 (AS4) exons from each of the Neurexin1-3 genes, and exon 23 of the Stxbp5l gene. T-STAR protein was most highly concentrated in forebrain-derived structures like the hippocampus, which also showed maximal Neurexin1-3 AS4 splicing repression. In the absence of endogenous T-STAR protein, Nrxn1-3 AS4 splicing repression dramatically decreased, despite physiological co-expression of Sam68. In transfected cells Neurexin3 AS4 alternative splicing was regulated by either T-STAR or Sam68 proteins. In contrast, Neurexin2 AS4 splicing was only regulated by T-STAR, through a UWAA-rich response element immediately downstream of the regulated exon conserved since the radiation of bony vertebrates. The AS4 exons in the Nrxn1 and Nrxn3 genes were also associated with distinct patterns of conserved UWAA repeats. Consistent with an ancient mechanism of splicing control, human T-STAR protein was able to repress splicing inclusion of the zebrafish Nrxn3 AS4 exon. Although Neurexin1-3 and Stxbp5l encode critical synaptic proteins, T-STAR null mice had no detectable spatial memory deficits, despite an almost complete absence of AS4 splicing repression in the hippocampus. Our work identifies T-STAR as an ancient and potent tissue-specific splicing regulator that uses a concentration-dependent mechanism to co-ordinately regulate regional splicing patterns of the Neurexin1-3 AS4 exons in the mouse brain.
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Affiliation(s)
- Ingrid Ehrmann
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Caroline Dalgliesh
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Yilei Liu
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Marina Danilenko
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Moira Crosier
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Lynn Overman
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Helen M. Arthur
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Susan Lindsay
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Gavin J. Clowry
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Julian P. Venables
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Philippe Fort
- Universités Montpellier 2 et 1, UMR 5237, Centre de Recherche de Biochimie Macromoléculaire, CNRS, Montpellier, France
| | - David J. Elliott
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
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16
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Abstract
For most of our 25,000 genes, the removal of introns by pre-messenger RNA (pre-mRNA) splicing represents an essential step toward the production of functional messenger RNAs (mRNAs). Alternative splicing of a single pre-mRNA results in the production of different mRNAs. Although complex organisms use alternative splicing to expand protein function and phenotypic diversity, patterns of alternative splicing are often altered in cancer cells. Alternative splicing contributes to tumorigenesis by producing splice isoforms that can stimulate cell proliferation and cell migration or induce resistance to apoptosis and anticancer agents. Cancer-specific changes in splicing profiles can occur through mutations that are affecting splice sites and splicing control elements, and also by alterations in the expression of proteins that control splicing decisions. Recent progress in global approaches that interrogate splicing diversity should help to obtain specific splicing signatures for cancer types. The development of innovative approaches for annotating and reprogramming splicing events will more fully establish the essential contribution of alternative splicing to the biology of cancer and will hopefully provide novel targets and anticancer strategies. Metazoan genes are usually made up of several exons interrupted by introns. The introns are removed from the pre-mRNA by RNA splicing. In conjunction with other maturation steps, such as capping and polyadenylation, the spliced mRNA is then transported to the cytoplasm to be translated into a functional protein. The basic mechanism of splicing requires accurate recognition of each extremity of each intron by the spliceosome. Introns are identified by the binding of U1 snRNP to the 5' splice site and the U2AF65/U2AF35 complex to the 3' splice site. Following these interactions, other proteins and snRNPs are recruited to generate the complete spliceosomal complex needed to excise the intron. While many introns are constitutively removed by the spliceosome, other splice junctions are not used systematically, generating the phenomenon of alternative splicing. Alternative splicing is therefore the process by which a single species of pre-mRNA can be matured to produce different mRNA molecules (Fig. 1). Depending on the number and types of alternative splicing events, a pre-mRNA can generate from two to several thousands different mRNAs leading to the production of a corresponding number of proteins. It is now believed that the expression of at least 70 % of human genes is subjected to alternative splicing, implying an enormous contribution to proteomic diversity, and by extension, to the development and the evolution of complex animals. Defects in splicing have been associated with human diseases (Caceres and Kornblihtt, Trends Genet 18(4):186-93, 2002, Cartegni et al., Nat Rev Genet 3(4):285-98, 2002, Pagani and Baralle, Nat Rev Genet 5(5):389-96, 2004), including cancer (Brinkman, Clin Biochem 37(7):584-94, 2004, Venables, Bioessays 28(4):378-86, 2006, Srebrow and Kornblihtt, J Cell Sci 119(Pt 13):2635-2641, 2006, Revil et al., Bull Cancer 93(9):909-919, 2006, Venables, Transworld Res Network, 2006, Pajares et al., Lancet Oncol 8(4):349-57, 2007, Skotheim and Nees, Int J Biochem Cell Biol 39:1432-1449, 2007). Numerous studies have now confirmed the existence of specific differences in the alternative splicing profiles between normal and cancer tissues. Although there are a few cases where specific mutations are the primary cause for these changes, global alterations in alternative splicing in cancer cells may be primarily derived from changes in the expression of RNA-binding proteins that control splice site selection. Overall, these cancer-specific differences in alternative splicing offer an immense potential to improve the diagnosis and the prognosis of cancer. This review will focus on the functional impact of cancer-associated alternative splicing variants, the molecular determinants that alter the splicing decisions in cancer cells, and future therapeutic strategies.
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Buchwald M, Pietschmann K, Brand P, Günther A, Mahajan NP, Heinzel T, Krämer OH. SIAH ubiquitin ligases target the nonreceptor tyrosine kinase ACK1 for ubiquitinylation and proteasomal degradation. Oncogene 2012. [PMID: 23208506 DOI: 10.1038/onc.2012.515] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Activated Cdc42-associated kinase 1 (ACK1) is a nonreceptor tyrosine kinase linked to cellular transformation. The aberrant regulation of ACK1 promotes tumor progression and metastasis. Therefore, ACK1 is regarded as a valid target in cancer therapy. Seven in absentia homolog (SIAH) ubiquitin ligases facilitate substrate ubiquitinylation that targets proteins to the proteasomal degradation pathway. Here we report that ACK1 and SIAH1 from Homo sapiens interact in a yeast two-hybrid screen. Protein-protein interaction studies and protein degradation analyses using deletion and point mutants of ACK1 verify that SIAH1 and the related SIAH2 interact with ACK1. The association between SIAHs and ACK1 depends on the integrity of a highly conserved SIAH-binding motif located in the far C-terminus of ACK1. Furthermore, we demonstrate that the interaction of ACK1 with SIAH1 and the induction of proteasomal degradation of ACK1 by SIAH1 are independent of ACK1's kinase activity. Chemical inhibitors blocking proteasomal activity corroborate that SIAH1 and SIAH2 destabilize the ACK1 protein by inducing its proteasomal turnover. This mechanism apparently differs from the lysosomal pathway targeting ACK1 after stimulation with the epidermal growth factor. Our data also show that ACK1, but not ACK1 mutants lacking the SIAH binding motif, has a discernable negative effect on SIAH levels. Additionally, knockdown approaches targeting the SIAH2 mRNA uncover specifically that the induction of SIAH2 expression, by hormonally-induced estrogen receptor (ER) activation, decreases the levels of ACK1 in luminal human breast cancer cells. Collectively, our data provide novel insights into the molecular mechanisms modulating ACK1 and they position SIAH ubiquitin ligases as negative regulators of ACK1 in transformed cells.
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Affiliation(s)
- M Buchwald
- Institute of Biochemistry and Biophysics, Center for Molecular Biomedicine, Friedrich-Schiller University, Jena, Germany
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18
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Wang D, Lu Q, Shao B, Cui G, Wang Y, Liu Y, Wu Q, Zhao J, Cui Z, Xu J, Yang H, Shen A, Gu X. An Upregulation of SIAH1 After Spinal Cord Injury in Adult Rats. J Mol Neurosci 2011; 45:134-44. [PMID: 21336655 DOI: 10.1007/s12031-011-9501-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 12/08/2010] [Indexed: 11/25/2022]
Affiliation(s)
- Donglin Wang
- The Jiangsu Province Key Laboratory of Neuroregeneration, Nantong University, Nantong 226001, People's Republic of China
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Robbins CM, Tembe WA, Baker A, Sinari S, Moses TY, Beckstrom-Sternberg S, Beckstrom-Sternberg J, Barrett M, Long J, Chinnaiyan A, Lowey J, Suh E, Pearson JV, Craig DW, Agus DB, Pienta KJ, Carpten JD. Copy number and targeted mutational analysis reveals novel somatic events in metastatic prostate tumors. Genome Res 2010; 21:47-55. [PMID: 21147910 DOI: 10.1101/gr.107961.110] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Advanced prostate cancer can progress to systemic metastatic tumors, which are generally androgen insensitive and ultimately lethal. Here, we report a comprehensive genomic survey for somatic events in systemic metastatic prostate tumors using both high-resolution copy number analysis and targeted mutational survey of 3508 exons from 577 cancer-related genes using next generation sequencing. Focal homozygous deletions were detected at 8p22, 10q23.31, 13q13.1, 13q14.11, and 13q14.12. Key genes mapping within these deleted regions include PTEN, BRCA2, C13ORF15, and SIAH3. Focal high-level amplifications were detected at 5p13.2-p12, 14q21.1, 7q22.1, and Xq12. Key amplified genes mapping within these regions include SKP2, FOXA1, and AR. Furthermore, targeted mutational analysis of normal-tumor pairs has identified somatic mutations in genes known to be associated with prostate cancer including AR and TP53, but has also revealed novel somatic point mutations in genes including MTOR, BRCA2, ARHGEF12, and CHD5. Finally, in one patient where multiple independent metastatic tumors were available, we show common and divergent somatic alterations that occur at both the copy number and point mutation level, supporting a model for a common clonal progenitor with metastatic tumor-specific divergence. Our study represents a deep genomic analysis of advanced metastatic prostate tumors and has revealed candidate somatic alterations, possibly contributing to lethal prostate cancer.
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Affiliation(s)
- Christiane M Robbins
- Division of Integrated Cancer Genomics, Translational Genomics Research Institute, Phoenix, Arizona 85004, USA
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Shkreta L, Michelle L, Toutant J, Tremblay ML, Chabot B. The DNA damage response pathway regulates the alternative splicing of the apoptotic mediator Bcl-x. J Biol Chem 2010; 286:331-40. [PMID: 20980256 DOI: 10.1074/jbc.m110.162644] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Alternative splicing often produces effectors with opposite functions in apoptosis. Splicing decisions must therefore be tightly connected to stresses, stimuli, and pathways that control cell survival and cell growth. We have shown previously that PKC signaling prevents the production of proapoptotic Bcl-x(S) to favor the accumulation of the larger antiapoptotic Bcl-x(L) splice variant in 293 cells. Here we show that the genotoxic stress induced by oxaliplatin elicits an ATM-, CHK2-, and p53-dependent splicing switch that favors the production of the proapoptotic Bcl-x(S) variant. This DNA damage-induced splicing shift requires the activity of protein-tyrosine phosphatases. Interestingly, the ATM/CHK2/p53/tyrosine phosphatases pathway activated by oxaliplatin regulates Bcl-x splicing through the same regulatory sequence element (SB1) that receives signals from the PKC pathway. Convergence of the PKC and DNA damage signaling routes may control the abundance of a key splicing repressor because SB1-mediated repression is lost when protein synthesis is impaired but is rescued by blocking proteasome-mediated protein degradation. The SB1 splicing regulatory module therefore receives antagonistic signals from the PKC and the p53-dependent DNA damage response pathways to control the balance of pro- and antiapoptotic Bcl-x splice variants.
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Affiliation(s)
- Lulzim Shkreta
- RNA/RNP Group, Département de Microbiologie et d'Infectiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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Wen L, Liu J, Chen Y, Wu D. Identification and preliminary functional analysis of alternative splicing of Siah1 in Xenopus laevis. Biochem Biophys Res Commun 2010; 396:419-424. [PMID: 20417182 DOI: 10.1016/j.bbrc.2010.04.107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2010] [Accepted: 04/19/2010] [Indexed: 05/29/2023]
Abstract
Siah proteins are vertebrate homologs of the Drosophila 'seven in absentia' gene. In this study, we characterized two splicing forms, Siah1a and Siah1b, of the Xenopus seven in absentia homolog 1 gene (Siah1). Overexpression of xSiah1a led to severe suppression of embryo cleavage, while that of xSiah1b was not effective even at a high dose. Competition analysis demonstrated that co-expression of xSiah1a and 1b generated the same phenotype as overexpression of xSiah1a alone, suggesting that xSiah1b does not interfere with the function of xSiah1a. Since xSiah1b has an additional 31 amino acids in the N-terminus compared to xSiah1a, progressive truncation of xSiah1b from the N-terminus showed that inability of xSiah1b to affect embryo cleavage was associated with the length of the N-terminal extension of extra amino acids. The possible implication of this finding is discussed.
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Affiliation(s)
- Luan Wen
- Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, 190 Kaiyuan Road, Guangzhou Science Park, 510530 Guangzhou, China
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Brooks SA. Functional interactions between mRNA turnover and surveillance and the ubiquitin proteasome system. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 1:240-52. [PMID: 21935888 DOI: 10.1002/wrna.11] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The proteasome is a critical regulator of protein levels within the cell and is essential for maintaining homeostasis. A functional proteasome is required for effective mRNA surveillance and turnover. During transcription, the proteasome localizes to sites of DNA breaks, degrading RNA polymerase II and terminating transcription. For fully transcribed and processed messages, cytoplasmic surveillance is initiated with the pioneer round of translation. The proteasome is recruited to messages bearing premature termination codons, which trigger nonsense-mediated decay (NMD), as well as messages lacking a termination codon, which trigger nonstop decay, to degrade the aberrant protein produced from these messages. A number of proteins involved in mRNA translation are regulated in part by proteasome-mediated decay, including the initiation factors eIF4G, eIF4E, and eIF3a, and the poly(A)-binding protein (PABP) interacting protein, Paip2. eIF4E-BP (4E-BP) is differentially regulated by the proteasome: truncated to generate a protein with higher eIF4B binding or completely degraded, depending on its phosphorylation status. Finally, a functional proteasome is required for AU-rich-element (ARE)-mediated decay but the specific role the proteasome plays is unclear. There is data indicating the proteasome can bind to AREs, act as an endonuclease, and degrade ARE-binding proteins. How these events interact with the 5'-to-3' and 3'-to-5' decay pathways is unclear at this time; however, data is provided indicating that proteasomes colocalize with Xrn1 and the exosome RNases Rrp44 and Rrp6 in untreated HeLa cells.
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Affiliation(s)
- Seth A Brooks
- Veterans Administration Medical Center Research, White River Junction, VT 05009, USA.
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Sellier C, Rau F, Liu Y, Tassone F, Hukema RK, Gattoni R, Schneider A, Richard S, Willemsen R, Elliott DJ, Hagerman PJ, Charlet-Berguerand N. Sam68 sequestration and partial loss of function are associated with splicing alterations in FXTAS patients. EMBO J 2010; 29:1248-61. [PMID: 20186122 DOI: 10.1038/emboj.2010.21] [Citation(s) in RCA: 286] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Accepted: 01/20/2010] [Indexed: 01/22/2023] Open
Abstract
Fragile X-associated Tremor/Ataxia Syndrome (FXTAS) is a neurodegenerative disorder caused by expansion of 55-200 CGG repeats in the 5'-UTR of the FMR1 gene. FXTAS is characterized by action tremor, gait ataxia and impaired executive cognitive functioning. It has been proposed that FXTAS is caused by titration of RNA-binding proteins by the expanded CGG repeats. Sam68 is an RNA-binding protein involved in alternative splicing regulation and its ablation in mouse leads to motor coordination defects. Here, we report that mRNAs containing expanded CGG repeats form large and dynamic intranuclear RNA aggregates that recruit several RNA-binding proteins sequentially, first Sam68, then hnRNP-G and MBNL1. Importantly, Sam68 is sequestered by expanded CGG repeats and thereby loses its splicing-regulatory function. Consequently, Sam68-responsive splicing is altered in FXTAS patients. Finally, we found that regulation of Sam68 tyrosine phosphorylation modulates its localization within CGG aggregates and that tautomycin prevents both Sam68 and CGG RNA aggregate formation. Overall, these data support an RNA gain-of-function mechanism for FXTAS neuropathology, and suggest possible target routes for treatment options.
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Affiliation(s)
- Chantal Sellier
- Department of Neurobiology and Genetics, IGBMC, INSERM U964, CNRS UMR7104, University of Strasbourg, Illkirch, France
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Expression and functions of the star proteins Sam68 and T-STAR in mammalian spermatogenesis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 693:67-81. [PMID: 21189686 DOI: 10.1007/978-1-4419-7005-3_5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Spermatogenesis is one of the few major developmental pathways which are still ongoing in the adult. In this chapter we review the properties of Sam68 and T-STAR, which are the STAR proteins functionally implicated in mammalian spermatogenesis. Sam68 is a ubiquitously expressed member of the STAR family, but has an essential role in spermatogenesis. Sam68 null mice are male infertile and at least in part this is due to a failure in important translational controls that operate during and after meiosis. The homologous T-STAR protein has a much more restricted anatomic expression pattern than Sam68, with highest levels seen in the testis and the developing brain. The focus of this chapter is the functional role of Sam68 and T-STAR proteins in male germ cell development. Since these proteins are known to have many cellular functions we extrapolate from other cell types and tissues to speculate on each of their likely functions within male germ cells, including control of alternative pre-mRNA splicing patterns in male germ cells.
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Rajan P, Dalgliesh C, Bourgeois CF, Heiner M, Emami K, Clark EL, Bindereif A, Stevenin J, Robson CN, Leung HY, Elliott DJ. Proteomic identification of heterogeneous nuclear ribonucleoprotein L as a novel component of SLM/Sam68 Nuclear Bodies. BMC Cell Biol 2009; 10:82. [PMID: 19912651 PMCID: PMC2784748 DOI: 10.1186/1471-2121-10-82] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Accepted: 11/13/2009] [Indexed: 11/25/2022] Open
Abstract
Background Active pre-mRNA splicing occurs co-transcriptionally, and takes place throughout the nucleoplasm of eukaryotic cells. Splicing decisions are controlled by networks of nuclear RNA-binding proteins and their target sequences, sometimes in response to signalling pathways. Sam68 (Src-associated in mitosis 68 kDa) is the prototypic member of the STAR (Signal Transduction and Activation of RNA) family of RNA-binding proteins, which regulate splicing in response to signalling cascades. Nuclear Sam68 protein is concentrated within subnuclear organelles called SLM/Sam68 Nuclear Bodies (SNBs), which also contain some other splicing regulators, signalling components and nucleic acids. Results We used proteomics to search for the major interacting protein partners of nuclear Sam68. In addition to Sam68 itself and known Sam68-associated proteins (heterogeneous nuclear ribonucleoproteins hnRNP A1, A2/B1 and G), we identified hnRNP L as a novel Sam68-interacting protein partner. hnRNP L protein was predominantly present within small nuclear protein complexes approximating to the expected size of monomers and dimers, and was quantitatively associated with nucleic acids. hnRNP L spatially co-localised with Sam68 as a novel component of SNBs and was also observed within the general nucleoplasm. Localisation within SNBs was highly specific to hnRNP L and was not shared by the closely-related hnRNP LL protein, nor any of the other Sam68-interacting proteins we identified by proteomics. The interaction between Sam68 and hnRNP L proteins was observed in a cell line which exhibits low frequency of SNBs suggesting that this association also takes place outside SNBs. Although ectopic expression of hnRNP L and Sam68 proteins independently affected splicing of CD44 variable exon v5 and TJP1 exon 20 minigenes, these proteins did not, however, co-operate with each other in splicing regulation of these target exons. Conclusion Here we identify hnRNP L as a novel SNB component. We show that, compared with other identified Sam68-associated hnRNP proteins and hnRNP LL, this co-localisation within SNBs is specific to hnRNP L. Our data suggest that the novel Sam68-hnRNP L protein interaction may have a distinct role within SNBs.
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Affiliation(s)
- Prabhakar Rajan
- Institute of Human Genetics, Newcastle University, Central Parkway, Newcastle-upon-Tyne, NE1 3BZ, UK.
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Lu Y, Ryan SL, Elliott DJ, Bignell GR, Futreal PA, Ellison DW, Bailey S, Clifford SC. Amplification and Overexpression of Hsa-miR-30b, Hsa-miR-30d and KHDRBS3 at 8q24.22-q24.23 in Medulloblastoma. PLoS One 2009; 4:e6159. [PMID: 19584924 PMCID: PMC2702821 DOI: 10.1371/journal.pone.0006159] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Accepted: 06/07/2009] [Indexed: 01/01/2023] Open
Abstract
Background Medulloblastoma is the most common malignant brain tumour of childhood. The identification of critical genes involved in its pathogenesis will be central to advances in our understanding of its molecular basis, and the development of improved therapeutic approaches. Methodology/Principal Findings We performed a SNP-array based genome-wide copy number analysis in medulloblastoma cell lines, to identify regions of genomic amplification and homozygous deletion, which may harbour critical disease genes. A series of novel and established medulloblastoma defects were detected (MYC amplification (n = 4), 17q21.31 high-level gain (n = 1); 9p21.1–p21.3 (n = 1) and 6q23.1 (n = 1) homozygous deletion). Most notably, a novel recurrent region of genomic amplification at 8q24.22–q24.23 was identified (n = 2), and selected for further investigation. Additional analysis by interphase fluorescence in situ hybridisation (iFISH), PCR-based mapping and SNP-array revealed this novel amplification at 8q24.22–q24.23 is independent of MYC amplification at 8q24.21, and is unique to medulloblastoma in over 800 cancer cell lines assessed from different tumour types, suggesting it contains key genes specifically involved in medulloblastoma development. Detailed mapping identified a 3Mb common minimal region of amplification harbouring 3 coding genes (ZFAT1, LOC286094, KHDRBS3) and two genes encoding micro-RNAs (hsa-miR-30b, hsa-miR-30d). Of these, only expression of hsa-miR-30b, hsa-miR-30d and KHDRBS3 correlated with copy number status, and all three of these transcripts also displayed evidence of elevated expression in sub-sets of primary medulloblastomas, measured relative to the normal cerebellum. Conclusions/Significance These data implicate hsa-miR-30b, hsa-miR-30d and KHDRBS3 as putative oncogenic target(s) of a novel recurrent medulloblastoma amplicon at 8q24.22–q24.23. Our findings suggest critical roles for these genes in medulloblastoma development, and further support the contribution of micro-RNA species to medulloblastoma pathogenesis.
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Affiliation(s)
- Yuan Lu
- Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Sarra L. Ryan
- Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - David J. Elliott
- Institute of Human Genetics, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Graham R. Bignell
- Cancer Genome Project, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - P. Andrew Futreal
- Cancer Genome Project, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - David W. Ellison
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, Tennessee, United States of America
| | - Simon Bailey
- Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Steven C. Clifford
- Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, United Kingdom
- * E-mail:
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Abstract
Growing evidence indicates that ubiquitin ligases play a critical role in the hypoxia response. Among them, Siah2, a RING finger ligase, is an important regulator of pathways activated under hypoxia. Siah2 regulates prolyl hydroxylases PHD3 and 1 under oxygen concentration of 2% to 5%, thereby allowing accumulation of hypoxia-inducible factor (HIF)-1alpha, a master regulator of the hypoxia response within the range of physiological normoxic to mild hypoxic conditions. Growing evidence also indicates an important function for Siah2 in tumor development and progression based on pancreatic cancer, mammary tumor, and melanoma mouse models. This review summarizes our current understanding of Siah2 regulation and function with emphasis on hypoxia and tumorigenesis.
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Affiliation(s)
- Koh Nakayama
- Burnham Institute for Medical Research, La Jolla, CA, USA.
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Katzenberger RJ, Marengo MS, Wassarman DA. Control of alternative splicing by signal-dependent degradation of splicing-regulatory proteins. J Biol Chem 2009; 284:10737-46. [PMID: 19218244 DOI: 10.1074/jbc.m809506200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Alternative pre-mRNA splicing is a major gene expression regulatory mechanism in metazoan organisms. Proteins that bind pre-mRNA elements and control assembly of splicing complexes regulate utilization of pre-mRNA alternative splice sites. To understand how signaling pathways impact this mechanism, an RNA interference screen in Drosophila S2 cells was used to identify proteins that regulate TAF1 (TBP-associated factor 1) alternative splicing in response to activation of the ATR (ATM-RAD3-related) signaling pathway by the chemotherapeutic drug camptothecin (CPT). The screen identified 15 proteins that, when knocked down, caused the same change in TAF1 alternative splicing as CPT treatment. However, combined RNA interference and CPT treatment experiments indicated that only a subset of the identified proteins are targets of the CPT-induced signal, suggesting that multiple independent pathways regulate TAF1 alternative splicing. To understand how signals modulate the function of splicing factors, we characterized one of the CPT targets, Tra2 (Transformer-2). CPT was found to down-regulate Tra2 protein levels. CPT-induced Tra2 down-regulation was ATR-dependent and temporally paralleled the change in TAF1 alternative splicing, supporting the conclusion that Tra2 directly regulates TAF1 alternative splicing. Additionally, CPT-induced Tra2 down-regulation occurred independently of new protein synthesis, suggesting a post-translational mechanism. The proteasome inhibitor MG132 reduced CPT-induced Tra2 degradation and TAF1 alternative splicing, and mutation of evolutionarily conserved Tra2 lysine 81, a potential ubiquitin conjugation site, to arginine inhibited CPT-induced Tra2 degradation, supporting a proteasome-dependent alternative splicing mechanism. We conclude that CPT-induced TAF1 alternative splicing occurs through ATR-signaled degradation of a subset of splicing-regulatory proteins.
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Affiliation(s)
- Rebeccah J Katzenberger
- Department of Pharmacology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
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Rajan P, Gaughan L, Dalgliesh C, El-Sherif A, Robson CN, Leung HY, Elliott DJ. The RNA-binding and adaptor protein Sam68 modulates signal-dependent splicing and transcriptional activity of the androgen receptor. J Pathol 2008; 215:67-77. [PMID: 18273831 DOI: 10.1002/path.2324] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The RNA-binding protein Sam68 has been reported to be up-regulated in clinical cases of prostate cancer (PCa), where it is thought to contribute to cell proliferation and survival. Consistent with this, we observed over-expression of Sam68 in a panel of clinical prostate tumours as compared with benign controls. Since Sam68 is implicated in a number of signalling pathways, we reasoned that its role in PCa may involve modulation of the androgen receptor (AR) signalling cascade, which drives the onset and progression of PCa. We found that Sam68 interacts with the AR in vivo in LNCaP cells, and is dynamically recruited to androgen response elements within the promoter region of the prostate-specific antigen (PSA) gene. Based on its known functions and nuclear location, Sam68 might either: (a) co-regulate AR-dependent transcription positively or negatively; or (b) modulate AR-dependent alternative splicing by enhancing incorporation of a Sam68-responsive exon transcribed under the control of an androgen-responsive promoter. We tested these possibilities using functional assays. Both wild-type Sam68 protein and the Sam68(V229F) mutant, which is impaired in RNA binding, functioned as a ligand-dependent AR co-activator on an androgen-regulated reporter gene. In contrast, splicing of a Sam68-responsive variable exon, transcribed under control of an androgen-responsive promoter, was strongly repressed in the presence of AR and androgens. This splicing inhibition was reversed by ectopic expression of Sam68 but enhanced by Sam68(V229F). These results demonstrate that Sam68 has separable effects on AR-regulated transcriptional activity and alternative splicing, both of which may affect PCa phenotypes.
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Affiliation(s)
- P Rajan
- Institute of Human Genetics, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
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Ehrmann I, Dalgliesh C, Tsaousi A, Paronetto MP, Heinrich B, Kist R, Cairns P, Li W, Mueller C, Jackson M, Peters H, Nayernia K, Saunders P, Mitchell M, Stamm S, Sette C, Elliott DJ. Haploinsufficiency of the germ cell-specific nuclear RNA binding protein hnRNP G-T prevents functional spermatogenesis in the mouse. Hum Mol Genet 2008; 17:2803-18. [PMID: 18562473 DOI: 10.1093/hmg/ddn179] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Human HNRNPGT, encoding the protein hnRNP G-T, is one of several autosomal retrogenes derived from RBMX. It has been suggested that HNRNPGT functionally replaces the sex-linked RBMX and RBMY genes during male meiosis. We show here that during normal mouse germ cell development, hnRNP G-T protein is strongly expressed during and after meiosis when proteins expressed from Rbmx or Rbmx-like genes are absent. Amongst these Rbmx-like genes, DNA sequence analyses indicate that two other mouse autosomal Rbmx-derived retrogenes have evolved recently in rodents and one already shows signs of degenerating into a non-expressed pseudogene. In contrast, orthologues of Hnrnpgt are present in all four major groups of placental mammals. The sequence of Hnrnpgt is under considerable positive selection suggesting it performs an important germ cell function in eutherians. To test this, we inactivated Hnrnpgt in ES cells and studied its function during spermatogenesis in chimaeric mice. Although germ cells heterozygous for this targeted allele could produce sperm, they did not contribute to the next generation. Chimaeric mice with a high level of mutant germ cells were infertile with low sperm counts and a high frequency of degenerate seminiferous tubules and abnormal sperm. Chimaeras made from a 1:1 mix of targeted and wild-type ES cell clones transmitted wild-type germ cells only. Our data show that haploinsufficiency of Hnrnpgt results in abnormal sperm production in the mouse. Genetic defects resulting in reduced levels of HNRNPGT could, therefore, be a cause of male infertility in humans.
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Affiliation(s)
- Ingrid Ehrmann
- Institute of Human Genetics, Newcastle University, Central Parkway, Newcastle NE1 3BZ, UK
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Paronetto MP, Bianchi E, Geremia R, Sette C. Dynamic expression of the RNA-binding protein Sam68 during mouse pre-implantation development. Gene Expr Patterns 2008; 8:311-22. [PMID: 18321792 DOI: 10.1016/j.gep.2008.01.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Accepted: 01/25/2008] [Indexed: 12/23/2022]
Abstract
The STAR protein Sam68 (KHDRBS1) is involved in several aspects of post-transcriptional mRNA metabolism. Herein, we have investigated the expression and subcellular localization of Sam68 during early mouse embryogenesis. We found that mouse oocytes express high levels of Sam68 mRNA, low levels of the transcript for Khdrbs2 (current symbol for Slm-1) and no Khdrbs3 (current symbol for Slm-2), two highly homologous STAR genes. Sam68 protein is expressed throughout oocyte meiotic maturation and early embryogenesis. It is released in the cytoplasm upon meiotic resumption and it slowly accumulates in the nucleus after fertilization. Unlike what was observed for other RNA-binding proteins, nuclear accumulation of Sam68 was independent of de novo mRNA transcription. However, we found that inhibition of mRNA translation by either cycloheximide or puromycin in one-cell embryos caused the accumulation of Sam68 in cytoplasmic granules. Analysis of these granules by deconvolution microscopy demonstrated that they are sites of accumulation for proteins involved in the initiation of mRNA translation, such as eIF4A1, eIF4E and eIF4G. These granules contained RNA and were dissolved by treatment with RNase A. Other proteins expressed by the zygote, like the splicing factor SC35 or the cytoplasmic kinase ERK2, did not accumulate in such structures after treatment with inhibitors of mRNA translation, indicating that the localization of Sam68 and of the translation initiation factors in these granules is a specific event. These results indicate that Sam68 is involved in translational regulation of maternal mRNAs in the zygote and in the early signaling events triggered by fertilization.
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Affiliation(s)
- Maria Paola Paronetto
- Department of Public Health and Cell Biology, Section of Anatomy, University of Rome Tor Vergata, Via Montpellier 1, 00133 Rome, Italy
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SIAH-1 interacts with the Kaposi's sarcoma-associated herpesvirus-encoded ORF45 protein and promotes its ubiquitylation and proteasomal degradation. J Virol 2007; 82:2230-40. [PMID: 18077711 DOI: 10.1128/jvi.02285-07] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV), also referred to as human herpesvirus 8, is a potentially tumorigenic virus implicated in the etiology of Kaposi's sarcoma, primary effusion lymphoma, and some forms of multicentric Castleman's disease. The open reading frame 45 (ORF45) protein, encoded by the KSHV genome, is capable of inhibiting virus-dependent interferon induction and appears to be essential for both early and late stages of infection. In the present study, we show, both in yeast two-hybrid assays and in mammalian cells, that the ORF45 protein interacts with the cellular ubiquitin E3 ligase family designated seven in absentia homologue (SIAH). We provide evidence that SIAH-1 promotes the degradation of KSHV ORF45 through a RING domain-dependent mechanism and via the ubiquitin-proteasome system. Furthermore, our data indicate the involvement of SIAH-1 in the regulation of the expression of ORF45 in KSHV-infected cells. Since the availability of KSHV ORF45 is expected to influence the course of KSHV infection, our findings identify a novel biological role for SIAH proteins as modulators of virus infection.
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Abstract
Alternative splicing regulation has been shown to be critically important for several developmental pathways. It is particularly prevalent in the testis, which is the site of an extensive adult developmental programme. Alternative splicing is controlled by a splicing code, in which transcripts respond to subtle cell type-specific variations in positive and negative trans-acting RNA-binding proteins according to their unique set of binding sites for these proteins. Because of their unique combinations of cis-acting sequence elements, specific transcripts are able to respond individually to this code. In this review, we discuss how this code may be deciphered in germ cells to mediate a splicing response.
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Affiliation(s)
- David J Elliott
- Institute of Human Genetics, University of Newcastle, International Centre for Life, Central Parkway, Newcastle NE1 3BZ, UK.
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Mei Y, Xie C, Xie W, Wu Z, Wu M. Siah-1S, a novel splice variant of Siah-1 (seven in absentia homolog), counteracts Siah-1-mediated downregulation of beta-catenin. Oncogene 2007; 26:6319-31. [PMID: 17420721 DOI: 10.1038/sj.onc.1210449] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Siah-1 (seven in absentia homolog) is known to cause indirect degradation of beta-catenin through formation of a complex with Siah-interacting protein (SIP), Skp1 and Ebi. Here, we report the characterization of a novel splice variant of human Siah-1, designated Siah-1S, which is produced by an alternative splicing mechanism. The novel intron/exon junctions used to generate Siah-1S follow a non-conventional CT-AC rule. Siah-1S exhibits an even shorter half-life than Siah-1 and is able to catalyse self-ubiquitination that results in its subsequent degradation by proteasome. Siah-1S is shown to upregulate beta-catenin-dependent Tcf/Lef transcriptional activation and antagonize Siah-1's potentiation effect on the apoptosis induced by etoposide in MCF-7 cells. Additionally, Siah-1S is found to interact with Siah-1 to form heterodimer or with itself to form homodimer. Unlike homodimer Siah-1*Siah-1, neither Siah-1*Siah-1S nor Siah-1S*Siah-1S is able to bind to Siah-1-interacting protein, which may explain the underlying mechanism for Siah-1S's dominant negative effect on Siah-1. Importantly, results from in vitro soft agar assay demonstrated that Siah-1S displays a promotion effect on cells tumorigenicity.
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Affiliation(s)
- Y Mei
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, PR China
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Sergeant KA, Bourgeois CF, Dalgliesh C, Venables JP, Stevenin J, Elliott DJ. Alternative RNA splicing complexes containing the scaffold attachment factor SAFB2. J Cell Sci 2007; 120:309-19. [PMID: 17200140 DOI: 10.1242/jcs.03344] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The scaffold attachment factor SAFB1 and its recently discovered homologue SAFB2 might provide an important link between pre-mRNA splicing, intracellular signalling and transcription. Using novel mono-specific antisera, we found endogenous SAFB2 protein has a different spatial distribution from SAFB1 within the nucleus where it is found in much larger nuclear complexes (up to 670 kDa in size), and a distinct pattern of expression in adult human testis. By contrast, SAFB1 protein predominantly exists either as smaller complexes or as a monomeric protein. Our results suggest stable core complexes containing components comprised of SAFB1, SAFB2 and the RNA binding proteins Sam68 and hnRNPG exist in parallel with free SAFB1 protein. We found that SAFB2 protein, like SAFB1, acts as a negative regulator of a tra2β variable exon. Despite showing an involvement in splicing, we detected no stable interaction between SAFB proteins and SR or SR-related splicing regulators, although these were also found in stable higher molecular mass complexes. Each of the detected alternative splicing regulator complexes exists independently of intact nucleic acids, suggesting they might be pre-assembled and recruited to nascent transcripts as modules to facilitate alternative splicing, and/or they represent nuclear storage compartments from which active proteins are recruited.
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Affiliation(s)
- Kate A Sergeant
- Institute of Human Genetics, University of Newcastle, International Centre for Life, Central Parkway, Newcastle, NE1 3BZ, UK
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Zhang L, Guo L, Peng Y, Chen B. Expression of T-STAR gene is associated with regulation of telomerase activity in human colon cancer cell line HCT-116. World J Gastroenterol 2006; 12:4056-60. [PMID: 16810759 PMCID: PMC4087721 DOI: 10.3748/wjg.v12.i25.4056] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the effects on telomerase activity of transfection of human T-STAR gene full-length sense cDNA or partial antisense cDNA into human colon cancer cell line HCT-116.
METHODS: mRNA and protein expression levels of T-STAR gene were determined by RT-PCR and western blot, and telomerase activity was measured by PCR-ELISA, after transfection of T-STAR sense or antisense gene into HCT-116 cells with lipofectamine.
RESULTS: T-STAR gene expression was enhanced or knocked down both at mRNA and protein levels, and telomerase activity was significantly increased or decreased.
CONCLUSION: The T-STAR gene may participate in regulation of telomerase activity in human colon cancer HCT-116 cells in a parallel fashion.
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Affiliation(s)
- Ling Zhang
- Department of Disease Prevention and Health Protection, Southwest Hospital, The Third Military Medical University, Chongqing 400038, China
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Thornton JK, Dalgleish C, Venables JP, Sergeant KA, Ehrmann IE, Lu X, Saunders PTK, Elliott DJ. The tumour-suppressor protein ASPP1 is nuclear in human germ cells and can modulate ratios of CD44 exon V5 spliced isoforms in vivo. Oncogene 2006; 25:3104-12. [PMID: 16474851 DOI: 10.1038/sj.onc.1209341] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The ASPP1 (Apoptosis Stimulating Protein of p53) protein is an important tumour-suppressor. We have detected a novel protein interaction between the human ASPP1 (hASPP1) protein and the predominantly nuclear adaptor protein SAM68. In the human testis, full-length endogenous hASPP1 protein is located in the nucleus like SAM68, predominantly within meiotic and postmeiotic cells. Mouse ASPP1 (mASPP1) protein is mainly expressed in the brain and testis. The interaction with nuclear SAM68 is likely to be restricted to human germ cells, since endogenous mASPP1 protein is exclusively cytoplasmic. The C-terminal region of hASPP1 efficiently targeted a fused GFP molecule to the nucleus, whereas the N-terminus of hASPP1 targeted GFP to the cytoplasm. In the context of the full-length molecule this cytoplasmic targeting sequence is dominant in HEK293 and Saos-2 cells, since full-length hASPP1-GFP is almost exclusively cytoplasmic. Despite its predominantly cytoplasmic location, we show that ASPP1-GFP expression in HEK293 cells can regulate the ratio of alternative spliced isoforms derived from a pre-mRNA regulated downstream of cytoplasmic signalling pathways, and our data suggest that ASPP1 may operate in this case downstream or parallel to RAS signalling pathways.
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Affiliation(s)
- J K Thornton
- Institute of Human Genetics, University of Newcastle, International Centre for Life, Central Parkway, Newcastle, UK
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Moore CR, Bishop GA. Differential regulation of CD40-mediated TNF receptor-associated factor degradation in B lymphocytes. THE JOURNAL OF IMMUNOLOGY 2005; 175:3780-9. [PMID: 16148124 DOI: 10.4049/jimmunol.175.6.3780] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Engagement of CD40 on murine B cells by its ligand CD154 induces the binding of TNFR-associated factors (TRAFs) 1, 2, 3, and 6, followed by the rapid degradation of TRAFs 2 and 3. TRAF degradation occurs in response to signaling by other TNFR superfamily members, and is likely to be a normal regulatory component of signaling by this receptor family. In this study, we found that receptor-induced TRAF degradation limits TRAF2-dependent CD40 signals to murine B cells. However, TRAFs 1 and 6 are not degraded in response to CD40 engagement, despite their association with CD40. To better understand the mechanisms underlying differential TRAF degradation, mixed protein domain TRAF chimeras were analyzed in murine B cells. Chimeras containing the TRAF2 zinc (Zn) domains induced effective degradation, if attached to a TRAF domain that binds to the PXQXT motif of CD40. However, the Zn domains of TRAF3 and TRAF6 could not induce degradation in response to CD40, regardless of the TRAF domains to which they were attached. Our data indicate that TRAF2 serves as the master regulator of TRAF degradation in response to CD40 signaling, and this function is dependent upon both the TRAF Zn domains and receptor binding position.
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Affiliation(s)
- Carissa R Moore
- Interdisciplinary Graduate Program in Immunology, Veterans Affairs Medical Center, Iowa City, IA 52242, USA
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Santelli E, Leone M, Li C, Fukushima T, Preece NE, Olson AJ, Ely KR, Reed JC, Pellecchia M, Liddington RC, Matsuzawa SI. Structural analysis of Siah1-Siah-interacting protein interactions and insights into the assembly of an E3 ligase multiprotein complex. J Biol Chem 2005; 280:34278-87. [PMID: 16085652 DOI: 10.1074/jbc.m506707200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Siah1 is the central component of a multiprotein E3 ubiquitin ligase complex that targets beta-catenin for destruction in response to p53 activation. The E3 complex comprises, in addition to Siah1, Siah-interacting protein (SIP), the adaptor protein Skp1, and the F-box protein Ebi. Here we show that SIP engages Siah1 by means of two elements, both of which are required for mediating beta-catenin destruction in cells. An N-terminal dimerization domain of SIP sits across the saddle-shaped upper surface of Siah1, with two extended legs packing against the sides of Siah1 by means of a consensus PXAXVXP motif that is common to a family of Siah-binding proteins. The C-terminal domain of SIP, which binds to Skp1, protrudes from the lower surface of Siah1, and we propose that this surface provides the scaffold for bringing substrate and the E2 enzyme into apposition in the functional complex.
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Venables JP, Bourgeois CF, Dalgliesh C, Kister L, Stevenin J, Elliott DJ. Up-regulation of the ubiquitous alternative splicing factor Tra2β causes inclusion of a germ cell-specific exon. Hum Mol Genet 2005; 14:2289-303. [PMID: 16000324 DOI: 10.1093/hmg/ddi233] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We have discovered a new exon of the homeodomain-interacting kinase HipK3 that incorporates a premature stop codon and is included only in the human testis. To investigate this, we tested the effects of transfecting cells with green fluorescent protein fusions of RNA-binding proteins implicated in spermatogenesis using a novel assay based on multi-fraction fluorescence-activated cell sorting (MF-FACS). This allows the effect of a controlled titration of any splicing factor on the splicing of endogenous genes to be studied in vivo. We found that Tra2beta recapitulates testis-specific splicing of endogenous HipK3 in a concentration-dependent manner and binds specifically to a long purine-rich sequence in the novel exon. This sequence was also specifically bound by hnRNP A1, hnRNP H, ASF/SF2 and SRp40, but not by 9G8. Consistent with these observations, in vitro studies showed that this sequence shifts splicing to a downstream 5' splice site within a heterologous pre-mRNA substrate in the presence of Tra2beta, ASF/SF2 and SRp40, whereas hnRNP A1 specifically inhibits this choice. By mutating the purine-rich sequence in the context of the HipK3 gene, we also show that it is the major determinant of Tra2beta- and hnRNP A1-mediated regulation. Tra2 is essential for sex determination and spermatogenesis in flies, and Tra2beta protein was most highly expressed in testis out of six mouse tissues, whereas hnRNP A1 is down-regulated during germ cell development. Therefore, our data imply an evolutionarily conserved role for Tra2 proteins in spermatogenesis and suggest that an elevated concentration of Tra2beta may convert it into a tissue-specific splicing factor.
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Affiliation(s)
- Julian P Venables
- Institute of Human Genetics, University of Newcastle upon Tyne, International Centre for Life, Central Parkway, Newcastle upon Tyne NE1 3BZ, UK.
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Zhang L, Guo L, Peng Y, Chen B. Effects of T-STAR gene on activity of telomerase in colon cancer cell line HCT-116. Shijie Huaren Xiaohua Zazhi 2005; 13:1267-1271. [DOI: 10.11569/wcjd.v13.i11.1267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the effects of testis-signal transduction and activator of RNA (T-STAR) on telomerase activity in human colon cancer cell line HCT-116.
METHODS: The T-STAR sense or antisense gene was transfected into HCT-116 cells with lipofectamine. The mRNA and protein expression of T-STAR were determined by reverse transcription polymerase chain reaction (RT-PCR) and western blot, and the activity of telomerase was measured by PCR-ELISA.
RESULTS: The expression of T-STAR mRNA and protein were significantly increased in T-STAR transfected cells (296% and 180% respectively, P<0.01), while markedly decreased in antisense T-STAR transfected ones (59% and 83.8% respectively, P<0.01). The activity of telomerase was significantly increased in T-STAR transfected cells, but decreased in antisense T-STAR transfected ones. The expression of T-STAR and the activity of telomerase manifested no significant difference between HCT-116 cells transfected with empty vector and non-transfected ones.
CONCLUSION: T-STAR gene may play an important role in the positive regulation of telomerase activtity in human colon cancer HCT-116 cells.
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Cohen CD, Doran PP, Blattner SM, Merkle M, Wang GQ, Schmid H, Mathieson PW, Saleem MA, Henger A, Rastaldi MP, Kretzler M. Sam68-like mammalian protein 2, identified by digital differential display as expressed by podocytes, is induced in proteinuria and involved in splice site selection of vascular endothelial growth factor. J Am Soc Nephrol 2005; 16:1958-65. [PMID: 15901763 DOI: 10.1681/asn.2005020204] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Podocytes, the glomerular epithelial cells of the kidney, share important features with neuronal cells. In addition to phenotypical and functional similarities, a number of gene products have been found to be expressed exclusively or predominantly by both cell types. With the hypothesis of a common transcriptome shared by podocytes and neurons, digital differential display was used to identify novel podocyte-expressed gene products. Comparison of brain and kidney cDNA libraries with those of other organs identified Sam68-like mammalian protein 2 (SLM-2), a member of the STAR family of RNA processing proteins, as expressed by podocytes. SLM-2 expression was found to be restricted in the kidney to podocytes. In proteinuric diseases, SLM-2, a known regulator of neuronal mRNA splice site selection, was found significantly upregulated on mRNA and protein levels. Knockdown of SLM-2 by short interfering RNA in podocytes was performed to evaluate its biologic role. RNA splicing of vascular endothelial growth factor (VEGF), a key regulator of the filtration barrier and expressed as functionally distinct splice isoforms, was evaluated. VEGF(165) expression was found to be reduced by 25% after SLM-2 knockdown. In vivo, the glomerular expression of SLM-2 correlated with the mRNA levels of VEGF(165). This study demonstrates the power of digital differential display to predict cell type-specific gene expression by hypothesis-driven analysis of tissue cDNA libraries. SLM-2-dependent VEGF splicing indicates the importance of mRNA splice site selection for glomerular filtration barrier function.
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Affiliation(s)
- Clemens D Cohen
- Medizinische Poliklinik, Ludwig-Maximilians-University, Pettenkoferstrasse 8A, Munich, 80336, Germany.
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Oliver PL, Davies KE. Analysis of human neurological disorders using mutagenesis in the mouse. Clin Sci (Lond) 2005; 108:385-97. [PMID: 15831088 DOI: 10.1042/cs20050041] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The mouse continues to play a vital role in the deciphering of mammalian gene function and the modelling of human neurological disease. Advances in gene targeting technologies have facilitated the efficiency of generating new mouse mutants, although this valuable resource has rapidly expanded in recent years due to a number of major random mutagenesis programmes. The phenotype-driven mutagenesis screen at the MRC Mammalian Genetics Unit has generated a significant number of mice with potential neurological defects, and our aim has been to characterize selected mutants on a pathological and molecular level. Four lines are discussed, one displaying late-onset ataxia caused by Purkinje cell loss and an allelic series of three tremor mutants suffering from hypomyelination of the peripheral nerve. Molecular analysis of the causative mutation in each case has provided new insights into functional aspects of the mutated proteins, illustrating the power of mutagenesis screens to generate both novel and clinically relevant disease models.
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Affiliation(s)
- Peter L Oliver
- MRC Functional Genetics Unit, Department of Human Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
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Abstract
Post-transcriptional mechanisms play an important role in the biology of germ cells, where they control key developmental decisions in cell division, differentiation and death. Because these post-transcriptional controls are cell-type-specific, and often utilize germ-cell-specific RNA-binding proteins, they provide useful diagnostic markers for male infertility and testicular cancer. Investigation of the genetics of male infertility in men and model organisms suggests that disruption of post-transcriptional control mechanisms can cause specific germ cell pathologies, and these studies point to future possible therapeutic routes for restoring spermatogenesis.
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Affiliation(s)
- Ingrid Ehrmann
- Institute of Human Genetics, International Centre for Life, Central Parkway, Newcastle NE1 3BZ, UK
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Bitoun E, Davies KE. The robotic mouse: unravelling the function of AF4 in the cerebellum. CEREBELLUM (LONDON, ENGLAND) 2005; 4:250-60. [PMID: 16321881 DOI: 10.1080/14734220500325897] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The devastating nature and lack of effective treatments associated with neurodegenerative diseases have stimulated a world-wide search for the elucidation of their molecular basis to which mouse models have made a major contribution. In combination with transgenic and knockout technologies, large-scale mouse mutagenesis is a powerful approach for the identification of new genes and associated signalling pathways controlling neuronal cell death and survival. Here we review the characterization of the robotic mouse, a novel model of autosomal dominant cerebellar ataxia isolated from an ENU-mutagenesis programme, which develops adult-onset region-specific Purkinje cell loss and cataracts, and displays defects in early T-cell maturation and general growth retardation. The mutated protein, Af4, is a member of the AF4/LAF4/FMR2 (ALF) family of putative transcription factors previously implicated in childhood leukaemia and FRAXE mental retardation. The mutation, which lies in a highly conserved region among the ALF family members, significantly reduces the binding affinity of Af4 to the E3 ubiquitin-ligase Siah-1a, isolated with Siah-2 as interacting proteins in the brain. This leads to a markedly slower turnover of mutant Af4 by the ubiquitin-proteasome pathway and consequently to its abnormal accumulation in the robotic mouse. Importantly, the conservation of the Siah-binding domain of Af4 in all other family members reveals that Siah-mediated proteasomal degradation is a common regulatory mechanism that controls the levels, and thereby the function, of the ALF family. The robotic mouse represents a unique model in which to study the newly revealed role of Af4 in the maintenance of vital functions of Purkinje cells in the cerebellum and further the understanding of its implication in lymphopoeisis.
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Affiliation(s)
- Emmanuelle Bitoun
- MRC Functional Genetics Unit, Department of Human Anatomy and Genetics, University of Oxford, Oxford, UK
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Haegebarth A, Heap D, Bie W, Derry JJ, Richard S, Tyner AL. The nuclear tyrosine kinase BRK/Sik phosphorylates and inhibits the RNA-binding activities of the Sam68-like mammalian proteins SLM-1 and SLM-2. J Biol Chem 2004; 279:54398-404. [PMID: 15471878 DOI: 10.1074/jbc.m409579200] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Expression of the intracellular tyrosine kinase BRK/Sik is epithelial-specific and regulated during differentiation. Only a few substrates have been identified for BRK/Sik, including the KH domain containing RNA-binding protein Sam68 and the novel adaptor protein BKS. Although the physiological role of Sam68 is unknown, it has been shown to regulate mRNA transport, pre-mRNA splicing, and polyadenylation. Here we demonstrate that the Sam68-like mammalian proteins SLM-1 and SLM-2 but not the related KH domain containing heterogeneous nuclear ribonucleoprotein K are novel substrates of BRK/Sik. The expression of active BRK/Sik results in increased SLM-1 and SLM-2 phosphorylation and increased retention of BRK/Sik within the nucleus. The phosphorylation of SLM-1 and SLM-2 has functional relevance and leads to inhibition of their RNA-binding abilities. We show that SLM-1, SLM-2, and BRK/Sik have restricted patterns of expression unlike the ubiquitously expressed Sam68. Moreover, BRK/Sik, SLM-1, and Sam68 transcripts were coexpressed in the mouse gastrointestinal tract and skin, suggesting that SLM-1 and Sam68 could be physiologically relevant BRK/Sik targets in vivo. The ability of BRK/Sik to negatively regulate the RNA-binding activities of the KH domain RNA binding proteins SLM-1 and Sam68 may have an impact on the posttranscriptional regulation of epithelial cell gene expression.
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Affiliation(s)
- Andrea Haegebarth
- Departments of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607, USA
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