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Chang YC, Chan MH, Yang YF, Li CH, Hsiao M. Glucose transporter 4: Insulin response mastermind, glycolysis catalyst and treatment direction for cancer progression. Cancer Lett 2023; 563:216179. [PMID: 37061122 DOI: 10.1016/j.canlet.2023.216179] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 03/27/2023] [Accepted: 04/07/2023] [Indexed: 04/17/2023]
Abstract
The glucose transporter family (GLUT) consists of fourteen members. It is responsible for glucose homeostasis and glucose transport from the extracellular space to the cell cytoplasm to further cascade catalysis. GLUT proteins are encoded by the solute carrier family 2 (SLC2) genes and are members of the major facilitator superfamily of membrane transporters. Moreover, different GLUTs also have their transporter kinetics and distribution, so each GLUT member has its uniqueness and importance to play essential roles in human physiology. Evidence from many studies in the field of diabetes showed that GLUT4 travels between the plasma membrane and intracellular vesicles (GLUT4-storage vesicles, GSVs) and that the PI3K/Akt pathway regulates this activity in an insulin-dependent manner or by the AMPK pathway in response to muscle contraction. Moreover, some published results also pointed out that GLUT4 mediates insulin-dependent glucose uptake. Thus, dysfunction of GLUT4 can induce insulin resistance, metabolic reprogramming in diverse chronic diseases, inflammation, and cancer. In addition to the relationship between GLUT4 and insulin response, recent studies also referred to the potential upstream transcription factors that can bind to the promoter region of GLUT4 to regulating downstream signals. Combined all of the evidence, we conclude that GLUT4 has shown valuable unknown functions and is of clinical significance in cancers, which deserves our in-depth discussion and design compounds by structure basis to achieve therapeutic effects. Thus, we intend to write up a most updated review manuscript to include the most recent and critical research findings elucidating how and why GLUT4 plays an essential role in carcinogenesis, which may have broad interests and impacts on this field.
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Affiliation(s)
- Yu-Chan Chang
- Department of Biomedical Imaging and Radiological Science, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Ming-Hsien Chan
- Department of Biomedical Imaging and Radiological Science, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Yi-Fang Yang
- Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Chien-Hsiu Li
- Genomics Research Center, Academia Sinica, Taipei, Taiwan
| | - Michael Hsiao
- Genomics Research Center, Academia Sinica, Taipei, Taiwan; Department of Biochemistry, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
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2
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Krueger A, Łyszkiewicz M, Heissmeyer V. Post-transcriptional control of T-cell development in the thymus. Immunol Lett 2022; 247:1-12. [DOI: 10.1016/j.imlet.2022.04.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 03/18/2022] [Accepted: 04/26/2022] [Indexed: 11/05/2022]
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3
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Yang C, Yao C, Ji Z, Zhao L, Chen H, Li P, Tian R, Zhi E, Huang Y, Han X, Hong Y, Zhou Z, Li Z. RNA-binding protein ELAVL2 plays post-transcriptional roles in the regulation of spermatogonia proliferation and apoptosis. Cell Prolif 2021; 54:e13098. [PMID: 34296486 PMCID: PMC8450129 DOI: 10.1111/cpr.13098] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 06/22/2021] [Accepted: 06/24/2021] [Indexed: 12/27/2022] Open
Abstract
Objectives RNA‐binding proteins (RBPs) play essential post‐transcriptional roles in regulating spermatogonial stem cells (SSCs) maintenance and differentiation. We identified a conserved and SSCs‐enriched RBP ELAVL2 from our single‐cell sequencing data, but its function and mechanism in SSCs were unclear. Materials and methods Expressions of ELAVL2 during human and mouse testis development were validated. Stable C18‐4 and TCam‐2 cell lines with overexpression and knockdown of ELAVL2 were established, which were applied to proliferation and apoptosis analysis. RNA immunoprecipitation and sequencing were used to identify ELAVL2 targets, and regulatory functions of ELAVL2 on target mRNAs were studied. Proteins interacting with ELAVL2 in human and mouse testes were identified using immunoprecipitation and mass spectrometric, which were validated by in vivo and in vitro experiments. Results ELAVL2 was testis‐enriched and preferentially expressed in human and mouse SSCs. ELAVL2 was down‐regulated in NOA patients. ELAVL2 promoted proliferation and inhibited apoptosis of C18‐4 and TCam‐2 cell lines via activating ERK and AKT pathways. ELAVL2 associated with mRNAs encoding essential regulators of SSCs proliferation and survival, and promoted their protein expression at post‐transcriptional level. ELAVL2 interacted with DAZL in vivo and in vitro in both human and mouse testes. Conclusions Taken together, these results indicate that ELAVL2 is a conserved SSCs‐enriched RBP that down‐regulated in NOA, which regulates spermatogonia proliferation and apoptosis by promoting protein expression of targets.
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Affiliation(s)
- Chao Yang
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chencheng Yao
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhiyong Ji
- State Key Lab of Reproductive Medicine, Nanjing Medical University, Nanjing, China
| | - Liangyu Zhao
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Huixing Chen
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Peng Li
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Ruhui Tian
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Erlei Zhi
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yuhua Huang
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xia Han
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yan Hong
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhi Zhou
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Zheng Li
- Department of Andrology, The Center for Men's Health, Urologic Medical Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,State Key Lab of Reproductive Medicine, Nanjing Medical University, Nanjing, China
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4
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Lee S, Wei L, Zhang B, Goering R, Majumdar S, Wen J, Taliaferro JM, Lai EC. ELAV/Hu RNA binding proteins determine multiple programs of neural alternative splicing. PLoS Genet 2021; 17:e1009439. [PMID: 33826609 PMCID: PMC8055025 DOI: 10.1371/journal.pgen.1009439] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 04/19/2021] [Accepted: 02/22/2021] [Indexed: 12/15/2022] Open
Abstract
ELAV/Hu factors are conserved RNA binding proteins (RBPs) that play diverse roles in mRNA processing and regulation. The founding member, Drosophila Elav, was recognized as a vital neural factor 35 years ago. Nevertheless, little was known about its impacts on the transcriptome, and potential functional overlap with its paralogs. Building on our recent findings that neural-specific lengthened 3' UTR isoforms are co-determined by ELAV/Hu factors, we address their impacts on splicing. While only a few splicing targets of Drosophila are known, ectopic expression of each of the three family members (Elav, Fne and Rbp9) alters hundreds of cassette exon and alternative last exon (ALE) splicing choices. Reciprocally, double mutants of elav/fne, but not elav alone, exhibit opposite effects on both classes of regulated mRNA processing events in larval CNS. While manipulation of Drosophila ELAV/Hu RBPs induces both exon skipping and inclusion, characteristic ELAV/Hu motifs are enriched only within introns flanking exons that are suppressed by ELAV/Hu factors. Moreover, the roles of ELAV/Hu factors in global promotion of distal ALE splicing are mechanistically linked to terminal 3' UTR extensions in neurons, since both processes involve bypass of proximal polyadenylation signals linked to ELAV/Hu motifs downstream of cleavage sites. We corroborate the direct action of Elav in diverse modes of mRNA processing using RRM-dependent Elav-CLIP data from S2 cells. Finally, we provide evidence for conservation in mammalian neurons, which undergo broad programs of distal ALE and APA lengthening, linked to ELAV/Hu motifs downstream of regulated polyadenylation sites. Overall, ELAV/Hu RBPs orchestrate multiple broad programs of neuronal mRNA processing and isoform diversification in Drosophila and mammalian neurons.
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Affiliation(s)
- Seungjae Lee
- Developmental Biology Program, Sloan Kettering Institute, New York City, New York, United States of America
| | - Lu Wei
- Developmental Biology Program, Sloan Kettering Institute, New York City, New York, United States of America
| | - Binglong Zhang
- Developmental Biology Program, Sloan Kettering Institute, New York City, New York, United States of America
| | - Raeann Goering
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
- RNA Bioscience Initiative University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Sonali Majumdar
- Developmental Biology Program, Sloan Kettering Institute, New York City, New York, United States of America
| | - Jiayu Wen
- Department of Genome Sciences, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - J. Matthew Taliaferro
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
- RNA Bioscience Initiative University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Eric C. Lai
- Developmental Biology Program, Sloan Kettering Institute, New York City, New York, United States of America
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Kato Y, Iwamori T, Ninomiya Y, Kohda T, Miyashita J, Sato M, Saga Y. ELAVL2-directed RNA regulatory network drives the formation of quiescent primordial follicles. EMBO Rep 2019; 20:e48251. [PMID: 31657143 DOI: 10.15252/embr.201948251] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 09/28/2019] [Accepted: 10/04/2019] [Indexed: 12/14/2022] Open
Abstract
Formation of primordial follicles is a fundamental, early process in mammalian oogenesis. However, little is known about the underlying mechanisms. We herein report that the RNA-binding proteins ELAVL2 and DDX6 are indispensable for the formation of quiescent primordial follicles in mouse ovaries. We show that Elavl2 knockout females are infertile due to defective primordial follicle formation. ELAVL2 associates with mRNAs encoding components of P-bodies (cytoplasmic RNP granules involved in the decay and storage of RNA) and directs the assembly of P-body-like granules by promoting the translation of DDX6 in oocytes prior to the formation of primordial follicles. Deletion of Ddx6 disturbs the assembly of P-body-like granules and severely impairs the formation of primordial follicles, indicating the potential importance of P-body-like granules in the formation of primordial follicles. Furthermore, Ddx6-deficient oocytes are abnormally enlarged due to misregulated PI3K-AKT signaling. Our data reveal that an ELAVL2-directed post-transcriptional network is essential for the formation of quiescent primordial follicles.
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Affiliation(s)
- Yuzuru Kato
- Division of Mammalian Development, Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan.,Department of Genetics, SOKENDAI, Mishima, Shizuoka, Japan
| | - Tokuko Iwamori
- Department of Biomedicine, Research Center for Human Disease Modeling, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Youichirou Ninomiya
- Division of Mammalian Development, Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Takashi Kohda
- Faculty of Life and Environmental Sciences, University of Yamanashi, Kofu, Yamanashi, Japan
| | - Jyunko Miyashita
- Division of Mammalian Development, Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Mikiko Sato
- Division of Mammalian Development, Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Yumiko Saga
- Division of Mammalian Development, Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan.,Department of Genetics, SOKENDAI, Mishima, Shizuoka, Japan
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Tian P, Ou H, Wu F, Ma Y, Liu X, Chen Q, Dang H, Zou H. Interleukin-4-induced posttranscriptional gene regulation of CCL26 by the RNA-binding protein HuR in primary human nasal polyp-derived epithelial cells. Int Forum Allergy Rhinol 2018; 9:311-321. [PMID: 30472791 DOI: 10.1002/alr.22250] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 10/23/2018] [Accepted: 11/04/2018] [Indexed: 12/11/2022]
Abstract
BACKGROUND Much attention on the pathophysiology of nasal polyp (NP) has focused on eosinophils. Interleukin (IL)-4 and eotaxin-3 (C-C motif chemokine ligand 26, or CCL26) levels have been reported to be increased in eosinophilic nasal polyps. The aim of this study was to characterize CCL26 posttranscriptional regulation by the RNA-binding protein HuR in primary human nasal polyp-derived epithelial cells (hNPDECs) challenged with IL-4. METHODS A prospective, observational study was conducted. Nasal polyp tissues were obtained from eosinophilic (n = 12) and non-eosinophilic (n = 10) NP patients, and inferior turbinate (IT) tissues were taken from control subjects (n = 9) and cultured into hNPDECs. Expression of HuR and CCL26 were measured by immunohistochemistry, Western blot analysis, enzyme-linked immunoassay, and real-time polymerase chain reaction (PCR). The nucleocytoplasmic shuttling of HuR in hNPDECs was detected by immunofluorescence. Posttranscriptional regulation of CCL26 by HuR was tested by ribonucleoprotein immunoprecipitation assay (RIP) and dual-luciferase reporter assay. CCL26 mRNA stabilization was measured by quatititative PCR after treatment with actinomycin D. Student's t test and one-way analysis of variance were used. RESULTS Immunohistochemical data show that both HuR and CCL26 were highly expressed in NP tissues, especially eosinophilic NP tissues (p < 0.05). IL-4 stimulation increased CCL26 mRNA stability, and overexpression and knockdown of HuR affected CCL26 expression. Immunofluorescence data indicate that IL-4 altered the subcellular distribution of HuR. The RIP and dual-luciferase reporter assay results supply strong evidence for HuR binding to CCL26. CONCLUSION Our results provide strong support for the hypothesis that IL-4-induced expression of CCL26 in hNPDECs relies partly on CCL26 mRNA stabilization mediated by the interaction of HuR with CCL26 3'UTR.
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Affiliation(s)
- Peng Tian
- Department of Otorhinolaryngology-Head and Neck Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People's Republic of China
| | - Huashuang Ou
- Department of Otorhinolaryngology-Head and Neck Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People's Republic of China
| | - Fan Wu
- Department of Otorhinolaryngology-Head and Neck Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People's Republic of China
| | - Yun Ma
- Department of Otorhinolaryngology-Head and Neck Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People's Republic of China
| | - Xiang Liu
- Department of Otorhinolaryngology-Head and Neck Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People's Republic of China
| | - Qiujian Chen
- Department of Otorhinolaryngology-Head and Neck Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People's Republic of China
| | - Hua Dang
- Department of Otorhinolaryngology-Head and Neck Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People's Republic of China
| | - Hua Zou
- Department of Otorhinolaryngology-Head and Neck Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People's Republic of China
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7
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Klein N, Curatola AM, Schneider RJ. Calcium-induced stabilization of AU-rich short-lived mRNAs is a common default response. Gene Expr 2018; 7:357-65. [PMID: 10440236 PMCID: PMC6174662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
The AU-rich element (AUUUA)n, found in the 3' noncoding region of many short-lived cytokine and proto-oncogene mRNAs, is sufficient to specifically target these mRNAs for rapid degradation in mammalian cells. The mechanism by which the AU-rich element promotes rapid mRNA decay is not known. Previous studies have shown that release of intracellular stored calcium by ionophore treatment of thymocytes and mast cells inhibits the rapid turnover of AU-rich interleukin mRNAs. Increased cytoplasmic half-life of interleukin mRNAs was linked to calcium-induced activation of the N-terminal c-Jun kinase. In this report we have characterized the calcium-induced stabilization of AU-rich mRNAs. We show that calcium induces stabilization of mRNAs with canonical AU-rich elements in all cell types tested. These results indicate that short-lived mRNA stabilization by calcium is not unique to immune cells nor interleukin mRNAs, but is a widespread default response that includes generic AU-rich mRNAs. Stabilization is shown to be rapid but transient, and to act without altering nuclear transcription or cytoplasmic translation rates. These data support the view that calcium release likely stabilizes short-lived mRNAs by altering trans-acting decay factors that promote AU-rich mRNA turnover.
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Affiliation(s)
- Nicola Klein
- Department of Biochemistry and Microbiology, Kaplan Cancer Center, NYU Medical School, New York, NY 10016
| | - Anna Maria Curatola
- Department of Biochemistry and Microbiology, Kaplan Cancer Center, NYU Medical School, New York, NY 10016
| | - Robert J. Schneider
- Department of Biochemistry and Microbiology, Kaplan Cancer Center, NYU Medical School, New York, NY 10016
- Address correspondence to Robert J. Schneider, Department of Biochemistry and Microbiology, Kaplan Cancer Center, NYU Medical School, 550 First Avenue, New York, NY 10016. Tel: (212) 263-6006; Fax: (212) 263-8166; E-mail:
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8
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Zybura-Broda K, Wolder-Gontarek M, Ambrozek-Latecka M, Choros A, Bogusz A, Wilemska-Dziaduszycka J, Rylski M. HuR (Elavl1) and HuB (Elavl2) Stabilize Matrix Metalloproteinase-9 mRNA During Seizure-Induced Mmp-9 Expression in Neurons. Front Neurosci 2018; 12:224. [PMID: 29686606 PMCID: PMC5900018 DOI: 10.3389/fnins.2018.00224] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 03/22/2018] [Indexed: 01/28/2023] Open
Abstract
Matrix metalloproteinase-9 (Mmp-9) is involved in different general and cell-type–specific processes, both in neuronal and non-neuronal cells. Moreover, it is implicated in an induction or progression of various human disorders, including diseases of the central nervous system. Mechanisms regulating activity-driven Mmp-9 expression in neurons are still not fully understood. Here, we show that stabilization of Mmp-9 mRNA is one of the factors responsible for the neuronal activity-evoked upregulation of Mmp-9 mRNA expression in hippocampal neurons. Furthermore, we demonstrate that the molecular mechanism related to this stabilization is dependent on the neuronal seizure-triggered transiently increased binding of the mRNA stability-inducing protein, HuR, to ARE1 and ARE4 motifs of the 3′UTR for Mmp-9 mRNA as well as the stably augmented association of another mRNA-stabilizing protein, HuB, to the ARE1 element of the 3′UTR. Intriguingly, we demonstrate further that both HuR and HuB are crucial for an incidence of Mmp-9 mRNA stabilization after neuronal activation. This study identifies Mmp-9 mRNA as the first HuB target regulated by mRNA stabilization in neurons. Moreover, these results are the first to describe an existence of HuR-dependent mRNA stabilization in neurons of the brain.
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Affiliation(s)
- Katarzyna Zybura-Broda
- Department of Clinical Cytology, Centre of Postgraduate Medical Education, Warsaw, Poland
| | | | | | - Artur Choros
- Department of Clinical Cytology, Centre of Postgraduate Medical Education, Warsaw, Poland
| | - Agnieszka Bogusz
- Department of Clinical Cytology, Centre of Postgraduate Medical Education, Warsaw, Poland
| | | | - Marcin Rylski
- Department of Clinical Cytology, Centre of Postgraduate Medical Education, Warsaw, Poland
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9
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Neuron-specific alternative splicing of transcriptional machineries: Implications for neurodevelopmental disorders. Mol Cell Neurosci 2017; 87:35-45. [PMID: 29254826 DOI: 10.1016/j.mcn.2017.10.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Revised: 10/18/2017] [Accepted: 10/24/2017] [Indexed: 02/07/2023] Open
Abstract
The brain has long been known to display the most complex pattern of alternative splicing, thereby producing diverse protein isoforms compared to other tissues. Recent evidence indicates that many alternative exons are neuron-specific, evolutionarily conserved, and found in regulators of transcription including DNA-binding protein and histone modifying enzymes. This raises a possibility that neurons adopt unique mechanisms of transcription. Given that transcriptional machineries are frequently mutated in neurodevelopmental disorders with cognitive dysfunction, it is important to understand how neuron-specific alternative splicing contributes to proper transcriptional regulation in the brain. In this review, we summarize current knowledge regarding how neuron-specific splicing events alter the function of transcriptional regulators and shape unique gene expression patterns in the brain and the implications of neuronal splicing to the pathophysiology of neurodevelopmental disorders.
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10
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Del Vecchio G, De Vito F, Saunders SJ, Risi A, Mannironi C, Bozzoni I, Presutti C. RNA-binding protein HuR and the members of the miR-200 family play an unconventional role in the regulation of c-Jun mRNA. RNA (NEW YORK, N.Y.) 2016; 22:1510-1521. [PMID: 27473170 PMCID: PMC5029450 DOI: 10.1261/rna.057588.116] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 05/27/2016] [Indexed: 06/06/2023]
Abstract
Post-transcriptional gene regulation is a fundamental step for coordinating cellular response in a variety of processes. RNA-binding proteins (RBPs) and microRNAs (miRNAs) are the most important factors responsible for this regulation. Here we report that different components of the miR-200 family are involved in c-Jun mRNA regulation with the opposite effect. While miR-200b inhibits c-Jun protein production, miR-200a tends to increase the JUN amount through a stabilization of its mRNA. This action is dependent on the presence of the RBP HuR that binds the 3'UTR of c-Jun mRNA in a region including the mir-200a binding site. The position of the binding site is fundamental; by mutating this site, we demonstrate that the effect is not micro-RNA specific. These results indicate that miR-200a triggers a microRNA-mediated stabilization of c-Jun mRNA, promoting the binding of HuR with c-Jun mRNA. This is the first example of a positive regulation exerted by a microRNA on an important oncogene in proliferating cells.
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Affiliation(s)
- Giorgia Del Vecchio
- Dipartimento di Biologia e Biotecnologie, Università "Sapienza," 00185 Rome, Italy
| | - Francesca De Vito
- Dipartimento di Biologia e Biotecnologie, Università "Sapienza," 00185 Rome, Italy
| | - Sita J Saunders
- Bioinformatics Group, Department of Computer Science, Albert-Ludwigs-University Freiburg, 79110 Freiburg, Germany
| | - Adele Risi
- Dipartimento di Biologia e Biotecnologie, Università "Sapienza," 00185 Rome, Italy
| | | | - Irene Bozzoni
- Dipartimento di Biologia e Biotecnologie, Università "Sapienza," 00185 Rome, Italy
| | - Carlo Presutti
- Dipartimento di Biologia e Biotecnologie, Università "Sapienza," 00185 Rome, Italy
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Splicing Regulation of Pro-Inflammatory Cytokines and Chemokines: At the Interface of the Neuroendocrine and Immune Systems. Biomolecules 2015; 5:2073-100. [PMID: 26371053 PMCID: PMC4598789 DOI: 10.3390/biom5032073] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 08/28/2015] [Indexed: 01/13/2023] Open
Abstract
Alternative splicing plays a key role in posttranscriptional regulation of gene expression, allowing a single gene to encode multiple protein isoforms. As such, alternative splicing amplifies the coding capacity of the genome enormously, generates protein diversity, and alters protein function. More than 90% of human genes undergo alternative splicing, and alternative splicing is especially prevalent in the nervous and immune systems, tissues where cells need to react swiftly and adapt to changes in the environment through carefully regulated mechanisms of cell differentiation, migration, targeting, and activation. Given its prevalence and complexity, this highly regulated mode of gene expression is prone to be affected by disease. In the following review, we look at how alternative splicing of signaling molecules—cytokines and their receptors—changes in different pathological conditions, from chronic inflammation to neurologic disorders, providing means of functional interaction between the immune and neuroendocrine systems. Switches in alternative splicing patterns can be very dynamic and can produce signaling molecules with distinct or antagonistic functions and localization to different subcellular compartments. This newly discovered link expands our understanding of the biology of immune and neuroendocrine cells, and has the potential to open new windows of opportunity for treatment of neurodegenerative disorders.
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12
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Kim HH, Lee SJ, Gardiner AS, Perrone-Bizzozero NI, Yoo S. Different motif requirements for the localization zipcode element of β-actin mRNA binding by HuD and ZBP1. Nucleic Acids Res 2015; 43:7432-46. [PMID: 26152301 PMCID: PMC4551932 DOI: 10.1093/nar/gkv699] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 06/29/2015] [Indexed: 11/13/2022] Open
Abstract
Interactions of RNA-binding proteins (RBPs) with their target transcripts are essential for regulating gene expression at the posttranscriptional level including mRNA export/localization, stability, and translation. ZBP1 and HuD are RBPs that play pivotal roles in mRNA transport and local translational control in neuronal processes. While HuD possesses three RNA recognition motifs (RRMs), ZBP1 contains two RRMs and four K homology (KH) domains that either increase target specificity or provide a multi-target binding capability. Here we used isolated cis-element sequences of the target mRNA to examine directly protein-RNA interactions in cell-free systems. We found that both ZBP1 and HuD bind the zipcode element in rat β-actin mRNA's 3' UTR. Differences between HuD and ZBP1 were observed in their binding preference to the element. HuD showed a binding preference for U-rich sequence. In contrast, ZBP1 binding to the zipcode RNA depended more on the structural level, as it required the proper spatial organization of a stem-loop that is mainly determined by the U-rich element juxtaposed to the 3' end of a 5'-ACACCC-3' motif. On the basis of this work, we propose that ZBP1 and HuD bind to overlapping sites in the β-actin zipcode, but they recognize different features of this target sequence.
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Affiliation(s)
- Hak Hee Kim
- Nemours Biomedical Research, Alfred I. duPont Hosp. for Children, Wilmington, DE 19803, USA
| | - Seung Joon Lee
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Amy S Gardiner
- Department of Neuroscience, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
| | - Nora I Perrone-Bizzozero
- Department of Neuroscience, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
| | - Soonmoon Yoo
- Nemours Biomedical Research, Alfred I. duPont Hosp. for Children, Wilmington, DE 19803, USA
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Campos-Melo D, Droppelmann CA, Volkening K, Strong MJ. RNA-binding proteins as molecular links between cancer and neurodegeneration. Biogerontology 2014; 15:587-610. [PMID: 25231915 DOI: 10.1007/s10522-014-9531-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 09/11/2014] [Indexed: 12/12/2022]
Abstract
For many years, epidemiological studies have suggested an association between cancer and neurodegenerative disorders-two disease processes that seemingly have little in common. Although these two disease processes share disruptions in a wide range of cellular pathways, including cell survival, cell death and the cell cycle, the end result is very divergent: uncontrolled cell survival and proliferation in cancer and progressive neuronal cell death in neurodegeneration. Despite the clinical data connecting these two disease processes, little is known about the molecular links between them. Among the mechanisms affected in cancer and neurodegenerative diseases, alterations in RNA metabolism are obtaining significant attention given the critical role for RNA transcription, maturation, transport, stability, degradation and translation in normal cellular function. RNA-binding proteins (RBPs) are integral to each stage of RNA metabolism through their participation in the formation of ribonucleoprotein complexes (RNPs). RBPs have a broad range of functions including posttranscriptional regulation of mRNA stability, splicing, editing and translation, mRNA export and localization, mRNA polyadenylation and miRNA biogenesis, ultimately impacting the expression of every single gene in the cell. In this review, we examine the evidence for RBPs as being key a molecular linkages between cancer and neurodegeneration.
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Affiliation(s)
- Danae Campos-Melo
- Molecular Medicine Group, Robarts Research Institute, Western University, London, ON, Canada
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HuR regulates alternative splicing of the TRA2β gene in human colon cancer cells under oxidative stress. Mol Cell Biol 2014; 34:2857-73. [PMID: 24865968 DOI: 10.1128/mcb.00333-14] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Hu antigen R (HuR) regulates stress responses through stabilizing and/or facilitating the translation of target mRNAs. The human TRA2β gene encodes splicing factor transformer 2β (Tra2β) and generates 5 mRNA isoforms (TRA2β1 to -5) through alternative splicing. Exposure of HCT116 colon cancer cells to sodium arsenite stimulated checkpoint kinase 2 (Chk2)- and mitogen-activated protein kinase p38 (p38(MAPK))-mediated phosphorylation of HuR at positions S88 and T118. This induced an association between HuR and the 39-nucleotide (nt) proximal region of TRA2β exon 2, generating a TRA2β4 mRNA that includes exon 2, which has multiple premature stop codons. HuR knockdown or Chk2/p38(MAPK) double knockdown inhibited the arsenite-stimulated production of TRA2β4 and increased Tra2β protein, facilitating Tra2β-dependent inclusion of exons in target pre-mRNAs. The effects of HuR knockdown or Chk2/p38(MAPK) double knockdown were also confirmed using a TRA2β minigene spanning exons 1 to 4, and the effects disappeared when the 39-nt region was deleted from the minigene. In endogenous HuR knockdown cells, the overexpression of a HuR mutant that could not be phosphorylated (with changes of serine to alanine at position 88 [S88A], S100A, and T118A) blocked the associated TRA2β4 interaction and TRA2β4 generation, while the overexpression of a phosphomimetic HuR (with mutations S88D, S100D, and T118D) restored the TRA2β4-related activities. Our findings revealed the potential role of nuclear HuR in the regulation of alternative splicing programs under oxidative stress.
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RNA-binding proteins in neurological diseases. SCIENCE CHINA-LIFE SCIENCES 2014; 57:432-44. [DOI: 10.1007/s11427-014-4647-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 02/25/2014] [Indexed: 12/12/2022]
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Chalupnikova K, Solc P, Sulimenko V, Sedlacek R, Svoboda P. An oocyte-specific ELAVL2 isoform is a translational repressor ablated from meiotically competent antral oocytes. Cell Cycle 2014; 13:1187-200. [PMID: 24553115 PMCID: PMC4013169 DOI: 10.4161/cc.28107] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
At the end of the growth phase, mouse antral follicle oocytes acquire full developmental competence. In the mouse, this event is marked by the transition from the so-called non-surrounded nucleolus (NSN) chromatin configuration into the transcriptionally quiescent surrounded nucleolus (SN) configuration, which is named after a prominent perinucleolar condensed chromatin ring. However, the SN chromatin configuration alone is not sufficient for determining the developmental competence of the SN oocyte. There are additional nuclear and cytoplamic factors involved, while a little is known about the changes occurring in the cytoplasm during the NSN/SN transition. Here, we report functional analysis of maternal ELAVL2 an AU-rich element binding protein. Elavl2 gene encodes an oocyte-specific protein isoform (denoted ELAVL2°), which acts as a translational repressor. ELAVL2° is abundant in fully grown NSN oocytes, is ablated during the NSN/SN transition and remains low during the oocyte-to-embryo transition (OET). ELAVL2° overexpression during meiotic maturation causes errors in chromosome segregation, indicating the significance of naturally reduced ELAVL2° levels in SN oocytes. On the other hand, during oocyte growth, prematurely reduced Elavl2 expression results in lower yields of fully grown and meiotically matured oocytes, suggesting that Elavl2 is necessary for proper oocyte maturation. Moreover, Elavl2 knockdown showed stimulating effects on translation in fully grown oocytes. We propose that ELAVL2 has an ambivalent role in oocytes: it functions as a pleiotropic translational repressor in efficient production of fully grown oocytes, while its disposal during the NSN/SN transition contributes to the acquisition of full developmental competence.
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Affiliation(s)
| | - Petr Solc
- Institute of Animal Physiology and Genetics AS CR; Libechov, Czech Republic
| | - Vadym Sulimenko
- Institute of Molecular Genetics AS CR; Prague, Czech Republic
| | | | - Petr Svoboda
- Institute of Molecular Genetics AS CR; Prague, Czech Republic
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Mukherjee N, Jacobs NC, Hafner M, Kennington EA, Nusbaum JD, Tuschl T, Blackshear PJ, Ohler U. Global target mRNA specification and regulation by the RNA-binding protein ZFP36. Genome Biol 2014; 15:R12. [PMID: 24401661 PMCID: PMC4053807 DOI: 10.1186/gb-2014-15-1-r12] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 01/08/2013] [Indexed: 02/05/2023] Open
Abstract
Background ZFP36, also known as tristetraprolin or TTP, and ELAVL1, also known as HuR, are two disease-relevant RNA-binding proteins (RBPs) that both interact with AU-rich sequences but have antagonistic roles. While ELAVL1 binding has been profiled in several studies, the precise in vivo binding specificity of ZFP36 has not been investigated on a global scale. We determined ZFP36 binding preferences using cross-linking and immunoprecipitation in human embryonic kidney cells, and examined the combinatorial regulation of AU-rich elements by ZFP36 and ELAVL1. Results Targets bound and negatively regulated by ZFP36 include transcripts encoding proteins necessary for immune function and cancer, and transcripts encoding other RBPs. Using partial correlation analysis, we were able to quantify the association between ZFP36 binding sites and differential target RNA abundance upon ZFP36 overexpression independent of effects from confounding features. Genes with increased mRNA half-lives in ZFP36 knockout versus wild-type mouse cells were significantly enriched for our human ZFP36 targets. We identified thousands of overlapping ZFP36 and ELAVL1 binding sites, in 1,313 genes, and found that ZFP36 degrades transcripts through specific AU-rich sequences, representing a subset of the U-rich sequences ELAVL1 interacts with to stabilize transcripts. Conclusions ZFP36-RNA target specificities in vivo are quantitatively similar to previously reported in vitro binding affinities. ZFP36 and ELAVL1 bind an overlapping spectrum of RNA sequences, yet with differential relative preferences that dictate combinatorial regulatory potential. Our findings and methodology delineate an approach to unravel in vivo combinatorial regulation by RNA-binding proteins.
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Bronicki LM, Jasmin BJ. Emerging complexity of the HuD/ELAVl4 gene; implications for neuronal development, function, and dysfunction. RNA (NEW YORK, N.Y.) 2013; 19:1019-1037. [PMID: 23861535 PMCID: PMC3708524 DOI: 10.1261/rna.039164.113] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Precise control of messenger RNA (mRNA) processing and abundance are increasingly being recognized as critical for proper spatiotemporal gene expression, particularly in neurons. These regulatory events are governed by a large number of trans-acting factors found in neurons, most notably RNA-binding proteins (RBPs) and micro-RNAs (miRs), which bind to specific cis-acting elements or structures within mRNAs. Through this binding mechanism, trans-acting factors, particularly RBPs, control all aspects of mRNA metabolism, ranging from altering the transcription rate to mediating mRNA degradation. In this context the best-characterized neuronal RBP, the Hu/ELAVl family member HuD, is emerging as a key component in multiple regulatory processes--including pre-mRNA processing, mRNA stability, and translation--governing the fate of a substantial amount of neuronal mRNAs. Through its ability to regulate mRNA metabolism of diverse groups of functionally similar genes, HuD plays important roles in neuronal development and function. Furthermore, compelling evidence indicates supplementary roles for HuD in neuronal plasticity, in particular, recovery from axonal injury, learning and memory, and multiple neurological diseases. The purpose of this review is to provide a detailed overview of the current knowledge surrounding the expression and roles of HuD in the nervous system. Additionally, we outline the present understanding of the molecular mechanisms presiding over the localization, abundance, and function of HuD in neurons.
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Abstract
Neurons have their own systems for regulating RNA. Several multigene families encode RNA binding proteins (RNABPs) that are uniquely expressed in neurons, including the well-known neuron-specific markers ELAV and NeuN and the disease antigen NOVA. New technologies have emerged in recent years to assess the function of these proteins in vivo, and the answers are yielding insights into how and why neurons may regulate RNA in special ways-to increase cellular complexity, to localize messenger RNA (mRNA) spatially, and to regulate their expression in response to synaptic stimuli. The functions of such restricted neuronal proteins are likely to be complemented by more widely expressed RNABPs that may themselves have developed specialized functions in neurons, including Argonaute/microRNAs (miRNAs). Here we review what is known about such RNABPs and explore the potential biologic and neurologic significance of neuronal RNA regulatory systems.
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Affiliation(s)
- Robert B Darnell
- Department of Molecular Neuro-Oncology, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065, USA.
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20
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Ciafrè SA, Galardi S. microRNAs and RNA-binding proteins: a complex network of interactions and reciprocal regulations in cancer. RNA Biol 2013; 10:935-42. [PMID: 23696003 PMCID: PMC4111733 DOI: 10.4161/rna.24641] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In the last decade, an ever-growing number of connections between microRNAs (miRNAs) and RNA-binding proteins (RBPs) have uncovered a new level of complexity of gene expression regulation in cancer. In this review, we examine several aspects of the functional interactions between miRNAs and RBPs in cancer models. We will provide examples of reciprocal regulation: miRNAs regulating the expression of RBPs, or the converse, where an RNA-binding protein specifically regulates the expression of a specific miRNA, or when an RBP can exert a widespread effect on miRNAs via the modulation of a key protein for miRNA production or function. Moreover, we will focus on the ever-growing number of functional interactions that have been discovered in the last few years: RBPs that were shown to cooperate with microRNAs in the downregulation of shared target mRNAs or, on the contrary, that inhibit microRNA action, thus resulting in a protection of the specific target mRNAs. We surely need to obtain a deeper comprehension of such intricate networks to have a chance of understanding and, thus, fighting cancer.
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Affiliation(s)
- Silvia Anna Ciafrè
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, Via Montpellier, Roma, Italy.
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Colombrita C, Silani V, Ratti A. ELAV proteins along evolution: back to the nucleus? Mol Cell Neurosci 2013; 56:447-55. [PMID: 23439364 DOI: 10.1016/j.mcn.2013.02.003] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 02/11/2013] [Accepted: 02/14/2013] [Indexed: 12/16/2022] Open
Abstract
The complex interplay of post-transcriptional regulatory mechanisms mediated by RNA-binding proteins (RBP) at different steps of RNA metabolism is pivotal for the development of the nervous system and the maintenance of adult brain activities. In this review, we will focus on the highly conserved ELAV gene family encoding for neuronal-specific RBPs which are necessary for proper neuronal differentiation and important for synaptic plasticity process. In the evolution from Drosophila to man, ELAV proteins seem to have changed their biological functions in relation to their different subcellular localization. While in Drosophila, they are localized in the nuclear compartment of neuronal cells and regulate splicing and polyadenylation, in mammals, the neuronal ELAV proteins are mainly present in the cytoplasm where they participate in regulating mRNA target stability, translation and transport into neurites. However, recent data indicate that the mammalian ELAV RBPs also have nuclear activities, similarly to their fly counterpart, being them able to continuously shuttle between the cytoplasm and the nucleus. Here, we will review and comment on all the biological functions associated with neuronal ELAV proteins along evolution and will show that the post-transcriptional regulatory network mediated by these RBPs in the brain is highly complex and only at an initial stage of being fully understood. This article is part of a Special Issue entitled 'RNA and splicing regulation in neurodegeneration'.
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Affiliation(s)
- Claudia Colombrita
- Department of Neurology and Laboratory of Neuroscience, IRCCS Istituto Auxologico Italiano, Via Zucchi, 18, 20095 Cusano Milanino (Milan), Italy; Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, "Dino Ferrari" Center, Università degli Studi di Milano, Via Sforza, 35, 20122 Milan, Italy
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Simone LE, Keene JD. Mechanisms coordinating ELAV/Hu mRNA regulons. Curr Opin Genet Dev 2013; 23:35-43. [PMID: 23312841 PMCID: PMC3617084 DOI: 10.1016/j.gde.2012.12.006] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 12/05/2012] [Accepted: 12/12/2012] [Indexed: 12/25/2022]
Abstract
The 5' and 3' untranslated regions (UTRs) of messenger RNAs (mRNAs) function as platforms that can determine the fate of each mRNA individually and in aggregate. Multiple mRNAs that encode proteins that are functionally related often interact with RNA-binding proteins (RBPs) and noncoding RNAs (ncRNAs) that coordinate their expression in time and space as RNA regulons within the ribonucleoprotein (RNP) infrastructure we term the ribonome. Recent ribonomic methods have emerged that can determine which mRNAs are bound and regulated by RBPs and ncRNAs, some of which act in combination to determine global outcomes. ELAV/Hu proteins bind to AU-rich elements (ARE) in mRNAs and regulate their stability from splicing to translation, and the ubiquitous HuR protein has been implicated in cancerous cell growth. Recent work is focused on mechanistic models of how ELAV/Hu proteins increase mRNA stability and translation by repressing microRNAs (miRs) and the RNA induced silencing complex (RISC) via ARE-based ribonucleosomes that may affect global functions of mRNA regulons.
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Affiliation(s)
- Laura E. Simone
- Department of Molecular Genetics & Microbiology Duke University Medical Center Durham, NC 27710
| | - Jack D. Keene
- Department of Molecular Genetics & Microbiology Duke University Medical Center Durham, NC 27710
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Bronicki LM, Jasmin BJ. Trans-acting factors governing acetylcholinesterase mRNA metabolism in neurons. Front Mol Neurosci 2012; 5:36. [PMID: 22461767 PMCID: PMC3309972 DOI: 10.3389/fnmol.2012.00036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 03/06/2012] [Indexed: 11/13/2022] Open
Abstract
The most characterized function of acetylcholinesterase (AChE) is to terminate cholinergic signaling at neuron-neuron and neuro-muscular synapses. In addition, AChE is causally or casually implicated in neuronal development, stress-response, cognition, and neurodegenerative diseases. Given the importance of AChE, many studies have focused on identifying the molecular mechanisms that govern its expression. Despite these efforts, post-transcriptional control of AChE mRNA expression is still relatively unclear. Here, we review the trans-acting factors and cis-acting elements that are known to control AChE pre-mRNA splicing, mature mRNA stability and translation. Moreover, since the Hu/ELAV family of RNA-binding proteins (RBPs) have emerged in recent years as “master” post-transcriptional regulators, we discuss the possibility that predominantly neuronal ELAVs (nELAVs) play multiple roles in regulating splicing, stability, localization, and translation of AChE mRNA.
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Affiliation(s)
- Lucas M Bronicki
- Faculty of Medicine, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa ON, Canada
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24
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Pascale A, Govoni S. The complex world of post-transcriptional mechanisms: is their deregulation a common link for diseases? Focus on ELAV-like RNA-binding proteins. Cell Mol Life Sci 2012; 69:501-17. [PMID: 21909784 PMCID: PMC11114966 DOI: 10.1007/s00018-011-0810-7] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 08/23/2011] [Accepted: 08/25/2011] [Indexed: 12/14/2022]
Abstract
Post-transcriptional mechanisms are key determinants in the modulation of the expression of final gene products. Within this context, fundamental players are RNA-binding proteins (RBPs), and among them ELAV-like proteins. RBPs are able to affect every aspect in the processing of transcripts, from alternative splicing, polyadenylation, and nuclear export to cytoplasmic localization, stability, and translation. Of interest, more than one RBP can bind simultaneously the same mRNA; therefore, since each RBP is endowed with different properties, the balance of these interactions dictates the ultimate fate of the transcript, especially in terms of both stability and rate of translation. Besides RBPs, microRNAs are also important contributors to the post-transcriptional control of gene expression. Within this general context, the present review focuses on ELAV-like proteins describing their roles in the nucleus and in the cytoplasm, also highlighting some examples of interactions with other RBPs and with microRNAs. We also examine the putative role and the observed changes of ELAV-like proteins and of their interactions with other regulatory elements in Alzheimer's disease, cancer, and inflammation. The changes in the expression of proteins involved in these diseases are examples of how a derangement in the mRNA stabilization process may be associated with disease development and contribute to pathology. Overall, we hope that the topics handled in the present manuscript provide a hint to look at ELAV-like-mediated mRNA stabilization as a mechanism relevant to disease as well as a novel putative drug target.
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Affiliation(s)
- Alessia Pascale
- Section of Pharmacology, Department of Drug Sciences, University of Pavia, Via Taramelli 14, 27100, Pavia, Italy.
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25
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Zheng C, Baum BJ. Including the p53 ELAV-like protein-binding site in vector cassettes enhances transgene expression in rat submandibular gland. Oral Dis 2012; 18:477-84. [PMID: 22251132 DOI: 10.1111/j.1601-0825.2011.01895.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE ELAV-like proteins regulate mRNA stability and/or translation. We evaluated whether inclusion of binding sites for ELAV-like HuR proteins in vector cassettes could improve transgene expression in the salivary gland. METHODS Western blots and immunofluorescence staining were used to determine whether HuR protein was expressed in salivary cells and tissue. HuR binding sites were inserted into the pACEF1α-luc-BGH expression plasmid. Cell lines were transfected with plasmids in vitro and luciferase expression measured. Rat submandibular glands were transfected in vivo with plasmids containing ELAV-like HuR protein-binding sites. An adenoviral vector with p53 ELAV-like HuR protein-binding site was generated and also tested in vivo. Four unique 29mer HuR shRNA constructs were used in A5 cells to evaluate whether there was a specific interaction between HuR protein and the p53 HuR protein-binding site. RESULTS Salivary cells express HuR protein. Inclusion of the p53 ELAV-like HuR protein-binding site resulted in high luciferase activity in salivary cells in vitro, with similar results in vivo. In vitro shRNA data demonstrated that the high luciferase activity was mediated by the interaction between HuR protein and the p53 HuR protein-binding site. The AdEF1α-luc-p53BGH, including this binding site, mediated very high luciferase activity, ~4-fold that seen with the CMV promoter, in rat submandibular glands. CONCLUSIONS Including the p53 ELAV-like protein-binding site in transgene cassettes may enhance therapeutic vectors intended for use with salivary glands.
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Affiliation(s)
- C Zheng
- Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892-1190, USA.
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26
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Mansfield KD, Keene JD. Neuron-specific ELAV/Hu proteins suppress HuR mRNA during neuronal differentiation by alternative polyadenylation. Nucleic Acids Res 2011; 40:2734-46. [PMID: 22139917 PMCID: PMC3315332 DOI: 10.1093/nar/gkr1114] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The ubiquitously expressed RNA-binding protein HuR increases the stability and translation of mRNAs encoding growth regulatory proteins that promote proliferation in a variety of cell types. However, the three neuron-specific ELAV/Hu proteins, HuB, HuC and HuD, while binding to the same types of mRNAs, are required instead for neuronal differentiation, and it becomes difficult to reconcile these contrary functions when all four Hu proteins are expressed in the same neuron. HuR mRNA exists as three alternatively polyadenylated variants, a 1.5-kb testes-specific mRNA isoform, a ubiquitous 2.4-kb isoform and a 6.0-kb isoform that we now show is induced during neuronal differentiation and appears to be neuron-specific. This 6.0-kb neuron-specific mRNA isoform is inherently less stable and produces less HuR protein than the ubiquitous 2.4-kb mRNA. Furthermore, we show that neuronal HuB, HuC and HuD, as well as HuR itself, can bind at the 2.4-kb mRNA polyadenylation site, and when overexpressed can affect alternative polyadenylation to generate an extended HuR 3'-UTR that is translationally suppressed. We propose that the regulation of HuR protein expression by alternative polyadenylation allows neurons to post-transcriptionally regulate mRNAs-encoding factors required for proliferation versus differentiation to facilitate neuronal differentiation.
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Affiliation(s)
- Kyle D Mansfield
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27701, USA.
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27
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Calder MD, Watson PH, Watson AJ. Culture medium, gas atmosphere and MAPK inhibition affect regulation of RNA-binding protein targets during mouse preimplantation development. Reproduction 2011; 142:689-98. [PMID: 21846809 DOI: 10.1530/rep-11-0082] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
During oogenesis, mammalian oocytes accumulate maternal mRNAs that support the embryo until embryonic genome activation. RNA-binding proteins (RBP) may regulate the stability and turnover of maternal and embryonic mRNAs. We hypothesised that varying embryo culture conditions, such as culture medium, oxygen tension and MAPK inhibition, affects regulation of RBPs and their targets during preimplantation development. STAU1, ELAVL1, KHSRP and ZFP36 proteins and mRNAs were detected throughout mouse preimplantation development, whereas Elavl2 mRNA decreased after the two-cell stage. Potential target mRNAs of RBP regulation, Gclc, Slc2a1 and Slc7a1 were detected during mouse preimplantation development. Gclc mRNA was significantly elevated in embryos cultured in Whitten's medium compared with embryos cultured in KSOMaa, and Gclc mRNA was elevated under high-oxygen conditions. Inhibition of the p38 MAPK pathway reduced Slc7a1 mRNA expression while inhibition of ERK increased Slc2a1 mRNA expression. The half-lives of the potential RBP mRNA targets are not regulated in parallel; Slc2a1 mRNA displayed the longest half-life. Our results indicate that mRNAs and proteins encoding five RBPs are present during preimplantation development and more importantly, demonstrate that expression of RBP target mRNAs are regulated by culture medium, gas atmosphere and MAPK pathways.
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Affiliation(s)
- Michele D Calder
- Department of Physiology, The University of Western Ontario, London, Ontario, Canada A5-146.
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Mukherjee N, Corcoran DL, Nusbaum JD, Reid DW, Georgiev S, Hafner M, Ascano M, Tuschl T, Ohler U, Keene JD. Integrative regulatory mapping indicates that the RNA-binding protein HuR couples pre-mRNA processing and mRNA stability. Mol Cell 2011; 43:327-39. [PMID: 21723170 PMCID: PMC3220597 DOI: 10.1016/j.molcel.2011.06.007] [Citation(s) in RCA: 518] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 04/23/2011] [Accepted: 06/10/2011] [Indexed: 01/02/2023]
Abstract
RNA-binding proteins coordinate the fates of multiple RNAs, but the principles underlying these global interactions remain poorly understood. We elucidated regulatory mechanisms of the RNA-binding protein HuR, by integrating data from diverse high-throughput targeting technologies, specifically PAR-CLIP, RIP-chip, and whole-transcript expression profiling. The number of binding sites per transcript, degree of HuR association, and degree of HuR-dependent RNA stabilization were positively correlated. Pre-mRNA and mature mRNA containing both intronic and 3' UTR binding sites were more highly stabilized than transcripts with only 3' UTR or only intronic binding sites, suggesting that HuR couples pre-mRNA processing with mature mRNA stability. We also observed HuR-dependent splicing changes and substantial binding of HuR in polypyrimidine tracts of pre-mRNAs. Comparison of the spatial patterns surrounding HuR and miRNA binding sites provided functional evidence for HuR-dependent antagonism of proximal miRNA-mediated repression. We conclude that HuR coordinates gene expression outcomes at multiple interconnected steps of RNA processing.
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Affiliation(s)
- Neelanjan Mukherjee
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
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Zucconi BE, Wilson GM. Modulation of neoplastic gene regulatory pathways by the RNA-binding factor AUF1. FRONT BIOSCI-LANDMRK 2011; 16:2307-25. [PMID: 21622178 PMCID: PMC3589912 DOI: 10.2741/3855] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The mRNA-binding protein AUF1 regulates the expression of many key players in cancer including proto-oncogenes, regulators of apoptosis and the cell cycle, and pro-inflammatory cytokines, principally by directing the decay kinetics of their encoded mRNAs. Most studies support an mRNA-destabilizing role for AUF1, although other findings suggest additional functions for this factor. In this review, we explore how changes in AUF1 isoform distribution, subcellular localization, and post-translational protein modifications can influence the metabolism of targeted mRNAs. However, several lines of evidence also support a role for AUF1 in the initiation and/or development of cancer. Many AUF1-targeted transcripts encode products that control pro- and anti-oncogenic processes. Also, overexpression of AUF1 enhances tumorigenesis in murine models, and AUF1 levels are enhanced in some tumors. Finally, signaling cascades that modulate AUF1 function are deregulated in some cancerous tissues. Together, these features suggest that AUF1 may play a prominent role in regulating the expression of many genes that can contribute to tumorigenic phenotypes, and that this post-transcriptional regulatory control point may be subverted by diverse mechanisms in neoplasia.
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Affiliation(s)
- Beth E. Zucconi
- Department of Biochemistry and Molecular Biology and Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, 108 N. Greene St., Baltimore, MD 21201
| | - Gerald M. Wilson
- Department of Biochemistry and Molecular Biology and Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, 108 N. Greene St., Baltimore, MD 21201
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Cao H, Graves DJ, Anderson RA. Cinnamon extract regulates glucose transporter and insulin-signaling gene expression in mouse adipocytes. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2010; 17:1027-1032. [PMID: 20554184 DOI: 10.1016/j.phymed.2010.03.023] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 03/02/2010] [Accepted: 03/31/2010] [Indexed: 05/29/2023]
Abstract
Cinnamon extracts (CE) are reported to have beneficial effects on people with normal and impaired glucose tolerance, the metabolic syndrome, type 2 diabetes, and insulin resistance. However, clinical results are controversial. Molecular characterization of CE effects is limited. This study investigated the effects of CE on gene expression in cultured mouse adipocytes. Water-soluble CE was prepared from ground cinnamon (Cinnamomum burmannii). Quantitative real-time PCR was used to investigate CE effects on the expression of genes coding for adipokines, glucose transporter (GLUT) family, and insulin-signaling components in mouse 3T3-L1 adipocytes. CE (100 μg/ml) increased GLUT1 mRNA levels 1.91±0.15, 4.39±0.78, and 6.98±2.18-fold of the control after 2-, 4-, and 16-h treatments, respectively. CE decreased the expression of further genes encoding insulin-signaling pathway proteins including GSK3B, IGF1R, IGF2R, and PIK3R1. This study indicates that CE regulates the expression of multiple genes in adipocytes and this regulation could contribute to the potential health benefits of CE.
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Affiliation(s)
- Heping Cao
- Commodity Utilization Research Unit, Southern Regional Research Center, Agricultural Research Service, US Department of Agriculture, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA.
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Sekii K, Salvenmoser W, De Mulder K, Scharer L, Ladurner P. Melav2, an elav-like gene, is essential for spermatid differentiation in the flatworm Macrostomum lignano. BMC DEVELOPMENTAL BIOLOGY 2009; 9:62. [PMID: 19995429 PMCID: PMC2795745 DOI: 10.1186/1471-213x-9-62] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Accepted: 12/08/2009] [Indexed: 11/10/2022]
Abstract
Background Failure of sperm differentiation is one of the major causes of male sterility. During spermiogenesis, spermatids undergo a complex metamorphosis, including chromatin condensation and cell elongation. Although the resulting sperm morphology and property can vary depending on the species, these processes are fundamental in many organisms. Studying genes involved in such processes can thus provide important information for a better understanding of spermatogenesis, which might be universally applied to many other organisms. Results In a screen for genes that have gonad-specific expression we isolated an elav-like gene, melav2, from Macrostomum lignano, containing the three RNA recognition motifs characteristic of elav-like genes. We found that melav2 mRNA was expressed exclusively in the testis, as opposed to the known elav genes, which are expressed in the nervous system. The RNAi phenotype of melav2 was characterized by an aberrant spermatid morphology, where sperm elongation often failed, and an empty seminal vesicle. Melav2 RNAi treated worms were thus male-sterile. Further analysis revealed that in melav2 RNAi treated worms precocious chromatin condensation occurred during spermatid differentiation, resulting in an abnormally tightly condensed chromatin and large vacuoles in round spermatids. In addition, immunostaining using an early-spermatid specific antibody revealed that melav2 RNAi treated worms had a larger amount of signal positive cells, suggesting that many cells failed the transition from early spermatid stage. Conclusion We characterize a new function for elav-like genes, showing that melav2 plays a crucial role during spermatid differentiation, especially in the regulation of chromatin condensation and/or cell elongation.
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Affiliation(s)
- Kiyono Sekii
- Department of Evolutionary Biology, Zoological Institute, University of Basel, Basel, Switzerland.
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Zhang X, Zou T, Rao JN, Liu L, Xiao L, Wang PY, Cui YH, Gorospe M, Wang JY. Stabilization of XIAP mRNA through the RNA binding protein HuR regulated by cellular polyamines. Nucleic Acids Res 2009; 37:7623-37. [PMID: 19825980 PMCID: PMC2794158 DOI: 10.1093/nar/gkp755] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 08/26/2009] [Accepted: 08/27/2009] [Indexed: 12/23/2022] Open
Abstract
The X chromosome-linked inhibitor of apoptosis protein (XIAP) is the most potent intrinsic caspase inhibitor and plays an important role in the maintenance of intestinal epithelial integrity. The RNA binding protein, HuR, regulates the stability and translation of many target transcripts. Here, we report that HuR associated with both the 3'-untranslated region and coding sequence of the mRNA encoding XIAP, stabilized the XIAP transcript and elevated its expression in intestinal epithelial cells. Ectopic HuR overexpression or elevated cytoplasmic levels of endogenous HuR by decreasing cellular polyamines increased [HuR/XIAP mRNA] complexes, in turn promoting XIAP mRNA stability and increasing XIAP protein abundance. Conversely, HuR silencing in normal and polyamine-deficient cells rendered the XIAP mRNA unstable, thus reducing the steady state levels of XIAP. Inhibition of XIAP expression by XIAP silencing or by HuR silencing reversed the resistance of polyamine-deficient cells to apoptosis. Our findings demonstrate that HuR regulates XIAP expression by stabilizing its mRNA and implicates HuR-mediated XIAP in the control of intestinal epithelial apoptosis.
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Affiliation(s)
- Xian Zhang
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore Veterans Affairs Medical Center, Department of Pathology, University of Maryland School of Medicine and Laboratory of Cellular and Molecular Biology, National Institute on Aging-IRP, NIH, Baltimore, MD 21224, USA
| | - Tongtong Zou
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore Veterans Affairs Medical Center, Department of Pathology, University of Maryland School of Medicine and Laboratory of Cellular and Molecular Biology, National Institute on Aging-IRP, NIH, Baltimore, MD 21224, USA
| | - Jaladanki N. Rao
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore Veterans Affairs Medical Center, Department of Pathology, University of Maryland School of Medicine and Laboratory of Cellular and Molecular Biology, National Institute on Aging-IRP, NIH, Baltimore, MD 21224, USA
| | - Lan Liu
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore Veterans Affairs Medical Center, Department of Pathology, University of Maryland School of Medicine and Laboratory of Cellular and Molecular Biology, National Institute on Aging-IRP, NIH, Baltimore, MD 21224, USA
| | - Lan Xiao
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore Veterans Affairs Medical Center, Department of Pathology, University of Maryland School of Medicine and Laboratory of Cellular and Molecular Biology, National Institute on Aging-IRP, NIH, Baltimore, MD 21224, USA
| | - Peng-Yuan Wang
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore Veterans Affairs Medical Center, Department of Pathology, University of Maryland School of Medicine and Laboratory of Cellular and Molecular Biology, National Institute on Aging-IRP, NIH, Baltimore, MD 21224, USA
| | - Yu-Hong Cui
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore Veterans Affairs Medical Center, Department of Pathology, University of Maryland School of Medicine and Laboratory of Cellular and Molecular Biology, National Institute on Aging-IRP, NIH, Baltimore, MD 21224, USA
| | - Myriam Gorospe
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore Veterans Affairs Medical Center, Department of Pathology, University of Maryland School of Medicine and Laboratory of Cellular and Molecular Biology, National Institute on Aging-IRP, NIH, Baltimore, MD 21224, USA
| | - Jian-Ying Wang
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore Veterans Affairs Medical Center, Department of Pathology, University of Maryland School of Medicine and Laboratory of Cellular and Molecular Biology, National Institute on Aging-IRP, NIH, Baltimore, MD 21224, USA
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Mukherjee N, Lager PJ, Friedersdorf MB, Thompson MA, Keene JD. Coordinated posttranscriptional mRNA population dynamics during T-cell activation. Mol Syst Biol 2009; 5:288. [PMID: 19638969 PMCID: PMC2724974 DOI: 10.1038/msb.2009.44] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Accepted: 06/03/2009] [Indexed: 11/25/2022] Open
Abstract
Although RNA-binding proteins (RBPs) coordinate many key decisions during cell growth and differentiation, the dynamics of RNA–RBP interactions have not been extensively studied on a global basis. We immunoprecipitated endogenous ribonucleoprotein complexes containing HuR and PABP throughout a T-cell activation time course and identified the associated mRNA populations using microarrays. We used Gaussian mixture modeling as a discriminative model, treating RBP association as a discrete variable (target or not target), and as a generative model, treating RBP-association as a continuous variable (probability of association). We report that HuR interacts with different populations of mRNAs during T-cell activation. These populations encode functionally related proteins that are members of the Wnt pathway and proteins mediating T-cell receptor signaling pathways. Moreover, the mRNA targets of HuR were found to overlap with the targets of other posttranscriptional regulatory factors, indicating combinatorial interdependence of posttranscriptional regulatory networks and modules after activation. Applying HuR mRNA dynamics as a quantitative phenotype in the drug-gene-phenotype Connectivity Map, we identified candidate small molecule effectors of HuR and T-cell activation. We show that one of these candidates, resveratrol, exerts T-cell activation-dependent posttranscriptional effects that are rescued by HuR. Thus, we describe a strategy to systematically link an RBP and condition-specific posttranscriptional effects to small molecule drugs.
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Affiliation(s)
- Neelanjan Mukherjee
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
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Li X, Lu L, Bush DJ, Zhang X, Zheng L, Suswam EA, King PH. Mutant copper-zinc superoxide dismutase associated with amyotrophic lateral sclerosis binds to adenine/uridine-rich stability elements in the vascular endothelial growth factor 3'-untranslated region. J Neurochem 2009; 108:1032-44. [PMID: 19196430 DOI: 10.1111/j.1471-4159.2008.05856.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Vascular endothelial growth factor (VEGF) is a neurotrophic factor essential for maintenance of motor neurons. Loss of this factor produces a phenotype similar to amyotrophic lateral sclerosis (ALS). We recently showed that ALS-producing mutations of Cu/Zn-superoxide dismutase (SOD1) disrupt post-transcriptional regulation of VEGF mRNA, leading to significant loss of expression [Lu et al., J. Neurosci.27 (2007), 7929]. Mutant SOD1 was present in the ribonucleoprotein complex associated with adenine/uridine-rich elements (ARE) of the VEGF 3'-untranslated region (UTR). Here, we show by electrophoretic mobility shift assay that mutant SOD1 bound directly to the VEGF 3'-UTR with a predilection for AREs similar to the RNA stabilizer HuR. SOD1 mutants A4V and G37R showed higher affinity for the ARE than L38V or G93A. Wild-type SOD1 bound very weakly with an apparent K(d) 11- to 72-fold higher than mutant forms. Mutant SOD1 showed an additional lower shift with VEGF ARE that was accentuated in the metal-free state. A similar pattern of binding was observed with AREs of tumor necrosis factor-alpha and interleukin-8, except only a single shift predominated. Using an ELISA-based assay, we demonstrated that mutant SOD1 competes with HuR and neuronal HuC for VEGF 3'-UTR binding. To define potential RNA-binding domains, we truncated G37R, G93A and wild-type SOD1 and found that peptides from the N-terminal portion of the protein that included amino acids 32-49 could recapitulate the binding pattern of full-length protein. Thus, the strong RNA-binding affinity conferred by ALS-associated mutations of SOD1 may contribute to the post-transcriptional dysregulation of VEGF mRNA.
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Affiliation(s)
- Xuelin Li
- Department of Neurology, University of Alabama at Birmingham, Alabama, USA
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Duan H, Cherradi N, Feige JJ, Jefcoate C. cAMP-dependent posttranscriptional regulation of steroidogenic acute regulatory (STAR) protein by the zinc finger protein ZFP36L1/TIS11b. Mol Endocrinol 2009; 23:497-509. [PMID: 19179481 DOI: 10.1210/me.2008-0296] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Star is expressed in steroidogenic cells as 3.5- and 1.6-kb transcripts that differ only in their 3'-untranslated regions (3'-UTR). In mouse MA10 testis and Y-1 adrenal lines, Br-cAMP preferentially stimulates 3.5-kb mRNA. ACTH is similarly selective in primary bovine adrenocortical cells. The 3.5-kb form harbors AU-rich elements (AURE) in the extended 3'-UTR, which enhance turnover. After peak stimulation of 3.5-kb mRNA, degradation is seen. Star mRNA turnover is enhanced by the zinc finger protein ZFP36L1/TIS11b, which binds to UAUUUAUU repeats in the extended 3'-UTR. TIS11b is rapidly stimulated in each cell type in parallel with Star mRNA. Cotransfection of TIS11b selectively decreases cytomegalovirus-promoted Star mRNA and luciferase-Star 3'-UTR reporters harboring the extended 3'-UTR. Direct complex formation was demonstrated between TIS11b and the extended 3'-UTR of the 3.5-kb Star. AURE mutations revealed that TIS11b-mediated destabilization required the first two UAUUUAUU motifs. HuR, which also binds AURE, did not affect Star expression. Targeted small interfering RNA knockdown of TIS11b specifically enhanced stimulation of 3.5-kb Star mRNA in bovine adrenocortical cells, MA-10, and Y-1 cells but did not affect the reversals seen after peak stimulation. Direct transfection of Star mRNA demonstrated that Br-cAMP stimulated a selective turnover of 3.5-kb mRNA independent of AURE, which may correspond to these reversal processes. Steroidogenic acute regulatory (STAR) protein induction was halved by TIS11b knockdown, concomitant with decreased cholesterol metabolism. TIS11b suppression of 3.5-kb mRNA is therefore surprisingly coupled to enhanced Star translation leading to increased cholesterol metabolism.
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Affiliation(s)
- Haichuan Duan
- Department of Pharmacology, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
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36
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Amadio M, Pascale A, Wang J, Ho L, Quattrone A, Gandy S, Haroutunian V, Racchi M, Pasinetti GM. nELAV proteins alteration in Alzheimer's disease brain: a novel putative target for amyloid-beta reverberating on AbetaPP processing. J Alzheimers Dis 2009; 16:409-19. [PMID: 19221430 PMCID: PMC6057145 DOI: 10.3233/jad-2009-0967] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Neuronal ELAV (nELAV) proteins are RNA-binding proteins which play a physiological role in controlling gene expression in memory formation, and their alteration may contribute to cognitive impairment associated with neurodegenerative pathologies such as Alzheimer's disease (AD). Indeed, we found that the content of nELAV proteins is significantly decreased along with clinical dementia progression in the hippocampi of AD brains, where it inversely correlates with the amount of amyloid-beta (Abeta). To check the direct influence of Abeta on nELAV, we performed in vitro experiments using human SH-SY5Y cells, finding that Abeta(1-42) specifically determines nELAV proteins reduction. Since ADAM10 mRNA has the predicted sequences targeted by nELAV, we investigated whether Abeta, through nELAV proteins, could originate a vicious circle affecting amyloid-beta protein precursor (AbetaPP) processing. Immunoprecipitation experiments showed that indeed nELAV proteins bind to ADAM10 mRNA and that this binding is disrupted by Abeta(1-42) exposure, resulting in a decreased ADAM10 protein expression. ADAM10 protein diminution was also found in AD hippocampi. These data show for the first time the involvement of nELAV in AD pathology and suggest that their alteration may affect genes implicated in AbetaPP processing.
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Affiliation(s)
- Marialaura Amadio
- Department of Experimental and Applied Pharmacology and Centre of Excellence in Applied Biology, University of Pavia, Pavia, Italy.
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37
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Cherry J, Jones H, Karschner VA, Pekala PH. Post-transcriptional control of CCAAT/enhancer-binding protein beta (C/EBPbeta) expression: formation of a nuclear HuR-C/EBPbeta mRNA complex determines the amount of message reaching the cytosol. J Biol Chem 2008; 283:30812-20. [PMID: 18678862 PMCID: PMC2576548 DOI: 10.1074/jbc.m805659200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Indexed: 12/27/2022] Open
Abstract
In 3T3-L1 cells, HuR is constitutively expressed and prior to induction of differentiation localized predominantly to the nucleus. Within minutes of induction of differentiation, nuclear HuR binds to its target ligand mRNAs, and the complexes appear to move to the cytosol. One ligand mRNA is the CCAAT/enhancer-binding protein beta (C/EBPbeta) message. To examine the function and importance of the HuR-C/EBPbeta interaction, retroviral expression constructs were created in which the HuR binding site was altered by deletion (betadel) or deletion and substitution (betad/s). Expression of these constructs in murine embryonic fibroblasts resulted in significant adipose conversion relative to those cells expressing wild type C/EBPbeta. C/EBPbeta protein content was increased markedly in both betadel and betad/s, which correlated with the acquisition of the adipocyte phenotype. Analysis of the betad/s cell line demonstrated a robust expression of C/EBPalpha coincident with peroxisome proliferator-activated receptor gamma expression. Total C/EBPbeta mRNA accumulation indicated no difference between cells harboring either the wild type C/EBPbeta cDNA or betad/s construct. However, cytosolic C/EBPbeta mRNA in the cells expressing the betad/s construct was maintained at levels between 2- and 7-fold greater than in the cells expressing the wild type construct. Alteration in mRNA half-life was not responsible for the increased accumulation. Mechanistically, these data suggest that HuR binding results in nuclear retention of the C/EBPbeta mRNA and is consistent with HuR control, at least in part, of mRNA processing.
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Affiliation(s)
- Joy Cherry
- Department of Biochemistry and Molecular Biology, The Brody School of Medicine at East Carolina University, Greenville, North Carolina 27858, USA
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Abstract
Hu proteins are RNA-binding proteins involved in diverse biological processes. The neuronal members of the Hu family, HuB, HuC, and HuD play important roles in neuronal differentiation and plasticity, while the ubiquitously expressed family member, HuR, has numerous functions mostly related to cellular stress response. The pivotal roles of Hu proteins are dictated by their molecular functions affecting a large number of target genes. Hu proteins affect many post-transcriptional aspects of RNA metabolism, from splicing to translation. In this communication, we will focus on these molecular events and review our current understanding of how Hu proteins mediate them. In particular, emphasis will be put on the nuclear functions of these proteins, which were recently discovered. Three examples including calcitonin/calcitonin gene-related peptide, neurofibromatosis type 1, and Ikaros will be discussed in detail. In addition, an intriguing theme of antagonism between Hu proteins and other AU-rich sequence binding proteins will be discussed.
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Affiliation(s)
- M. N. Hinman
- Department of Genetics, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, Ohio 44106 USA
| | - H. Lou
- Department of Genetics, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, Ohio 44106 USA
- Case Comprehensive Cancer Center, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, Ohio 44106 USA
- Center for RNA Molecular Biology, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, Ohio 44106 USA
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Abstract
SummaryRNA-binding proteins (RBP) influence RNA editing, localization, stability and translation and may contribute to oocyte developmental competence by regulating the stability and turnover of oogenetic mRNAs. The expression of Staufen 1 and 2 and ELAVL1, ELAVL2 RNA-binding proteins during cow early development was characterized. Cumulus–oocyte complexes were collected from slaughterhouse ovaries, matured, inseminated and subjected to embryo culturein vitro. Oocyte or preimplantation embryo pools were processed for RT-PCR and whole-mount immunofluorescence analysis of mRNA expression and protein distribution. STAU1 and STAU2 and ELAVL1 mRNAs and proteins were detected throughout cow preimplantation development from the germinal vesicle (GV) oocyte to the blastocyst stage. ELAVL2 mRNAs were detectable from the GV to the morula stage, whereas ELAVL2 protein was in all stages examined and localized to both cytoplasm and nuclei. The findings provide a foundation for investigating the role of RBPs during mammalian oocyte maturation and early embryogenesis.
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Regulation of neuron-specific alternative splicing of neurofibromatosis type 1 pre-mRNA. Mol Cell Biol 2007; 28:1240-51. [PMID: 18086893 DOI: 10.1128/mcb.01509-07] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Neurofibromatosis type 1 (NF1) is one of the most common heritable autosomal dominant disorders. Alternative splicing modulates the function of neurofibromin, the NF1 gene product, by inserting the in-frame exon 23a into the region of NF1 mRNA that encodes the GTPase-activating protein-related domain. This insertion, which is predominantly skipped in neurons, reduces the ability of neurofibromin to regulate Ras by 10-fold. Here, we report that the neuron-specific Hu proteins control the production of the short protein isoform by suppressing inclusion of NF1 exon 23a, while TIA-1/TIAR proteins promote inclusion of this exon. We identify two binding sites for Hu proteins, located upstream and downstream of the regulated exon, and provide biochemical evidence that Hu proteins specifically block exon definition by preventing binding of essential splicing factors. In vitro analyses using nuclear extracts show that at the downstream site, Hu proteins prevent binding of U1 and U6 snRNPs to the 5' splice site, while TIAR increases binding. Hu proteins also decrease U2AF binding at the 3' splice site located upstream of exon 23a. In addition to providing the first mechanistic insight into tissue-specific control of NF1 splicing, these studies establish a novel strategy whereby Hu proteins regulate RNA processing.
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Fornaro M, Raimondo S, Lee JM, Giacobini-Robecchi MG. Neuron-specific Hu proteins sub-cellular localization in primary sensory neurons. Ann Anat 2007; 189:223-8. [PMID: 17534028 DOI: 10.1016/j.aanat.2006.11.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Hu family of RNA-binding proteins is involved in many post-transcriptional mechanisms for the development and maintenance of the nervous system. Three members of the Hu family (HuB, HuC and HuD) are neuron-specific proteins. In this study, we present data using light and electron microscopy to show the sub-cellular localization of neuron-specific Hu proteins in rat primary sensory neurons taken from dorsal root ganglia (DRG). Using these techniques we morphologically revealed the presence of neuron-specific-Hu proteins in the nucleus and in the cytoplasm and discriminated the presence of Hu proteins within different cellular organelles, specifically mitochondria and Golgi apparatus, thus supporting previous ideas that NS-Hu proteins enable RNA interactions with sub-cellular organelles and may be involved in mRNA cellular localization.
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Affiliation(s)
- Michele Fornaro
- Department of Clinical and Biological Sciences, University of Turin, Ospedale San Luigi, Regione Gonzole 10, 10043 Orbassano (TO), Italy.
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42
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Lu L, Zheng L, Viera L, Suswam E, Li Y, Li X, Estévez AG, King PH. Mutant Cu/Zn-superoxide dismutase associated with amyotrophic lateral sclerosis destabilizes vascular endothelial growth factor mRNA and downregulates its expression. J Neurosci 2007; 27:7929-38. [PMID: 17652584 PMCID: PMC6672720 DOI: 10.1523/jneurosci.1877-07.2007] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Vascular endothelial growth factor (VEGF) plays a neuroprotective role in mice harboring mutations of copper-zinc superoxide dismutase 1 (SOD1) in familial amyotrophic lateral sclerosis (ALS). Conversely, the loss of VEGF expression through genetic depletion can give rise to a phenotype resembling ALS independent of SOD1 mutations. Here, we observe a profound downregulation of VEGF mRNA expression in spinal cords of G93A SOD1 mice that occurred early in the course of the disease. Using an in vitro culture model of glial cells expressing mutant SOD1, we demonstrate destabilization and downregulation of VEGF RNA with concomitant loss of protein expression that correlates with level of transgene expression. Using a luciferase reporter assay, we show that this molecular effect is mediated through a portion of the VEGF 3'-untranslated region (UTR) that harbors a class II adenylate/uridylate-rich element. Other mutant forms of SOD1 produced a similar negative effect on luciferase RNA and protein expression. Mobility shift assay with a VEGF 3'-UTR probe reveals an aberrantly migrating complex that contains mutant SOD1. We further show that the RNA stabilizing protein, HuR (human antigen R), is translocated from nucleus to cytoplasm in mutant SOD1 cells in vitro and mouse motor neurons in vivo. In summary, our data suggest that mutant SOD1 gains a novel function, possibly by altering the ribonucleoprotein complex with the VEGF 3'-UTR. We postulate that the resultant dysregulation of VEGF posttranscriptional processing critically reduces the level of this neuroprotective growth factor and accelerates the neurodegenerative process in ALS.
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Affiliation(s)
- Liang Lu
- Departments of Neurology
- Birmingham Veterans Affairs Medical Center, Birmingham, Alabama 35295, and
| | | | - Liliana Viera
- Laboratory of Motor Neuron Biology, Burke Medical Research Institute
| | | | - Yanyan Li
- Departments of Neurology
- Birmingham Veterans Affairs Medical Center, Birmingham, Alabama 35295, and
| | - Xuelin Li
- Departments of Neurology
- Birmingham Veterans Affairs Medical Center, Birmingham, Alabama 35295, and
| | - Alvaro G. Estévez
- Laboratory of Motor Neuron Biology, Burke Medical Research Institute
- Department of Neurology and Neurosciences, Weill Medical College of Cornell University, White Plains, New York 10605
| | - Peter H. King
- Departments of Neurology
- Genetics, and
- Physiology and Biophysics, University of Alabama, Birmingham, and
- Birmingham Veterans Affairs Medical Center, Birmingham, Alabama 35295, and
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Hau HH, Walsh RJ, Ogilvie RL, Williams DA, Reilly CS, Bohjanen PR. Tristetraprolin recruits functional mRNA decay complexes to ARE sequences. J Cell Biochem 2007; 100:1477-92. [PMID: 17133347 DOI: 10.1002/jcb.21130] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
AU-rich elements (AREs) in the 3' untranslated region (UTR) of numerous mammalian transcripts function as instability elements that promote rapid mRNA degradation. Tristetraprolin (TTP) is an ARE-binding protein that promotes rapid mRNA decay through mechanisms that are poorly understood. A 31 nucleotide ARE sequences from the TNF-alpha 3' UTR promoted TTP-dependent mRNA decay when it was inserted into the 3' UTR of a beta-globin reporter transcript, indicating that this short sequence was sufficient for TTP function. We used a gel shift assay to identify a TTP-containing complex in cytoplasmic extracts from TTP-transfected HeLa cells that bound specifically to short ARE sequences. This TTP-containing complex also contained the 5'-3' exonuclease Xrn1 and the exosome component PM-scl75 because it was super-shifted with anti-Xrn1 or anti-PMscl75 antibodies. RNA affinity purification verified that these proteins associated specifically with ARE sequences in a TTP-dependent manner. Using a competition binding assay, we found that the TTP-containing complex bound with high affinity to short ARE sequences from GM-CSF, IL-3, TNF-alpha, IL-2, and c-fos, but did not bind to a U-rich sequence from c-myc, a 22 nucleotide poly U sequence or a mutated GM-CSF control sequence. High affinity binding by the TTP-containing complex correlated with TTP-dependent deadenylation and decay of capped, polyadenylated transcripts in a cell-free mRNA decay assay, suggesting that the TTP-containing complex was functional. These data support a model whereby TTP functions to enhance mRNA decay by recruiting components of the cellular mRNA decay machinery to the transcript.
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Affiliation(s)
- Heidi H Hau
- Department of Microbiology, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Abstract
Recent findings demonstrate that multiple mRNAs are co-regulated by one or more sequence-specific RNA-binding proteins that orchestrate their splicing, export, stability, localization and translation. These and other observations have given rise to a model in which mRNAs that encode functionally related proteins are coordinately regulated during cell growth and differentiation as post-transcriptional RNA operons or regulons, through a ribonucleoprotein-driven mechanism. Here I describe several recently discovered examples of RNA operons in budding yeast, fruitfly and mammalian cells, and their potential importance in processes such as immune response, oxidative metabolism, stress response, circadian rhythms and disease. I close by considering the evolutionary wiring and rewiring of these combinatorial post-transcriptional gene-expression networks.
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Affiliation(s)
- Jack D Keene
- Department of Molecular Genetics & Microbiology, Duke University Medical Center, Box 3020, Durham, North Carolina 27710, USA.
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Jones H, Carver M, Pekala PH. HuR binds to a single site on the C/EBPbeta mRNA of 3T3-L1 adipocytes. Biochem Biophys Res Commun 2007; 355:217-20. [PMID: 17288991 PMCID: PMC1839008 DOI: 10.1016/j.bbrc.2007.01.136] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Accepted: 01/26/2007] [Indexed: 12/19/2022]
Abstract
HuR is a ligand for nuclear mRNAs containing adenylate-uridylate rich elements in the 3'-untranslated region. Once bound to the mRNA, HuR is recognized by adapter proteins which then facilitate nuclear export of the complex. In the cytosol HuR is thought to function to control stability and translation of its ligand message. In the 3T3-L1 cells HuR is constitutively expressed and localized predominantly to the nucleus in the preadipocytes. However within 30 min of exposure to the differentiation stimulus, the HuR content in the cytosol increases consistent with HuR regulating the availability of relevant mRNAs for translation. Using in vitro RNA gel shifts, we have demonstrated that the C/EBPbeta message is a ligand for HuR and that the single binding site is an adenylate-uridylate rich element in the 3'-untranslated region.
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Affiliation(s)
- Heath Jones
- Department of Biochemistry and Molecular Biology, The Brody School of Medicine at East Carolina University, Greenville, NC 27858, USA
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Keene JD. Biological clocks and the coordination theory of RNA operons and regulons. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2007; 72:157-165. [PMID: 18419273 DOI: 10.1101/sqb.2007.72.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
One of the regulatory models of circadian rhythms involves the oscillation of transcription and translation. Although transcription factors have been widely examined during circadian processes, posttranscriptional mechanisms are less well-studied. Several laboratories have used microarrays to detect changes in mRNA expression throughout the circadian cycle and have found that mRNAs encoding the RNA-binding proteins (RBPs) nocturnin and butyrate response factor (BRF1) undergo rhythmic changes. Nocturnin is a deadenylation enzyme that removes poly(A) from the 3' ends of mRNAs, whereas BRF1 destabilizes mRNAs encoding early response gene (ERG) transcripts that contain AU-rich sequences in their 3'-untranslated regions (UTRs). Moroni and coworkers proposed that BRF1 functions as an oscillating posttranscriptional RNA operon (PTRO) that diurnally degrades ERG transcripts in peripheral organs (Keene and Tenenbaum 2002; Benjamin et al. 2006). The PTRO model posits that mRNAs can be members of one or more discrete functionally related subsets of mRNAs as determined by cis elements in mRNA and trans-acting RBPs or microRNAs that collectively recognize these cis elements (Keene 2007). This chapter describes the basis of posttranscriptional coordination by RNA operons and their potential for horizontal transfer among cells and discusses the potential for RBPs and microRNAs to participate in coordinating circadian rhythms and other biological clocks.
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Affiliation(s)
- J D Keene
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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Zhu H, Hasman RA, Barron VA, Luo G, Lou H. A nuclear function of Hu proteins as neuron-specific alternative RNA processing regulators. Mol Biol Cell 2006; 17:5105-14. [PMID: 17035636 PMCID: PMC1679676 DOI: 10.1091/mbc.e06-02-0099] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Revised: 09/08/2006] [Accepted: 09/29/2006] [Indexed: 12/12/2022] Open
Abstract
Recent advances in genome-wide analysis of alternative splicing indicate that extensive alternative RNA processing is associated with many proteins that play important roles in the nervous system. Although differential splicing and polyadenylation make significant contributions to the complexity of the nervous system, our understanding of the regulatory mechanisms underlying the neuron-specific pathways is very limited. Mammalian neuron-specific embryonic lethal abnormal visual-like Hu proteins (HuB, HuC, and HuD) are a family of RNA-binding proteins implicated in neuronal differentiation and maintenance. It has been established that Hu proteins increase expression of proteins associated with neuronal function by up-regulating mRNA stability and/or translation in the cytoplasm. We report here a novel function of these proteins as RNA processing regulators in the nucleus. We further elucidate the underlying mechanism of this regulation. We show that in neuron-like cells, Hu proteins block the activity of TIA-1/TIAR, two previously identified, ubiquitously expressed proteins that promote the nonneuronal pathway of calcitonin/calcitonin gene-related peptide (CGRP) pre-mRNA processing. These studies define not only the first neuron-specific regulator of the calcitonin/CGRP system but also the first nuclear function of Hu proteins.
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Affiliation(s)
| | | | | | - Guangbin Luo
- *Department of Genetics
- Case Comprehensive Cancer Center, and
| | - Hua Lou
- *Department of Genetics
- Case Comprehensive Cancer Center, and
- Center for RNA Molecular Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106
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Gantt KR, Cherry J, Richardson M, Karschner V, Atasoy U, Pekala PH. The regulation of glucose transporter (GLUT1) expression by the RNA binding protein HuR. J Cell Biochem 2006; 99:565-74. [PMID: 16639702 DOI: 10.1002/jcb.20950] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
HuR is a ligand for nuclear mRNAs containing adenylate-uridylate-rich (ARE) elements in the 3'-untranslated region. Once bound to the mRNA, HuR is recognized by adapter proteins that then facilitate nuclear export of the complex. In the cytosol, HuR is thought to function to control stability and translation of its ligand message. We have previously demonstrated that HuR is constitutively expressed in the 3T3-L1 cells and shuttles from the nucleus to the cytosol, but remains predominantly nuclear in the preadipocytes and that as the cells differentiate, there is a marked increase in the proportion of HuR in the cytosol at any time. The GLUT1 glucose transporter is also expressed in both preadipocytes and adipocytes and in vitro RNA gel shifts indicate the mRNA is a ligand for HuR. However, HuR complexes containing the GLUT1 mRNA can only be isolated from the terminally differentiated adipocytes. Moreover, position analysis of the GLUT1 mRNA and HuR protein in polysome profiles demonstrates a shift to the most dense region of the gradient for both message and protein with adipocyte differentiation. Consistent with a regulatory role in the control of GLUT1 expression, siRNA-mediated decrease in HuR protein resulted in a decreased expression of GLUT1 protein. These data suggest that HuR contributes to the metabolic function of the adipocyte through mediation of post-transcriptional regulatory events.
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Affiliation(s)
- Kira R Gantt
- Department of Biochemistry & Molecular Biology, The Brody School of Medicine, Greenville, North Carolina 27858, USA
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Sorensen BS, Ornskov D, Nexo E. The chemotherapeutic agent VP16 increases the stability of HB-EGF mRNA by a mechanism involving the 3′-UTR. Exp Cell Res 2006; 312:3651-8. [PMID: 16996055 DOI: 10.1016/j.yexcr.2006.08.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2006] [Revised: 07/05/2006] [Accepted: 08/11/2006] [Indexed: 10/24/2022]
Abstract
VP16 is a chemotherapeutic agent that introduces DNA damage. We demonstrate that cellular stress induced by VP16 in the human cervix cancer cell line HeLa increases the HB-EGF (heparin binding epidermal growth factor like growth factor) mRNA level dose dependently. Maximal induction (10-fold) was observed at 20-40 microM VP16. Increased HB-EGF peptide levels accompanied the increase in HB-EGF mRNA. We investigated the molecular mechanism involved in HB-EGF mRNA induction by VP16. Transcription was only slightly increased (60%) as determined by real-time PCR quantification of transcription from a reporter plasmid containing the HB-EGF promoter in front of the luciferase gene. In contrast, HB-EGF mRNA stability was increased significantly by VP16 as demonstrated by monitoring HB-EGF mRNA decay in cells treated with the transcriptional inhibitor actinomycin D. The 3'-UTR (3'-untranslated region) of HB-EGF was inserted at the 3'-end of LacZ mRNA. VP16 treatment of the cells caused a 5-fold increase in this chimeric mRNA, as compared to LacZ without this 3'-UTR. A 186 nucleotide region of HB-EGF contains five of the six AUUUA sequences found in the 1454 nucleotide 3'-UTR of HB-EGF and we demonstrate that this region caused an approximately 3-fold induction of LacZ mRNA when inserted at the 3'-end, as compared to LacZ without any insertion at the 3'-end, demonstrating that a significant proportion of the effect resides in this region. Induction of HB-EGF by VP16 has important implications as HB-EGF has been reported to prevent cell death, which might lower the efficacy of chemotherapy. We demonstrate that mRNA stability and in particular the HB-EGF 3'-UTR is involved in the HB-EGF mRNA induction.
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Affiliation(s)
- Boe S Sorensen
- Department of Clinical-Biochemistry, NBG, AS, Aarhus University Hospital, AS Norrebrogade 44, DK 8000 Aarhus C, Denmark.
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Fujiwara T, Mori Y, Chu DL, Koyama Y, Miyata S, Tanaka H, Yachi K, Kubo T, Yoshikawa H, Tohyama M. CARM1 regulates proliferation of PC12 cells by methylating HuD. Mol Cell Biol 2006; 26:2273-85. [PMID: 16508003 PMCID: PMC1430293 DOI: 10.1128/mcb.26.6.2273-2285.2006] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
HuD is an RNA-binding protein that has been shown to induce neuronal differentiation by stabilizing labile mRNAs carrying AU-rich instability elements. Here, we show a novel mechanism of arginine methylation of HuD by coactivator-associated arginine methyltransferase 1 (CARM1) that affected mRNA turnover of p21cip1/waf1 mRNA in PC12 cells. CARM1 specifically methylated HuD in vitro and in vivo and colocalized with HuD in the cytoplasm. Inhibition of HuD methylation by CARM1 knockdown elongated the p21cip1/waf1 mRNA half-life and resulted in a slow growth rate and robust neuritogenesis in response to nerve growth factor (NGF). Methylation-resistant HuD bound more p21cip1/waf1 mRNA than did the wild type, and its overexpression upregulated p21cip1/waf1 protein expression. These results suggested that CARM1-methylated HuD maintains PC12 cells in the proliferative state by committing p21cip1/waf1 mRNA to its decay system. Since the methylated population of HuD was reduced in NGF-treated PC12 cells, downregulation of HuD methylation is a possible pathway through which NGF induces differentiation of PC12 cells.
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Affiliation(s)
- Tatsuji Fujiwara
- Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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