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de Oliveira Freitas Machado C, Schafranek M, Brüggemann M, Hernández Cañás M, Keller M, Di Liddo A, Brezski A, Blümel N, Arnold B, Bremm A, Wittig I, Jaé N, McNicoll F, Dimmeler S, Zarnack K, Müller-McNicoll M. Poison cassette exon splicing of SRSF6 regulates nuclear speckle dispersal and the response to hypoxia. Nucleic Acids Res 2023; 51:870-890. [PMID: 36620874 PMCID: PMC9881134 DOI: 10.1093/nar/gkac1225] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 12/06/2022] [Accepted: 12/10/2022] [Indexed: 01/10/2023] Open
Abstract
Hypoxia induces massive changes in alternative splicing (AS) to adapt cells to the lack of oxygen. Here, we identify the splicing factor SRSF6 as a key factor in the AS response to hypoxia. The SRSF6 level is strongly reduced in acute hypoxia, which serves a dual purpose: it allows for exon skipping and triggers the dispersal of nuclear speckles. Our data suggest that cells use dispersal of nuclear speckles to reprogram their gene expression during hypoxic adaptation and that SRSF6 plays an important role in cohesion of nuclear speckles. Down-regulation of SRSF6 is achieved through inclusion of a poison cassette exon (PCE) promoted by SRSF4. Removing the PCE 3' splice site using CRISPR/Cas9 abolishes SRSF6 reduction in hypoxia. Aberrantly high SRSF6 levels in hypoxia attenuate hypoxia-mediated AS and impair dispersal of nuclear speckles. As a consequence, proliferation and genomic instability are increased, while the stress response is suppressed. The SRSF4-PCE-SRSF6 hypoxia axis is active in different cancer types, and high SRSF6 expression in hypoxic tumors correlates with a poor prognosis. We propose that the ultra-conserved PCE of SRSF6 acts as a tumor suppressor and that its inclusion in hypoxia is crucial to reduce SRSF6 levels. This may prevent tumor cells from entering the metastatic route of hypoxia adaptation.
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Affiliation(s)
- Camila de Oliveira Freitas Machado
- Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany,Institute of Cardiovascular Regeneration, Goethe University, Frankfurt am Main, Germany
| | - Michal Schafranek
- Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany
| | - Mirko Brüggemann
- Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany,Buchmann Institute for Molecular Life Sciences (BMLS), Frankfurt am Main, Germany
| | | | - Mario Keller
- Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany,Buchmann Institute for Molecular Life Sciences (BMLS), Frankfurt am Main, Germany
| | - Antonella Di Liddo
- Buchmann Institute for Molecular Life Sciences (BMLS), Frankfurt am Main, Germany
| | - Andre Brezski
- Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany,Buchmann Institute for Molecular Life Sciences (BMLS), Frankfurt am Main, Germany
| | - Nicole Blümel
- Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany
| | - Benjamin Arnold
- Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany
| | - Anja Bremm
- Institute of Biochemistry II, Goethe University, Frankfurt am Main, Germany
| | - Ilka Wittig
- Functional Proteomics, Institute of Cardiovascular Physiology, Goethe University, Frankfurt am Main, Germany
| | - Nicolas Jaé
- Institute of Cardiovascular Regeneration, Goethe University, Frankfurt am Main, Germany
| | - François McNicoll
- Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany
| | - Stefanie Dimmeler
- Institute of Cardiovascular Regeneration, Goethe University, Frankfurt am Main, Germany
| | - Kathi Zarnack
- Correspondence may also be addressed to Kathi Zarnack.
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Maschio DA, Hernandes LHP, Alvares LE, Marques-Souza H, Collares-Buzato CB. Differential expression of regulators of the canonical Wnt pathway during the compensatory beta-cell hyperplasia in prediabetic mice. Biochem Biophys Res Commun 2022; 611:183-189. [DOI: 10.1016/j.bbrc.2022.04.047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 04/11/2022] [Indexed: 11/02/2022]
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Kandigian SE, Ethier EC, Kitchen RR, Lam TT, Arnold SE, Carlyle BC. Proteomic characterization of post-mortem human brain tissue following ultracentrifugation-based subcellular fractionation. Brain Commun 2022; 4:fcac103. [PMID: 35611312 PMCID: PMC9123841 DOI: 10.1093/braincomms/fcac103] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 01/27/2022] [Accepted: 04/19/2022] [Indexed: 11/13/2022] Open
Abstract
Abstract
Proteomic characterization of human brain tissue is increasingly utilized to identify potential novel biomarker and drug targets for a variety of neurological diseases. In whole tissue studies, results may be driven by changes in the proportion of the largest and most abundant organelles or tissue cell-type composition. Spatial proteomics approaches enhance our knowledge of disease mechanisms and changing signaling pathways at the subcellular level by taking into account the importance of cellular localization, which critically influences protein function. Density gradient-based ultracentrifugation methods allow for subcellular fractionation and have been utilized in cell lines, mouse, and human brain tissue to quantify thousands of proteins in specific enriched organelles such as the pre- and post-synapse. Serial ultra-centrifugation methods allow for the analysis of multiple cellular organelles from the same biological sample, and to our knowledge have not been previously applied to frozen post-mortem human brain tissue. The use of frozen human tissue for tissue fractionation faces two major challenges, the post-mortem interval, during which proteins may leach from their usual location into the cytosol, and freezing, which results in membrane breakdown. Despite these challenges, in this proof-of-concept study, we show that the majority of proteins segregate reproducibly into crude density-based centrifugation fractions, that the fractions are enriched for the appropriate organellar markers, and that significant differences in protein localization can be observed between tissue from individuals with Alzheimer’s Disease and control individuals.
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Affiliation(s)
- Savannah E. Kandigian
- Harvard Medical School, Massachusetts General Hospital Department of Neurology, Charlestown, Boston, MA, 02129, USA
| | - Elizabeth C. Ethier
- Harvard Medical School, Massachusetts General Hospital Department of Neurology, Charlestown, Boston, MA, 02129, USA
| | - Robert R. Kitchen
- Harvard Medical School Department of Medicine, Charlestown, Boston, MA, 02129, USA
| | - Tukiet T. Lam
- Yale University School of Medicine, Keck MS & Proteomics Resource, New Haven, CT, 06511, USA
- Yale University School of Medicine, Dept. of Molecular Biophysics and Biochemistry, New Haven, CT, 06511, USA
| | - Steven E. Arnold
- Harvard Medical School, Massachusetts General Hospital Department of Neurology, Charlestown, Boston, MA, 02129, USA
| | - Becky C. Carlyle
- Harvard Medical School, Massachusetts General Hospital Department of Neurology, Charlestown, Boston, MA, 02129, USA
- University of Oxford, Department of Physiology, Anatomy & Genetics, South Parks Rd, Oxford, OX1 3QU, UK
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Li K, Wang Z. Splicing factor SRSF2-centric gene regulation. Int J Biol Sci 2021; 17:1708-1715. [PMID: 33994855 PMCID: PMC8120470 DOI: 10.7150/ijbs.58888] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 04/04/2021] [Indexed: 01/14/2023] Open
Abstract
Serine/arginine-rich splicing factor 2 (SRSF2) is a splicing factor that is widely expressed in a variety of mammalian cell types. Increasing evidence has confirmed that SRSF2 plays vital roles in a number of biological and pathological processes. Therefore, it is important to understand how its expression is regulated, and how it regulates the expression of its target genes. Recently, we found that SRSF2 expression could be upregulated by herpes simplex virus-1 (HSV-1) infection, and that altered SRSF2 expression, in turn, epigenetically regulates the transcription of HSV-1 genes. Further studies on T cell exhaustion demonstrated that upregulated SRSF2 in exhausted T cells elevated the levels of multiple immune checkpoint molecules by associating with the acyl-transferases, P300 and CBP, and by altering histone modification near the transcription start sites of these genes, thereby influencing signal transducer and activator of transcription 3 binding to these gene promoters. These findings suggest that SRSF2 acts as an important sensor and effector during disease progression. Here, we discuss the molecules that regulate SRSF2 gene expression and their associated mechanisms, and the mechanisms via which SRSF2 regulates the expression of target genes, thus providing novel insights into the central role of SRSF2 in gene regulation.
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Affiliation(s)
- Kun Li
- Department of Nuclear Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan 250014, China
| | - Ziqiang Wang
- Department of Nuclear Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan 250014, China.,Biomedical Sciences College & Shandong Medicinal Biotechnology Centre, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan 250062, China
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Evangelisti C, Chiarini F, Paganelli F, Marmiroli S, Martelli AM. Crosstalks of GSK3 signaling with the mTOR network and effects on targeted therapy of cancer. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1867:118635. [PMID: 31884070 DOI: 10.1016/j.bbamcr.2019.118635] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 12/18/2019] [Indexed: 02/06/2023]
Abstract
The introduction of therapeutics targeting specific tumor-promoting oncogenic or non-oncogenic signaling pathways has revolutionized cancer treatment. Mechanistic (previously mammalian) target of rapamycin (mTOR), a highly conserved Ser/Thr kinase, is a central hub of the phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR network, one of the most frequently deregulated signaling pathways in cancer, that makes it an attractive target for therapy. Numerous mTOR inhibitors have progressed to clinical trials and two of them have been officially approved as anticancer therapeutics. However, mTOR-targeting drugs have met with a very limited success in cancer patients. Frequently, the primary impediment to a successful targeted therapy in cancer is drug-resistance, either from the very beginning of the therapy (innate resistance) or after an initial response and upon repeated drug treatment (evasive or acquired resistance). Drug-resistance leads to treatment failure and relapse/progression of the disease. Resistance to mTOR inhibitors depends, among other reasons, on activation/deactivation of several signaling pathways, included those regulated by glycogen synthase kinase-3 (GSK3), a protein that targets a vast number of substrates in its repertoire, thereby orchestrating many processes that include cell proliferation and survival, metabolism, differentiation, and stemness. A detailed knowledge of the rewiring of signaling pathways triggered by exposure to mTOR inhibitors is critical to our understanding of the consequences such perturbations cause in tumors, including the emergence of drug-resistant cells. Here, we provide the reader with an updated overview of intricate circuitries that connect mTOR and GSK3 and we relate them to the efficacy (or lack of efficacy) of mTOR inhibitors in cancer cells.
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Affiliation(s)
- Camilla Evangelisti
- CNR Institute of Molecular Genetics, 40136 Bologna, BO, Italy; IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, BO, Italy
| | - Francesca Chiarini
- CNR Institute of Molecular Genetics, 40136 Bologna, BO, Italy; IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, BO, Italy
| | - Francesca Paganelli
- Department of Biomedical and Neuromotor Sciences, University of Bologna, 40126 Bologna, BO, Italy
| | - Sandra Marmiroli
- Department of Biomedical, Metabolical, and Neurological Sciences, University of Modena and Reggio Emilia, 41124 Modena, MO, Italy
| | - Alberto M Martelli
- Department of Biomedical and Neuromotor Sciences, University of Bologna, 40126 Bologna, BO, Italy.
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