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Zhao B, Deng J, Ma M, Li N, Zhou J, Li X, Luan T. Environmentally relevant concentrations of 2,3,7,8-TCDD induced inhibition of multicellular alternative splicing and transcriptional dysregulation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 919:170892. [PMID: 38346650 DOI: 10.1016/j.scitotenv.2024.170892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 02/07/2024] [Accepted: 02/09/2024] [Indexed: 02/17/2024]
Abstract
Alternative splicing (AS), found in approximately 95 % of human genes, significantly amplifies protein diversity and is implicated in disease pathogenesis when dysregulated. However, the precise involvement of AS in the toxic mechanisms induced by TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) remains incompletely elucidated. This study conducted a thorough global AS analysis in six human cell lines following TCDD exposure. Our findings revealed that environmentally relevant concentration (0.1 nM) of TCDD significantly suppressed AS events in all cell types, notably inhibiting diverse splicing events and reducing transcript diversity, potentially attributed to modifications in the splicing patterns of the inhibitory factor family, particularly hnRNP. And we identified 151 genes with substantial AS alterations shared among these cell types, particularly enriched in immune and metabolic pathways. Moreover, TCDD induced cell-specific changes in splicing patterns and transcript levels, with increased sensitivity notably in THP-1 monocyte, potentially linked to aberrant expression of pivotal genes within the spliceosome pathway (DDX5, EFTUD2, PUF60, RBM25, SRSF1, and CRNKL1). This study extends our understanding of disrupted alternative splicing and its relation to the multisystem toxicity of TCDD. It sheds light on how environmental toxins affect post-transcriptional regulatory processes, offering a fresh perspective for toxicology and disease etiology investigations.
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Affiliation(s)
- Bilin Zhao
- Guangdong Provincial Laboratory of Chemistry and Fine Chemical Engineering Jieyang Center, Jieyang 515200, China; Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Jiewei Deng
- Guangdong Provincial Laboratory of Chemistry and Fine Chemical Engineering Jieyang Center, Jieyang 515200, China; School of Biomedical and Pharmaceutical Sciences, Guangdong University of Technology, Guangzhou 510006, China; Smart Medical Innovation Technology Center, Guangdong University of Technology, Guangzhou 510006, China
| | - Mei Ma
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Na Li
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Junlin Zhou
- Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Xinyan Li
- Guangdong Provincial Laboratory of Chemistry and Fine Chemical Engineering Jieyang Center, Jieyang 515200, China; School of Biomedical and Pharmaceutical Sciences, Guangdong University of Technology, Guangzhou 510006, China; Smart Medical Innovation Technology Center, Guangdong University of Technology, Guangzhou 510006, China.
| | - Tiangang Luan
- Guangdong Provincial Laboratory of Chemistry and Fine Chemical Engineering Jieyang Center, Jieyang 515200, China; Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China; Smart Medical Innovation Technology Center, Guangdong University of Technology, Guangzhou 510006, China
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2
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Fackenthal JD. Alternative mRNA Splicing and Promising Therapies in Cancer. Biomolecules 2023; 13:biom13030561. [PMID: 36979496 PMCID: PMC10046298 DOI: 10.3390/biom13030561] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 03/09/2023] [Accepted: 03/16/2023] [Indexed: 03/30/2023] Open
Abstract
Cancer is among the leading causes of mortality worldwide. While considerable attention has been given to genetic and epigenetic sources of cancer-specific cellular activities, the role of alternative mRNA splicing has only recently received attention as a major contributor to cancer initiation and progression. The distribution of alternate mRNA splicing variants in cancer cells is different from their non-cancer counterparts, and cancer cells are more sensitive than non-cancer cells to drugs that target components of the splicing regulatory network. While many of the alternatively spliced mRNAs in cancer cells may represent "noise" from splicing dysregulation, certain recurring splicing variants have been shown to contribute to tumor progression. Some pathogenic splicing disruption events result from mutations in cis-acting splicing regulatory sequences in disease-associated genes, while others may result from shifts in balance among naturally occurring alternate splicing variants among mRNAs that participate in cell cycle progression and the regulation of apoptosis. This review provides examples of cancer-related alternate splicing events resulting from each step of mRNA processing and the promising therapies that may be used to address them.
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Affiliation(s)
- James D Fackenthal
- Department of Biological Sciences, College of Science and Health, Benedictine University, Lisle, IL 60532, USA
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3
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Wang D, Quesnel-Vallieres M, Jewell S, Elzubeir M, Lynch K, Thomas-Tikhonenko A, Barash Y. A Bayesian model for unsupervised detection of RNA splicing based subtypes in cancers. Nat Commun 2023; 14:63. [PMID: 36599821 PMCID: PMC9813260 DOI: 10.1038/s41467-022-35369-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 11/29/2022] [Indexed: 01/06/2023] Open
Abstract
Identification of cancer sub-types is a pivotal step for developing personalized treatment. Specifically, sub-typing based on changes in RNA splicing has been motivated by several recent studies. We thus develop CHESSBOARD, an unsupervised algorithm tailored for RNA splicing data that captures "tiles" in the data, defined by a subset of unique splicing changes in a subset of patients. CHESSBOARD allows for a flexible number of tiles, accounts for uncertainty of splicing quantification, and is able to model missing values as additional signals. We first apply CHESSBOARD to synthetic data to assess its domain specific modeling advantages, followed by analysis of several leukemia datasets. We show detected tiles are reproducible in independent studies, investigate their possible regulatory drivers and probe their relation to known AML mutations. Finally, we demonstrate the potential clinical utility of CHESSBOARD by supplementing mutation based diagnostic assays with discovered splicing profiles to improve drug response correlation.
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Affiliation(s)
- David Wang
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Graduate Group in Genomics and Computational Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Mathieu Quesnel-Vallieres
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - San Jewell
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Moein Elzubeir
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Kristen Lynch
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Andrei Thomas-Tikhonenko
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Division of Cancer Pathobiology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Yoseph Barash
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- Department of Computer and Information Sciences, School of Engineering, University of Pennsylvania, Philadelphia, PA, USA.
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4
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Gurunathan S, Kim JH. Graphene Oxide Enhances Biogenesis and Release of Exosomes in Human Ovarian Cancer Cells. Int J Nanomedicine 2022; 17:5697-5731. [PMID: 36466784 PMCID: PMC9717435 DOI: 10.2147/ijn.s385113] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 11/04/2022] [Indexed: 07/20/2023] Open
Abstract
BACKGROUND Exosomes, which are nanovesicles secreted by almost all the cells, mediate intercellular communication and are involved in various physiological and pathological processes. We aimed to investigate the effects of graphene oxide (GO) on the biogenesis and release of exosomes in human ovarian cancer (SKOV3) cells. METHODS Exosomes were isolated using ultracentrifugation and ExoQuick and characterized by various analytical techniques. The expression levels of exosome markers were analyzed via quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. RESULTS Graphene oxide (10-50 μg/mL), cisplatin (2-10 μg/mL), and C6-ceramide (5-25 μM) inhibited the cell viability, proliferation, and cytotoxicity in a dose-dependent manner. We observed that graphene oxide (GO), cisplatin (CIS), and C6-Ceramide (C6-Cer) stimulated acetylcholine esterase and neutral sphingomyelinase activity, total exosome protein concentration, and exosome counts associated with increased level of apoptosis, oxidative stress and endoplasmic reticulum stress. In contrast, GW4869 treatment inhibits biogenesis and release of exosomes. We observed that the human ovarian cancer cells secreted exosomes with typical cup-shaped morphology and surface protein biomarkers. The expression levels of TSG101, CD9, CD63, and CD81 were significantly higher in GO-treated cells than in control cells. Further, cytokine and chemokine levels were significantly higher in exosomes isolated from GO-treated SKOV3 cells than in those isolated from control cells. SKOV3 cells pre-treated with N-acetylcysteine or GW4869 displayed a significant reduction in GO-induced exosome biogenesis and release. Furthermore, endocytic inhibitors decrease exosome biogenesis and release by impairing endocytic pathways. CONCLUSION This study identifies GO as a potential tool for targeting the exosome pathway and stimulating exosome biogenesis and release. We believe that the knowledge acquired in this study can be potentially extended to other exosome-dominated pathologies and model systems. Furthermore, these nanoparticles can provide a promising means to enhance exosome production in SKOV3 cells.
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Affiliation(s)
- Sangiliyandi Gurunathan
- Department of Stem Cell and Regenerative Biotechnology, Konkuk University, Seoul, 05029, Korea
| | - Jin Hoi Kim
- Department of Stem Cell and Regenerative Biotechnology, Konkuk University, Seoul, 05029, Korea
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5
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Multilevel Regulation of Protein Kinase CδI Alternative Splicing by Lithium Chloride. Mol Cell Biol 2021; 41:e0033820. [PMID: 33288642 PMCID: PMC8088272 DOI: 10.1128/mcb.00338-20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Lithium chloride (LiCl) is commonly used in treatment of mood disorders; however, its usage leads to weight gain, which promotes metabolic disorders. Protein kinase C delta (PKCδ), a serine/threonine kinase, is alternatively spliced to PKCδI and PKCδII in 3T3-L1 cells. We previously demonstrated that PKCδI is the predominantly expressed isoform in 3T3-L1 preadipocytes. Here, we demonstrate that LiCl treatment decreases PKCδI levels, increases formation of lipid droplets, and increases oxidative stress. Hence, we investigated the molecular mechanisms underlying the regulation of PKCδI alternative splicing by LiCl. We previously demonstrated that the splice factor SFRS10 is essential for PKCδI splicing. Our results demonstrate that glycogen synthase kinase 3 beta (GSK3β) phosphorylates SFRS10, and SFRS10 is in a complex with long noncoding RNA NEAT1 to promote PKCδI splicing. Using PKCδ splicing minigene and RNA immunoprecipitation assays, our results demonstrate that upon LiCl treatment, NEAT1 levels are reduced, GSK3β activity is inhibited, and SFRS10 phosphorylation is decreased, which leads to decreased expression of PKCδI. Integration of the GSK3β signaling pathway with the ribonucleoprotein complex of long noncoding RNA (lncRNA) NEAT1 and SFRS10 enables fine-tuning of PKCδI expression during adipogenesis. Knowledge of the molecular pathways impacted by LiCl provides an understanding of the ascent of obesity as a comorbidity in disease management.
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Medatwal N, Ansari MN, Kumar S, Pal S, Jha SK, Verma P, Rana K, Dasgupta U, Bajaj A. Hydrogel-mediated delivery of celastrol and doxorubicin induces a synergistic effect on tumor regression via upregulation of ceramides. NANOSCALE 2020; 12:18463-18475. [PMID: 32941570 DOI: 10.1039/d0nr01066a] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The release of anticancer drugs in systemic circulation and their associated toxicity are responsible for the poor efficacy of chemotherapy. Therefore, the identification of new chemotherapeutic combinations designed to be released near the tumor site in a sustained manner has the potential to enhance the efficacy and reduce the toxicity associated with chemotherapy. Here, we present the identification of a combination of doxorubicin, a DNA-binding topoisomerase inhibitor, with a naturally occurring triterpenoid, celastrol, that induces a synergistic effect on the apoptosis of colon cancer cells. Hydrogel-mediated sustained release of a combination of doxorubicin and celastrol in a murine tumor model abrogates tumor proliferation, and increases the median survival with enhanced apoptosis and concurrent reduction in proliferation. Sphingolipid profiling (LC-MS/MS) of treated tumors showed that the combination of celastrol and doxorubicin induces global changes in the expression of sphingolipids with an increase in levels of ceramides. We further demonstrate that this dual drug combination induces a significant increase in the expression of ceramide synthase 1, 4, and 6, thereby increasing the level of ceramides that contribute to the synergistic apoptotic effect. Therefore, hydrogel-mediated localized delivery of a combination of celastrol and doxorubicin provides a new therapeutic combination that induces a sphingolipid-mediated synergistic effect against colon cancer.
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Affiliation(s)
- Nihal Medatwal
- Laboratory of Nanotechnology and Chemical Biology, Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, NCR Biotech Science Cluster, Faridabad-121001, Haryana, India.
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7
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Konieczny P, Artero R. Drosophila SMN2 minigene reporter model identifies moxifloxacin as a candidate therapy for SMA. FASEB J 2019; 34:3021-3036. [PMID: 31909520 DOI: 10.1096/fj.201802554rrr] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 12/12/2019] [Accepted: 12/16/2019] [Indexed: 12/24/2022]
Abstract
Spinal muscular atrophy is a rare and fatal neuromuscular disorder caused by the loss of alpha motor neurons. The affected individuals have mutated the ubiquitously expressed SMN1 gene resulting in the loss or reduction in the survival motor neuron (SMN) protein levels. However, an almost identical paralog exists in humans: SMN2. Pharmacological activation of SMN2 exon 7 inclusion by small molecules or modified antisense oligonucleotides is a valid approach to treat SMA. Here we describe an in vivo SMN2 minigene reporter system in Drosophila motor neurons that serves as a cost-effective, feasible, and stringent primary screening model for identifying chemicals capable of crossing the conserved Drosophila blood-brain barrier and modulating exon 7 inclusion. The model was used for the screening of 1100 drugs from the Prestwick Chemical Library, resulting in 2.45% hit rate. The most promising candidate drugs were validated in patient-derived fibroblasts where they proved to increase SMN protein levels. Among them, moxifloxacin modulated SMN2 splicing by promoting exon 7 inclusion. The recovery of SMN protein levels was confirmed by increased colocalization of nuclear gems with Cajal Bodies. Thus, a Drosophila-based drug screen allowed the discovery of an FDA-approved small molecule with the potential to become a novel therapy for SMA.
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Affiliation(s)
- Piotr Konieczny
- Interdisciplinary Research Structure for Biotechnology and Biomedicine (ERI BIOTECMED), University of Valencia, Valencia, Spain.,Translational Genomics Group, Incliva Health Research Institute, Valencia, Spain.,Incliva-CIPF Joint Unit, Valencia, Spain
| | - Rubén Artero
- Interdisciplinary Research Structure for Biotechnology and Biomedicine (ERI BIOTECMED), University of Valencia, Valencia, Spain.,Translational Genomics Group, Incliva Health Research Institute, Valencia, Spain.,Incliva-CIPF Joint Unit, Valencia, Spain
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8
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Koganti S, Burgula S, Bhaduri-McIntosh S. STAT3 activates the anti-apoptotic form of caspase 9 in oncovirus-infected B lymphocytes. Virology 2019; 540:160-164. [PMID: 31928997 DOI: 10.1016/j.virol.2019.11.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 11/05/2019] [Accepted: 11/18/2019] [Indexed: 10/25/2022]
Abstract
The cancer-causing Epstein-Barr virus (EBV) activates the transcription factor STAT3 upon infecting B-lymphocytes. STAT3 then activates caspase 7 to degrade cellular claspin, resulting in impaired Chk1 phosphorylation. This blockade of ATR-Chk1 signaling allows EBV-transformed cells to proliferate despite DNA lesions from virus-induced replication stress. In addressing the mechanism of caspase 7 activation, we now report that in newly-infected B-cells, STAT3 transcriptionally activates the initiator caspase, caspase 9. Caspase 9 then activates caspase 7 to impair phosphorylation of Chk1 at S345. Importantly, although cleaved products of caspase 9 are detectable in infected cells, there is simultaneous increase in the alternatively-spliced dominant-negative form of caspase 9 - and - expression of dominant-negative caspase 9 is abrogated when STAT3 activation is impaired. Thus EBV, via STAT3, activates caspase 9 but also shifts the balance of transcripts towards its dominant-negative form to allow activation of caspase 7 while avoiding death of EBV-infected cells.
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Affiliation(s)
- Siva Koganti
- Division of Infectious Diseases, Department of Pediatrics, Stony Brook University, NY, USA
| | - Sandeepta Burgula
- Division of Infectious Diseases, Department of Pediatrics, Stony Brook University, NY, USA
| | - Sumita Bhaduri-McIntosh
- Division of Infectious Diseases, Department of Pediatrics, University of Florida, Gainesville, FL, USA; Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA.
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9
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Pearson JM, Tan SF, Sharma A, Annageldiyev C, Fox TE, Abad JL, Fabrias G, Desai D, Amin S, Wang HG, Cabot MC, Claxton DF, Kester M, Feith DJ, Loughran TP. Ceramide Analogue SACLAC Modulates Sphingolipid Levels and MCL-1 Splicing to Induce Apoptosis in Acute Myeloid Leukemia. Mol Cancer Res 2019; 18:352-363. [PMID: 31744877 DOI: 10.1158/1541-7786.mcr-19-0619] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/30/2019] [Accepted: 11/15/2019] [Indexed: 02/06/2023]
Abstract
Acute myeloid leukemia (AML) is a disease characterized by uncontrolled proliferation of immature myeloid cells in the blood and bone marrow. The 5-year survival rate is approximately 25%, and recent therapeutic developments have yielded little survival benefit. Therefore, there is an urgent need to identify novel therapeutic targets. We previously demonstrated that acid ceramidase (ASAH1, referred to as AC) is upregulated in AML and high AC activity correlates with poor patient survival. Here, we characterized a novel AC inhibitor, SACLAC, that significantly reduced the viability of AML cells with an EC50 of approximately 3 μmol/L across 30 human AML cell lines. Treatment of AML cell lines with SACLAC effectively blocked AC activity and induced a decrease in sphingosine 1-phosphate and a 2.5-fold increase in total ceramide levels. Mechanistically, we showed that SACLAC treatment led to reduced levels of splicing factor SF3B1 and alternative MCL-1 mRNA splicing in multiple human AML cell lines. This increased proapoptotic MCL-1S levels and contributed to SACLAC-induced apoptosis in AML cells. The apoptotic effects of SACLAC were attenuated by SF3B1 or MCL-1 overexpression and by selective knockdown of MCL-1S. Furthermore, AC knockdown and exogenous C16-ceramide supplementation induced similar changes in SF3B1 level and MCL-1S/L ratio. Finally, we demonstrated that SACLAC treatment leads to a 37% to 75% reduction in leukemic burden in two human AML xenograft mouse models. IMPLICATIONS: These data further emphasize AC as a therapeutic target in AML and define SACLAC as a potent inhibitor to be further optimized for future clinical development.
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Affiliation(s)
- Jennifer M Pearson
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia
| | - Su-Fern Tan
- Department of Medicine, Division of Hematology & Oncology, University of Virginia, Charlottesville, Virginia
| | - Arati Sharma
- Penn State Cancer Institute, Hershey, Pennsylvania.,Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania
| | | | - Todd E Fox
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia
| | - Jose Luis Abad
- Department of Biological Chemistry, Networking Biomedical Research Centre on Liver and Digestive Diseases (CIBER-EHD), Institute for Advanced Chemistry of Catalonia, Spanish National Research Council (IQAC-CSIC), Barcelona, Spain
| | - Gemma Fabrias
- Department of Biological Chemistry, Networking Biomedical Research Centre on Liver and Digestive Diseases (CIBER-EHD), Institute for Advanced Chemistry of Catalonia, Spanish National Research Council (IQAC-CSIC), Barcelona, Spain
| | - Dhimant Desai
- Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania
| | - Shantu Amin
- Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania
| | - Hong-Gang Wang
- Penn State Cancer Institute, Hershey, Pennsylvania.,Department of Pediatrics, Penn State College of Medicine, Hershey, Pennsylvania
| | - Myles C Cabot
- Department of Biochemistry and Molecular Biology, East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | | | - Mark Kester
- Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania.,University of Virginia Cancer Center, Charlottesville, Virginia
| | - David J Feith
- Department of Medicine, Division of Hematology & Oncology, University of Virginia, Charlottesville, Virginia.,University of Virginia Cancer Center, Charlottesville, Virginia
| | - Thomas P Loughran
- Department of Medicine, Division of Hematology & Oncology, University of Virginia, Charlottesville, Virginia. .,University of Virginia Cancer Center, Charlottesville, Virginia
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10
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Dumont AA, Dumont L, Berthiaume J, Auger-Messier M. p38α MAPK proximity assay reveals a regulatory mechanism of alternative splicing in cardiomyocytes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:118557. [PMID: 31505169 DOI: 10.1016/j.bbamcr.2019.118557] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 08/30/2019] [Accepted: 09/05/2019] [Indexed: 11/26/2022]
Abstract
The p38 mitogen-activated protein kinase (MAPK) signaling pathway is essential for normal heart function. However, p38 also contributes to heart failure pathogenesis by affecting cardiomyocytes contractility and survival. To unravel part of the complex role of p38 in cardiac function, we performed an APEX2-based proximity assay in cultured neonatal rat ventricular myocytes and identified the protein interaction networks (interactomes) of two highly expressed p38 isoforms in the heart. We found that p38α and p38γ have distinct interactomes in cardiomyocytes under both basal and osmotic stress-activated states. Interestingly, the activated p38α interactome contains many RNA-binding proteins implicated in splicing, including the serine/arginine-rich splicing factor 3 (SRSF3). Its interaction with the activated p38α was validated by co-immunoprecipitation. The cytoplasmic abundance and alternative splicing function of SRSF3 are also both modulated by the p38 signaling pathway. Our findings reveal a new function for p38 as a specific regulator of SRSF3 in cardiomyocytes.
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Affiliation(s)
- Audrey-Ann Dumont
- Département de Médecine, Service de Cardiologie, Centre de Recherche du CHUS, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Lauralyne Dumont
- Département de Médecine, Service de Cardiologie, Centre de Recherche du CHUS, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Jonathan Berthiaume
- Département de Médecine, Service de Cardiologie, Centre de Recherche du CHUS, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Mannix Auger-Messier
- Département de Médecine, Service de Cardiologie, Centre de Recherche du CHUS, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada.
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11
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Lu P, White-Gilbertson S, Nganga R, Kester M, Voelkel-Johnson C. Expression of the SNAI2 transcriptional repressor is regulated by C 16-ceramide. Cancer Biol Ther 2019; 20:922-930. [PMID: 30836822 DOI: 10.1080/15384047.2019.1579962] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Ceramide synthase 6 (CerS6) is an enzyme that preferentially generates pro-apoptotic C16-ceramide in the sphingolipid metabolic pathway. Reduced expression of CerS6 has been associated with apoptosis resistance and recent studies point to a role for CerS6 in epithelial mesenchymal transition (EMT). Because cells that undergo EMT are also more resistant to apoptosis, we hypothesized that reduced expression of CerS6 could induce changes that are associated with EMT. We found that shRNA-mediated knockdown of CerS6 increases expression of the EMT transcription factor SNAI2 but not SNAI1 or TWIST. Treatment with C6-ceramide nanoliposomes (CNL) resulted in a preferential increase in C16-ceramide and suppressed SNAI2 transcriptional activation and protein expression. The increase in C16-ceramide following CNL treatment was dependent on CerS activity and occurred even when CerS6 shRNA was expressed. shRNA against CerS5, which like CerS6 preferentially generates C16-ceramide, also decreased transcriptional activation of SNAI2, suggesting a role for C16-ceramide rather than a specific enzyme in the regulation of this transcription factor. While loss of CerS6 has been associated with apoptosis resistance, we found that cells lacking this protein are more susceptible to the effects CNL. In summary, our study identifies SNAI2 as a novel target whose expression can be influenced by C16-ceramide levels. The potential of CNL to suppress SNAI2 expression has important clinical implications, since elevated expression of this transcription factor has been associated with an aggressive phenotype or poor outcomes in several types of solid tumors.
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Affiliation(s)
- Ping Lu
- a Department of Microbiology & Immunology , Medical University of South Carolina , Charleston , SC , USA.,b Hollings Cancer Center , Medical University of South Carolina , Charleston , SC , USA
| | - Shai White-Gilbertson
- a Department of Microbiology & Immunology , Medical University of South Carolina , Charleston , SC , USA.,b Hollings Cancer Center , Medical University of South Carolina , Charleston , SC , USA
| | - Rose Nganga
- b Hollings Cancer Center , Medical University of South Carolina , Charleston , SC , USA.,c Department of Biochemistry & Molecular Biology , Medical University of South Carolina , Charleston , SC , USA
| | - Mark Kester
- d Department of Pharmacology, Biomedical Engineering, Molecular Physiology and Biophysics , University of Virginia , Charlottesville , VA , USA
| | - Christina Voelkel-Johnson
- a Department of Microbiology & Immunology , Medical University of South Carolina , Charleston , SC , USA.,b Hollings Cancer Center , Medical University of South Carolina , Charleston , SC , USA
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12
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Wang SB, Ma YY, Chen XY, Zhao YY, Mou XZ. Ceramide-Graphene Oxide Nanoparticles Enhance Cytotoxicity and Decrease HCC Xenograft Development: A Novel Approach for Targeted Cancer Therapy. Front Pharmacol 2019; 10:69. [PMID: 30800068 PMCID: PMC6376252 DOI: 10.3389/fphar.2019.00069] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 01/21/2019] [Indexed: 12/19/2022] Open
Abstract
Despite substantial efforts to develop novel therapeutic strategies for treating hepatocellular carcinoma (HCC), the effectiveness and specificity of available drugs still require further improvement. Previous work has shown that exogenous ceramide can play a key role in inducing the apoptotic death of cancer cells, however, the poor water-solubility of this compound has hampered its use for cancer treatment. In the present study, we used polyethylene glycol (PEG) and polyethylenimine (PEI) co-conjugated ultra-small nano-GO (NGO-PEG-PEI) loaded with C6-ceramide (NGO-PEG-PEI/Cer) as a strategy for HCC treatment. We assessed the biological role of NGO-PEG-PEI/Cer, and we assessed its antitumor efficacy against HCC both in vitro and in vivo in combination with the chemotherapeutic drug sorafenib. We found that NGO-PEG-PEI significantly enhanced the cellular uptake of C6-ceramide. By investigating the mechanism of cellular delivery, we determined that the internalization of NGO-PEG-PEI/Cer progressed primarily via a clathrin-mediated mechanism. The combination of NGO-PEG-PEI/Cer and sorafenib exhibited synergy between these two drugs. Further work revealed that NGO-PEG-PEI/Cer may play a role in subverting multidrug resistance (MDR) in HCC cells by inactivating MDR and Akt signaling. NGO-PEG-PEI/Cer also significantly inhibited tumor growth and improved survival times in vivo, and the synergetic effect of NGO-PEG-PEI/Cer combined with sorafenib was also observed in drug-resistant HCC xenografts. In conclusion, our NGO-PEG-PEI nanocomposite is an effective nano-platform for loading C6-ceramide for therapeutic use in treating HCC, exhibiting high cancer cell killing potency in this tumor model. The NGO-PEG-PEI/Cer/sorafenib combination additionally represents a promising potential therapeutic strategy for the treatment of drug-resistant HCC.
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Affiliation(s)
- Shi-Bing Wang
- Key Laboratory of Tumor Molecular Diagnosis and Individualized Medicine of Zhejiang Province, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China.,Clinical Research Institute, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Ying-Yu Ma
- Clinical Research Institute, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Xiao-Yi Chen
- Key Laboratory of Tumor Molecular Diagnosis and Individualized Medicine of Zhejiang Province, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Yuan-Yuan Zhao
- Key Laboratory of Tumor Molecular Diagnosis and Individualized Medicine of Zhejiang Province, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Xiao-Zhou Mou
- Key Laboratory of Tumor Molecular Diagnosis and Individualized Medicine of Zhejiang Province, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China.,Clinical Research Institute, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
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13
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Uddin MB, Roy KR, Hosain SB, Khiste SK, Hill RA, Jois SD, Zhao Y, Tackett AJ, Liu YY. An N 6-methyladenosine at the transited codon 273 of p53 pre-mRNA promotes the expression of R273H mutant protein and drug resistance of cancer cells. Biochem Pharmacol 2018; 160:134-145. [PMID: 30578766 DOI: 10.1016/j.bcp.2018.12.014] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 12/18/2018] [Indexed: 02/06/2023]
Abstract
Mutant p53 proteins that promote cancer cell invasive growth, metastasis and drug resistance emerge as therapeutic targets. Previously, we reported that suppression of ceramide glycosylation restored wild-type p53 protein and tumor suppressing function in cancer cells heterozygously carrying p53 R273H, a hot-spot missense mutation; however, the mechanisms underlying the control of mutant protein expression remain elusive. Herein, we report that an N6-methyladenosine (m6A) at the point-mutated codon 273 (G > A) of p53 pre-mRNA determines the mutant protein expression. Methylation of the transited adenosine was catalyzed by methyltransferase like 3 (METTL3), and this m6A-RNA promoted a preferential pre-mRNA splicing; consequently, the produced p53 R273H mutant protein resulted in acquired multidrug resistance in colon cancer cells. Furthermore, glycosphingolipids (particularly globotriaosylceramide) generated from serial ceramide glycosylation were seen to activate cSrc and β-catenin signaling so as to upregulate METTL3 expression, in turn promoting expression of p53 R273H mutant protein, with consequent drug resistance. Conversely, either silencing METTL3 expression by using small interfering RNA (siRNA) or inhibiting RNA methylation with neplanocin A suppressed m6A formation in p53 pre-mRNA, and substantially increased the level of phosphorylated p53 protein (Ser15) and its function in cells heterozygously carrying the R273H mutation, thereby re-sensitizing these cells to anticancer drugs. Concordantly, suppression of ceramide glycosylation repressed METTL3 expression and m6A formation in p53 pre-mRNA, thus sensitizing cells carrying R273H to anticancer drugs. This study uncovers a novel function of pre-mRNA m6A as a determinant of mutant protein expression in cancer cells heterozygously carrying the TP53 R273H mutation. Suppressing both RNA methylation and ceramide glycosylation might constitute an efficacious and specific approach for targeting TP53 missense mutations coding for a G > A transition, thereby improving cancer treatments.
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Affiliation(s)
- Mohammad B Uddin
- School of Basic Pharmaceutical and Toxicological Sciences, University of Louisiana at Monroe, Monroe, LA 71201, USA
| | - Kartik R Roy
- School of Basic Pharmaceutical and Toxicological Sciences, University of Louisiana at Monroe, Monroe, LA 71201, USA
| | - Salman B Hosain
- School of Basic Pharmaceutical and Toxicological Sciences, University of Louisiana at Monroe, Monroe, LA 71201, USA
| | - Sachin K Khiste
- School of Basic Pharmaceutical and Toxicological Sciences, University of Louisiana at Monroe, Monroe, LA 71201, USA
| | - Ronald A Hill
- School of Basic Pharmaceutical and Toxicological Sciences, University of Louisiana at Monroe, Monroe, LA 71201, USA
| | - Seetharama D Jois
- School of Basic Pharmaceutical and Toxicological Sciences, University of Louisiana at Monroe, Monroe, LA 71201, USA
| | - Yunfeng Zhao
- Department of Pharmacology, Toxicology & Neuroscience, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - Alan J Tackett
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Yong-Yu Liu
- School of Basic Pharmaceutical and Toxicological Sciences, University of Louisiana at Monroe, Monroe, LA 71201, USA.
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14
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Xu L, Zhang H, Mei M, Du C, Huang X, Li J, Wang Y, Bao S, Zheng H. Phosphorylation of serine/arginine-rich splicing factor 1 at tyrosine 19 promotes cell proliferation in pediatric acute lymphoblastic leukemia. Cancer Sci 2018; 109:3805-3815. [PMID: 30320932 PMCID: PMC6272096 DOI: 10.1111/cas.13834] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 09/21/2018] [Accepted: 10/04/2018] [Indexed: 12/21/2022] Open
Abstract
Serine/arginine‐rich splicing factor 1 (SRSF1) has been linked to various human cancers including pediatric acute lymphoblastic leukemia (ALL). Our previous study has shown that SRSF1 potentially contributes to leukemogenesis; however, its underlying mechanism remains unclear. In this study, leukemic cells were isolated from pediatric ALL bone marrow samples, followed by immunoprecipitation assays and mass spectrometry analysis specific to SRSF1. Subcellular localization of the SRSF1 protein and its mutants were analyzed by immunofluorescence staining. Cell growth, colony formation, cell apoptosis, and the cell cycle were investigated using stable leukemic cell lines generated with lentivirus‐mediated overexpressed WT or mutant plasmids. Cytotoxicity of the Tie2 kinase inhibitor was also evaluated. Our results showed the phosphorylation of SRSF1 at tyrosine 19 (Tyr‐19) was identified in newly diagnosed ALL samples, but not in complete remission or normal control samples. Compared to the SRSF1 WT cells, the missense mutants of the Tyr‐19 phosphorylation affected the subcellular localization of SRSF1. In addition, the Tyr‐19 phosphorylation of SRSF1 also led to increased cell proliferation and enhanced colony‐forming properties by promoting the cell cycle. Remarkably, we further identified the kinase Tie2 as a potential therapeutic target in leukemia cells. In conclusion, we identify for the first time that the phosphorylation state of SRSF1 is linked to different phases in pediatric ALL. The Tyr‐19 phosphorylation of SRSF1 disrupts its subcellular localization and promotes proliferation in leukemia cells by driving cell‐cycle progression. Inhibitors targeting Tie2 kinase that could catalyze Tyr‐19 phosphorylation of SRSF1 offer a promising therapeutic target for treatment of pediatric ALL.
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Affiliation(s)
- Liting Xu
- Beijing Key Laboratory of Pediatric Hematology Oncology, National Key Discipline of Pediatrics, Ministry of Education, Key Laboratory of Major Diseases in Children, Ministry of Education, Hematology Oncology Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, China
| | - Han Zhang
- Beijing Key Laboratory of Pediatric Hematology Oncology, National Key Discipline of Pediatrics, Ministry of Education, Key Laboratory of Major Diseases in Children, Ministry of Education, Hematology Oncology Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, China
| | - Mei Mei
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Chaohao Du
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Xiahe Huang
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Jing Li
- Beijing Key Laboratory of Pediatric Hematology Oncology, National Key Discipline of Pediatrics, Ministry of Education, Key Laboratory of Major Diseases in Children, Ministry of Education, Hematology Oncology Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, China
| | - Yingchun Wang
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Shilai Bao
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Huyong Zheng
- Beijing Key Laboratory of Pediatric Hematology Oncology, National Key Discipline of Pediatrics, Ministry of Education, Key Laboratory of Major Diseases in Children, Ministry of Education, Hematology Oncology Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, China
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15
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Abstract
Ceramides, important players in signal transduction, interact with multiple cellular pathways, including p53 pathways. However, the relationship between ceramide and p53 is very complex, and mechanisms underlying their coregulation are diverse and not fully characterized. The role of p53, an important cellular regulator and a transcription factor, is linked to its tumor suppressor function. Ceramides are involved in the regulation of fundamental processes in cancer cells including cell death, proliferation, autophagy, and drug resistance. This regulation, however, can be pro-death or pro-survival depending on cancer type, the balance between ceramide species, the rate of their synthesis and utilization, and the availability of a specific array of downstream targets. This chapter highlights the central role of ceramide in sphingolipid metabolism, its role in cancer, specific effectors in ceramide pathways controlled by p53, and coregulation of ceramide and p53 signaling. We discuss the recent studies, which underscore the function of p53 in the regulation of ceramide pathways and the reciprocal regulation of p53 by ceramide. This complex relationship is based on several molecular mechanisms including the p53-dependent transcriptional regulation of enzymes in sphingolipid pathways, the activation of mutant p53 through ceramide-mediated alternative splicing, as well as modulation of the p53 function through direct and indirect effects on p53 coregulators and downstream targets. Further insight into the connections between ceramide and p53 will allow simultaneous targeting of the two pathways with a potential to yield more efficient anticancer therapeutics.
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Affiliation(s)
- Kristen A Jeffries
- Nutrition Research Institute, UNC Chapel Hill, Kannapolis, NC, United States
| | - Natalia I Krupenko
- Nutrition Research Institute, UNC Chapel Hill, Kannapolis, NC, United States; Department of Nutrition, UNC Chapel Hill, Chapel Hill, NC, United States
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16
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Li P, Zhou L, Zhao T, Liu X, Zhang P, Liu Y, Zheng X, Li Q. Caspase-9: structure, mechanisms and clinical application. Oncotarget 2017; 8:23996-24008. [PMID: 28177918 PMCID: PMC5410359 DOI: 10.18632/oncotarget.15098] [Citation(s) in RCA: 173] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 01/22/2017] [Indexed: 12/27/2022] Open
Abstract
As the most intensively studied initiator caspase, caspase-9 is a key player in the intrinsic or mitochondrial pathway which is involved in various stimuli, including chemotherapies, stress agents and radiation. Caspase-9 is activated on the apoptosome complex to remain catalytic status and is thought of involving homo-dimerization monomeric zymogens. Failing to activate caspase-9 has profound physiological and pathophysiological outcomes, leading to degenerative and developmental disorders even cancer. To govern the apoptotic commitment process appropriately, plenty of proteins and small molecules involved in regulating caspase-9. Therefore, this review is to summarize recent pertinent literature on the comprehensive description of the molecular events implicated in caspase-9 activation and inhibition, as well as the clinical trials in progress to give deep insight into caspase-9 for suppressing cancer. We hope that our concerns will be helpful for further clinical studies addressing the roles of caspase-9 and its regulators demanded to identify more effective solutions to overcome intrinsic apoptosis-related diseases especially cancer.
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Affiliation(s)
- Ping Li
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Basic Research on Heavy Ion Radiation Application in Medicine, Gansu Province, Lanzhou, People's Republic of China
| | - Libin Zhou
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, People's Republic of China
| | - Ting Zhao
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Basic Research on Heavy Ion Radiation Application in Medicine, Gansu Province, Lanzhou, People's Republic of China
| | - Xiongxiong Liu
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Basic Research on Heavy Ion Radiation Application in Medicine, Gansu Province, Lanzhou, People's Republic of China
| | - Pengcheng Zhang
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Basic Research on Heavy Ion Radiation Application in Medicine, Gansu Province, Lanzhou, People's Republic of China.,University of Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Yan Liu
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Basic Research on Heavy Ion Radiation Application in Medicine, Gansu Province, Lanzhou, People's Republic of China.,University of Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Xiaogang Zheng
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Basic Research on Heavy Ion Radiation Application in Medicine, Gansu Province, Lanzhou, People's Republic of China.,University of Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Qiang Li
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, People's Republic of China.,Key Laboratory of Basic Research on Heavy Ion Radiation Application in Medicine, Gansu Province, Lanzhou, People's Republic of China
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17
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Kędzierska H, Piekiełko-Witkowska A. Splicing factors of SR and hnRNP families as regulators of apoptosis in cancer. Cancer Lett 2017; 396:53-65. [PMID: 28315432 DOI: 10.1016/j.canlet.2017.03.013] [Citation(s) in RCA: 146] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 03/08/2017] [Accepted: 03/08/2017] [Indexed: 12/19/2022]
Abstract
SR and hnRNP proteins were initially discovered as regulators of alternative splicing: the process of controlled removal of introns and selective joining of exons through which multiple transcripts and, subsequently, proteins can be expressed from a single gene. Alternative splicing affects genes involved in all crucial cellular processes, including apoptosis. During cancerogenesis impaired apoptotic control facilitates survival of cells bearing molecular aberrations, contributing to their unrestricted proliferation and chemoresistance. Apparently, SR and hnRNP proteins regulate all levels of expression of apoptotic genes, including transcription initiation and elongation, alternative splicing, mRNA stability, translation, and protein degradation. The frequently disturbed expressions of SR/hnRNP proteins in cancers lead to impaired functioning of target apoptotic genes, including regulators of the extrinsic (Fas, caspase-8, caspase-2, c-FLIP) and the intrinsic pathway (Apaf-1, caspase-9, ICAD), genes encoding Bcl-2 proteins, IAPs, and p53 tumor suppressor. Prototypical members of SR/hnRNP families, SRSF1 and hnRNP A1, promote synthesis of anti-apoptotic splice variants of Bcl-x and Mcl-1, which results in attenuation of programmed cell death in breast cancer and chronic myeloid leukemia. SR/hnRNP proteins significantly affect responses to chemotherapy, acting as mediators or modulators of drug-induced apoptosis. Aberrant expression of SRSF1 and hnRNP K can interfere with tumor responses to chemotherapy in pancreatic and liver cancers. Currently, a number of splicing factor inhibitors is being tested in pre-clinical and clinical trials. In this review we discuss recent findings on the role of SR and hnRNP proteins in apoptotic control in cancer cells as well as their significance in anticancer treatments.
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Affiliation(s)
- Hanna Kędzierska
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, ul. Marymoncka 99/103, 01-813 Warsaw, Poland
| | - Agnieszka Piekiełko-Witkowska
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, ul. Marymoncka 99/103, 01-813 Warsaw, Poland.
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18
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Kędzierska H, Popławski P, Hoser G, Rybicka B, Rodzik K, Sokół E, Bogusławska J, Tański Z, Fogtman A, Koblowska M, Piekiełko-Witkowska A. Decreased Expression of SRSF2 Splicing Factor Inhibits Apoptotic Pathways in Renal Cancer. Int J Mol Sci 2016; 17:ijms17101598. [PMID: 27690003 PMCID: PMC5085631 DOI: 10.3390/ijms17101598] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 08/31/2016] [Accepted: 09/05/2016] [Indexed: 12/14/2022] Open
Abstract
Serine and arginine rich splicing factor 2(SRSF2) belongs to the serine/arginine (SR)-rich family of proteins that regulate alternative splicing. Previous studies suggested that SRSF2 can contribute to carcinogenic processes. Clear cell renal cell carcinoma (ccRCC) is the most common subtype of kidney cancer, highly aggressive and difficult to treat, mainly due to resistance to apoptosis. In this study we hypothesized that SRSF2 contributes to the regulation of apoptosis in ccRCC. Using tissue samples obtained from ccRCC patients, as well as independent validation on The Cancer Genome Atlas (TCGA) data, we demonstrate for the first time that expression of SRSF2 is decreased in ccRCC tumours when compared to non-tumorous control tissues. Furthermore, by employing a panel of ccRCC-derived cell lines with silenced SRSF2 expression and qPCR arrays we show that SRSF2 contributes not only to splicing patterns but also to expression of multiple apoptotic genes, including new SRSF2 targets: DIABLO, BIRC5/survivin, TRAIL, BIM, MCL1, TNFRSF9, TNFRSF1B, CRADD, BCL2L2, BCL2A1, and TP53. We also identified a new splice variant of CFLAR, an inhibitor of caspase activity. These changes culminate in diminished caspase-9 activity and inhibition of apoptosis. In summary, we show for the first time that decreased expression of SRSF2 in ccRCC contributes to protection of cancer cells viability.
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Affiliation(s)
- Hanna Kędzierska
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland.
| | - Piotr Popławski
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland.
| | - Grażyna Hoser
- Laboratory of Flow Cytometry, Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland.
| | - Beata Rybicka
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland.
| | - Katarzyna Rodzik
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland.
| | - Elżbieta Sokół
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland.
| | - Joanna Bogusławska
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland.
| | - Zbigniew Tański
- Department of Urology, Regional Hospital, 07-410 Ostrołęka, Poland.
| | - Anna Fogtman
- Laboratory for Microarray Analysis, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland.
| | - Marta Koblowska
- Laboratory for Microarray Analysis, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland.
- Laboratory of Systems Biology, Faculty of Biology, University of Warsaw, 02-106 Warsaw, Poland.
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19
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Ma YY, Mou XZ, Ding YH, Zou H, Huang DS. Delivery systems of ceramide in targeted cancer therapy: ceramide alone or in combination with other anti-tumor agents. Expert Opin Drug Deliv 2016; 13:1397-406. [PMID: 27168034 DOI: 10.1080/17425247.2016.1188803] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Ying-Yu Ma
- Clinical Research Institute, Zhejiang Provincial People’s Hospital, Hangzhou, China
- Medical School and Jiangsu Laboratory of Molecular Medicine, Nanjing University, Nanjing, China
| | - Xiao-Zhou Mou
- Clinical Research Institute, Zhejiang Provincial People’s Hospital, Hangzhou, China
| | - Ya-Hui Ding
- Department of Cardiology, Zhejiang Provincial People’s Hospital, Hangzhou, China
| | - Hai Zou
- Department of Cardiology, Zhejiang Provincial People’s Hospital, Hangzhou, China
| | - Dong-Sheng Huang
- Clinical Research Institute, Zhejiang Provincial People’s Hospital, Hangzhou, China
- Department of Hepatobiliary Surgery, Zhejiang Provincial People’s Hospital, Hangzhou, China
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20
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Towards understanding pre-mRNA splicing mechanisms and the role of SR proteins. Gene 2016; 587:107-19. [PMID: 27154819 DOI: 10.1016/j.gene.2016.04.057] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 04/30/2016] [Indexed: 01/04/2023]
Abstract
Alternative pre-mRNA splicing provides a source of vast protein diversity by removing non-coding sequences (introns) and accurately linking different exonic regions in the correct reading frame. The regulation of alternative splicing is essential for various cellular functions in both pathological and physiological conditions. In eukaryotic cells, this process is commonly used to increase proteomic diversity and to control gene expression either co- or post-transcriptionally. Alternative splicing occurs within a megadalton-sized, multi-component machine consisting of RNA and proteins; during the splicing process, this complex undergoes dynamic changes via RNA-RNA, protein-protein and RNA-protein interactions. Co-transcriptional splicing functionally integrates the transcriptional machinery, thereby enabling the two processes to influence one another, whereas post-transcriptional splicing facilitates the coupling of RNA splicing with post-splicing events. This review addresses the structural aspects of spliceosomes and the mechanistic implications of their stepwise assembly on the regulation of pre-mRNA splicing. Moreover, the role of phosphorylation-based, signal-induced changes in the regulation of the splicing process is demonstrated.
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21
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Vu NT, Park MA, Shultz MD, Bulut GB, Ladd AC, Chalfant CE. Caspase-9b Interacts Directly with cIAP1 to Drive Agonist-Independent Activation of NF-κB and Lung Tumorigenesis. Cancer Res 2016; 76:2977-89. [PMID: 27197231 DOI: 10.1158/0008-5472.can-15-2512] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 02/23/2016] [Indexed: 01/06/2023]
Abstract
Alternate RNA processing of caspase-9 generates the splice variants caspase 9a (C9a) and caspase 9b (C9b). C9b lacks a domain present in C9a, revealing a tumorigenic function that drives the phenotype of non-small cell lung cancer (NSCLC) cells. In this study, we elucidated the mechanistic underpinnings of the malignant character of this splice isoform. In NSCLC cells, C9b expression correlated with activation of the canonical arm of the NF-κB pathway, a major pathway linked to the NSCLC tumorigenesis. Mechanistic investigations revealed that C9b activates this pathway via direct interaction with cellular inhibitor of apoptosis 1 (cIAP1) and subsequent induction of the E3 ligase activity of this IAP family member. The C9b:cIAP1 interaction occurred via the BIR3 domain of cIAP1 and the IAP-binding motif of C9b, but did not require proteolytic cleavage of C9b. This protein:protein interaction was essential for C9b to promote viability and malignant growth of NSCLC cells in vitro and in vivo, broadly translating to diverse NSCLC oncogenotypes. Overall, our findings identified a novel point for therapeutic invention in NSCLC that may be tractable to small-molecule inhibitors, as a new point to broadly address this widespread deadly disease. Cancer Res; 76(10); 2977-89. ©2016 AACR.
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Affiliation(s)
- Ngoc T Vu
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia. Vietnam Education Foundation, Arlington, Virginia
| | - Margaret A Park
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia. Research and Development, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia. The VCU Institute of Molecular Medicine, The VCU Massey Cancer Center, and The VCU Johnson Center, Virginia Commonwealth University, Richmond, Virginia
| | - Michael D Shultz
- Research and Development, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia
| | - Gamze B Bulut
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia
| | - Amy C Ladd
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia
| | - Charles E Chalfant
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia. Research and Development, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia. The VCU Institute of Molecular Medicine, The VCU Massey Cancer Center, and The VCU Johnson Center, Virginia Commonwealth University, Richmond, Virginia.
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22
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Tiloke C, Phulukdaree A, Anand K, Gengan RM, Chuturgoon AA. Moringa oleiferaGold Nanoparticles Modulate Oncogenes, Tumor Suppressor Genes, and Caspase-9 Splice Variants in A549 Cells. J Cell Biochem 2016; 117:2302-14. [DOI: 10.1002/jcb.25528] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 02/25/2016] [Indexed: 01/17/2023]
Affiliation(s)
- Charlette Tiloke
- Discipline of Medical Biochemistry and Chemical Pathology; School of Laboratory Medicine and Medical Sciences; College of Health Sciences; University of KwaZulu-Natal; Congella Durban 4013 South Africa
| | - Alisa Phulukdaree
- Discipline of Medical Biochemistry and Chemical Pathology; School of Laboratory Medicine and Medical Sciences; College of Health Sciences; University of KwaZulu-Natal; Congella Durban 4013 South Africa
- Department of Physiology; School of Medicine; Faculty of Health Sciences; University of Pretoria; Pretoria South Africa
| | - Krishnan Anand
- Department of Chemistry; Faculty of Applied Sciences; Durban University of Technology; Durban 4001 South Africa
| | - Robert M. Gengan
- Department of Chemistry; Faculty of Applied Sciences; Durban University of Technology; Durban 4001 South Africa
| | - Anil A. Chuturgoon
- Discipline of Medical Biochemistry and Chemical Pathology; School of Laboratory Medicine and Medical Sciences; College of Health Sciences; University of KwaZulu-Natal; Congella Durban 4013 South Africa
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23
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Johnson RM, Vu NT, Griffin BP, Gentry AE, Archer KJ, Chalfant CE, Park MA. The Alternative Splicing of Cytoplasmic Polyadenylation Element Binding Protein 2 Drives Anoikis Resistance and the Metastasis of Triple Negative Breast Cancer. J Biol Chem 2015; 290:25717-27. [PMID: 26304115 DOI: 10.1074/jbc.m115.671206] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Indexed: 12/13/2022] Open
Abstract
Triple negative breast cancer (TNBC) represents an anomalous subset of breast cancer with a greatly reduced (30%) 5-year survival rate. The enhanced mortality and morbidity of TNBC arises from the high metastatic rate, which requires the acquisition of AnR, a process whereby anchorage-dependent cells become resistant to cell death induced by detachment. In this study TNBC cell lines were selected for AnR, and these cell lines demonstrated dramatic enhancement in the formation of lung metastases as compared with parental cells. Genetic analysis of the AnR subclones versus parental cells via next generation sequencing and analysis of global alternative RNA splicing identified that the mRNA splicing of cytoplasmic polyadenylation element binding 2 (CPEB2), a translational regulator, was altered in AnR TNBC cells. Specifically, increased inclusion of exon 4 into the mature mRNA to produce the CPEB2B isoform was observed in AnR cell lines. Molecular manipulations of CPEB2 splice variants demonstrated a key role for this RNA splicing event in the resistance of cells to anoikis. Specifically, down-regulation of the CPEB2B isoform using siRNA re-sensitized the AnR cell lines to detachment-induced cell death. The ectopic expression of CPEB2B in parental TNBC cell lines induced AnR and dramatically increased metastatic potential. Importantly, alterations in the alternative splicing of CPEB2 were also observed in human TNBC and additional subtypes of human breast cancer tumors linked to a high metastatic rate. Our findings demonstrate that the regulation of CPEB2 mRNA splicing is a key mechanism in AnR and a driving force in TNBC metastasis.
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Affiliation(s)
- Ryan M Johnson
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond Virginia 23298
| | - Ngoc T Vu
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond Virginia 23298, Vietnam Education Foundation, Arlington, Virginia 22201
| | - Brian P Griffin
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond Virginia 23298
| | - Amanda E Gentry
- Department of Biostatistics, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Kellie J Archer
- Department of Biostatistics, Virginia Commonwealth University, Richmond, Virginia 23298, Virginia Commonwealth University Massey Cancer Center Biostatistics Shared Resource, Richmond, Virginia 23298, Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Charles E Chalfant
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond Virginia 23298, Virginia Commonwealth University Massey Cancer Center Massey Cancer Center, Richmond, Virginia 23298, Research and Development, Hunter Holmes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23224, Virginia Commonwealth University Institute of Molecular Medicine, Richmond Virginia, 23298, and Virginia Commonwealth University Johnson Center, Richmond, Virginia, 23298
| | - Margaret A Park
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond Virginia 23298, Virginia Commonwealth University Massey Cancer Center Massey Cancer Center, Richmond, Virginia 23298,
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Ceramide modulates pre-mRNA splicing to restore the expression of wild-type tumor suppressor p53 in deletion-mutant cancer cells. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:1571-80. [PMID: 25195822 DOI: 10.1016/j.bbalip.2014.08.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 07/25/2014] [Accepted: 08/27/2014] [Indexed: 11/20/2022]
Abstract
Mutants of tumor suppressor p53 not only lose the activity in genome stabilizing and in tumor suppression, but also exhibit oncogenic function in cancer cells. Most efforts in restoring p53 biological activity focus on either altering mutant-protein conformation or introducing an exogenous p53 gene into cells to eliminate p53-mutant cancer cells. Being different from these, we report that ceramide can restore the expression of wild-type p53 and induce p53-dependent apoptosis in deletion-mutant cancer cells. We show that endogenous long-carbon chain ceramide species (C16- to C24-ceramides) and exogenous C6-ceramide, rather than other sphingolipids, restore wild-type mRNA (intact exon-5), phosphorylated protein (Ser15 in exon-5) of p53, and p53-responsive proteins, including p21 and Bax, in ovarian cancer cells, which predominantly express a deleted exon-5 of p53 mutant before treatments. Consequently, the restored p53 sensitizes these p53-mutant cancer cells to DNA damage-induced growth arrest and apoptosis. Furthermore, we elucidate that ceramide activates protein phosphatase-1, and then the dephosphorylated serine/arginine-rich splicing-factor 1 (SRSF1) is translocated to the nucleus, thus promoting pre-mRNA splicing preferentially to wild-type p53 expression. These findings disclose an unrecognized mechanism that pre-mRNA splicing dysfunction can result in p53 deletion-mutants. Ceramide through SRSF1 restores wild-type p53 expression versus deletion-mutant and leads cancer cells to apoptosis. This suggests that heterozygous deletion-mutants of p53 can be restored in posttranscriptional level by using epigenetic approaches.
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25
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Das S, Krainer AR. Emerging functions of SRSF1, splicing factor and oncoprotein, in RNA metabolism and cancer. Mol Cancer Res 2014; 12:1195-204. [PMID: 24807918 DOI: 10.1158/1541-7786.mcr-14-0131] [Citation(s) in RCA: 194] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Serine/Arginine Splicing Factor 1 (SRSF1) is the archetype member of the SR protein family of splicing regulators. Since its discovery over two decades ago, SRSF1 has been repeatedly surprising and intriguing investigators by the plethora of complex biologic pathways it regulates. These include several key aspects of mRNA metabolism, such as mRNA splicing, stability, and translation, as well as other mRNA-independent processes, such as miRNA processing, protein sumoylation, and the nucleolar stress response. In this review, the structural features of SRSF1 are discussed as they relate to the intricate mechanism of splicing and the multiplicity of functions it performs. Similarly, a list of relevant alternatively spliced transcripts and SRSF1 interacting proteins is provided. Finally, emphasis is given to the deleterious consequences of overexpression of the SRSF1 proto-oncogene in human cancers, and the complex mechanisms and pathways underlying SRSF1-mediated transformation. The accumulated knowledge about SRSF1 provides critical insight into the integral role it plays in maintaining cellular homeostasis and suggests new targets for anticancer therapy. Mol Cancer Res; 12(9); 1195-204. ©2014 AACR.
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Affiliation(s)
- Shipra Das
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York
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26
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de Miguel FJ, Sharma RD, Pajares MJ, Montuenga LM, Rubio A, Pio R. Identification of alternative splicing events regulated by the oncogenic factor SRSF1 in lung cancer. Cancer Res 2013; 74:1105-15. [PMID: 24371231 DOI: 10.1158/0008-5472.can-13-1481] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abnormal alternative splicing has been associated with cancer. Genome-wide microarrays can be used to detect differential splicing events. In this study, we have developed ExonPointer, an algorithm that uses data from exon and junction probes to identify annotated cassette exons. We used the algorithm to profile differential splicing events in lung adenocarcinoma A549 cells after downregulation of the oncogenic serine/arginine-rich splicing factor 1 (SRSF1). Data were generated using two different microarray platforms. The PCR-based validation rate of the top 20 ranked genes was 60% and 100%. Functional enrichment analyses found a substantial number of splicing events in genes related to RNA metabolism. These analyses also identified genes associated with cancer and developmental and hereditary disorders, as well as biologic processes such as cell division, apoptosis, and proliferation. Most of the top 20 ranked genes were validated in other adenocarcinoma and squamous cell lung cancer cells, with validation rates of 80% to 95% and 70% to 75%, respectively. Moreover, the analysis allowed us to identify four genes, ATP11C, IQCB1, TUBD1, and proline-rich coiled-coil 2C (PRRC2C), with a significantly different pattern of alternative splicing in primary non-small cell lung tumors compared with normal lung tissue. In the case of PRRC2C, SRSF1 downregulation led to the skipping of an exon overexpressed in primary lung tumors. Specific siRNA downregulation of the exon-containing variant significantly reduced cell growth. In conclusion, using a novel analytical tool, we have identified new splicing events regulated by the oncogenic splicing factor SRSF1 in lung cancer.
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Affiliation(s)
- Fernando J de Miguel
- Authors' Affiliations: Division of Oncology, Center for Applied Medical Research (CIMA); Departments of Histology and Pathology and Biochemistry and Genetics, Schools of Science and Medicine, University of Navarra, Pamplona; and CEIT and TECNUN, University of Navarra, San Sebastian, Spain
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27
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Oncogenic alternative splicing switches: role in cancer progression and prospects for therapy. Int J Cell Biol 2013; 2013:962038. [PMID: 24285959 PMCID: PMC3826442 DOI: 10.1155/2013/962038] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 08/12/2013] [Indexed: 01/30/2023] Open
Abstract
Alterations in the abundance or activities of alternative splicing regulators generate alternatively spliced variants that contribute to multiple aspects of tumor establishment, progression and resistance to therapeutic treatments. Notably, many cancer-associated genes are regulated through alternative splicing suggesting a significant role of this post-transcriptional regulatory mechanism in the production of oncogenes and tumor suppressors. Thus, the study of alternative splicing in cancer might provide a better understanding of the malignant transformation and identify novel pathways that are uniquely relevant to tumorigenesis. Understanding the molecular underpinnings of cancer-associated alternative splicing isoforms will not only help to explain many fundamental hallmarks of cancer, but will also offer unprecedented opportunities to improve the efficacy of anti-cancer treatments.
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28
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Montecucco A, Biamonti G. Pre-mRNA processing factors meet the DNA damage response. Front Genet 2013; 4:102. [PMID: 23761808 PMCID: PMC3674313 DOI: 10.3389/fgene.2013.00102] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 05/20/2013] [Indexed: 12/04/2022] Open
Abstract
It is well-known that DNA-damaging agents induce genome instability, but only recently have we begun to appreciate that chromosomes are fragile per se and frequently subject to DNA breakage. DNA replication further magnifies such fragility, because it leads to accumulation of single-stranded DNA. Recent findings suggest that chromosome fragility is similarly increased during transcription. Transcripts produced by RNA polymerase II (RNAPII) are subject to multiple processing steps, including maturation of 5′ and 3′ ends and splicing, followed by transport to the cytoplasm. RNA maturation starts on nascent transcripts and is mediated by a number of diverse proteins and ribonucleoprotein particles some of which are recruited cotranscriptionally through interactions with the carboxy-terminal domain of RNAPII. This coupling is thought to maximize efficiency of pre-mRNA maturation and directly impacts the choice of alternative splice sites. Mounting evidence suggests that lack of coordination among different RNA maturation steps, by perturbing the interaction of nascent transcripts with the DNA template, has deleterious effects on genome stability. Thus, in the absence of proper surveillance mechanisms, transcription could be a major source of DNA damage in cancer. Recent high-throughput screenings in human cells and budding yeast have identified several factors implicated in RNA metabolism that are targets of DNA damage checkpoint kinases: ATM (ataxia telangiectasia mutated) and ATR (ATM-Rad3 related) (Tel1 and Mec1 in budding yeast, respectively). Moreover, inactivation of various RNA processing factors induces accumulation of γH2AX foci, an early sign of DNA damage. Thus, a complex network is emerging that links DNA repair and RNA metabolism. In this review we provide a comprehensive overview of the role played by pre-mRNA processing factors in the cell response to DNA damage and in the maintenance of genome stability.
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29
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Corbo C, Orrù S, Salvatore F. SRp20: an overview of its role in human diseases. Biochem Biophys Res Commun 2013; 436:1-5. [PMID: 23685143 DOI: 10.1016/j.bbrc.2013.05.027] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 05/07/2013] [Indexed: 10/26/2022]
Abstract
Alternative splicing in mRNA maturation has emerged as a major field of study also because of its implications in various diseases. The SR proteins play an important role in the regulation of this process. Evidence indicates that SRp20 (SFSR3), the smallest member of the SR protein family, is involved in numerous biological processes. Here we review the state-of-the-art of knowledge about the SR proteins, in particular SRp20, in terms of its function and misregulation in human diseases including cancer also in view of its potential as a therapeutic target.
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30
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Vu NT, Park MA, Shultz JC, Goehe RW, Hoeferlin LA, Shultz MD, Smith SA, Lynch KW, Chalfant CE. hnRNP U enhances caspase-9 splicing and is modulated by AKT-dependent phosphorylation of hnRNP L. J Biol Chem 2013; 288:8575-8584. [PMID: 23396972 DOI: 10.1074/jbc.m112.443333] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Caspase-9 has two splice variants, pro-apoptotic caspase-9a and anti-apoptotic caspase-9b, which are regulated by RNA trans-factors associated with exon 3 of caspase-9 pre-mRNA (C9/E3). In this study, we identified hnRNP U as an RNA trans-factor associated with C9/E3. Down-regulation of hnRNP U led to a decrease in the caspase-9a/9b mRNA ratio, demonstrating a novel enhancing function. Importantly, hnRNP U bound specifically to C9/E3 at an RNA cis-element previously reported as the binding site for the splicing repressor, hnRNP L. Phosphorylated hnRNP L interfered with hnRNP U binding to C9/E3, and our results demonstrate the importance of the phosphoinositide 3-kinase/AKT pathway in modulating the association of hnRNP U to C9/E3. Taken together, these findings show that hnRNP U competes with hnRNP L for binding to C9/E3 to enhance the inclusion of the four-exon cassette, and this splice-enhancing function is blocked by the AKT pathway via phosphorylation of hnRNP L.
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Affiliation(s)
- Ngoc T Vu
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298; Vietnam Education Foundation, Arlington, Virginia 22201
| | - Margaret A Park
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Jacqueline C Shultz
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Rachel W Goehe
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - L Alexis Hoeferlin
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Michael D Shultz
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Sarah A Smith
- Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
| | - Kristen W Lynch
- Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
| | - Charles E Chalfant
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298; Research and Development, Hunter Holmes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249; The Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia 23298.
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31
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Ruirui K, Ray P, Yang M, Wen P, Zhu L, Liu J, Fushimi K, Kar A, Liu Y, He R, Kuo D, Wu JY. Alternative Pre-mRNA Splicing, Cell Death, and Cancer. Cancer Treat Res 2013; 158:181-212. [PMID: 24222359 DOI: 10.1007/978-3-642-31659-3_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Alternative splicing is one of the most powerful mechanisms for generating functionally distinct products from a single genetic loci and for fine-tuning gene activities at the post-transcriptional level. Alternative splicing plays important roles in regulating genes critical for cell death. These cell death genes encode death ligands, cell surface death receptors, intracellular death regulators, signal transduction molecules, and death executor enzymes such as caspases and nucleases. Alternative splicing of these genes often leads to the formation of functionally different products, some of which have antagonistic effects that are either cell death-promoting or cell death-preventing. Differential alternative splicing can affect expression, subcellular distribution, and functional activities of the gene products. Molecular defects in splicing regulation of cell death genes have been associated with cancer development and resistance to treatment. Studies using molecular, biochemical, and systems-based approaches have begun to reveal mechanisms underlying the regulation of alternative splicing of cell death genes. Systematic studies have begun to uncover the multi-level interconnected networks that regulate alternative splicing. A global picture of the complex mechanisms that regulate cell death genes at the pre-mRNA splicing level has thus begun to emerge.
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Affiliation(s)
- Kong Ruirui
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Science, Beijing, China
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32
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Ghigna C, Riva S, Biamonti G. Alternative splicing of tumor suppressors and oncogenes. Cancer Treat Res 2013; 158:95-117. [PMID: 24222355 DOI: 10.1007/978-3-642-31659-3_4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Alternative splicing is a fundamental mechanism to modulate gene expression programs in response to different growth and environmental stimuli. There is now ample evidence that alternative splicing errors, caused by mutations in cis-acting elements and defects and/or imbalances in trans-acting factors, may be causatively associated to cancer progression. Recent work indicates the existence of an intricate network of interactions between alternative splicing events and signal transduction pathways. In this network, splicing factors occupy a central position and appear to function both as targets and effectors of regulatory circuits. Thus, a change in their activity deeply affects alternative splicing profiles and hence the cell behavior. Here, we discuss a number of cases that exemplify the involvement of deregulated alternative splicing in tumor progression.
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Affiliation(s)
- Claudia Ghigna
- Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche, Pavia, 27100, Italy
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33
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Spraggon L, Cartegni L. Antisense Modulation of RNA Processing as a Therapeutic Approach in Cancer Therapy. ACTA ACUST UNITED AC 2013; 10:e139-e148. [PMID: 25589899 DOI: 10.1016/j.ddstr.2013.06.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Next-generation antisense technologies are re-emerging as viable and powerful approaches to the treatment of several genetic diseases. Similar strategies are also being applied to cancer therapy. Re-programming of the expression of endogenous oncogenic products to replace them with functional antagonists, by interfering with alternative splicing or polyadenylation, provides a promising novel approach to address acquired drug resistance and previously undruggable targets.
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Affiliation(s)
- Lee Spraggon
- Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, USA
| | - Luca Cartegni
- Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, USA
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Zha X, Yan X, Shen Q, Zhang Y, Wu X, Chen S, Li B, Yang L, Geng S, Weng J, Du X, Li Y. Alternative expression of TCRζ related genes in patients with chronic myeloid leukemia. J Hematol Oncol 2012; 5:74. [PMID: 23228155 PMCID: PMC3544630 DOI: 10.1186/1756-8722-5-74] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 12/04/2012] [Indexed: 01/01/2023] Open
Abstract
A previous study has demonstrated a significant decrease in the TCRζ gene expression level in chronic myeloid leukemia (CML); thus, we further investigated the expression of TCRζ-regulating factors, the distribution of the TCRζ 3' untranslated region (3'-UTR) splice variants, and the expression level and correlation of the alternative splicing factor/splicing factor 2 (ASF/SF-2), FcεRIγ and ZAP-70 genes. TCRζ 3'-UTR splice variants were identified in peripheral blood mononuclear cells (PBMCs) from 14 healthy individuals, 40 patients with CML and 22 patients with CML in complete remission (CML-CR) by RT-PCR. The expression level of the TCRζ, FcεRIγ, ASF/SF-2 and ZAP-70 genes was analyzed by real-time quantitative PCR. While the expression of TCRζ gene in the CML group was significantly lower than that in the healthy individual and CML-CR groups, a significantly higher expression of the FceRIγ and ASF/SF-2 genes was found in the CML group. Two types of splicing forms were detected in all of the healthy individual CML-CR cases: wild type (WT) TCRζ 3'-UTR and alternatively splieced (AS) TCRζ 3'-UTR which have been alternatively splieced in the WT TCRζ 3'-UTR . However, 35% of the CML cases contained only the wild type TCRζ 3'-UTR isoform. Based on the TCRζ 3'-UTR isoform expression characteristic, we divided the patients with CML into two subgroups: the WT+AS- CML group, containing patients that express only the wild type TCRζ 3'-UTR, and the WT+AS+ CML group, which contained patients that expressed two TCRζ 3'-UTR isoforms. A significantly different ASF/SF-2 and FcεRIγ gene expression pattern was found between the WT+AS- and WT+AS+CML groups. We concluded that defective TCRζ expression may be characterized in the WT+AS-and WT+AS+CML subgroups by the different gene expression pattern. The overexpression of ASF/SF2, which alternatively splices the TCRζ 3'-UTR, is thought to participate in feedback regulation. The characteristics of TCRζ 3'-UTR alternative splicing may be a novel immunological marker for the evaluation of the CML immune status.
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Affiliation(s)
- Xianfeng Zha
- Institute of Hematology, Medical College, Jinan University, Guangzhou, 510632, China
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35
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Alternative splicing interference by xenobiotics. Toxicology 2012; 296:1-12. [DOI: 10.1016/j.tox.2012.01.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 01/21/2012] [Accepted: 01/23/2012] [Indexed: 12/21/2022]
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36
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Sumanasekera C, Kelemen O, Beullens M, Aubol BE, Adams JA, Sunkara M, Morris A, Bollen M, Andreadis A, Stamm S. C6 pyridinium ceramide influences alternative pre-mRNA splicing by inhibiting protein phosphatase-1. Nucleic Acids Res 2011; 40:4025-39. [PMID: 22210893 PMCID: PMC3351148 DOI: 10.1093/nar/gkr1289] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Alternative pre-mRNA processing is a central element of eukaryotic gene regulation. The cell frequently alters the use of alternative exons in response to physiological stimuli. Ceramides are lipid-signaling molecules composed of sphingosine and a fatty acid. Previously, water-insoluble ceramides were shown to change alternative splicing and decrease SR-protein phosphorylation by activating protein phosphatase-1 (PP1). To gain further mechanistical insight into ceramide-mediated alternative splicing, we analyzed the effect of C6 pyridinium ceramide (PyrCer) on alternative splice site selection. PyrCer is a water-soluble ceramide analog that is under investigation as a cancer drug. We found that PyrCer binds to the PP1 catalytic subunit and inhibits the dephosphorylation of several splicing regulatory proteins containing the evolutionarily conserved RVxF PP1-binding motif (including PSF/SFPQ, Tra2-beta1 and SF2/ASF). In contrast to natural ceramides, PyrCer promotes phosphorylation of splicing factors. Exons that are regulated by PyrCer have in common suboptimal splice sites, are unusually short and share two 4-nt motifs, GAAR and CAAG. They are dependent on PSF/SFPQ, whose phosphorylation is regulated by PyrCer. Our results indicate that lipids can influence pre-mRNA processing by regulating the phosphorylation status of specific regulatory factors, which is mediated by protein phosphatase activity.
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Affiliation(s)
- Chiranthani Sumanasekera
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA
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37
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Lamour NF, Wijesinghe DS, Mietla JA, Ward KE, Stahelin RV, Chalfant CE. Ceramide kinase regulates the production of tumor necrosis factor α (TNFα) via inhibition of TNFα-converting enzyme. J Biol Chem 2011; 286:42808-17. [PMID: 22009748 PMCID: PMC3234830 DOI: 10.1074/jbc.m111.310169] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Tumor necrosis factor α (TNFα) is a well known cytokine involved in systemic and acute inflammation. In this study, we demonstrate that ceramide 1-phosphate (C1P) produced by ceramide kinase (CERK) is a negative regulator of LPS-induced TNFα secretion. Specifically, bone marrow-derived macrophages isolated from CERK knock-out mice (CERK−/−) generated higher levels of TNFα than the wild-type mice (CERK+/+) in response to LPS. An increase in basal TNFα secretion was also observed in CERK−/− murine embryonic fibroblasts, which was rescued by re-expression of wild-type CERK. This effect was due to increased secretion and not transcription. The secretion of TNFα is regulated by TNFα-converting enzyme (TACE also known as ADAM17), and importantly, the activity of TACE was higher in cell extracts from CERK−/− as compared with wild type. In vitro analysis also demonstrated that C1P is a potent inhibitor of this enzyme, in stark contrast to ceramide and sphingosine 1-phosphate. Furthermore, TACE specifically bound C1P with high affinity. Finally, several putative C1P-binding sites were identified via homology throughout the protein sequence of TACE. These results indicate that C1P produced by CERK has a negative effect on the processing/secretion of TNFα via modulation of TACE activity.
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Affiliation(s)
- Nadia F Lamour
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298, USA
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38
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Pan D, Boon-Unge K, Govitrapong P, Zhou J. Emetine regulates the alternative splicing of caspase 9 in tumor cells. Oncol Lett 2011; 2:1309-1312. [PMID: 22848307 DOI: 10.3892/ol.2011.395] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Accepted: 08/17/2011] [Indexed: 01/03/2023] Open
Abstract
Exons 3 to 6 in the caspase 9 gene undergo alternative splicing in which the larger caspase 9 splice variant promotes apoptosis, in contrast to the dominant negative anti-apoptotic splice variant, the smaller caspase 9b. In this study, the regulation of the alternative splicing of caspase 9 pre-mRNA was examined in response to Emetine. Treatment of C33A cells, breast cancer MCF-7 cells and MCF-7/Adr cells with Emetine dihydrochloride upregulated the level of smaller caspase 9b mRNA and concomitantly decreased the mRNA level of larger caspase 9 in a dose- and time-dependent manner, indicating that Emetine desensitizes C33A, MCF-7 and MCF-7/Adr to cell death. In contrast, treatment of PC3 cells, a prostate cancer cell line, manifested an opposite effect: a greater production of the larger caspase 9 mRNA with a concomitant decrease of caspase 9b mRNA. Pretreatment with calyculin A, an inhibitor of protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A) blocked Emetine-induced alternative splicing in cells, in contrast to okadaic acid, a specific inhibitor of PP2A, demonstrating a PP1-mediated mechanism. These results suggest that the various splicing patterns of the caspase 9 gene that are regulated by chemotherapy reagents may contribute to the resistance or sensitization of the tumors to other cell death inducers.
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Affiliation(s)
- Danmin Pan
- JiangSu Key Laboratory of Neuroregeneration, Nantong University, Nantong, Jiangsu 226001, P.R. China
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39
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Aubol BE, Adams JA. Applying the brakes to multisite SR protein phosphorylation: substrate-induced effects on the splicing kinase SRPK1. Biochemistry 2011; 50:6888-900. [PMID: 21728354 DOI: 10.1021/bi2007993] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To investigate how a protein kinase interacts with its protein substrate during extended, multisite phosphorylation, the kinetic mechanism of a protein kinase involved in mRNA splicing control was investigated using rapid quench flow techniques. The protein kinase SRPK1 phosphorylates ~10 serines in the arginine--serine-rich domain (RS domain) of the SR protein SRSF1 in a C- to N-terminal direction, a modification that directs this essential splicing factor from the cytoplasm to the nucleus. Transient-state kinetic experiments illustrate that the first phosphate is added rapidly onto the RS domain of SRSF1 (t(1/2) = 0.1 s) followed by slower, multisite phosphorylation at the remaining serines (t(1/2) = 15 s). Mutagenesis experiments suggest that efficient phosphorylation rates are maintained by an extensive hydrogen bonding and electrostatic network between the RS domain of the SR protein and the active site and docking groove of the kinase. Catalytic trapping and viscosometric experiments demonstrate that while the phosphoryl transfer step is fast, ADP release limits multisite phosphorylation. By studying phosphate incorporation into selectively pre-phosphorylated forms of the enzyme-substrate complex, the kinetic mechanism for site-specific phosphorylation along the reaction coordinate was assessed. The binding affinity of the SR protein, the phosphoryl transfer rate, and ADP exchange rate were found to decline significantly as a function of progressive phosphorylation in the RS domain. These findings indicate that the protein substrate actively modulates initiation, extension, and termination events associated with prolonged, multisite phosphorylation.
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Affiliation(s)
- Brandon E Aubol
- Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0636, United States
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Ghigna C, Valacca C, Biamonti G. Alternative splicing and tumor progression. Curr Genomics 2011; 9:556-70. [PMID: 19516963 PMCID: PMC2694562 DOI: 10.2174/138920208786847971] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2008] [Revised: 08/12/2008] [Accepted: 08/18/2008] [Indexed: 12/15/2022] Open
Abstract
Alternative splicing is a key molecular mechanism for increasing the functional diversity of the eukaryotic proteomes. A large body of experimental data implicates aberrant splicing in various human diseases, including cancer. Both mutations in cis-acting splicing elements and alterations in the expression and/or activity of splicing regulatory factors drastically affect the splicing profile of many cancer-associated genes. In addition, the splicing profile of several cancer-associated genes is altered in particular types of cancer arguing for a direct role of specific splicing isoforms in tumor progression. Deciphering the mechanisms underlying aberrant splicing in cancer may prove crucial to understand how splicing machinery is controlled and integrated with other cellular processes, in particular transcription and signaling pathways. Moreover, the characterization of splicing deregulation in cancer will lead to a better comprehension of malignant transformation. Cancer-associated alternative splicing variants may be new tools for the diagnosis and classification of cancers and could be the targets for innovative therapeutical interventions based on highly selective splicing correction approaches.
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Affiliation(s)
- Claudia Ghigna
- Istituto di Genetica Molecolare - Consiglio Nazionale delle Ricerche, Via Abbiategrasso 207. 27100 Pavia, Italy
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Shultz JC, Goehe RW, Murudkar CS, Wijesinghe DS, Mayton EK, Massiello A, Hawkins AJ, Mukerjee P, Pinkerman RL, Park MA, Chalfant CE. SRSF1 regulates the alternative splicing of caspase 9 via a novel intronic splicing enhancer affecting the chemotherapeutic sensitivity of non-small cell lung cancer cells. Mol Cancer Res 2011; 9:889-900. [PMID: 21622622 DOI: 10.1158/1541-7786.mcr-11-0061] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Increasing evidence points to the functional importance of alternative splice variations in cancer pathophysiology with the alternative pre-mRNA processing of caspase 9 as one example. In this study, we delve into the underlying molecular mechanisms that regulate the alternative splicing of caspase 9. Specifically, the pre-mRNA sequence of caspase 9 was analyzed for RNA cis-elements known to interact with SRSF1, a required enhancer for caspase 9 RNA splicing. This analysis revealed 13 possible RNA cis-elements for interaction with SRSF1 with mutagenesis of these RNA cis-elements identifying a strong intronic splicing enhancer located in intron 6 (C9-I6/ISE). SRSF1 specifically interacted with this sequence, which was required for SRSF1 to act as a splicing enhancer of the inclusion of the 4 exon cassette. To further determine the biological importance of this mechanism, we employed RNA oligonucleotides to redirect caspase 9 pre-mRNA splicing in favor of caspase 9b expression, which resulted in an increase in the IC(50) of non-small cell lung cancer (NSCLC) cells to daunorubicin, cisplatinum, and paclitaxel. In contrast, downregulation of caspase 9b induced a decrease in the IC(50) of these chemotherapeutic drugs. Finally, these studies showed that caspase 9 RNA splicing was a major mechanism for the synergistic effects of combination therapy with daunorubicin and erlotinib. Overall, we have identified a novel intronic splicing enhancer that regulates caspase 9 RNA splicing and specifically interacts with SRSF1. Furthermore, we showed that the alternative splicing of caspase 9 is an important molecular mechanism with therapeutic relevance to NSCLCs.
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Affiliation(s)
- Jacqueline C Shultz
- Department of Biochemistry, Virginia Commonwealth University-School of Medicine, Richmond, VA 23298-0614, USA
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Plocinik RM, Li S, Liu T, Hailey KL, Whitesides J, Whitehouse J, Ma CT, Fu XD, Gosh G, Woods VL, Jennings PA, Adams JA. Regulating SR protein phosphorylation through regions outside the kinase domain of SRPK1. J Mol Biol 2011; 410:131-45. [PMID: 21600902 DOI: 10.1016/j.jmb.2011.04.077] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 04/11/2011] [Accepted: 04/29/2011] [Indexed: 10/18/2022]
Abstract
SR proteins (splicing factors containing arginine-serine repeats) are essential splicing factors whose phosphorylation by the SR-specific protein kinase (SRPK) family regulates nuclear localization and mRNA processing activity. In addition to an N-terminal extension with unknown function, SRPKs contain a large, nonhomologous spacer insert domain (SID) that bifurcates the kinase domain and anchors the kinase in the cytoplasm through interactions with chaperones. While structures for the kinase domain are now available, constructs that include regions outside this domain have been resistant to crystallographic elucidation. To investigate the conformation of the full-length kinase and the functional role of noncatalytic regions, we performed hydrogen-deuterium exchange and steady-state kinetic experiments on SRPK1. Unlike the kinase core, the large SID lacks stable, hydrogen-bonded structure and may provide an intrinsically disordered region for chaperone interactions. Conversely, the N-terminus, which positively regulates SR protein binding, adopts a stable structure when the insert domain is present and stabilizes a docking groove in the large lobe of the kinase domain. The N-terminus and SID equally enhance SR protein turnover by altering the stability of several catalytic loop segments. These studies reveal that SRPK1 uses an N-terminal extension and a large, intrinsically disordered region juxtaposed to a stable structure to facilitate high-affinity SR protein interactions and phosphorylation rates.
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Affiliation(s)
- Ryan M Plocinik
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
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43
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Abstract
The splicing of mRNA requires a group of essential factors known as SR proteins, which participate in the maturation of the spliceosome. These proteins contain one or two RNA recognition motifs and a C-terminal domain rich in Arg-Ser repeats (RS domain). SR proteins are phosphorylated at numerous serines in the RS domain by the SR-specific protein kinase (SRPK) family of protein kinases. RS domain phosphorylation is necessary for entry of SR proteins into the nucleus, and may also play important roles in alternative splicing, mRNA export, and other processing events. Although SR proteins are polyphosphorylated in vivo, the mechanism underlying this complex reaction has only been recently elucidated. Human alternative splicing factor [serine/arginine-rich splicing factor 1 (SRSF1)], a prototype for the SR protein family, is regiospecifically phosphorylated by SRPK1, a post-translational modification that controls cytoplasmic-nuclear localization. SRPK1 binds SRSF1 with unusually high affinity, and rapidly modifies about 10-12 serines in the N-terminal region of the RS domain (RS1), using a mechanism that incorporates sequential, C-terminal to N-terminal phosphorylation and several processive steps. SRPK1 employs a highly dynamic feeding mechanism for RS domain phosphorylation in which the N-terminal portion of RS1 is initially bound to a docking groove in the large lobe of the kinase domain. Upon subsequent rounds of phosphorylation, this N-terminal segment translocates into the active site, and a β-strand in RNA recognition motif 2 unfolds and occupies the docking groove. These studies indicate that efficient regiospecific phosphorylation of SRSF1 is the result of a contoured binding cavity in SRPK1, a lengthy Arg-Ser repetitive segment in the RS domain, and a highly directional processing mechanism.
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Affiliation(s)
- Gourisankar Ghosh
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, USA
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Shultz JC, Goehe RW, Wijesinghe DS, Murudkar C, Hawkins AJ, Shay JW, Minna JD, Chalfant CE. Alternative splicing of caspase 9 is modulated by the phosphoinositide 3-kinase/Akt pathway via phosphorylation of SRp30a. Cancer Res 2010; 70:9185-96. [PMID: 21045158 DOI: 10.1158/0008-5472.can-10-1545] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Increasing evidence points to the functional importance of alternative splice variations in cancer pathophysiology. Two splice variants are derived from the CASP9 gene via the inclusion (Casp9a) or exclusion (Casp9b) of a four-exon cassette. Here we show that alternative splicing of Casp9 is dysregulated in non-small cell lung cancers (NSCLC) regardless of their pathologic classification. Based on these findings we hypothesized that survival pathways activated by oncogenic mutation regulated this mechanism. In contrast to K-RasV12 expression, epidermal growth factor receptor (EGFR) overexpression or mutation dramatically lowered the Casp9a/9b splice isoform ratio. Moreover, Casp9b downregulation blocked the ability of EGFR mutations to induce anchorage-independent growth. Furthermore, Casp9b expression blocked inhibition of clonogenic colony formation by erlotinib. Interrogation of oncogenic signaling pathways showed that inhibition of phosphoinositide 3-kinase or Akt dramatically increased the Casp9a/9b ratio in NSCLC cells. Finally, Akt was found to mediate exclusion of the exon 3,4,5,6 cassette of Casp9 via the phosphorylation state of the RNA splicing factor SRp30a via serines 199, 201, 227, and 234. Taken together, our findings show that oncogenic factors activating the phosphoinositide 3-kinase/Akt pathway can regulate alternative splicing of Casp9 via a coordinated mechanism involving the phosphorylation of SRp30a.
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Affiliation(s)
- Jacqueline C Shultz
- Department of Biochemistry, Virginia Commonwealth University, VAMC, and Massey Cancer Center, Richmond, Virginia 23298, USA
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Goehe RW, Shultz JC, Murudkar C, Usanovic S, Lamour NF, Massey DH, Zhang L, Camidge DR, Shay JW, Minna JD, Chalfant CE. hnRNP L regulates the tumorigenic capacity of lung cancer xenografts in mice via caspase-9 pre-mRNA processing. J Clin Invest 2010; 120:3923-39. [PMID: 20972334 PMCID: PMC2964989 DOI: 10.1172/jci43552] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Accepted: 08/18/2010] [Indexed: 02/03/2023] Open
Abstract
Caspase-9 is involved in the intrinsic apoptotic pathway and suggested to play a role as a tumor suppressor. Little is known about the mechanisms governing caspase-9 expression, but post-transcriptional pre-mRNA processing generates 2 splice variants from the caspase-9 gene, pro-apoptotic caspase-9a and anti-apoptotic caspase-9b. Here we demonstrate that the ratio of caspase-9 splice variants is dysregulated in non-small cell lung cancer (NSCLC) tumors. Mechanistic analysis revealed that an exonic splicing silencer (ESS) regulated caspase-9 pre-mRNA processing in NSCLC cells. Heterogeneous nuclear ribonucleoprotein L (hnRNP L) interacted with this ESS, and downregulation of hnRNP L expression induced an increase in the caspase-9a/9b ratio. Although expression of hnRNP L lowered the caspase-9a/9b ratio in NSCLC cells, expression of hnRNP L produced the opposite effect in non-transformed cells, suggesting a post-translational modification specific for NSCLC cells. Indeed, Ser52 was identified as a critical modification regulating the caspase-9a/9b ratio. Importantly, in a mouse xenograft model, downregulation of hnRNP L in NSCLC cells induced a complete loss of tumorigenic capacity that was due to the changes in caspase-9 pre-mRNA processing. This study therefore identifies a cancer-specific mechanism of hnRNP L phosphorylation and subsequent lowering of the caspase-9a/9b ratio, which is required for the tumorigenic capacity of NSCLC cells.
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Affiliation(s)
- Rachel Wilson Goehe
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
| | - Jacqueline C. Shultz
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
| | - Charuta Murudkar
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
| | - Sanja Usanovic
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
| | - Nadia F. Lamour
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
| | - Davis H. Massey
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
| | - Lian Zhang
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
| | - D. Ross Camidge
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
| | - Jerry W. Shay
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
| | - John D. Minna
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
| | - Charles E. Chalfant
- Department of Biochemistry and Molecular Biology,
Department of Physiology, and
Department of Pathology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
Thoracic Oncology and Developmental Therapeutics Programs, University of Colorado Cancer Center, Aurora, Colorado, USA.
Department of Cell Biology and
Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia, USA.
Massey Cancer Center, Richmond, Virginia, USA
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Piekielko-Witkowska A, Wiszomirska H, Wojcicka A, Poplawski P, Boguslawska J, Tanski Z, Nauman A. Disturbed expression of splicing factors in renal cancer affects alternative splicing of apoptosis regulators, oncogenes, and tumor suppressors. PLoS One 2010; 5:e13690. [PMID: 21082031 PMCID: PMC2972751 DOI: 10.1371/journal.pone.0013690] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 10/07/2010] [Indexed: 12/02/2022] Open
Abstract
Background Clear cell renal cell carcinoma (ccRCC) is the most common type of renal cancer. One of the processes disturbed in this cancer type is alternative splicing, although phenomena underlying these disturbances remain unknown. Alternative splicing consists of selective removal of introns and joining of residual exons of the primary transcript, to produce mRNA molecules of different sequence. Splicing aberrations may lead to tumoral transformation due to synthesis of impaired splice variants with oncogenic potential. In this paper we hypothesized that disturbed alternative splicing in ccRCC may result from improper expression of splicing factors, mediators of splicing reactions. Methodology/Principal Findings Using real-time PCR and Western-blot analysis we analyzed expression of seven splicing factors belonging to SR proteins family (SF2/ASF, SC35, SRp20, SRp75, SRp40, SRp55 and 9G8), and one non-SR factor, hnRNP A1 (heterogeneous nuclear ribonucleoprotein A1) in 38 pairs of tumor-control ccRCC samples. Moreover, we analyzed splicing patterns of five genes involved in carcinogenesis and partially regulated by analyzed splicing factors: RON, CEACAM1, Rac1, Caspase-9, and GLI1. Conclusions/Significance We found that the mRNA expression of splicing factors was disturbed in tumors when compared to paired controls, similarly as levels of SF2/ASF and hnRNP A1 proteins. The correlation coefficients between expression levels of specific splicing factors were increased in tumor samples. Moreover, alternative splicing of five analyzed genes was also disturbed in ccRCC samples and splicing pattern of two of them, Caspase-9 and CEACAM1 correlated with expression of SF2/ASF in tumors. We conclude that disturbed expression of splicing factors in ccRCC may possibly lead to impaired alternative splicing of genes regulating tumor growth and this way contribute to the process of carcinogenesis.
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Affiliation(s)
| | - Hanna Wiszomirska
- Department of Biochemistry and Molecular Biology, The Medical Centre of Postgraduate Education, Warsaw, Poland
| | - Anna Wojcicka
- Department of Biochemistry and Molecular Biology, The Medical Centre of Postgraduate Education, Warsaw, Poland
| | - Piotr Poplawski
- Department of Biochemistry and Molecular Biology, The Medical Centre of Postgraduate Education, Warsaw, Poland
| | - Joanna Boguslawska
- Department of Biochemistry and Molecular Biology, The Medical Centre of Postgraduate Education, Warsaw, Poland
| | | | - Alicja Nauman
- Department of Biochemistry and Molecular Biology, The Medical Centre of Postgraduate Education, Warsaw, Poland
- * E-mail:
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47
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Patwardhan GA, Liu YY. Sphingolipids and expression regulation of genes in cancer. Prog Lipid Res 2010; 50:104-14. [PMID: 20970453 DOI: 10.1016/j.plipres.2010.10.003] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 10/05/2010] [Accepted: 10/11/2010] [Indexed: 12/29/2022]
Abstract
Sphingolipids including glycosphingolipids have myriad effects on cell functions and affect cancer in aspects of tumorigenesis, metastasis and tumor response to treatments. Bioactive ones like ceramide, sphingosine 1-phosphate and globotriaosylceramide initiate and process cellular signaling to alter cell behaviors immediately responding to oncogenic stress or treatment challenges. Recent studies pinpoint that sphingolipid-mediated gene expression has long and profound impacts on cancer cells, and these play crucial roles in tumor progression and in treatment outcome. More than 10 sphingolipids and glycosphingolipids selectively mediate expressions of approximately 50 genes including c-myc, p21, c-fos, telomerase reverse transcriptase, caspase-9, Bcl-x, cyclooxygenase-2, matrix metalloproteinases, integrins, Oct-4, glucosylceramide synthase and multidrug-resistant gene 1. By diverse functions of these genes, sphingolipids enduringly affect cellular processes of mitosis, apoptosis, migration, stemness of cancer stem cells and cellular resistance to therapies. Mechanistic studies indicate that sphingolipids regulate particular gene expression by modulating phosphorylation and acetylation of proteins that serve as transcription factors (β-catenin, Sp1), repressor of transcription (histone H3), and regulators (SRp30a) in RNA splicing. Disclosing molecular mechanisms by which sphingolipids selectively regulate particular gene expression, instead of other relevant ones, requires understanding of the exact roles of individual lipid instead of a group, the signaling pathways that are implicated in and interaction with proteins or other lipids in details. These studies not only expand our knowledge of sphingolipids, but can also suggest novel targets for cancer treatments.
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Affiliation(s)
- Gauri A Patwardhan
- Department of Basic Pharmaceutical Sciences, University of Louisiana at Monroe, 700 University Avenue, Monroe, LA 71209, USA
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48
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Moore MJ, Wang Q, Kennedy CJ, Silver PA. An alternative splicing network links cell-cycle control to apoptosis. Cell 2010; 142:625-36. [PMID: 20705336 DOI: 10.1016/j.cell.2010.07.019] [Citation(s) in RCA: 246] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 02/18/2010] [Accepted: 06/15/2010] [Indexed: 12/25/2022]
Abstract
Alternative splicing is a vast source of biological regulation and diversity that is misregulated in cancer and other diseases. To investigate global control of alternative splicing in human cells, we analyzed splicing of mRNAs encoding Bcl2 family apoptosis factors in a genome-wide siRNA screen. The screen identified many regulators of Bcl-x and Mcl1 splicing, notably an extensive network of cell-cycle factors linked to aurora kinase A. Drugs or siRNAs that induce mitotic arrest promote proapoptotic splicing of Bcl-x, Mcl1, and caspase-9 and alter splicing of other apoptotic transcripts. This response precedes mitotic arrest, indicating coordinated upregulation of prodeath splice variants that promotes apoptosis in arrested cells. These shifts correspond to posttranslational turnover of splicing regulator ASF/SF2, which directly binds and regulates these target mRNAs and globally regulates apoptosis. Broadly, our results reveal an alternative splicing network linking cell-cycle control to apoptosis.
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Affiliation(s)
- Michael J Moore
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
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49
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Ezponda T, Pajares MJ, Agorreta J, Echeveste JI, López-Picazo JM, Torre W, Pio R, Montuenga LM. The Oncoprotein SF2/ASF Promotes Non–Small Cell Lung Cancer Survival by Enhancing Survivin Expression. Clin Cancer Res 2010; 16:4113-25. [DOI: 10.1158/1078-0432.ccr-10-0076] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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50
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Moulton VR, Tsokos GC. Alternative splicing factor/splicing factor 2 regulates the expression of the zeta subunit of the human T cell receptor-associated CD3 complex. J Biol Chem 2010; 285:12490-6. [PMID: 20118245 DOI: 10.1074/jbc.m109.091660] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
T cells from patients with systemic lupus erythematosus express decreased levels of the T cell receptor-associated CD3 zeta chain, a feature directly linked to their aberrant function. The decrease in CD3zeta protein expression is in part due to decreased levels of functional wild type isoform of the 3'-untranslated region (UTR) of CD3zeta mRNA with concomitant increased levels of an unstable alternatively spliced isoform. In order to identify factors involved in the post-transcriptional regulation of CD3zeta, we performed mass spectrometric analysis of Jurkat T cell nuclear proteins "pulled down" by a CD3zeta 3'-UTR oligonucleotide, which identified the splicing protein alternative splicing factor/splicing factor 2 (ASF/SF2). We show for the first time that ASF/SF2 binds specifically to the 3'-UTR of CD3zeta and regulates expression of CD3zeta protein by limiting the production of the alternatively spliced isoform. During activation of human T cells, an increase in the wild type CD3zeta mRNA is associated with increased expression of ASF/SF2. Finally, we show a significant correlation between ASF/SF2 and CD3zeta protein levels in T cells from systemic lupus erythematosus patients. Thus, our results identify ASF/SF2 as a novel factor in the regulation of alternative splicing of the 3'-UTR of CD3zeta and protein expression in human T cells.
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Affiliation(s)
- Vaishali R Moulton
- Division of Rheumatology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA
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