1
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Wedler A, Bley N, Glaß M, Müller S, Rausch A, Lederer M, Urbainski J, Schian L, Obika KB, Simon T, Peters L, Misiak C, Fuchs T, Köhn M, Jacob R, Gutschner T, Ihling C, Sinz A, Hüttelmaier S. RAVER1 hinders lethal EMT and modulates miR/RISC activity by the control of alternative splicing. Nucleic Acids Res 2024; 52:3971-3988. [PMID: 38300787 PMCID: PMC11039986 DOI: 10.1093/nar/gkae046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 12/24/2023] [Accepted: 01/12/2024] [Indexed: 02/03/2024] Open
Abstract
The RAVER1 protein serves as a co-factor in guiding the polypyrimidine tract-binding protein (PTBP)-dependent control of alternative splicing (AS). Whether RAVER1 solely acts in concert with PTBPs and how it affects cancer cell fate remained elusive. Here, we provide the first comprehensive investigation of RAVER1-controlled AS in cancer cell models. This reveals a pro-oncogenic role of RAVER1 in modulating tumor growth and epithelial-mesenchymal-transition (EMT). Splicing analyses and protein-association studies indicate that RAVER1 guides AS in association with other splicing regulators, including PTBPs and SRSFs. In cancer cells, one major function of RAVER1 is the stimulation of proliferation and restriction of apoptosis. This involves the modulation of AS events within the miR/RISC pathway. Disturbance of RAVER1 impairs miR/RISC activity resulting in severely deregulated gene expression, which promotes lethal TGFB-driven EMT. Among others, RAVER1-modulated splicing events affect the insertion of protein interaction modules in factors guiding miR/RISC-dependent gene silencing. Most prominently, in all three human TNRC6 proteins, RAVER1 controls AS of GW-enriched motifs, which are essential for AGO2-binding and the formation of active miR/RISC complexes. We propose, that RAVER1 is a key modulator of AS events in the miR/RISC pathway ensuring proper abundance and composition of miR/RISC effectors. This ensures balanced expression of TGFB signaling effectors and limits TGFB induced lethal EMT.
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Affiliation(s)
- Alice Wedler
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Nadine Bley
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Markus Glaß
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Simon Müller
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
- New York Genome Center, New York, NY, USA
- Department of Biology, New York University, New York, NY, USA
| | - Alexander Rausch
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Marcell Lederer
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Julia Urbainski
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Laura Schian
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Kingsley-Benjamin Obika
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Theresa Simon
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Lara Meret Peters
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Claudia Misiak
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Tommy Fuchs
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Marcel Köhn
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Roland Jacob
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Tony Gutschner
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Christian Ihling
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Andrea Sinz
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Stefan Hüttelmaier
- Institute of Molecular Medicine, Section for Molecular Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
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2
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Carico C, Placzek WJ. Reviewing PTBP1 Domain Modularity in the Pre-Genomic Era: A Foundation to Guide the Next Generation of Exploring PTBP1 Structure-Function Relationships. Int J Mol Sci 2023; 24:11218. [PMID: 37446395 DOI: 10.3390/ijms241311218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 06/28/2023] [Accepted: 07/06/2023] [Indexed: 07/15/2023] Open
Abstract
Polypyrimidine tract binding protein 1 (PTBP1) is one of the most well-described RNA binding proteins, known initially for its role as a splicing repressor before later studies revealed its numerous roles in RNA maturation, stability, and translation. While PTBP1's various biological roles have been well-described, it remains unclear how its four RNA recognition motif (RRM) domains coordinate these functions. The early PTBP1 literature saw extensive effort placed in detailing structures of each of PTBP1's RRMs, as well as their individual RNA sequence and structure preferences. However, limitations in high-throughput and high-resolution genomic approaches (i.e., next-generation sequencing had not yet been developed) precluded the functional translation of these findings into a mechanistic understanding of each RRM's contribution to overall PTBP1 function. With the emergence of new technologies, it is now feasible to begin elucidating the individual contributions of each RRM to PTBP1 biological functions. Here, we review all the known literature describing the apo and RNA bound structures of each of PTBP1's RRMs, as well as the emerging literature describing the dependence of specific RNA processing events on individual RRM domains. Our goal is to provide a framework of the structure-function context upon which to facilitate the interpretation of future studies interrogating the dynamics of PTBP1 function.
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Affiliation(s)
- Christine Carico
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - William J Placzek
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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3
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Malireddi RS, Bynigeri RR, Mall R, Nadendla EK, Connelly JP, Pruett-Miller SM, Kanneganti TD. Whole-genome CRISPR screen identifies RAVER1 as a key regulator of RIPK1-mediated inflammatory cell death, PANoptosis. iScience 2023; 26:106938. [PMID: 37324531 PMCID: PMC10265528 DOI: 10.1016/j.isci.2023.106938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 04/24/2023] [Accepted: 05/18/2023] [Indexed: 06/17/2023] Open
Abstract
Transforming growth factor-β-activated kinase 1 (TAK1) is a central regulator of innate immunity, cell death, inflammation, and cellular homeostasis. Therefore, many pathogens carry TAK1 inhibitors (TAK1i). As a host strategy to counteract this, inhibition or deletion of TAK1 induces spontaneous inflammatory cell death, PANoptosis, through the RIPK1-PANoptosome complex, containing the NLRP3 inflammasome and caspase-8/FADD/RIPK3 as integral components; however, PANoptosis also promotes pathological inflammation. Therefore, understanding molecular mechanisms that regulate TAK1i-induced cell death is essential. Here, we report a genome-wide CRISPR screen in macrophages that identified TAK1i-induced cell death regulators, including polypyrimidine tract-binding (PTB) protein 1 (PTBP1), a known regulator of RIPK1, and a previously unknown regulator RAVER1. RAVER1 blocked alternative splicing of Ripk1, and its genetic depletion inhibited TAK1i-induced, RIPK1-mediated inflammasome activation and PANoptosis. Overall, our CRISPR screen identified several positive regulators of PANoptosis. Moreover, our study highlights the utility of genome-wide CRISPR-Cas9 screens in myeloid cells for comprehensive characterization of complex cell death pathways to discover therapeutic targets.
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Affiliation(s)
| | - Ratnakar R. Bynigeri
- Department of Immunology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Raghvendra Mall
- Department of Immunology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Eswar Kumar Nadendla
- Department of Immunology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Jon P. Connelly
- Center for Advanced Genome Engineering (CAGE), St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Shondra M. Pruett-Miller
- Center for Advanced Genome Engineering (CAGE), St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
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Zimmerman KD, Chan J, Glenn JP, Birnbaum S, Li C, Nathanielsz PW, Olivier M, Cox LA. Moderate maternal nutrient reduction in pregnancy alters fatty acid oxidation and RNA splicing in the nonhuman primate fetal liver. J Dev Orig Health Dis 2023; 14:381-388. [PMID: 36924159 PMCID: PMC10202844 DOI: 10.1017/s204017442300003x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
Abstract
Fetal liver tissue collected from a nonhuman primate (NHP) baboon model of maternal nutrient reduction (MNR) at four gestational time points (90, 120, 140, and 165 days gestation [dG], term in the baboon is ∼185 dG) was used to quantify MNR effects on the fetal liver transcriptome. 28 transcripts demonstrated different expression patterns between MNR and control livers during the second half of gestation, a developmental period when the fetus undergoes rapid weight gain and fat accumulation. Differentially expressed transcripts were enriched for fatty acid oxidation and RNA splicing-related pathways. Increased RNA splicing activity in MNR was reflected in greater abundances of transcript splice variant isoforms in the MNR group. It can be hypothesized that the increase in splice variants is deployed in an effort to adapt to the poor in utero environment and ensure near-normal development and energy metabolism. This study is the first to study developmental programming across four critical gestational stages during primate fetal liver development and reveals a potentially novel cellular response mechanism mediating fetal programming in response to MNR.
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Affiliation(s)
- Kip D. Zimmerman
- Center for Precision Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Jeannie Chan
- Center for Precision Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Jeremy P. Glenn
- Southwest National Primate Research Center, Texas Biomedical Research Institute, San Antonio, TX, USA and
| | - Shifra Birnbaum
- Southwest National Primate Research Center, Texas Biomedical Research Institute, San Antonio, TX, USA and
| | - Cun Li
- Animal Science, University of Wyoming, Laramie, WY, USA
| | - Peter W. Nathanielsz
- Southwest National Primate Research Center, Texas Biomedical Research Institute, San Antonio, TX, USA and
- Animal Science, University of Wyoming, Laramie, WY, USA
| | - Michael Olivier
- Center for Precision Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Laura A. Cox
- Center for Precision Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, USA
- Southwest National Primate Research Center, Texas Biomedical Research Institute, San Antonio, TX, USA and
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5
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Chen XD, Liu HL, Li S, Hu KB, Wu QY, Liao P, Wang HY, Long ZY, Lu XM, Wang YT. The latest role of nerve-specific splicing factor PTBP1 in the transdifferentiation of glial cells into neurons. WILEY INTERDISCIPLINARY REVIEWS. RNA 2023; 14:e1740. [PMID: 35574699 DOI: 10.1002/wrna.1740] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 04/16/2022] [Accepted: 04/21/2022] [Indexed: 11/07/2022]
Abstract
Central nervous system injury diseases can cause the loss of many neurons, and it is difficult to regenerate. The field of regenerative medicine believes that supplementing the missing neurons may be an ideal method for nerve injury repair. Recent studies have found that down-regulation of polypyrimidine tract binding protein 1 (PTBP1) expression can make glial cells transdifferentiate into different types of neurons, which is expected to be an alternative therapy to restore neuronal function. This article summarized the research progress on the structure and biological function of the PTBP family, the mutual regulation of PTBP1 and PTBP2, their role in neurogenesis, and the latest research progress in targeting PTBP1 to mediate the transdifferentiation of glial cells into neurons, which may provide some new strategies and new ideas for the future treatment of central nervous system injury and neurodegenerative diseases. This article is categorized under: RNA Processing > Splicing Regulation/Alternative Splicing.
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Affiliation(s)
- Xing-Dong Chen
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China.,State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
| | - Hui-Lin Liu
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
| | - Sen Li
- State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
| | - Kai-Bin Hu
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
| | - Qing-Yun Wu
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
| | - Ping Liao
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
| | - Hai-Yan Wang
- State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
| | - Zai-Yun Long
- State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
| | - Xiu-Min Lu
- College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
| | - Yong-Tang Wang
- State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
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6
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Elucidation of the Landscape of Alternatively Spliced Genes and Features in the Dorsal Striatum of Aggressive/Aggression-Deprived Mice in the Model of Chronic Social Conflicts. Genes (Basel) 2023; 14:genes14030599. [PMID: 36980872 PMCID: PMC10048575 DOI: 10.3390/genes14030599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 02/20/2023] [Accepted: 02/21/2023] [Indexed: 03/03/2023] Open
Abstract
Both aggressive and aggression-deprived (AD) individuals represent pathological cases extensively studied in psychiatry and substance abuse disciplines. We employed the animal model of chronic social conflicts curated in our laboratory for over 30 years. In the study, we pursued the task of evaluation of the key events in the dorsal striatum transcriptomes of aggression-experienced mice and AD species, as compared with the controls, using RNA-seq profiling. We evaluated the alternative splicing-mediated transcriptome dynamics based on the RNA-seq data. We confined our attention to the exon skipping (ES) events as the major AS type for animals. We report the concurrent posttranscriptional and posttranslational regulation of the ES events observed in the phosphorylation cycles (in phosphoproteins and their targets) in the neuron-specific genes of the striatum. Strikingly, we found that major neurospecific splicing factors (Nova1, Ptbp1, 2, Mbnl1, 2, and Sam68) related to the alternative splicing regulation of cAMP genes (Darpp-32, Grin1, Ptpn5, Ppp3ca, Pde10a, Prkaca, Psd95, and Adora1) are upregulated specifically in aggressive individuals as compared with the controls and specifically AD animals, assuming intense switching between isoforms in the cAMP-mediated (de)phosphorylation signaling cascade. We found that the coding alternative splicing events were mostly attributed to synaptic plasticity and neural development-related proteins, while the nonsense-mediated decay-associated splicing events are mostly attributed to the mRNA processing of genes, including the spliceosome and splicing factors. In addition, considering the gene families, the transporter (Slc) gene family manifested most of the ES events. We found out that the major molecular systems employing AS for their plasticity are the ‘spliceosome’, ‘chromatin rearrangement complex’, ‘synapse’, and ‘neural development/axonogenesis’ GO categories. Finally, we state that approximately 35% of the exon skipping variants in gene coding regions manifest the noncoding variants subject to nonsense-mediated decay, employed as a homeostasis-mediated expression regulation layer and often associated with the corresponding gene expression alteration.
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Huang Q, Gu S, Fang J, Li X, Lin L. A pan-cancer analysis of the oncogenic role of polypyrimidine tract binding protein 1 (PTBP1) in human tumors. Medicine (Baltimore) 2022; 101:e32428. [PMID: 36595978 PMCID: PMC9803410 DOI: 10.1097/md.0000000000032428] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Polypyrimidine tract-binding protein 1 (PTBP1) is an RNA-binding protein that regulates several posttranscriptional events and is closely related to the development of multiple tumors. However, little is known about PTBP1. Thus, we carried out a systematic pan-cancer analysis to explore the relationship between PTBP1 and cancer. METHODS We used The Cancer Genome Atlas, Gene Expression Omnibus, and Human Protein Atlas datasets, as well as several bioinformatics tools, to explore the role of PTBP1 in 33 tumor types. RESULTS The expression of PTBP1 in most tumor tissues was higher than that in normal tissues. Survival analysis indicated that overexpression of PTBP1 generally predicted poor overall survival in patients with tumors such as adrenocortical carcinoma, liver hepatocellular carcinoma, lung adenocarcinoma, and skin cutaneous melanoma. In addition, we compared the phosphorylation and immune infiltration of PTBP1 in cancer-associated fibroblasts between normal and primary tumor tissues and explored the putative functional mechanism of tumorigenesis mediated by PTBP1. CONCLUSION These results provide clues to better understand PTBP1 from the perspective of bioinformatics and highlight its importance in various human cancers.
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Affiliation(s)
- Qing Huang
- College of Environment and Public Health, Xiamen Huaxia University, Xiamen, Fujian, P.R. China
| | - Shinong Gu
- College of Environment and Public Health, Xiamen Huaxia University, Xiamen, Fujian, P.R. China
| | - Jianqi Fang
- Department of Women’s Health Care, Fujian Maternity and Child Health Hospital, Fuzhou, Fujian, P.R. China
| | - Xuanwen Li
- Graduate School of Health Science, Suzuka University of Medical Science, Suzuka, Mie, Japan
| | - Lili Lin
- College of Environment and Public Health, Xiamen Huaxia University, Xiamen, Fujian, P.R. China
- * Correspondence: Lili Lin, College of Environment and Public Health, Xiamen Huaxia University, Xiamen, Fujian 361000, P.R. China (e-mail: )
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Shetty SP, Kiledjian NT, Copeland PR. The selenoprotein P 3' untranslated region is an RNA binding protein platform that fine tunes selenocysteine incorporation. PLoS One 2022; 17:e0271453. [PMID: 35905095 PMCID: PMC9337670 DOI: 10.1371/journal.pone.0271453] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 07/01/2022] [Indexed: 11/19/2022] Open
Abstract
Selenoproteins contain the 21st amino acid, selenocysteine (Sec), which is incorporated at select UGA codons when a specialized hairpin sequence, the Sec insertion sequence (SECIS) element, is present in the 3' UTR. Aside from the SECIS, selenoprotein mRNA 3' UTRs are not conserved between different selenoproteins within a species. In contrast, the 3'-UTR of a given selenoprotein is often conserved across species, which supports the hypothesis that cis-acting elements in the 3'-UTR other than the SECIS exert post-transcriptional control on selenoprotein expression. In order to determine the function of one such SECIS context, we chose to focus on the plasma selenoprotein, SELENOP, which is required to maintain selenium homeostasis as a selenium transport protein that contains 10 Sec residues. It is unique in that its mRNA contains two SECIS elements in the context of a highly conserved 843-nucleotide 3' UTR. Here we have used RNA affinity chromatography and identified PTBP1 as the major RNA binding protein that specifically interacts with the sequence between the two SECIS elements. We then used CRISPR/Cas9 genome editing to delete two regions surrounding the first SECIS element. We found that these sequences are involved in regulating SELENOP mRNA and protein levels, which are inversely altered as a function of selenium concentrations.
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Affiliation(s)
- Sumangala P. Shetty
- Department of Biochemistry and Molecular Biology, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ, United States of America
| | - Nora T. Kiledjian
- Department of Biochemistry and Molecular Biology, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ, United States of America
| | - Paul R. Copeland
- Department of Biochemistry and Molecular Biology, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ, United States of America
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Pina JM, Hernandez LA, Keppetipola NM. Polypyrimidine tract binding proteins PTBP1 and PTBP2 interact with distinct proteins under splicing conditions. PLoS One 2022; 17:e0263287. [PMID: 35113929 PMCID: PMC8812845 DOI: 10.1371/journal.pone.0263287] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 01/17/2022] [Indexed: 11/18/2022] Open
Abstract
RNA binding proteins play an important role in regulating alternative pre-mRNA splicing and in turn cellular gene expression. Polypyrimidine tract binding proteins, PTBP1 and PTBP2, are paralogous RNA binding proteins that play a critical role in the process of neuronal differentiation and maturation; changes in the concentration of PTBP proteins during neuronal development direct splicing changes in many transcripts that code for proteins critical for neuronal differentiation. How the two related proteins regulate different sets of neuronal exons is unclear. The distinct splicing activities of PTBP1 and PTBP2 can be recapitulated in an in vitro splicing system with the differentially regulated N1 exon of the c-src pre-mRNA. Here, we conducted experiments under these in vitro splicing conditions to identify PTBP1 and PTBP2 interacting partner proteins. Our results highlight that both PTBPs interact with proteins that participate in chromatin remodeling and transcription regulation. Our data reveal that PTBP1 interacts with many proteins involved in mRNA processing including splicing regulation while PTBP2 does not. Our results also highlight enzymes that can serve as potential "writers" and "erasers" in adding chemical modifications to the PTB proteins. Overall, our study highlights important differences in protein-protein interactions between the PTBP proteins under splicing conditions and supports a role for post-translational modifications in dictating their distinct splicing activities.
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Affiliation(s)
- Jeffrey M. Pina
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, CA, United States of America
| | - Luis A. Hernandez
- Department of Biological Sciences, California State University Fullerton, Fullerton, CA, United States of America
| | - Niroshika M. Keppetipola
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, CA, United States of America
- * E-mail:
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Georgiou M, Yang C, Atkinson R, Pan K, Buskin A, Molina MM, Collin J, Al‐Aama J, Goertler F, Ludwig SEJ, Davey T, Lührmann R, Nagaraja‐Grellscheid S, Johnson CA, Ali R, Armstrong L, Korolchuk V, Urlaub H, Mozaffari‐Jovin S, Lako M. Activation of autophagy reverses progressive and deleterious protein aggregation in PRPF31 patient-induced pluripotent stem cell-derived retinal pigment epithelium cells. Clin Transl Med 2022; 12:e759. [PMID: 35297555 PMCID: PMC8926896 DOI: 10.1002/ctm2.759] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Revised: 02/21/2022] [Accepted: 02/23/2022] [Indexed: 01/18/2023] Open
Abstract
INTRODUCTION Mutations in pre-mRNA processing factor 31 (PRPF31), a core protein of the spliceosomal tri-snRNP complex, cause autosomal-dominant retinitis pigmentosa (adRP). It has remained an enigma why mutations in ubiquitously expressed tri-snRNP proteins result in retina-specific disorders, and so far, the underlying mechanism of splicing factors-related RP is poorly understood. METHODS We used the induced pluripotent stem cell (iPSC) technology to generate retinal organoids and RPE models from four patients with severe and very severe PRPF31-adRP, unaffected individuals and a CRISPR/Cas9 isogenic control. RESULTS To fully assess the impacts of PRPF31 mutations, quantitative proteomics analyses of retinal organoids and RPE cells were carried out showing RNA splicing, autophagy and lysosome, unfolded protein response (UPR) and visual cycle-related pathways to be significantly affected. Strikingly, the patient-derived RPE and retinal cells were characterised by the presence of large amounts of cytoplasmic aggregates containing the mutant PRPF31 and misfolded, ubiquitin-conjugated proteins including key visual cycle and other RP-linked tri-snRNP proteins, which accumulated progressively with time. The mutant PRPF31 variant was not incorporated into splicing complexes, but reduction of PRPF31 wild-type levels led to tri-snRNP assembly defects in Cajal bodies of PRPF31 patient retinal cells, altered morphology of nuclear speckles and reduced formation of active spliceosomes giving rise to global splicing dysregulation. Moreover, the impaired waste disposal mechanisms further exacerbated aggregate formation, and targeting these by activating the autophagy pathway using Rapamycin reduced cytoplasmic aggregates, leading to improved cell survival. CONCLUSIONS Our data demonstrate that it is the progressive aggregate accumulation that overburdens the waste disposal machinery rather than direct PRPF31-initiated mis-splicing, and thus relieving the RPE cells from insoluble cytoplasmic aggregates presents a novel therapeutic strategy that can be combined with gene therapy studies to fully restore RPE and retinal cell function in PRPF31-adRP patients.
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Affiliation(s)
- Maria Georgiou
- Newcastle University Biosciences InstituteNewcastle upon TyneUK
| | - Chunbo Yang
- Newcastle University Biosciences InstituteNewcastle upon TyneUK
| | - Robert Atkinson
- Newcastle University Biosciences InstituteNewcastle upon TyneUK
| | - Kuan‐Ting Pan
- Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Adriana Buskin
- Newcastle University Biosciences InstituteNewcastle upon TyneUK
| | | | - Joseph Collin
- Newcastle University Biosciences InstituteNewcastle upon TyneUK
| | - Jumana Al‐Aama
- Faculty of MedicineKing Abdulaziz UniversitySaudi Arabia
| | | | | | - Tracey Davey
- Newcastle University Biosciences InstituteNewcastle upon TyneUK
| | | | | | | | | | - Lyle Armstrong
- Newcastle University Biosciences InstituteNewcastle upon TyneUK
| | | | - Henning Urlaub
- Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Bioanalytics, Department of Clinical ChemistryUniversity Medical CenterGoettingenGermany
| | - Sina Mozaffari‐Jovin
- Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Medical Genetics Research CenterMashhad University of Medical SciencesMashhadIran
- Department of Medical Genetics, Faculty of MedicineMashhad University of Medical SciencesMashhadIran
| | - Majlinda Lako
- Newcastle University Biosciences InstituteNewcastle upon TyneUK
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Merlevede A, Legault EM, Drugge V, Barker RA, Drouin-Ouellet J, Olariu V. A quantitative model of cellular decision making in direct neuronal reprogramming. Sci Rep 2021; 11:1514. [PMID: 33452356 PMCID: PMC7810861 DOI: 10.1038/s41598-021-81089-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 01/01/2021] [Indexed: 12/25/2022] Open
Abstract
The direct reprogramming of adult skin fibroblasts to neurons is thought to be controlled by a small set of interacting gene regulators. Here, we investigate how the interaction dynamics between these regulating factors coordinate cellular decision making in direct neuronal reprogramming. We put forward a quantitative model of the governing gene regulatory system, supported by measurements of mRNA expression. We found that nPTB needs to feed back into the direct neural conversion network most likely via PTB in order to accurately capture quantitative gene interaction dynamics and correctly predict the outcome of various overexpression and knockdown experiments. This was experimentally validated by nPTB knockdown leading to successful neural conversion. We also proposed a novel analytical technique to dissect system behaviour and reveal the influence of individual factors on resulting gene expression. Overall, we demonstrate that computational analysis is a powerful tool for understanding the mechanisms of direct (neuronal) reprogramming, paving the way for future models that can help improve cell conversion strategies.
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Affiliation(s)
- Adriaan Merlevede
- Computational Biology and Biological Physics, Department of Astronomy and Theoretical Physics, Lund University, 223 62, Lund, Sweden
| | - Emilie M Legault
- Faculté de Pharmacie, Université de Montréal, Montreal, QC, H3T 1J4, Canada
| | - Viktor Drugge
- Computational Biology and Biological Physics, Department of Astronomy and Theoretical Physics, Lund University, 223 62, Lund, Sweden
| | - Roger A Barker
- Cambridge Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge, CB2 2PY, UK
| | | | - Victor Olariu
- Computational Biology and Biological Physics, Department of Astronomy and Theoretical Physics, Lund University, 223 62, Lund, Sweden.
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12
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Du JX, Zhu GQ, Cai JL, Wang B, Luo YH, Chen C, Cai CZ, Zhang SJ, Zhou J, Fan J, Zhu W, Dai Z. Splicing factors: Insights into their regulatory network in alternative splicing in cancer. Cancer Lett 2020; 501:83-104. [PMID: 33309781 DOI: 10.1016/j.canlet.2020.11.043] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 11/24/2020] [Accepted: 11/26/2020] [Indexed: 12/18/2022]
Abstract
More than 95% of all human genes are alternatively spliced after transcription, which enriches the diversity of proteins and regulates transcript and/or protein levels. The splicing isoforms produced from the same gene can manifest distinctly, even exerting opposite effects. Mounting evidence indicates that the alternative splicing (AS) mechanism is ubiquitous in various cancers and drives the generation and maintenance of various hallmarks of cancer, such as enhanced proliferation, inhibited apoptosis, invasion and metastasis, and angiogenesis. Splicing factors (SFs) play pivotal roles in the recognition of splice sites and the assembly of spliceosomes during AS. In this review, we mainly discuss the similarities and differences of SF domains, the details of SF function in AS, the effect of SF-driven pathological AS on different hallmarks of cancer, and the main drivers of SF expression level and subcellular localization. In addition, we briefly introduce the application prospects of targeted therapeutic strategies, including small-molecule inhibitors, siRNAs and splice-switching oligonucleotides (SSOs), from three perspectives (drivers, SFs and pathological AS). Finally, we share our insights into the potential direction of research on SF-centric AS-related regulatory networks.
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Affiliation(s)
- Jun-Xian Du
- Department of General Surgery, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China
| | - Gui-Qi Zhu
- Liver Cancer Institute, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China; Key Laboratory of Carcinogenesis and Cancer Invasion, Fudan University, Ministry of Education, Shanghai, 200032, China
| | - Jia-Liang Cai
- Liver Cancer Institute, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China; Key Laboratory of Carcinogenesis and Cancer Invasion, Fudan University, Ministry of Education, Shanghai, 200032, China
| | - Biao Wang
- Liver Cancer Institute, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China; Key Laboratory of Carcinogenesis and Cancer Invasion, Fudan University, Ministry of Education, Shanghai, 200032, China
| | - Yi-Hong Luo
- Department of General Surgery, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China
| | - Cong Chen
- Department of General Surgery, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China
| | - Cheng-Zhe Cai
- Department of General Surgery, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China
| | - Si-Jia Zhang
- Department of General Surgery, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China
| | - Jian Zhou
- Liver Cancer Institute, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China; Key Laboratory of Carcinogenesis and Cancer Invasion, Fudan University, Ministry of Education, Shanghai, 200032, China
| | - Jia Fan
- Liver Cancer Institute, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China; Key Laboratory of Carcinogenesis and Cancer Invasion, Fudan University, Ministry of Education, Shanghai, 200032, China
| | - Wei Zhu
- Department of General Surgery, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China.
| | - Zhi Dai
- Liver Cancer Institute, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China; Key Laboratory of Carcinogenesis and Cancer Invasion, Fudan University, Ministry of Education, Shanghai, 200032, China.
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13
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Ontiveros RJ, Hernandez L, Nguyen H, Hernandez Lopez AL, Shankar A, Kim E, Keppetipola NM. Identification and Characterization of a Minimal Functional Splicing Regulatory Protein, PTBP1. Biochemistry 2020; 59:4766-4774. [PMID: 33284593 DOI: 10.1021/acs.biochem.0c00664] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polypyrimidine tract binding protein 1 (PTBP1) is a well-studied RNA binding protein that serves as an important model for understanding molecular mechanisms underlying alternative splicing regulation. PTBP1 has four RNA binding domains (RBDs) connected via linker regions. Additionally, PTBP1 has an N-terminal unstructured region that contains nuclear import and export sequences. Each RBD can bind to pyrimidine rich elements with high affinity to mediate splicing activity. Studies support a variety of models for how PTBP1 can mediate splicing regulation on target exons. Obtaining a detailed atomic view hinges on determining a crystal structure of PTBP1 bound to a target RNA transcript. Here, we created a minimal functional PTBP1 with deletions in both linker 1 and linker 2 regions and assayed for activity on certain regulated exons, including the c-Src N1 exon. We show that for a subset of PTBP1-regulated exons the linker regions are not necessary for splicing repression activity. Gel mobility shift assays reveal the linker deletion mutant binds with 12-fold higher affinity to a target RNA sequence compared to wild-type PTBP1. A minimal PTBP1 that also contains an N-terminal region deletion binds to a target RNA with an affinity higher than that of wild-type PTBP1. Moreover, this minimal protein oligomerizes readily to form a distinct higher-order complex previously shown to be required for mediating splicing repression. This minimal functional PTBP1 protein can serve as a candidate for future structure studies to understand the mechanism of splicing repression for certain regulated exons.
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Affiliation(s)
- Robert J Ontiveros
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Luis Hernandez
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Haylena Nguyen
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California 92831, United States
| | - Adrian Lino Hernandez Lopez
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90035, United States
| | - Archana Shankar
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Enoch Kim
- Department of Biological Sciences, California State University Fullerton, Fullerton, California 92831, United States
| | - Niroshika M Keppetipola
- Department of Chemistry and Biochemistry, California State University Fullerton, Fullerton, California 92831, United States
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Chen J, Wang Y, Wang C, Hu JF, Li W. LncRNA Functions as a New Emerging Epigenetic Factor in Determining the Fate of Stem Cells. Front Genet 2020; 11:277. [PMID: 32296461 PMCID: PMC7137347 DOI: 10.3389/fgene.2020.00277] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 03/09/2020] [Indexed: 12/12/2022] Open
Abstract
Pluripotent stem cells have broad applications in regenerative medicine and offer ideal models for understanding the biological process of embryonic development and specific diseases. Studies suggest that the self-renewal and multi-lineage differentiation of stem cells are regulated by a complex network consisting of transcription factors, chromatin regulators, signaling factors, and non-coding RNAs. It is of great interest to identify RNA regulatory factors that determine the fate of stem cells. Long non-coding RNA (lncRNA), a class of non-coding RNAs with more than 200 bp in length, has been shown to act as essential epigenetic regulators of stem cell pluripotency and specific lineage commitment. In this review, we focus on recent research progress related to the function and epigenetic mechanisms of lncRNA in determining the fate of stem cells, particularly pluripotency maintenance and lineage-specific differentiation. We discuss the role of the Oct4 and Sox2 promoter-interacting lncRNA as identified by Chromatin RNA In Situ reverse Transcription sequencing (CRIST-seq). Further understanding of their potential actions will provide a basis for the development of regenerative medicine for clinical application. This work offers comprehensive details and better understanding of the role of lncRNA in determining the fate of stem cells and paves the way for clinical stem cell applications.
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Affiliation(s)
- Jingcheng Chen
- Cancer Center, The First Hospital of Jilin University, Changchun, China.,VA Palo Alto Health Care System, Stanford Medical School, Stanford University, Palo Alto, CA, United States
| | - Yizhuo Wang
- Cancer Center, The First Hospital of Jilin University, Changchun, China
| | - Cong Wang
- Cancer Center, The First Hospital of Jilin University, Changchun, China.,VA Palo Alto Health Care System, Stanford Medical School, Stanford University, Palo Alto, CA, United States
| | - Ji-Fan Hu
- Cancer Center, The First Hospital of Jilin University, Changchun, China.,VA Palo Alto Health Care System, Stanford Medical School, Stanford University, Palo Alto, CA, United States
| | - Wei Li
- Cancer Center, The First Hospital of Jilin University, Changchun, China
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15
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ASCOT identifies key regulators of neuronal subtype-specific splicing. Nat Commun 2020; 11:137. [PMID: 31919425 PMCID: PMC6952364 DOI: 10.1038/s41467-019-14020-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 12/12/2019] [Indexed: 12/22/2022] Open
Abstract
Public archives of next-generation sequencing data are growing exponentially, but the difficulty of marshaling this data has led to its underutilization by scientists. Here, we present ASCOT, a resource that uses annotation-free methods to rapidly analyze and visualize splice variants across tens of thousands of bulk and single-cell data sets in the public archive. To demonstrate the utility of ASCOT, we identify novel cell type-specific alternative exons across the nervous system and leverage ENCODE and GTEx data sets to study the unique splicing of photoreceptors. We find that PTBP1 knockdown and MSI1 and PCBP2 overexpression are sufficient to activate many photoreceptor-specific exons in HepG2 liver cancer cells. This work demonstrates how large-scale analysis of public RNA-Seq data sets can yield key insights into cell type-specific control of RNA splicing and underscores the importance of considering both annotated and unannotated splicing events.
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Fico A, Fiorenzano A, Pascale E, Patriarca EJ, Minchiotti G. Long non-coding RNA in stem cell pluripotency and lineage commitment: functions and evolutionary conservation. Cell Mol Life Sci 2019; 76:1459-1471. [PMID: 30607432 PMCID: PMC6439142 DOI: 10.1007/s00018-018-3000-z] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 11/13/2018] [Accepted: 12/17/2018] [Indexed: 02/07/2023]
Abstract
LncRNAs have recently emerged as new and fundamental transcriptional and post-transcriptional regulators acting at multiple levels of gene expression. Indeed, lncRNAs participate in a wide variety of stem cell and developmental processes, acting in cis and/or in trans in the nuclear and/or in the cytoplasmic compartments, and generating an intricate network of interactions with RNAs, enhancers, and chromatin-modifier complexes. Given the versatility of these molecules to operate in different subcellular compartments, via different modes of action and with different target specificity, the interest in this research field is rapidly growing. Here, we review recent progress in defining the functional role of lncRNAs in stem cell biology with a specific focus on the underlying mechanisms. We also discuss recent findings on a new family of evolutionary conserved lncRNAs transcribed from ultraconserved elements, which show perfect conservation between human, mouse, and rat genomes, and that are emerging as new player in this complex scenario.
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Affiliation(s)
- Annalisa Fico
- Stem Cell Fate Laboratory, Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, 80131, Naples, Italy.
- Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, 80131, Naples, Italy.
| | - Alessandro Fiorenzano
- Stem Cell Fate Laboratory, Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, 80131, Naples, Italy
- Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, 80131, Naples, Italy
- Developmental and Regenerative Neurobiology, Wallenberg Neuroscience Center, and Lund Stem Cell Centre, Department of Experimental Medical Science, Lund University, 22184, Lund, Sweden
| | - Emilia Pascale
- Stem Cell Fate Laboratory, Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, 80131, Naples, Italy
- Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, 80131, Naples, Italy
| | - Eduardo Jorge Patriarca
- Stem Cell Fate Laboratory, Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, 80131, Naples, Italy
- Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, 80131, Naples, Italy
| | - Gabriella Minchiotti
- Stem Cell Fate Laboratory, Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, 80131, Naples, Italy
- Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, 80131, Naples, Italy
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17
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Belanger K, Nutter CA, Li J, Yu P, Kuyumcu-Martinez MN. A developmentally regulated spliced variant of PTBP1 is upregulated in type 1 diabetic hearts. Biochem Biophys Res Commun 2018; 509:384-389. [PMID: 30594394 DOI: 10.1016/j.bbrc.2018.12.150] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 12/20/2018] [Indexed: 01/09/2023]
Abstract
Alternative splicing (AS) is dysregulated in Type 1 diabetic (T1D) hearts but mechanisms responsible are unclear. Here, we provide evidence that the RNA binding protein (RBP) PTBP1 is modulated in adult T1D hearts contributing to AS changes. We show that a spliced variant of PTBP1 that is highly expressed in normal newborn mouse hearts is aberrantly expressed in adult T1D mouse hearts. Comparing known PTBP1-target datasets to our T1D mouse transcriptome datasets, we discovered a group of genes with PTBP1 binding sites in their pre-mRNAs that are differentially spliced in T1D mouse hearts. We demonstrated that inducible expression of diabetes-induced PTBP1 spliced variant has less repressive splicing function. Notably, PTBP1 regulates AS of some of its targets antagonistically to RBFOX2. In sum, our results indicate that diabetic conditions disrupt developmental regulation of PTBP1 leading to differential AS of PTBP1 target genes. Identification of PTBP1 and PTBP1-regulated RNA networks can provide RNA-based therapies for the treatment of diabetes cardiac complications.
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Affiliation(s)
- KarryAnne Belanger
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Curtis A Nutter
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA
| | - Jin Li
- Department of Electrical and Computer Engineering & TEES-AgriLife Center for Bioinformatics and Genomic Systems Engineering, Texas A&M University, College Station, TX, 77843, USA
| | - Peng Yu
- Department of Electrical and Computer Engineering & TEES-AgriLife Center for Bioinformatics and Genomic Systems Engineering, Texas A&M University, College Station, TX, 77843, USA
| | - Muge N Kuyumcu-Martinez
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, 77555, USA; Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, 77555, USA; Institute for Translational Sciences, University of Texas Medical Branch, Galveston, TX, 77555, USA.
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Structural-functional interactions of NS1-BP protein with the splicing and mRNA export machineries for viral and host gene expression. Proc Natl Acad Sci U S A 2018; 115:E12218-E12227. [PMID: 30538201 DOI: 10.1073/pnas.1818012115] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The influenza virulence factor NS1 protein interacts with the cellular NS1-BP protein to promote splicing and nuclear export of the viral M mRNAs. The viral M1 mRNA encodes the M1 matrix protein and is alternatively spliced into the M2 mRNA, which is translated into the M2 ion channel. These proteins have key functions in viral trafficking and budding. To uncover the NS1-BP structural and functional activities in splicing and nuclear export, we performed proteomics analysis of nuclear NS1-BP binding partners and showed its interaction with constituents of the splicing and mRNA export machineries. NS1-BP BTB domains form dimers in the crystal. Full-length NS1-BP is a dimer in solution and forms at least a dimer in cells. Mutations suggest that dimerization is important for splicing. The central BACK domain of NS1-BP interacts directly with splicing factors such as hnRNP K and PTBP1 and with the viral NS1 protein. The BACK domain is also the site for interactions with mRNA export factor Aly/REF and is required for viral M mRNA nuclear export. The crystal structure of the C-terminal Kelch domain shows that it forms a β-propeller fold, which is required for the splicing function of NS1-BP. This domain interacts with the polymerase II C-terminal domain and SART1, which are involved in recruitment of splicing factors and spliceosome assembly, respectively. NS1-BP functions are not only critical for processing a subset of viral mRNAs but also impact levels and nuclear export of a subset of cellular mRNAs encoding factors involved in metastasis and immunity.
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19
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Rawcliffe DFR, Österman L, Nordin A, Holmberg M. PTBP1 acts as a dominant repressor of the aberrant tissue-specific splicing of ISCU in hereditary myopathy with lactic acidosis. Mol Genet Genomic Med 2018; 6:887-897. [PMID: 30209894 PMCID: PMC6305642 DOI: 10.1002/mgg3.413] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 03/23/2018] [Accepted: 04/17/2018] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Hereditary myopathy with lactic acidosis (HML) is an autosomal recessive disease caused by an intron mutation in the iron-sulfur cluster assembly (ISCU) gene. The mutation results in aberrant splicing, where part of the intron is retained in the final mRNA transcript, giving rise to a truncated nonfunctional ISCU protein. Using an ISCU mini-gene system, we have previously shown that PTBP1 can act as a repressor of the mis-splicing of ISCU, where overexpression of PTBP1 resulted in a decrease of the incorrect splicing. In this study, we wanted to, in more detail, analyze the role of PTBP1 in the regulation of endogenous ISCU mis-splicing. METHODS Overexpression and knockdown of PTBP1 was performed in myoblasts from two HML patients and a healthy control. Quantification of ISCU mis-splicing was done by qRTPCR. Biotinylated ISCU RNA, representing wildtype and mutant intron sequence, was used in a pull-down assay with nuclear extracts from myoblasts. Levels of PTBP1 in human cell lines and mice tissues were analyzed by qRTPCR and western blot. RESULTS PTBP1 overexpression in HML patient myoblasts resulted in a substantial decrease of ISCU mis-splicing while knockdown of PTBP1 resulted in a drastic increase. The effect could be observed in both patient and control myoblasts. We could also show that PTBP1 interacts with both the mutant and wild-type ISCU intron sequence, but with a higher affinity to the mutant sequence. Furthermore, low levels of PTBP1 among examined mouse tissues correlated with high levels of incorrect splicing of ISCU. CONCLUSION Our results show that PTBP1 acts as a dominant repressor of ISCU mis-splicing. We also show an inverse correlation between the levels of PTBP1 and ISCU mis-splicing, suggesting that the high level of mis-splicing in the skeletal muscle is primarily due to the low levels of PTBP1.
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Affiliation(s)
- Denise F. R. Rawcliffe
- Unit for Medical and Clinical GeneticsDepartment of Medical BiosciencesUmeå UniversityUmeåSweden
| | - Lennart Österman
- Unit for Medical and Clinical GeneticsDepartment of Medical BiosciencesUmeå UniversityUmeåSweden
| | - Angelica Nordin
- Unit for Medical and Clinical GeneticsDepartment of Medical BiosciencesUmeå UniversityUmeåSweden
| | - Monica Holmberg
- Unit for Medical and Clinical GeneticsDepartment of Medical BiosciencesUmeå UniversityUmeåSweden
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20
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Pina JM, Reynaga JM, Truong AAM, Keppetipola NM. Post-Translational Modifications in Polypyrimidine Tract Binding Proteins PTBP1 and PTBP2. Biochemistry 2018; 57:3873-3882. [PMID: 29851470 PMCID: PMC6211845 DOI: 10.1021/acs.biochem.8b00256] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
RNA binding proteins play an important role in regulating alternative pre-mRNA splicing and in turn cellular gene expression. Many of these RNA binding proteins occur as gene families with members sharing a high degree of primary structure identity and domain organization yet have tissue-specific expression patterns and regulate different sets of target exons. How highly similar members in a gene family can exert different splicing outcomes is not well understood. We conducted mass spectrometry analysis of post-translational phosphorylation and acetylation modifications for two paralogs of the polypyrimidine tract binding protein family, PTBP1 and PTBP2, to discover modifications that occur in splicing reaction mixtures and to identify discrete modifications that may direct their different splicing activities. We find that PTBP1 and PTBP2 have many distinct phosphate modifications located in the unstructured N-terminal, linker 1, and linker 2 regions. We find that the two proteins have many overlapping acetate modifications in the RNA recognition motifs (RRMs) with a few distinct sites in PTBP1 RRM2 and RRM3. Our data also reveal that lysine residues in the nuclear localization sequence of PTBP2 are acetylated. Collectively, our results highlight important differences in post-translational modifications between the paralogs and suggest a role for them in the differential splicing activity of PTBP1 and PTBP2.
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Affiliation(s)
- Jeffrey M. Pina
- Department of Chemistry and Biochemistry, California State University, Fullerton, 800 North State College Boulevard, Fullerton, California 92831, United States
| | - Janice M. Reynaga
- Department of Chemistry and Biochemistry, California State University, Fullerton, 800 North State College Boulevard, Fullerton, California 92831, United States
| | - Anthony A. M. Truong
- Department of Chemistry and Biochemistry, California State University, Fullerton, 800 North State College Boulevard, Fullerton, California 92831, United States
| | - Niroshika M. Keppetipola
- Department of Chemistry and Biochemistry, California State University, Fullerton, 800 North State College Boulevard, Fullerton, California 92831, United States
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21
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Vuong JK, Lin CH, Zhang M, Chen L, Black DL, Zheng S. PTBP1 and PTBP2 Serve Both Specific and Redundant Functions in Neuronal Pre-mRNA Splicing. Cell Rep 2017; 17:2766-2775. [PMID: 27926877 DOI: 10.1016/j.celrep.2016.11.034] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 10/10/2016] [Accepted: 11/09/2016] [Indexed: 02/06/2023] Open
Abstract
Families of alternative splicing regulators often contain multiple paralogs presumed to fulfill different functions. Polypyrimidine tract binding proteins PTBP1 and PTBP2 reprogram developmental pre-mRNA splicing in neurons, but how their regulatory networks differ is not understood. To compare their targeting, we generated a knockin allele that conditionally expresses PTBP1. Bred to a Ptbp2 knockout, the transgene allowed us to compare the developmental and molecular phenotypes of mice expressing only PTBP1, only PTBP2, or neither protein in the brain. This knockin Ptbp1 rescued a forebrain-specific, but not a pan-neuronal, Ptbp2 knockout, demonstrating both redundant and distinct roles for the proteins. Many developmentally regulated exons exhibited different sensitivities to PTBP1 and PTBP2. Nevertheless, the two paralogs displayed similar RNA binding across the transcriptome, indicating that their differential targeting does not derive from their RNA interactions, but from possible different cofactor interactions.
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Affiliation(s)
- John K Vuong
- Division of Biomedical Science, University of California, Riverside, Riverside, CA 92521, USA
| | - Chia-Ho Lin
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Min Zhang
- Division of Biomedical Science, University of California, Riverside, Riverside, CA 92521, USA
| | - Liang Chen
- Division of Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Douglas L Black
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Sika Zheng
- Division of Biomedical Science, University of California, Riverside, Riverside, CA 92521, USA.
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22
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PTBP1 and PTBP2 Repress Nonconserved Cryptic Exons. Cell Rep 2017; 17:104-113. [PMID: 27681424 DOI: 10.1016/j.celrep.2016.08.071] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 06/16/2016] [Accepted: 08/20/2016] [Indexed: 01/06/2023] Open
Abstract
The fidelity of RNA splicing is maintained by a network of factors, but the molecular mechanisms that govern this process have yet to be fully elucidated. We previously found that TDP-43, an RNA-binding protein implicated in neurodegenerative disease, utilizes UG microsatellites to repress nonconserved cryptic exons and prevent their incorporation into mRNA. Here, we report that two well-characterized splicing factors, polypyrimidine tract-binding protein 1 (PTBP1) and polypyrimidine tract-binding protein 2 (PTBP2), are also nonconserved cryptic exon repressors. In contrast to TDP-43, PTBP1 and PTBP2 utilize CU microsatellites to repress both conserved tissue-specific exons and nonconserved cryptic exons. Analysis of these conserved splicing events suggests that PTBP1 and PTBP2 repression is titrated to generate the transcriptome diversity required for neuronal differentiation. We establish that PTBP1 and PTBP2 are members of a family of cryptic exon repressors.
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Hillebrand F, Peter JO, Brillen AL, Otte M, Schaal H, Erkelenz S. Differential hnRNP D isoform incorporation may confer plasticity to the ESSV-mediated repressive state across HIV-1 exon 3. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2016; 1860:205-217. [PMID: 27919832 DOI: 10.1016/j.bbagrm.2016.12.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 11/22/2016] [Accepted: 12/01/2016] [Indexed: 11/27/2022]
Abstract
Even though splicing repression by hnRNP complexes bound to exonic sequences is well-documented, the responsible effector domains of hnRNP proteins have been described for only a select number of hnRNP constituents. Thus, there is only limited information available for possible varying silencer activities amongst different hnRNP proteins and composition changes within possible hnRNP complex assemblies. In this study, we identified the glycine-rich domain (GRD) of hnRNP proteins as a unifying feature in splice site repression. We also show that all four hnRNP D isoforms can act as genuine splicing repressors when bound to exonic positions. The presence of an extended GRD, however, seemed to potentiate the hnRNP D silencer activity of isoforms p42 and p45. Moreover, we demonstrate that hnRNP D proteins associate with the HIV-1 ESSV silencer complex, probably through direct recognition of "UUAG" sequences overlapping with the previously described "UAGG" motifs bound by hnRNP A1. Consequently, this spatial proximity seems to cause mutual interference between hnRNP A1 and hnRNP D. This interplay between hnRNP A1 and D facilitates a dynamic regulation of the repressive state of HIV-1 exon 3 which manifests as fluctuating relative levels of spliced vpr- and unspliced gag/pol-mRNAs.
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Affiliation(s)
- Frank Hillebrand
- Institute of Virology, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Jan Otto Peter
- Institute of Virology, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Anna-Lena Brillen
- Institute of Virology, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Marianne Otte
- Institute of Evolutionary Genetics, Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany
| | - Heiner Schaal
- Institute of Virology, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Steffen Erkelenz
- Institute of Virology, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany; Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany.
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