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da Silva AM, Yevdokimova V, Benoit YD. Sam68 is a druggable vulnerability point in cancer stem cells. Cancer Metastasis Rev 2024; 43:441-456. [PMID: 37792222 PMCID: PMC11016129 DOI: 10.1007/s10555-023-10145-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2023] [Accepted: 09/27/2023] [Indexed: 10/05/2023]
Abstract
Sam68 (Src associated in mitosis of 68 kDa) is an RNA-binding and multifunctional protein extensively characterized in numerous cellular functions, such as RNA processing, cell cycle regulation, kinase- and growth factor signaling. Recent investigations highlighted Sam68 as a primary target of a class of reverse-turn peptidomimetic drugs, initially developed as inhibitors of Wnt/β-catenin mediated transcription. Further investigations on such compounds revealed their capacity to selectively eliminate cancer stem cell (CSC) activity upon engaging Sam68. This work highlighted previously unappreciated roles for Sam68 in the maintenance of neoplastic self-renewal and tumor-initiating functions. Here, we discuss the implication of Sam68 in tumorigenesis, where central findings support its contribution to chromatin regulation processes essential to CSCs. We also review advances in CSC-targeting drug discovery aiming to modulate Sam68 cellular distribution and protein-protein interactions. Ultimately, Sam68 constitutes a vulnerability point of CSCs and an attractive therapeutic target to impede neoplastic stemness in human tumors.
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Affiliation(s)
- Amanda Mendes da Silva
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, K1H 8M5, Canada
| | - Veronika Yevdokimova
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, K1H 8M5, Canada
| | - Yannick D Benoit
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, K1H 8M5, Canada.
- School of Pharmaceutical Sciences, Faculty of Medicine, University of Ottawa, Ottawa, ON, K1H 8M5, Canada.
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2
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Demongin C, Tranier S, Joshi V, Ceschi L, Desforges B, Pastré D, Hamon L. RNA and the RNA-binding protein FUS act in concert to prevent TDP-43 spatial segregation. J Biol Chem 2024; 300:105716. [PMID: 38311174 PMCID: PMC10912363 DOI: 10.1016/j.jbc.2024.105716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 01/15/2024] [Accepted: 01/19/2024] [Indexed: 02/10/2024] Open
Abstract
FUS and TDP-43 are two self-adhesive aggregation-prone mRNA-binding proteins whose pathological mutations have been linked to neurodegeneration. While TDP-43 and FUS form reversible mRNA-rich compartments in the nucleus, pathological mutations promote their respective cytoplasmic aggregation in neurons with no apparent link between the two proteins except their intertwined function in mRNA processing. By combining analyses in cellular context and at high resolution in vitro, we unraveled that TDP-43 is specifically recruited in FUS assemblies to form TDP-43-rich subcompartments but without reciprocity. The presence of mRNA provides an additional scaffold to promote the mixing between TDP-43 and FUS. Accordingly, we also found that the pathological truncated form of TDP-43, TDP-25, which has an impaired RNA-binding ability, no longer mixes with FUS. Together, these results suggest that the binding of FUS along nascent mRNAs enables TDP-43, which is highly aggregation-prone, to mix with FUS phase to form mRNA-rich subcompartments. A functional link between FUS and TDP-43 may explain their common implication in amyotrophic lateral sclerosis.
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Affiliation(s)
- Clément Demongin
- SABNP, Univ Evry, INSERM, U1204, Université Paris-Saclay, Evry, France
| | - Samuel Tranier
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Vandana Joshi
- SABNP, Univ Evry, INSERM, U1204, Université Paris-Saclay, Evry, France
| | - Léa Ceschi
- SABNP, Univ Evry, INSERM, U1204, Université Paris-Saclay, Evry, France
| | | | - David Pastré
- SABNP, Univ Evry, INSERM, U1204, Université Paris-Saclay, Evry, France
| | - Loic Hamon
- SABNP, Univ Evry, INSERM, U1204, Université Paris-Saclay, Evry, France.
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3
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Nadal M, Anton R, Dorca‐Arévalo J, Estébanez‐Perpiñá E, Tizzano EF, Fuentes‐Prior P. Structure and function analysis of Sam68 and hnRNP A1 synergy in the exclusion of exon 7 from SMN2 transcripts. Protein Sci 2023; 32:e4553. [PMID: 36560896 PMCID: PMC10031812 DOI: 10.1002/pro.4553] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 12/13/2022] [Accepted: 12/17/2022] [Indexed: 12/24/2022]
Abstract
Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by the absence of a functional copy of the Survival of Motor Neuron 1 gene (SMN1). The nearly identical paralog, SMN2, cannot compensate for the loss of SMN1 because exon 7 is aberrantly skipped from most SMN2 transcripts, a process mediated by synergistic activities of Src-associated during mitosis, 68 kDa (Sam68/KHDRBS1) and heterogeneous nuclear ribonucleoprotein (hnRNP) A1. This results in the production of a truncated, nonfunctional protein that is rapidly degraded. Here, we present several crystal structures of Sam68 RNA-binding domain (RBD). Sam68-RBD forms stable symmetric homodimers by antiparallel association of helices α3 from two monomers. However, the details of domain organization and the dimerization interface differ significantly from previously characterized homologs. We demonstrate that Sam68 and hnRNP A1 can simultaneously bind proximal motifs within the central region of SMN2 (ex7). Furthermore, we show that the RNA-binding pockets of the two proteins are close to each other in their heterodimeric complex and identify contact residues using crosslinking-mass spectrometry. We present a model of the ternary Sam68·SMN2 (ex7)·hnRNP A1 complex that reconciles all available information on SMN1/2 splicing. Our findings have important implications for the etiology of SMA and open new avenues for the design of novel therapeutics to treat splicing diseases.
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Affiliation(s)
- Marta Nadal
- Molecular Bases of DiseaseBiomedical Research Institute Sant Pau (IIB Sant Pau)BarcelonaSpain
| | - Rosa Anton
- Molecular Bases of DiseaseBiomedical Research Institute Sant Pau (IIB Sant Pau)BarcelonaSpain
| | - Jonatan Dorca‐Arévalo
- Molecular Bases of DiseaseBiomedical Research Institute Sant Pau (IIB Sant Pau)BarcelonaSpain
- Present address:
Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Campus of BellvitgeHospitalet de Llobregat, University of BarcelonaBarcelonaSpain
| | - Eva Estébanez‐Perpiñá
- Structural Biology of Nuclear Receptors, Department of Biochemistry and Molecular Biomedicine, Faculty of BiologyInstitute of Biomedicine (IBUB) of the University of Barcelona (UB)BarcelonaSpain
| | - Eduardo F. Tizzano
- Medicine Genetics GroupVall d'Hebron Research Institute (VHIR)BarcelonaSpain
- Department of Clinical and Molecular GeneticsHospital Vall d'HebronBarcelonaSpain
| | - Pablo Fuentes‐Prior
- Molecular Bases of DiseaseBiomedical Research Institute Sant Pau (IIB Sant Pau)BarcelonaSpain
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4
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Traunmüller L, Schulz J, Ortiz R, Feng H, Furlanis E, Gomez AM, Schreiner D, Bischofberger J, Zhang C, Scheiffele P. A cell-type-specific alternative splicing regulator shapes synapse properties in a trans-synaptic manner. Cell Rep 2023; 42:112173. [PMID: 36862556 PMCID: PMC10066595 DOI: 10.1016/j.celrep.2023.112173] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 12/07/2022] [Accepted: 02/12/2023] [Indexed: 03/03/2023] Open
Abstract
The specification of synaptic properties is fundamental for the function of neuronal circuits. "Terminal selector" transcription factors coordinate terminal gene batteries that specify cell-type-specific properties. Moreover, pan-neuronal splicing regulators have been implicated in directing neuronal differentiation. However, the cellular logic of how splicing regulators instruct specific synaptic properties remains poorly understood. Here, we combine genome-wide mapping of mRNA targets and cell-type-specific loss-of-function studies to uncover the contribution of the RNA-binding protein SLM2 to hippocampal synapse specification. Focusing on pyramidal cells and somatostatin (SST)-positive GABAergic interneurons, we find that SLM2 preferentially binds and regulates alternative splicing of transcripts encoding synaptic proteins. In the absence of SLM2, neuronal populations exhibit normal intrinsic properties, but there are non-cell-autonomous synaptic phenotypes and associated defects in a hippocampus-dependent memory task. Thus, alternative splicing provides a critical layer of gene regulation that instructs specification of neuronal connectivity in a trans-synaptic manner.
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Affiliation(s)
| | - Jan Schulz
- Department of Biomedicine, University of Basel, 4056 Basel, Switzerland
| | - Raul Ortiz
- Biozentrum of the University of Basel, 4056 Basel, Switzerland
| | - Huijuan Feng
- Department of Systems Biology, Department of Biochemistry and Molecular Biophysics, Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA
| | | | - Andrea M Gomez
- Biozentrum of the University of Basel, 4056 Basel, Switzerland
| | | | | | - Chaolin Zhang
- Department of Systems Biology, Department of Biochemistry and Molecular Biophysics, Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA
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5
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Malki I, Liepina I, Kogelnik N, Watmuff H, Robinson S, Lightfoot A, Gonchar O, Bottrill A, Fry AM, Dominguez C. Cdk1-mediated threonine phosphorylation of Sam68 modulates its RNA binding, alternative splicing activity and cellular functions. Nucleic Acids Res 2022; 50:13045-13062. [PMID: 36537190 PMCID: PMC9825155 DOI: 10.1093/nar/gkac1181] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 11/17/2022] [Accepted: 11/28/2022] [Indexed: 12/24/2022] Open
Abstract
Sam68, also known as KHDRBS1, is a member of the STAR family of proteins that directly link signal transduction with post-transcriptional gene regulation. Sam68 controls the alternative splicing of many oncogenic proteins and its role is modulated by post-translational modifications, including serine/threonine phosphorylation, that differ at various stages of the cell cycle. However, the molecular basis and mechanisms of these modulations remain largely unknown. Here, we combined mass spectrometry, nuclear magnetic resonance spectroscopy and cell biology techniques to provide a comprehensive post-translational modification mapping of Sam68 at different stages of the cell cycle in HEK293 and HCT116 cells. We established that Sam68 is specifically phosphorylated at T33 and T317 by Cdk1, and demonstrated that these phosphorylation events reduce the binding of Sam68 to RNA, control its cellular localization and reduce its alternative splicing activity, leading to a reduction in the induction of apoptosis and an increase in the proliferation of HCT116 cells.
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Affiliation(s)
- Idir Malki
- The Leicester Institute of Structural and Chemical Biology and Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, UK
| | - Inara Liepina
- The Leicester Institute of Structural and Chemical Biology and Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, UK
| | - Nora Kogelnik
- The Leicester Institute of Structural and Chemical Biology and Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, UK
| | - Hollie Watmuff
- The Leicester Institute of Structural and Chemical Biology and Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, UK
| | - Sue Robinson
- The Leicester Institute of Structural and Chemical Biology and Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, UK
| | - Adam Lightfoot
- The Leicester Institute of Structural and Chemical Biology and Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, UK
| | - Oksana Gonchar
- The Leicester Institute of Structural and Chemical Biology and Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, UK
| | - Andrew Bottrill
- Proteomics RTP, School of Life Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Andrew M Fry
- Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, UK
| | - Cyril Dominguez
- The Leicester Institute of Structural and Chemical Biology and Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, UK
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6
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Wu Z, Peng Y, Xiong L, Wang J, Li Z, Ning K, Deng M, Wang N, Wei W, Li Z, Dong P, Yu C, Zhou F, Zhang Z. Role of Sam68 in Sunitinib induced renal cell carcinoma apoptosis. Cancer Med 2022; 11:3674-3686. [PMID: 35476809 PMCID: PMC9554455 DOI: 10.1002/cam4.4743] [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: 08/26/2021] [Revised: 03/12/2022] [Accepted: 03/30/2022] [Indexed: 11/18/2022] Open
Abstract
Sunitinib is one of the first-line targeted drugs for metastatic renal cell carcinoma (RCC) with dual effects of antiangiogensis and proapoptosis. Sam68 (Src-associated in mitosis, 68 KDa), is found being involved in cell apoptosis. This article reveals that Sam68 impacts the sensitivity to sunitinib by mediating the apoptosis of RCC cells. Immunohistochemical staining indicated that the Sam68 expression levels in sunitinib sensitive tumor tissues were markedly higher than those in sunitinib resistant tumor tissues. Sunitinib induced RCC cell apoptosis in a concentration-dependent manner and inhibited the expression of total and phosphorylated Sam68 (p-Sam68). Downregulation of Sam68 expression inhibited RCC cell apoptosis induced by sunitinib. While upregulation of Sam68 expression could enhance apoptosis induced by sunitinib. Xenograft models showed that tumors in the Sam68-knockdown group did not shrink as much as those in the control group after treatment with sunitinib for 4 weeks. Together, our results suggest that Sam68 expression is associated with the sensitivity of ccRCC patients to sunitinib. Sam68 may promote cell apoptosis induced by sunitinib, and the Sam68 expression level may be a biomarker for predicting sunitinib sensitivity in ccRCC patients.
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Affiliation(s)
- Zeshen Wu
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Yulu Peng
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Longbin Xiong
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Jun Wang
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Zhen Li
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Kang Ning
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Minhua Deng
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Ning Wang
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Wensu Wei
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Zhiyong Li
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Pei Dong
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Chunping Yu
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Fangjian Zhou
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
| | - Zhiling Zhang
- Department of UrologySun Yat‐sen University Cancer CenterGuangzhouChina
- State Key Laboratory of Oncology in Southern ChinaGuangzhouChina
- Collaborative Innovation Center for Cancer MedicineGuangzhouChina
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7
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Antifeeva IA, Fonin AV, Fefilova AS, Stepanenko OV, Povarova OI, Silonov SA, Kuznetsova IM, Uversky VN, Turoverov KK. Liquid-liquid phase separation as an organizing principle of intracellular space: overview of the evolution of the cell compartmentalization concept. Cell Mol Life Sci 2022; 79:251. [PMID: 35445278 PMCID: PMC11073196 DOI: 10.1007/s00018-022-04276-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 03/24/2022] [Accepted: 03/27/2022] [Indexed: 12/14/2022]
Abstract
At the turn of the twenty-first century, fundamental changes took place in the understanding of the structure and function of proteins and then in the appreciation of the intracellular space organization. A rather mechanistic model of the organization of living matter, where the function of proteins is determined by their rigid globular structure, and the intracellular processes occur in rigidly determined compartments, was replaced by an idea that highly dynamic and multifunctional "soft matter" lies at the heart of all living things. According this "new view", the most important role in the spatio-temporal organization of the intracellular space is played by liquid-liquid phase transitions of biopolymers. These self-organizing cellular compartments are open dynamic systems existing at the edge of chaos. They are characterized by the exceptional structural and compositional dynamics, and their multicomponent nature and polyfunctionality provide means for the finely tuned regulation of various intracellular processes. Changes in the external conditions can cause a disruption of the biogenesis of these cellular bodies leading to the irreversible aggregation of their constituent proteins, followed by the transition to a gel-like state and the emergence of amyloid fibrils. This work represents a historical overview of changes in our understanding of the intracellular space compartmentalization. It also reflects methodological breakthroughs that led to a change in paradigms in this area of science and discusses modern ideas about the organization of the intracellular space. It is emphasized here that the membrane-less organelles have to combine a certain resistance to the changes in their environment and, at the same time, show high sensitivity to the external signals, which ensures the normal functioning of the cell.
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Affiliation(s)
- Iuliia A Antifeeva
- Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Av., 4, St. Petersburg, 194064, Russia
| | - Alexander V Fonin
- Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Av., 4, St. Petersburg, 194064, Russia
| | - Anna S Fefilova
- Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Av., 4, St. Petersburg, 194064, Russia
| | - Olesya V Stepanenko
- Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Av., 4, St. Petersburg, 194064, Russia
| | - Olga I Povarova
- Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Av., 4, St. Petersburg, 194064, Russia
| | - Sergey A Silonov
- Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Av., 4, St. Petersburg, 194064, Russia
| | - Irina M Kuznetsova
- Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Av., 4, St. Petersburg, 194064, Russia
| | - Vladimir N Uversky
- Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd. MDC07, Tampa, FL, 33612, USA.
| | - Konstantin K Turoverov
- Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Av., 4, St. Petersburg, 194064, Russia.
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8
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Mannen T, Goto M, Yoshizawa T, Yamashita A, Hirose T, Hayano T. Distinct RNA polymerase transcripts direct the assembly of phase-separated DBC1 nuclear bodies in different cell lines. Mol Biol Cell 2021; 32:ar33. [PMID: 34495685 PMCID: PMC8693952 DOI: 10.1091/mbc.e21-02-0081] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The mammalian cell nucleus is a highly organized organelle that contains membrane-less structures referred to as nuclear bodies (NBs). Some NBs carry specific RNA types that play architectural roles in their formation. Here, we show two types of RNase-sensitive DBC1-containing NBs, DBC1 nuclear body (DNB) in HCT116 cells and Sam68 nuclear body (SNB) in HeLa cells, that exhibit phase-separated features and are constructed using RNA polymerase I or II transcripts in a cell type–specific manner. We identified additional protein components present in DNB by immunoprecipitation–mass spectrometry, some of which (DBC1 and heterogeneous nuclear ribonucleoprotein L [HNRNPL]) are required for DNB formation. The rescue experiment using the truncated HNRNPL mutants revealed that two RNA-binding domains and intrinsically disordered regions of HNRNPL play significant roles in DNB formation. All these domains of HNRNPL promote in vitro droplet formation, suggesting the need for multivalent interactions between HNRNPL and RNA as well as proteins in DNB formation.
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Affiliation(s)
- Taro Mannen
- College of Life Sciences, Ritsumeikan University, Kusatsu 525-8577, Japan
| | - Masato Goto
- College of Life Sciences, Ritsumeikan University, Kusatsu 525-8577, Japan
| | - Takuya Yoshizawa
- College of Life Sciences, Ritsumeikan University, Kusatsu 525-8577, Japan
| | - Akio Yamashita
- Graduate School of Medicine, University of the Ryukyus, Nishihara-cho 903-0215, Japan
| | - Tetsuro Hirose
- Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Toshiya Hayano
- College of Life Sciences, Ritsumeikan University, Kusatsu 525-8577, Japan
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9
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ArcRNAs and the formation of nuclear bodies. Mamm Genome 2021; 33:382-401. [PMID: 34085114 DOI: 10.1007/s00335-021-09881-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 05/25/2021] [Indexed: 01/13/2023]
Abstract
Long noncoding RNAs (lncRNAs) have long been collectively and passively defined as transcripts that do not encode proteins. However, extensive functional studies performed over the last decade have enabled the classification of lncRNAs into multiple categories according to their functions and/or molecular properties. Architectual RNAs (arcRNAs) are a group of lncRNAs that serve as architectural components of submicron-scale cellular bodies or nonmembranous organelles, which are composed of specific sets of proteins and nucleic acids involved in particular molecular processes. In this review, we focus on arcRNAs that function in the nucleus, which provide a structural basis for the formation of nuclear bodies, nonmembranous organelles in the cell nucleus. We will summarize the current list of arcRNAs and proteins associated with classic and more recently discovered nuclear bodies and discuss general rules that govern the formation of nuclear bodies, emphasizing weak multivalent interactions mediated by innately flexible biomolecules.
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10
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Arva A, Kasu YAT, Duncan J, Alkhatatbeh MA, Brower CS. The Ligand of Ate1 is intrinsically disordered and participates in nucleolar phase separation regulated by Jumonji Domain Containing 6. Proc Natl Acad Sci U S A 2021; 118:e2015887118. [PMID: 33443146 PMCID: PMC7817205 DOI: 10.1073/pnas.2015887118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The Ligand of Ate1 (Liat1) is a protein of unknown function that was originally discovered through its interaction with arginyl-tRNA protein transferase 1 (Ate1), a component of the Arg/N-degron pathway of protein degradation. Here, we characterized the functional domains of mouse Liat1 and found that its N-terminal half comprises an intrinsically disordered region (IDR) that facilitates its liquid-liquid phase separation (LLPS) in the nucleolus. Using bimolecular fluorescence complementation and immunocytochemistry, we found that Liat1 is targeted to the nucleolus by a low-complexity poly-K region within its IDR. We also found that the lysyl-hydroxylase activity of Jumonji Domain Containing 6 (Jmjd6) modifies Liat1, in a manner that requires the Liat1 poly-K region, and inhibits its nucleolar targeting and potential functions. In sum, this study reveals that Liat1 participates in nucleolar LLPS regulated by Jmjd6.
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Affiliation(s)
- Akshaya Arva
- Department of Biology, Texas Woman's University, Denton, TX 76204
| | | | - Jennifer Duncan
- Department of Biology, Texas Woman's University, Denton, TX 76204
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11
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Leptin, Leptin Receptor, KHDRBS1 (KH RNA Binding Domain Containing, Signal Transduction Associated 1), and Adiponectin in Bone Metastasis from Breast Carcinoma: An Immunohistochemical Study. Biomedicines 2020; 8:biomedicines8110510. [PMID: 33213024 PMCID: PMC7698510 DOI: 10.3390/biomedicines8110510] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/09/2020] [Accepted: 11/12/2020] [Indexed: 02/07/2023] Open
Abstract
Breast cancer patients are at a high risk of complications from bone metastasis. Molecular characterization of bone metastases is essential for the discovery of new therapeutic targets. Here, we investigated the expression and the intracellular distribution of KH RNA binding domain containing, signal transduction associated 1 (KHDRBS1), leptin, leptin receptor (LEPR), and adiponectin in bone metastasis from breast carcinoma and looked for correlations between the data. The expression of these proteins is known in breast carcinoma, but it has not been investigated in bone metastatic tissue to date. Immunohistochemical analysis was carried out on bone metastasis specimens, then semiquantitative evaluation of the results and the Pearson test were performed to determine eventual correlations. KHDRBS1 expression was significantly higher in the nuclei than in the cytosol of metastatic cells; LEPR was prevalently observed in the cytosol and the nuclei; leptin and adiponectin were found in metastatic cells and stromal cells; the strongest positive correlation was between nuclear KHDRBS1 and nuclear LEPR expression. Taken together, our findings support the importance of the leptin/LEPR/KHDRBS1 axis and of adiponectin in the progression of bone metastasis and suggest their potential application in pharmacological interventions.
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12
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Pankivskyi S, Pastré D, Steiner E, Joshi V, Rynditch A, Hamon L. ITSN1 regulates SAM68 solubility through SH3 domain interactions with SAM68 proline-rich motifs. Cell Mol Life Sci 2020; 78:1745-1763. [PMID: 32780150 PMCID: PMC7904728 DOI: 10.1007/s00018-020-03610-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 06/03/2020] [Accepted: 07/22/2020] [Indexed: 02/06/2023]
Abstract
SAM68 is an mRNA-binding protein involved in mRNA processing in the nucleus that forms membraneless compartments called SAM68 Nuclear Bodies (SNBs). We found that intersectin 1 (ITSN1), a multidomain scaffold protein harboring five soluble SH3 domains, interacts with SAM68 proline-rich motifs (PRMs) surrounded by self-adhesive low complexity domains. While SAM68 is poorly soluble in vitro, the interaction of ITSN1 SH3 domains and mRNA with SAM68 enhances its solubility. In HeLa cells, the interaction between the first ITSN1 SH3 domain (SH3A) and P0, the N-terminal PRM of SAM68, induces the dissociation of SNBs. In addition, we reveal the ability of another SH3 domain (SH3D) of ITSN1 to bind to mRNAs. ITSN1 and mRNA may thus act in concert to promote SAM68 solubilization, consistent with the absence of mRNA in SNBs in cells. Together, these results support the notion of a specific chaperoning of PRM-rich SAM68 within nuclear ribonucleoprotein complexes by ITSN1 that may regulate the processing of a fraction of nuclear mRNAs, notably SAM68-controlled splicing events related to higher neuronal functions or cancer progression. This observation may also serve as a putative model of the interaction between other PRM-rich RBPs and signaling proteins harboring SH3 domains.
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Affiliation(s)
- S Pankivskyi
- SABNP, Univ Evry, INSERM U1204, Université Paris-Saclay, 91025, Evry, France.,Institute of Molecular Biology and Genetics, The National Academy of Sciences, 150 Zabolotnogo Street, Kyiv, 03680, Ukraine
| | - D Pastré
- SABNP, Univ Evry, INSERM U1204, Université Paris-Saclay, 91025, Evry, France
| | - E Steiner
- SABNP, Univ Evry, INSERM U1204, Université Paris-Saclay, 91025, Evry, France
| | - V Joshi
- SABNP, Univ Evry, INSERM U1204, Université Paris-Saclay, 91025, Evry, France
| | - A Rynditch
- Institute of Molecular Biology and Genetics, The National Academy of Sciences, 150 Zabolotnogo Street, Kyiv, 03680, Ukraine.
| | - L Hamon
- SABNP, Univ Evry, INSERM U1204, Université Paris-Saclay, 91025, Evry, France.
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13
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Dumbović G, Sanjuan X, Perucho M, Forcales SV. Stimulated emission depletion (STED) super resolution imaging of RNA- and protein-containing domains in fixed cells. Methods 2020; 187:68-76. [PMID: 32360441 DOI: 10.1016/j.ymeth.2020.04.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 04/25/2020] [Accepted: 04/26/2020] [Indexed: 12/20/2022] Open
Abstract
Super resolution microscopy has changed our capability to visualize and understand spatial arrangements of RNA- and protein-containing domains in individual cells. In a previous study, we described a novel lncRNA, Tumor-associated NBL2 transcript (TNBL), which originates from a primate specific macrosatellite repeat. We aimed to describe several aspects of TNBL lncRNA, with one focus being pinpointing its precise location in the nucleus, as well as visualizing its interactions with proteins to deduce its functionality. Using a combination of STimulated Emission Depletion (STED) super resolution microscopy, single molecule RNA (smRNA) FISH against TNBL, and immunofluorescence against SAM68 perinucleolar body, we resolved the spatial complexity of the interaction between TNBL aggregates and SAM68 bodies at the perinucleolar region. Here, we describe protocols for a step-by-step optimized smRNA FISH/IF and STED imaging, detailing parameter settings, and three-dimensional data analysis of spatial positioning of subnuclear structures. These protocols can be employed for single-cell imaging of complex nuclear RNA-protein structures.
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Affiliation(s)
- Gabrijela Dumbović
- BioFrontiers Institute, University of Colorado at Boulder, Boulder, CO, USA.
| | - Xavier Sanjuan
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain; Advanced Light Microscopy Unit, Center for Genomic Regulation, Barcelona, Spain
| | - Manuel Perucho
- Cancer Genetics and Epigenetics, Program of Predictive and Personalized Medicine of Cancer (PMPPC), Health Science Research Institute Germans Trias i Pujol (IGTP), Badalona, Spain; Tumor Initiation and Maintenance Program, Sanford Burnham Prebys (SBP) Medical Discovery Institute, La Jolla, CA, USA
| | - Sonia-V Forcales
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, University of Barcelona, L' Hospitalet de Llobregat, Barcelona, Spain.
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Vasileva E, Shuvalov O, Petukhov A, Fedorova O, Daks A, Nader R, Barlev N. KMT Set7/9 is a new regulator of Sam68 STAR-protein. Biochem Biophys Res Commun 2020; 525:1018-1024. [PMID: 32178870 DOI: 10.1016/j.bbrc.2020.03.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 03/03/2020] [Indexed: 12/12/2022]
Abstract
Lysine-specific methyltransferase Set7/9 (KMT7) belongs to the SET domain family of proteins. Besides the SET domain, Set7/9 also contains a so-called MORN (Membrane Occupation and Recognition Nexus) domain whose function in high eukaryotes is largely unknown. Set7/9 has been shown to specifically methylate both histones H1 and H3 as well as a number of non-histone substrates, including p53, E2F1, RelA, AR, and other important transcription factors. However, despite the ever growing list of potential substrates of Set7/9, the question of its substrate specificity is still debatable. To gain a better understanding of the Set7/9 substrate specificity and to clarify the importance of structural domains of Set7/9 for protein-protein interactions (PPIs) we determined interactomes for both MORN and SET domains of Set7/9 by pull-down assay coupled with mass-spectrometry. Importantly, we demonstrated that most of PPIs of Set7/9 are mediated via its MORN domain. The latter has preference towards positively charged amino acids that are often found in RNA-binding proteins. One of the Set7/9-interacting proteins was identified as Sam68, an RNA splicing protein with a KH (heterogeneous nuclear ribonucleoprotein K (hnRNP K) homology) domain. Importantly, the RG-rich domain of Sam68 that is also present in many splicing factors was found to interact with Set7/9. We revealed that Set7/9 not only co-immunoprecipitated with Sam68, but also methylated the latter on K208. Functionally, knockout of Set7/9 decreased the protein level of Sam68 in cells resulting in altered regulation of cell cycle and apoptosis. Finally, the bioinformatics analysis established a correlation between the high levels of Sam68/Set7/9 co-expression and better survival rates of patients with colon cancer.
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Affiliation(s)
- Elena Vasileva
- Institute of Cytology, Russian Academy of Sciences, 194064, Russian Federation
| | - Oleg Shuvalov
- Institute of Cytology, Russian Academy of Sciences, 194064, Russian Federation
| | - Alexey Petukhov
- Institute of Cytology, Russian Academy of Sciences, 194064, Russian Federation; Almazov National Medical Research Centre, Institute of Hematology, 197341, Russian Federation
| | - Olga Fedorova
- Institute of Cytology, Russian Academy of Sciences, 194064, Russian Federation
| | - Alexandra Daks
- Institute of Cytology, Russian Academy of Sciences, 194064, Russian Federation
| | - Rahimi Nader
- Department of Pathology & Laboratory Medicine, Boston University, 72 East Concord St., Boston, MA, 02118, USA
| | - Nickolai Barlev
- Institute of Cytology, Russian Academy of Sciences, 194064, Russian Federation; Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region, 141700, Russian Federation.
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15
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Maroni P. Leptin, Adiponectin, and Sam68 in Bone Metastasis from Breast Cancer. Int J Mol Sci 2020; 21:ijms21031051. [PMID: 32033341 PMCID: PMC7037668 DOI: 10.3390/ijms21031051] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 02/03/2020] [Accepted: 02/04/2020] [Indexed: 12/12/2022] Open
Abstract
The most serious aspect of neoplastic disease is the spread of cancer cells to secondary sites. Skeletal metastases can escape detection long after treatment of the primary tumour and follow-up. Bone tissue is a breeding ground for many types of cancer cells, especially those derived from the breast, prostate, and lung. Despite advances in diagnosis and therapeutic strategies, bone metastases still have a profound impact on quality of life and survival and are often responsible for the fatal outcome of the disease. Bone and the bone marrow environment contain a wide variety of cells. No longer considered a passive filler, bone marrow adipocytes have emerged as critical contributors to cancer progression. Released by adipocytes, adipokines are soluble factors with hormone-like functions and are currently believed to affect tumour development. Src-associated in mitosis of 68 kDa (Sam68), originally discovered as a protein physically associated with and phosphorylated by c-Src during mitosis, is now recognised as an important RNA-binding protein linked to tumour onset and progression of disease. Sam68 also regulates splicing events and recent evidence reports that dysregulation of these events is a key step in neoplastic transformation and tumour progression. The present review reports recent findings on adipokines and Sam68 and their role in breast cancer progression and metastasis.
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Affiliation(s)
- Paola Maroni
- IRCCS Istituto Ortopedico Galeazzi, Via R. Galeazzi 4, 20161 Milano, Italy
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The Oncogene Metadherin Interacts with the Known Splicing Proteins YTHDC1, Sam68 and T-STAR and Plays a Novel Role in Alternative mRNA Splicing. Cancers (Basel) 2019; 11:cancers11091233. [PMID: 31450747 PMCID: PMC6770463 DOI: 10.3390/cancers11091233] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 08/13/2019] [Accepted: 08/21/2019] [Indexed: 11/16/2022] Open
Abstract
Oncogenic metadherin is a key contributor to tumourigenesis with metadherin expression and cytoplasmic localisation previously linked to poor survival. A number of reports have shown metadherin localises specifically to nuclear speckles known to be rich in RNA-binding proteins including the splicing proteins YTHDC1, Sam68 and T-STAR, that have been shown to select alternative splice sites in mRNA of tumour-associated proteins including BRCA, MDM2 and VEGF. Here we investigate the interaction and relationship between metadherin and the splice factors YTHDC1, T-STAR and Sam68. Using a yeast two-hybrid assay and immunoprecipitation we show that metadherin interacts with YTHDC1, Sam68 and T-STAR and demonstrate that T-STAR is significantly overexpressed in prostate cancer tissue compared to benign prostate tissue. We also demonstrate that metadherin influences splice site selection in a dose-dependent manner in CD44v5-luc minigene reporter assays. Finally, we demonstrate that prostate cancer patients with higher metadherin expression have greater expression of the CD44v5 exon. CD44v5 expression could be used to discriminate patients with poor outcomes following radical prostatectomy. In this work we show for the first time that metadherin interacts with, and modulates, the function of key components of splicing associated with cancer development and progression.
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17
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Sawyer IA, Sturgill D, Dundr M. Membraneless nuclear organelles and the search for phases within phases. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 10:e1514. [DOI: 10.1002/wrna.1514] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 09/20/2018] [Accepted: 09/27/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Iain A. Sawyer
- Department of Cell Biology and Anatomy, Chicago Medical School Rosalind Franklin University of Medicine and Science North Chicago Illinois
- Laboratory of Receptor Biology and Gene Expression National Cancer Institute, National Institutes of Health Bethesda Maryland
| | - David Sturgill
- Laboratory of Receptor Biology and Gene Expression National Cancer Institute, National Institutes of Health Bethesda Maryland
| | - Miroslav Dundr
- Department of Cell Biology and Anatomy, Chicago Medical School Rosalind Franklin University of Medicine and Science North Chicago Illinois
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18
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Dumbović G, Biayna J, Banús J, Samuelsson J, Roth A, Diederichs S, Alonso S, Buschbeck M, Perucho M, Forcales SV. A novel long non-coding RNA from NBL2 pericentromeric macrosatellite forms a perinucleolar aggregate structure in colon cancer. Nucleic Acids Res 2018; 46:5504-5524. [PMID: 29912433 PMCID: PMC6009586 DOI: 10.1093/nar/gky263] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 03/19/2018] [Accepted: 04/03/2018] [Indexed: 12/22/2022] Open
Abstract
Primate-specific NBL2 macrosatellite is hypomethylated in several types of tumors, yet the consequences of this DNA hypomethylation remain unknown. We show that NBL2 conserved repeats are close to the centromeres of most acrocentric chromosomes. NBL2 associates with the perinucleolar region and undergoes severe demethylation in a subset of colorectal cancer (CRC). Upon DNA hypomethylation and histone acetylation, NBL2 repeats are transcribed in tumor cell lines and primary CRCs. NBL2 monomers exhibit promoter activity, and are contained within novel, non-polyA antisense lncRNAs, which we designated TNBL (Tumor-associated NBL2 transcript). TNBL is stable throughout the mitotic cycle, and in interphase nuclei preferentially forms a perinucleolar aggregate in the proximity of a subset of NBL2 loci. TNBL aggregates interact with the SAM68 perinucleolar body in a mirror-image cancer specific perinucleolar structure. TNBL binds with high affinity to several proteins involved in nuclear functions and RNA metabolism, such as CELF1 and NPM1. Our data unveil novel DNA and RNA structural features of a non-coding macrosatellite frequently altered in cancer.
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Affiliation(s)
- Gabrijela Dumbović
- Program of Predictive and Personalized Medicine of Cancer (PMPPC), Germans Trias i Pujol Research Institute (IGTP), Can Ruti Campus, Ctra Can Ruti, camí de les escoles s/n, Badalona, Barcelona 08916, Spain
| | - Josep Biayna
- Program of Predictive and Personalized Medicine of Cancer (PMPPC), Germans Trias i Pujol Research Institute (IGTP), Can Ruti Campus, Ctra Can Ruti, camí de les escoles s/n, Badalona, Barcelona 08916, Spain
- Institute for Research in Biomedicine (IRB Barcelona), Parc Científic de Barcelona, Carrer de Baldiri Reixac, 10–12, Barcelona 08028, Spain
| | - Jordi Banús
- Program of Predictive and Personalized Medicine of Cancer (PMPPC), Germans Trias i Pujol Research Institute (IGTP), Can Ruti Campus, Ctra Can Ruti, camí de les escoles s/n, Badalona, Barcelona 08916, Spain
| | | | - Anna Roth
- Division of RNA Biology & Cancer, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany
| | - Sven Diederichs
- Division of RNA Biology & Cancer, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany
- Division of Cancer Research, Dept. of Thoracic Surgery, Medical Center – University of Freiburg & Faculty of Medicine, University of Freiburg & German Cancer Consortium (DKTK), Freiburg, Germany
| | - Sergio Alonso
- Program of Predictive and Personalized Medicine of Cancer (PMPPC), Germans Trias i Pujol Research Institute (IGTP), Can Ruti Campus, Ctra Can Ruti, camí de les escoles s/n, Badalona, Barcelona 08916, Spain
| | - Marcus Buschbeck
- Program of Predictive and Personalized Medicine of Cancer (PMPPC), Germans Trias i Pujol Research Institute (IGTP), Can Ruti Campus, Ctra Can Ruti, camí de les escoles s/n, Badalona, Barcelona 08916, Spain
- Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Badalona, Barcelona 08916, Spain
| | - Manuel Perucho
- Program of Predictive and Personalized Medicine of Cancer (PMPPC), Germans Trias i Pujol Research Institute (IGTP), Can Ruti Campus, Ctra Can Ruti, camí de les escoles s/n, Badalona, Barcelona 08916, Spain
- Sanford-Burnham-Prebys Medical Discovery Institute (SBP), 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Sonia-V Forcales
- Program of Predictive and Personalized Medicine of Cancer (PMPPC), Germans Trias i Pujol Research Institute (IGTP), Can Ruti Campus, Ctra Can Ruti, camí de les escoles s/n, Badalona, Barcelona 08916, Spain
- Department of Pathology and Experimental Therapeutics, School of Medicine and Health Sciences, Campus of Bellvitge, University of Barcelona, Carrer de la Feixa Llarga, s/n, L’Hospitalet de Llobregat, Barcelona 08907, Spain
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19
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Goel RK, Paczkowska M, Reimand J, Napper S, Lukong KE. Phosphoproteomics Analysis Identifies Novel Candidate Substrates of the Nonreceptor Tyrosine Kinase, Src- related Kinase Lacking C-terminal Regulatory Tyrosine and N-terminal Myristoylation Sites (SRMS). Mol Cell Proteomics 2018; 17:925-947. [PMID: 29496907 DOI: 10.1074/mcp.ra118.000643] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Indexed: 01/23/2023] Open
Abstract
SRMS (Src-related kinase lacking C-terminal regulatory tyrosine and N-terminal myristoylation sites), also known as PTK 70 (Protein tyrosine kinase 70), is a non-receptor tyrosine kinase that belongs to the BRK family of kinases (BFKs). To date less is known about the cellular role of SRMS primarily because of the unidentified substrates or signaling intermediates regulated by the kinase. In this study, we used phosphotyrosine antibody-based immunoaffinity purification in large-scale label-free quantitative phosphoproteomics to identify novel candidate substrates of SRMS. Our analyses led to the identification of 1258 tyrosine-phosphorylated peptides which mapped to 663 phosphoproteins, exclusively from SRMS-expressing cells. DOK1, a previously characterized SRMS substrate, was also identified in our analyses. Functional enrichment analyses revealed that the candidate SRMS substrates were enriched in various biological processes including protein ubiquitination, mitotic cell cycle, energy metabolism and RNA processing, as well as Wnt and TNF signaling. Analyses of the sequence surrounding the phospho-sites in these proteins revealed novel candidate SRMS consensus substrate motifs. We utilized customized high-throughput peptide arrays to validate a subset of the candidate SRMS substrates identified in our MS-based analyses. Finally, we independently validated Vimentin and Sam68, as bona fide SRMS substrates through in vitro and in vivo assays. Overall, our study identified a number of novel and biologically relevant SRMS candidate substrates, which suggests the involvement of the kinase in a vast array of unexplored cellular functions.
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Affiliation(s)
- Raghuveera Kumar Goel
- From the ‡Department of Biochemistry, College of Medicine, 107 Wiggins Road, University of Saskatchewan, Saskatoon S7N 5E5, Saskatchewan, Canada
| | - Marta Paczkowska
- §Computational Biology Program, Ontario Institute for Cancer Research, 661 University Ave Suite 510, Toronto M5G 0A3, Ontario, Canada
| | - Jüri Reimand
- §Computational Biology Program, Ontario Institute for Cancer Research, 661 University Ave Suite 510, Toronto M5G 0A3, Ontario, Canada.,¶Department of Medical Biophysics, University of Toronto, 101 College Street Suite 15-701, Toronto M5G 1L7, Ontario, Canada
| | - Scott Napper
- From the ‡Department of Biochemistry, College of Medicine, 107 Wiggins Road, University of Saskatchewan, Saskatoon S7N 5E5, Saskatchewan, Canada.,‖Vaccine and Infectious Disease Organization - International Vaccine Centre (VIDO-InterVac), 120 Veterinary Road, University of Saskatchewan, Saskatoon S7N 5E3, Saskatchewan, Canada
| | - Kiven Erique Lukong
- From the ‡Department of Biochemistry, College of Medicine, 107 Wiggins Road, University of Saskatchewan, Saskatoon S7N 5E5, Saskatchewan, Canada;
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20
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Chapat C, Chettab K, Simonet P, Wang P, De La Grange P, Le Romancer M, Corbo L. Alternative splicing of CNOT7 diversifies CCR4-NOT functions. Nucleic Acids Res 2017; 45:8508-8523. [PMID: 28591869 PMCID: PMC5737658 DOI: 10.1093/nar/gkx506] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 05/26/2017] [Indexed: 12/11/2022] Open
Abstract
The CCR4-associated factor CAF1, also called CNOT7, is a catalytic subunit of the CCR4–NOT complex, which has been implicated in all aspects of the mRNA life cycle, from mRNA synthesis in the nucleus to degradation in the cytoplasm. In human cells, alternative splicing of the CNOT7 gene yields a second CNOT7 transcript leading to the formation of a shorter protein, CNOT7 variant 2 (CNOT7v2). Biochemical characterization indicates that CNOT7v2 interacts with CCR4–NOT subunits, although it does not bind to BTG proteins. We report that CNOT7v2 displays a distinct expression profile in human tissues, as well as a nuclear sub-cellular localization compared to CNOT7v1. Despite a conserved DEDD nuclease domain, CNOT7v2 is unable to degrade a poly(A) tail in vitro and preferentially associates with the protein arginine methyltransferase PRMT1 to regulate its activity. Using both in vitro and in cellulo systems, we have also demonstrated that CNOT7v2 regulates the inclusion of CD44 variable exons. Altogether, our findings suggest a preferential involvement of CNOT7v2 in nuclear processes, such as arginine methylation and alternative splicing, rather than mRNA turnover. These observations illustrate how the integration of a splicing variant inside CCR4–NOT can diversify its cell- and tissue-specific functions.
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Affiliation(s)
- Clément Chapat
- Univ. Lyon, Université Lyon 1, Inserm U1052, CNRS UMR5286, Centre Léon Bérard, Centre de Recherche en Cancérologie de Lyon, Lyon 69008, France
| | - Kamel Chettab
- Univ. Lyon, Université Lyon 1, Inserm U1052, CNRS UMR5286, Centre Léon Bérard, Centre de Recherche en Cancérologie de Lyon, Lyon 69008, France
| | - Pierre Simonet
- Univ. Lyon, Université Lyon 1, Inserm U1052, CNRS UMR5286, Centre Léon Bérard, Centre de Recherche en Cancérologie de Lyon, Lyon 69008, France
| | - Peng Wang
- McGill University, Department of Biochemistry, 1160 Pine Avenue West, Montreal, QC H3A 1A3, Canada
| | | | - Muriel Le Romancer
- Univ. Lyon, Université Lyon 1, Inserm U1052, CNRS UMR5286, Centre Léon Bérard, Centre de Recherche en Cancérologie de Lyon, Lyon 69008, France
| | - Laura Corbo
- Univ. Lyon, Université Lyon 1, Inserm U1052, CNRS UMR5286, Centre Léon Bérard, Centre de Recherche en Cancérologie de Lyon, Lyon 69008, France
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21
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Wen H, Li P, Ma H, Zheng J, Yu Y, Lv G. High expression of Sam68 in sacral chordomas is associated with worse clinical outcomes. Onco Targets Ther 2017; 10:4691-4700. [PMID: 29026317 PMCID: PMC5626414 DOI: 10.2147/ott.s147446] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Src-associated in mitosis of 68 kDa (Sam68), also known as KHDRBS1 (KH domain-containing, RNA-binding, signal transduction-associated 1), is a member of the signal transduction and activation of RNA family. Previous studies have demonstrated that the aberrant expression of Sam68 is associated with the progression and prognosis of a variety of cancers, but little is known about its expression and role in chordomas, which are rare and aggressive bone neoplasms. In this study, we analyzed 40 tumor tissues and 20 distant normal tissues obtained from 40 patients with sacral chordoma using immunohistochemistry, and observed the expression of Sam68 was significantly upregulated in sacral chordomas compared with normal tissues (P=0.001). A positive correlation between the expression of Sam68 and the cell proliferation index Ki-67 was determined using Spearman’s rank correlation test (γ =0.599, P<0.001). In addition, high expression of Sam68 was significantly associated with surrounding muscle invasion (P<0.001). Moreover, Kaplan–Meier curves showed that patients with overexpressed Sam68 had shorter local recurrence-free survival time (P<0.001). Lastly, multivariate analysis indicated that Sam68 is an independent prognostic factor for the local recurrence-free survival of sacral chordomas (hazard ratio =5.929, 95% CI: 1.092–32.188, P=0.039). Our findings suggest the use of Sam68 as a predictor for the recurrence of sacral chordomas.
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Affiliation(s)
- Hai Wen
- Department of Spine Surgery, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
| | - Pengzhi Li
- Department of Spine Surgery, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
| | - Hong Ma
- Department of Spine Surgery, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
| | - Jiaoyun Zheng
- Department of Pathology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
| | - Yipin Yu
- Department of Spine Surgery, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
| | - Guohua Lv
- Department of Spine Surgery, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
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22
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Gueroussov S, Weatheritt RJ, O’Hanlon D, Lin ZY, Narula A, Gingras AC, Blencowe BJ. Regulatory Expansion in Mammals of Multivalent hnRNP Assemblies that Globally Control Alternative Splicing. Cell 2017; 170:324-339.e23. [DOI: 10.1016/j.cell.2017.06.037] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 02/24/2017] [Accepted: 06/23/2017] [Indexed: 10/19/2022]
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23
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Mannen T, Yamashita S, Tomita K, Goshima N, Hirose T. The Sam68 nuclear body is composed of two RNase-sensitive substructures joined by the adaptor HNRNPL. J Cell Biol 2017; 214:45-59. [PMID: 27377249 PMCID: PMC4932371 DOI: 10.1083/jcb.201601024] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 06/14/2016] [Indexed: 01/21/2023] Open
Abstract
The mammalian cell nucleus contains membraneless suborganelles referred to as nuclear bodies (NBs). Some NBs are formed with an architectural RNA (arcRNA) as the structural core. Here, we searched for new NBs that are built on unidentified arcRNAs by screening for ribonuclease (RNase)-sensitive NBs using 32,651 fluorescently tagged human cDNA clones. We identified 32 tagged proteins that required RNA for their localization in distinct nuclear foci. Among them, seven RNA-binding proteins commonly localized in the Sam68 nuclear body (SNB), which was disrupted by RNase treatment. Knockdown of each SNB protein revealed that SNBs are composed of two distinct RNase-sensitive substructures. One substructure is present as a distinct NB, termed the DBC1 body, in certain conditions, and the more dynamic substructure including Sam68 joins to form the intact SNB. HNRNPL acts as the adaptor to combine the two substructures and form the intact SNB through the interaction of two sets of RNA recognition motifs with the putative arcRNAs in the respective substructures.
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Affiliation(s)
- Taro Mannen
- Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan
| | - Seisuke Yamashita
- Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8562, Japan
| | - Kozo Tomita
- Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8562, Japan
| | - Naoki Goshima
- Molecular Profiling Research Center for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Koutou 135-0064, Japan
| | - Tetsuro Hirose
- Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan
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Protein intrinsic disorder-based liquid-liquid phase transitions in biological systems: Complex coacervates and membrane-less organelles. Adv Colloid Interface Sci 2017; 239:97-114. [PMID: 27291647 DOI: 10.1016/j.cis.2016.05.012] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Accepted: 05/24/2016] [Indexed: 12/18/2022]
Abstract
It is clear now that eukaryotic cells contain numerous membrane-less organelles, many of which are formed in response to changes in the cellular environment. Being typically liquid in nature, many of these organelles can be described as products of the reversible and highly controlled liquid-liquid phase transitions in biological systems. Many of these membrane-less organelles are complex coacervates containing (almost invariantly) intrinsically disordered proteins and often nucleic acids. It seems that the lack of stable structure in major proteinaceous constituents of these organelles is crucial for the formation of phase-separated droplets. This review considers several biologically relevant liquid-liquid phase transitions, introduces some general features attributed to intrinsically disordered proteins, represents several illustrative examples of intrinsic disorder-based phase separation, and provides some reasons for the abundance of intrinsically disordered proteins in organelles formed as a result of biological liquid-liquid phase transitions.
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Wang Y, Zhang W, Wang X, Wang D, Xie J, Tang C, Xi Q, Zhong J, Deng Y. Expression of Sam68 Correlates With Cell Proliferation and Survival in Epithelial Ovarian Cancer. Reprod Sci 2016; 24:97-108. [PMID: 27222230 DOI: 10.1177/1933719116650757] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Src associated in mitosis, 68 kDa (Sam68) is a KH domain RNA-binding protein that belongs to the signal transduction and activation of RNA family. It is a multifunctional protein known to regulate cellular signal transduction, transcription, RNA metabolism, proliferation, and apoptosis, thus implicated in tumor growth. Herein, we investigated the clinical significance of Sam68 in human epithelial ovarian cancer (EOC). Western blot and immunohistochemical staining demonstrated that Sam68 expression was upregulated in EOC tissues and cell lines. Statistical analysis showed that high expression of Sam68 correlated with poor prognosis of patients with EOC. In vitro, serum starvation-refeeding experiment was primarily performed to confirm that Sam68 participated in the cell cycle progression of EOC cell lines. Then knocking down Sam68 level with small interfering RNA, cell cycle was arrested at G1 phase and cell proliferation impaired. Furthermore, we demonstrated that the antiproliferative effect of silencing Sam68 in EOC cells was associated with the upregulation of cyclin-dependent kinase inhibitors p21Cip1 and p27Kip1, along with the downregulation of p-FOXO3a, p-Akt, and p-GSK-3β. Taken together, our findings uncovered that Sam68 played an important role in promoting the proliferation of human ovarian cancer, thereby might be a novel therapeutic target for EOC.
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Affiliation(s)
- Yingying Wang
- 1 Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Department of Pathogen Biology, Medical College, Nantong University, Nantong, People's Republic of China
| | - Weiwei Zhang
- 2 Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, People's Republic of China
| | - Xia Wang
- 3 Center for Reproductive Medicine, Affiliated Hospital of Nantong University, Nantong, People's Republic of China
| | - Di Wang
- 3 Center for Reproductive Medicine, Affiliated Hospital of Nantong University, Nantong, People's Republic of China
| | - Juan Xie
- 3 Center for Reproductive Medicine, Affiliated Hospital of Nantong University, Nantong, People's Republic of China
| | - Chunhui Tang
- 2 Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, People's Republic of China
| | - Qinghua Xi
- 2 Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, People's Republic of China
| | - Jianxin Zhong
- 2 Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, People's Republic of China
| | - Yan Deng
- 2 Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, People's Republic of China
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Zhang H, Chen N, Li P, Pan Z, Ding Y, Zou D, Li L, Xiao L, Shen B, Liu S, Cao H, Cui Y. The nuclear protein Sam68 is recruited to the cytoplasmic stress granules during enterovirus 71 infection. Microb Pathog 2016; 96:58-66. [PMID: 27057671 DOI: 10.1016/j.micpath.2016.04.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 04/01/2016] [Indexed: 10/22/2022]
Abstract
Our previous study found that the nuclear protein, 68-kDa Src-associated in mitosis protein (Sam68), is translocated to the cytoplasm and forms punctate pattern during enterovirus 71 (EV71) infection [Virus Research, 180 (2014), 1-11]. However, the exact function of this punctate pattern in cytoplasm during EV71 infection remains unknown. In this study, we firstly have examined this punctate pattern of Sam68 re-localization in the cytoplasm, and observed the obvious recruitments of Sam68 to the EV71-induced stress granules (SGs). Sam68, belongs to the KH domain family of RNA binding proteins (RBPs), was then confirmed that its KH domain was essential for this recruitment. Nevertheless, Knockdown of Sam68 expression using ShRNA had no effects on SGs assembly, indicating that Sam68 is not a constitutive component of the SGs during EV71 infection. Lastly, we investigated the importance of microtubulin transport to SGs aggregation, and revealed that microtubule depolymerization inhibited SGs formation, suggesting that EV71-induced SGs move throughout the cytoplasm in a microtubule-dependent manner. Taken together, these results illuminated that EV71 infections can induce SGs formation, and Sam68, as a SGs component, migrates alone with SGs dependent on intact microtubule upon the viral infections. These findings may provide novel underlying mechanism for delineating the role of SGs during EV71 infection.
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Affiliation(s)
- Hua Zhang
- College of Animal Science and Veterinary Medicine, HeiLongJiang BaYi Agricultural University, Daqing 163319, China; College of Life Science and Technology, HeiLongJiang BaYi Agricultural University, Daqing 163319, China
| | - Ning Chen
- College of Life Science and Technology, HeiLongJiang BaYi Agricultural University, Daqing 163319, China
| | - Pengfei Li
- Department of Nephrology, The Fifth Affiliated Hospital of Harbin Medical University, Daqing 163319, China
| | - Ziye Pan
- College of Life Science and Technology, HeiLongJiang BaYi Agricultural University, Daqing 163319, China
| | - Yun Ding
- College of Life Science and Technology, HeiLongJiang BaYi Agricultural University, Daqing 163319, China
| | - Dehua Zou
- College of Life Science and Technology, HeiLongJiang BaYi Agricultural University, Daqing 163319, China
| | - Liyang Li
- College of Life Science and Technology, HeiLongJiang BaYi Agricultural University, Daqing 163319, China
| | - Lijie Xiao
- College of Life Science and Technology, HeiLongJiang BaYi Agricultural University, Daqing 163319, China
| | - Binglei Shen
- College of Animal Science and Veterinary Medicine, HeiLongJiang BaYi Agricultural University, Daqing 163319, China
| | - Shuxia Liu
- Daqing Branch of HeiLongJiang Academy of Sciences, Daqing 163319, China
| | - Hongwei Cao
- College of Animal Science and Veterinary Medicine, HeiLongJiang BaYi Agricultural University, Daqing 163319, China; College of Life Science and Technology, HeiLongJiang BaYi Agricultural University, Daqing 163319, China.
| | - Yudong Cui
- College of Animal Science and Veterinary Medicine, HeiLongJiang BaYi Agricultural University, Daqing 163319, China; College of Life Science and Technology, HeiLongJiang BaYi Agricultural University, Daqing 163319, China.
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27
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Even Y, Escande ML, Fayet C, Genevière AM. CDK13, a Kinase Involved in Pre-mRNA Splicing, Is a Component of the Perinucleolar Compartment. PLoS One 2016; 11:e0149184. [PMID: 26886422 PMCID: PMC4757566 DOI: 10.1371/journal.pone.0149184] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 01/07/2016] [Indexed: 02/07/2023] Open
Abstract
The perinucleolar compartment (PNC) is a subnuclear stucture forming predominantly in cancer cells; its prevalence positively correlates with metastatic capacity. Although several RNA-binding proteins have been characterized in PNC, the molecular function of this compartment remains unclear. Here we demonstrate that the cyclin-dependent kinase 13 (CDK13) is a newly identified constituent of PNC. CDK13 is a kinase involved in the regulation of gene expression and whose overexpression was found to alter pre-mRNA processing. In this study we show that CDK13 is enriched in PNC and co-localizes all along the cell cycle with the PNC component PTB. In contrast, neither the cyclins K and L, known to associate with CDK13, nor the potential kinase substrates accumulate in PNC. We further show that CDK13 overexpression increases PNC prevalence suggesting that CDK13 may be determinant for PNC formation. This result linked to the finding that CDK13 gene is amplified in different types of cancer indicate that this kinase can contribute to cancer development in human.
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Affiliation(s)
- Yasmine Even
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, F-66650, Banyuls/Mer, France
| | - Marie-Line Escande
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, F-66650, Banyuls/Mer, France
| | - Claire Fayet
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, F-66650, Banyuls/Mer, France
| | - Anne-Marie Genevière
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, F-66650, Banyuls/Mer, France
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Feracci M, Foot JN, Grellscheid SN, Danilenko M, Stehle R, Gonchar O, Kang HS, Dalgliesh C, Meyer NH, Liu Y, Lahat A, Sattler M, Eperon IC, Elliott DJ, Dominguez C. Structural basis of RNA recognition and dimerization by the STAR proteins T-STAR and Sam68. Nat Commun 2016; 7:10355. [PMID: 26758068 PMCID: PMC4735526 DOI: 10.1038/ncomms10355] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 12/01/2015] [Indexed: 11/13/2022] Open
Abstract
Sam68 and T-STAR are members of the STAR family of proteins that directly link signal transduction with post-transcriptional gene regulation. Sam68 controls the alternative splicing of many oncogenic proteins. T-STAR is a tissue-specific paralogue that regulates the alternative splicing of neuronal pre-mRNAs. STAR proteins differ from most splicing factors, in that they contain a single RNA-binding domain. Their specificity of RNA recognition is thought to arise from their property to homodimerize, but how dimerization influences their function remains unknown. Here, we establish at atomic resolution how T-STAR and Sam68 bind to RNA, revealing an unexpected mode of dimerization different from other members of the STAR family. We further demonstrate that this unique dimerization interface is crucial for their biological activity in splicing regulation, and suggest that the increased RNA affinity through dimer formation is a crucial parameter enabling these proteins to select their functional targets within the transcriptome. Sam68 and T-STAR are members of the STAR family of proteins, which regulate various aspects of RNA metabolism. Here, the authors reveal structural features required for alternative splicing regulation by these proteins.
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Affiliation(s)
- Mikael Feracci
- Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 9HN, UK
| | - Jaelle N Foot
- Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 9HN, UK
| | - Sushma N Grellscheid
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle NE1 3BZ, UK
| | - Marina Danilenko
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle NE1 3BZ, UK
| | - Ralf Stehle
- Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, Lichtenbergstr. 4, DE-85747 Garching, Germany
| | - Oksana Gonchar
- Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 9HN, UK
| | - Hyun-Seo Kang
- Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, Lichtenbergstr. 4, DE-85747 Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, DE-85764 Oberschleißheim, Germany
| | - Caroline Dalgliesh
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle NE1 3BZ, UK
| | - N Helge Meyer
- Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, Lichtenbergstr. 4, DE-85747 Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, DE-85764 Oberschleißheim, Germany
| | - Yilei Liu
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle NE1 3BZ, UK
| | - Albert Lahat
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | - Michael Sattler
- Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, Lichtenbergstr. 4, DE-85747 Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, DE-85764 Oberschleißheim, Germany
| | - Ian C Eperon
- Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 9HN, UK
| | - David J Elliott
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle NE1 3BZ, UK
| | - Cyril Dominguez
- Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 9HN, UK
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29
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Bergeman J, Caillier A, Houle F, Gagné LM, Huot MÉ. Localized translation regulates cell adhesion and transendothelial migration. J Cell Sci 2016; 129:4105-4117. [DOI: 10.1242/jcs.191320] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 09/08/2016] [Indexed: 12/31/2022] Open
Abstract
By progressing through the epithelial to mesenchymal transition (EMT), cancer cells gain the ability to leave the primary tumor site and invade surrounding tissues. These metastatic cancers cells can further increase their plasticity by adopting an amoeboid-like morphology, by undergoing mesenchymal to amoeboid transition (MAT). We found that adhering cells producing spreading initiation centers (SIC), a transient structure localized above nascent adhesion complexes, share common biological and morphological characteristics associated with amoeboid cells. Meanwhile, spreading cells seem to return to a mesenchymal-like morphology. Thus, our results indicate that SIC-induced adhesion recapitulate events associated with amoeboid to mesenchymal transition (AMT). We found that polyadenylated RNAs were enriched within SIC and blocking their translation decreased adhesion potential of metastatic cells that progressed through EMT. These results point to a novel checkpoint regulating cell adhesion and allowing metastatic cells to alter adhesion strength in order to modulate their dissemination.
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Affiliation(s)
- Jonathan Bergeman
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada, G1R 3S3
| | - Alexia Caillier
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada, G1R 3S3
| | - François Houle
- CRCHU de Québec: Hôtel-Dieu de Québec; Québec, Canada, G1R 3S3
| | - Laurence M. Gagné
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada, G1R 3S3
| | - Marc-Étienne Huot
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada, G1R 3S3
- CRCHU de Québec: Hôtel-Dieu de Québec; Québec, Canada, G1R 3S3
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30
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The RNA-binding protein Sam68 regulates tumor cell viability and hepatic carcinogenesis by inhibiting the transcriptional activity of FOXOs. J Mol Histol 2015; 46:485-97. [PMID: 26438629 DOI: 10.1007/s10735-015-9639-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 09/30/2015] [Indexed: 12/31/2022]
Abstract
Src associated in mitosis (Sam68; 68 kDa) is a KH domain RNA-binding protein that belongs to the signal transduction and activation of RNA family, and has been implicated in the oncogenesis and progression of several human cancers. Our study aimed to investigated the clinicopathologic significance of Sam68 expression and its role in cell proliferation and the underlying molecular mechanism in hepatocellular carcinoma (HCC). We demonstrated that Sam68 expression was significantly increased in HCC and high expression of Sam68 was significantly associated with Edmondson grade, tumor size, tumor nodule number, HBsAg status and Ki-67 expression. The Kaplan-Meier survival curves showed that increased expression of Sam68 was correlated with poor prognosis in HCC patients and served as an independent prognostic marker of overall survival in a multivariable analysis. In addition, through serum starvation and refeeding assay, we demonstrated that Sam68 was lowly expressed in serum-starved HCC cells, and was progressively increased after serum-additioning. Furthermore, siRNA knockdown of endogenous Sam68 inhibited cell proliferation and tumourigenicity of HCC cells in vitro, through blocking the G1 to S phase transition. Moreover, we reported that the anti-proliferative effect of silencing Sam68 was accompanied with up-regulated expression of cyclin-dependent kinase inhibitors, p21(Cip1) and p27(Kip1), enhanced transactivation of FOXO factors (FOXO4), and dysreuglation of Akt/GSK-3β signaling. Taken together, these findings provide a rational framework for the progression of HCC and thereby indicated that Sam68 might be a novel and useful prognostic marker and a potential target for human HCC treatment.
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31
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Wang Y, Liang L, Zhang J, Li M, Zhu J, Gong C, Yang L, Zhu J, Chen L, Ni R. Sam68 promotes cellular proliferation and predicts poor prognosis in esophageal squamous cell carcinoma. Tumour Biol 2015; 36:8735-45. [PMID: 26050229 DOI: 10.1007/s13277-015-3631-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 05/31/2015] [Indexed: 12/14/2022] Open
Abstract
Sam68 (Src-associated in mitosis of 68 kD) is a KH domain RNA-binding protein. The expression of Sam68 was correlated with kinds of tumors. Yet, the expression mechanisms and physiological significance of Sam68 in ESCC remains unclear. In this study, we clarified a potential role of Sam68 in the treatment of ESCC. Western blot and immunohistochemistry (IHC) analysis revealed that the protein level of Sam68 was higher in ESCC tumor tissues and cell lines. In addition, IHC stain revealed that Sam68 was positively correlated with clinical pathologic variables such as tumor grade and tumor invasion. In addition, Sam68 could be an independent prognostic indicator for patients' overall survival. In vitro studies such as starvation and refeeding assay along with Sam68-shRNA transfection assay demonstrated that Sam68 expression promoted proliferation of ESCC cells. And Sam68 downregulation caused decreased rate of cell growth and colony formation. Reasons are associated with growth arrest of cell cycle at G1/S phase. Moreover, our results clarified that Sam68 could promote ESCC cell proliferation via the activation of Akt/GSK-3β pathway. This research indicated that Sam68 might accelerate the cell cycle progression and be considered as a new therapy target in ESCC.
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Affiliation(s)
- Yayun Wang
- Department of Gastroenterology, Affiliated Hospital of Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Li Liang
- Department of Medical Oncology, Affiliated Hospital of Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Jianguo Zhang
- Department of Pathology, Affiliated Hospital of Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Mei Li
- Department of Medical Oncology, Affiliated Hospital of Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Junya Zhu
- Department of Gastroenterology, Affiliated Hospital of Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Chen Gong
- Department of Gastroenterology, Affiliated Hospital of Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Linlin Yang
- Department of Oncology, Affiliated Cancer Hospital of Nantong University, Nantong, 226361, Jiangsu, China
| | - Jia Zhu
- Department of Oncology, Affiliated Cancer Hospital of Nantong University, Nantong, 226361, Jiangsu, China
| | - Lingling Chen
- Department of Gastroenterology, Affiliated Hospital of Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China
| | - Runzhou Ni
- Department of Gastroenterology, Affiliated Hospital of Nantong University, 19 Qixiu Road, Nantong, 226001, Jiangsu, China.
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32
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Tsui T, Miller WT. Cancer-Associated Mutations in Breast Tumor Kinase/PTK6 Differentially Affect Enzyme Activity and Substrate Recognition. Biochemistry 2015; 54:3173-82. [PMID: 25940761 DOI: 10.1021/acs.biochem.5b00303] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Brk (breast tumor kinase, also known as PTK6) is a nonreceptor tyrosine kinase that is aberrantly expressed in several cancers and promotes cell proliferation and transformation. Genome sequencing studies have revealed a number of cancer-associated somatic mutations in the Brk gene; however, their effect on Brk activity has not been examined. We analyzed a panel of cancer-associated mutations and determined that several of the mutations activate Brk, while two eliminated enzymatic activity. Three of the mutations (L16F, R131L, and P450L) are located in important regulatory domains of Brk (the SH3, SH2 domains, and C-terminal tail, respectively). Biochemical data suggest that they activate Brk by disrupting intramolecular interactions that normally maintain Brk in an autoinhibited conformation. We also observed differential effects on recognition and phosphorylation of substrates, suggesting that the mutations can influence downstream Brk signaling by multiple mechanisms.
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Affiliation(s)
- Tiffany Tsui
- Department of Physiology and Biophysics, School of Medicine, Stony Brook University, Stony Brook, New York 11794, United States
| | - W Todd Miller
- Department of Physiology and Biophysics, School of Medicine, Stony Brook University, Stony Brook, New York 11794, United States
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33
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Sam68 Regulates S6K1 Alternative Splicing during Adipogenesis. Mol Cell Biol 2015; 35:1926-39. [PMID: 25776557 DOI: 10.1128/mcb.01488-14] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 03/11/2015] [Indexed: 01/13/2023] Open
Abstract
The requirement for alternative splicing during adipogenesis is poorly understood. The Sam68 RNA binding protein is a known regulator of alternative splicing, and mice deficient for Sam68 exhibit adipogenesis defects due to defective mTOR signaling. Sam68 null preadipocytes were monitored for alternative splicing imbalances in components of the mTOR signaling pathway. Herein, we report that Sam68 regulates isoform expression of the ribosomal S6 kinase gene (Rps6kb1). Sam68-deficient adipocytes express Rps6kb1-002 and its encoded p31S6K1 protein, in contrast to wild-type adipocytes that do not express this isoform. Sam68 binds an RNA sequence encoded by Rps6kb1 intron 6 and prevents serine/arginine-rich splicing factor 1 (SRSF1)-mediated alternative splicing of Rps6kb1-002, as assessed by cross-linking and immunoprecipitation (CLIP) and minigene assays. Depletion of p31S6K1 with small interfering RNAs (siRNAs) partially restored adipogenesis of Sam68-deficient preadipocytes. The ectopic expression of p31S6K1 in wild-type 3T3-L1 cells resulted in adipogenesis differentiation defects, showing that p31S6K1 is an inhibitor of adipogenesis. Our findings indicate that Sam68 is required to prevent the expression of p31S6K1 in adipocytes for adipogenesis to occur.
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34
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Cho SJ, Choi MH, Nam SY, Kim JY, Kim CS, Pyo S, Yang KH. Sam68 is cleaved by caspases under apoptotic cell death induced by ionizing radiation. JOURNAL OF RADIATION RESEARCH 2015; 56:287-293. [PMID: 25666188 PMCID: PMC4380058 DOI: 10.1093/jrr/rru113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 11/02/2014] [Accepted: 11/05/2014] [Indexed: 06/04/2023]
Abstract
The RNA-binding protein Sam68, a mitotic substrate of tyrosine kinases, has been reported to participate in the cell cycle, apoptosis, and signaling. In particular, overexpression of Sam68 protein is known to suppress cell growth and cell cycle progression in NIH3T3 cells. Although Sam68 is involved in many cellular activities, the function of Sam68, especially in response to apoptotic stimulation, is not well understood. In this study, we found that Sam68 protein is cleaved in immune cells undergoing apoptosis induced by γ-radiation. Moreover, we found that Sam68 cleavage was induced by apoptotic stimuli containing γ-radiation in a caspase-dependent manner. In particular, we showed that activated casepase-3, 7, 8 and 9 can directly cleave Sam68 protein through in vitro protease cleavage assay. Finally, we found that the knockdown of Sam68 attenuated γ-radiation-induced cell death and growth suppression. Conclusively, the cleavage of Sam68 is a new indicator for the cell damaging effects of ionizing radiation.
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Affiliation(s)
- Seong-Jun Cho
- KHNP Radiation Health Institute, Korea Hydro & Nuclear Power Co. Ltd, Seoul, Korea
| | - Moo Hyun Choi
- KHNP Radiation Health Institute, Korea Hydro & Nuclear Power Co. Ltd, Seoul, Korea
| | - Seon Young Nam
- KHNP Radiation Health Institute, Korea Hydro & Nuclear Power Co. Ltd, Seoul, Korea
| | - Ji Young Kim
- KHNP Radiation Health Institute, Korea Hydro & Nuclear Power Co. Ltd, Seoul, Korea
| | - Cha Soon Kim
- KHNP Radiation Health Institute, Korea Hydro & Nuclear Power Co. Ltd, Seoul, Korea
| | - Suhkneung Pyo
- College of Pharmacy, Sungkyunkwan University, Suwon City, Kyunggi-do, Korea
| | - Kwang Hee Yang
- KHNP Radiation Health Institute, Korea Hydro & Nuclear Power Co. Ltd, Seoul, Korea
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35
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Souquere S, Weil D, Pierron G. Comparative ultrastructure of CRM1-Nucleolar bodies (CNoBs), Intranucleolar bodies (INBs) and hybrid PML/p62 bodies uncovers new facets of nuclear body dynamic and diversity. Nucleus 2015; 6:326-38. [PMID: 26275159 PMCID: PMC4615761 DOI: 10.1080/19491034.2015.1082695] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 08/07/2015] [Accepted: 08/10/2015] [Indexed: 12/24/2022] Open
Abstract
In order to gain insights on the nuclear organization in mammalian cells, we characterized ultrastructurally nuclear bodies (NBs) previously described as fluorescent foci. Using high resolution immunoelectron microscopy (I-EM), we provide evidence that CNoBs (CRM1-Nucleolar bodies) and INBs (Intranucleolar bodies) are distinct genuine nucleolar structures in untreated HeLa cells. INBs are fibrillar and concentrate the post-translational modifiers SUMO1 and SUMO-2/3 as strongly as PML bodies. In contrast, the smallest CRM1-labeled CNoBs are vitreous, preferentially located at the periphery of the nucleolus and, intricately linked to the chromatin network. Upon blockage of the CRM1-dependent nuclear export by leptomycin B (LMB), CNoBs disappear while p62/SQSTM1-containing fibrillar nuclear bodies are induced. These p62 bodies are enriched in ubiquitinated proteins. They progressively associate with PML bodies to form hybrid bodies of which PML decorates the periphery while p62/SQSTM1 is centrally-located. Our study is expanding the repertoire of nuclear bodies; revealing a previously unrecognized composite nucleolar landscape and a new mode of interactions between ubiquitous (PML) and stress-induced (p62) nuclear bodies, resulting in the formation of hybrid bodies.
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Affiliation(s)
- Sylvie Souquere
- Functional Organization of the Cell; CNRS UMR-9196; Institut Gustave Roussy; Villejuif, France
| | - Dominique Weil
- UPMC Univ Paris 06; Institut de Biologie Paris-Seine (IBPS); CNRS UMR-7622; Paris, France
| | - Gérard Pierron
- Functional Organization of the Cell; CNRS UMR-9196; Institut Gustave Roussy; Villejuif, France
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Mahboubi H, Stochaj U. Nucleoli and Stress Granules: Connecting Distant Relatives. Traffic 2014; 15:1179-93. [DOI: 10.1111/tra.12191] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 06/30/2014] [Accepted: 06/30/2014] [Indexed: 12/19/2022]
Affiliation(s)
- Hicham Mahboubi
- Department of Physiology; McGill University; 3655 Promenade Sir William Osler Montreal Quebec H3G 1Y6 Canada
| | - Ursula Stochaj
- Department of Physiology; McGill University; 3655 Promenade Sir William Osler Montreal Quebec H3G 1Y6 Canada
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Miah S, Goel RK, Dai C, Kalra N, Beaton-Brown E, Bagu ET, Bonham K, Lukong KE. BRK targets Dok1 for ubiquitin-mediated proteasomal degradation to promote cell proliferation and migration. PLoS One 2014; 9:e87684. [PMID: 24523872 PMCID: PMC3921129 DOI: 10.1371/journal.pone.0087684] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 01/02/2014] [Indexed: 12/13/2022] Open
Abstract
Breast tumor kinase (BRK), also known as protein tyrosine kinase 6 (PTK6), is a non-receptor tyrosine kinase overexpressed in more that 60% of human breast carcinomas. The overexpression of BRK has been shown to sensitize mammary epithelial cells to mitogenic signaling and to promote cell proliferation and tumor formation. The molecular mechanisms of BRK have been unveiled by the identification and characterization of BRK target proteins. Downstream of tyrosine kinases 1 or Dok1 is a scaffolding protein and a substrate of several tyrosine kinases. Herein we show that BRK interacts with and phosphorylates Dok1 specifically on Y362. We demonstrate that this phosphorylation by BRK significantly downregulates Dok1 in a ubiquitin-proteasome-mediated mechanism. Together, these results suggest a novel mechanism of action of BRK in the promotion of tumor formation, which involves the targeting of tumor suppressor Dok1 for degradation through the ubiquitin proteasomal pathway.
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Affiliation(s)
- Sayem Miah
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Raghuveera Kumar Goel
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Chenlu Dai
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Natasha Kalra
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Erika Beaton-Brown
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- Cancer Research Unit, Health Research Division, Saskatchewan Cancer Agency, and Division of Oncology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Edward T. Bagu
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- Cancer Research Unit, Health Research Division, Saskatchewan Cancer Agency, and Division of Oncology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Keith Bonham
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- Cancer Research Unit, Health Research Division, Saskatchewan Cancer Agency, and Division of Oncology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Kiven E. Lukong
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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Abstract
The principles that determine the organization of the nucleus have become clearer in recent years, largely because of new insights into polymer, colloid, and soft-matter science. Macromolecules, together with the giant linear polymers that form the chromosomes, are confined at high concentrations within the nuclear envelope and their interactions are influenced strongly by short-range depletion or entropic forces which are negligible in dilute systems, in addition to the more familiar van der Waals, electrostatic, steric, hydrogen bonding, and hydrophobic forces. The studies described in this volume are consistent with the model that this complex and concentrated mixture of macromolecules is maintained in a delicate equilibrium by quite simple although unsuspected physicochemical principles. The sensitivity of this equilibrium to perturbation may underlie the controversies about the existence of a nuclear matrix or scaffold. In this volume, we underline the importance for cell biologists of being familiar with current work in colloid, polymer, soft matter, and nanoscience. This chapter presents a brief background to the aspects of the nucleus that are considered in detail in subsequent chapters.
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Affiliation(s)
- Ronald Hancock
- Laval University Cancer Research Centre, CRCHUQ-Oncology, Québec, Canada; Biosystems Group, Biotechnology Centre, Silesian University of Technology, Gliwice, Poland.
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Fu K, Sun X, Zheng W, Wier EM, Hodgson A, Tran DQ, Richard S, Wan F. Sam68 modulates the promoter specificity of NF-κB and mediates expression of CD25 in activated T cells. Nat Commun 2013; 4:1909. [PMID: 23715268 PMCID: PMC3684077 DOI: 10.1038/ncomms2916] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 04/19/2013] [Indexed: 12/23/2022] Open
Abstract
CD25, the alpha chain of the interleukin-2 receptor, is expressed in activated T cells and has a significant role in autoimmune disease and tumorigenesis; however, the mechanisms regulating transcription of CD25 remain elusive. Here we identify the Src-associated substrate during mitosis of 68 kDa (Sam68) as a novel non-Rel component in the nuclear factor-kappaB (NF-κB) complex that confers CD25 transcription. Our results demonstrate that Sam68 has an essential role in the induction and maintenance of CD25 in T cells. T-cell receptor engagement triggers translocation of the inhibitor of NF-κB kinase alpha (IKKα) from the cytoplasm to the nucleus, where it phosphorylates Sam68, causing complex formation with NF-κB in the nucleus. These findings reveal the important roles of KH domain-containing components and their spatial interactions with IKKs in determining the binding targets of NF-κB complexes, thus shedding novel insights into the regulatory specificity of NF-κB.
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Affiliation(s)
- Kai Fu
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21025, USA
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40
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Sánchez-Jiménez F, Sánchez-Margalet V. Role of Sam68 in post-transcriptional gene regulation. Int J Mol Sci 2013; 14:23402-19. [PMID: 24287914 PMCID: PMC3876053 DOI: 10.3390/ijms141223402] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 11/11/2013] [Accepted: 11/13/2013] [Indexed: 01/10/2023] Open
Abstract
The STAR family of proteins links signaling pathways to various aspects of post-transcriptional regulation and processing of RNAs. Sam68 belongs to this class of heteronuclear ribonucleoprotein particle K (hnRNP K) homology (KH) single domain-containing family of RNA-binding proteins that also contains some domains predicted to bind critical components in signal transduction pathways. In response to phosphorylation and other post-transcriptional modifications, Sam68 has been shown to have the ability to link signal transduction pathways to downstream effects regulating RNA metabolism, including transcription, alternative splicing or RNA transport. In addition to its function as a docking protein in some signaling pathways, this prototypic STAR protein has been identified to have a nuclear localization and to take part in the formation of both nuclear and cytosolic multi-molecular complexes such as Sam68 nuclear bodies and stress granules. Coupling with other proteins and RNA targets, Sam68 may play a role in the regulation of differential expression and mRNA processing and translation according to internal and external signals, thus mediating important physiological functions, such as cell death, proliferation or cell differentiation.
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Affiliation(s)
- Flora Sánchez-Jiménez
- Department of Medical Biochemistry and Molecular Biology and Immunology, UGC Clinical Biochemistry, Virgen Macarena University Hospital, Avenue. Sánchez Pizjuan 4, Medical School, University of Seville, Seville 41009, Spain.
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41
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Goel RK, Miah S, Black K, Kalra N, Dai C, Lukong KE. The unique N-terminal region of SRMS regulates enzymatic activity and phosphorylation of its novel substrate docking protein 1. FEBS J 2013; 280:4539-59. [PMID: 23822091 DOI: 10.1111/febs.12420] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 06/20/2013] [Accepted: 06/25/2013] [Indexed: 01/07/2023]
Abstract
SRMS (Src-related tyrosine kinase lacking C-terminal regulatory tyrosine and N-terminal myristoylation sites) belongs to a family of nonreceptor tyrosine kinases, which also includes breast tumour kinase and Fyn-related kinase. SRMS, similar to breast tumour kinase and Fyn-related kinase, harbours a Src homology 3 and Src homology 2, as well as a protein kinase domain. However, unlike breast tumour kinase and Fyn-related kinase, SRMS lacks a C-terminal regulatory tail but distinctively possesses an extended N-terminal region. Both breast tumour kinase and Fyn-related kinase play opposing roles in cell proliferation and signalling. SRMS, however, is an understudied member of this family. Although cloned in 1994, information on the biochemical, cellular and physiological roles of SRMS remains unreported. The present study is the first to explore the expression pattern of SRMS in breast cancers, its enzymatic activity and autoregulatory elements, and the characterization of docking protein 1 as its first bonafide substrate. We found that, similar to breast tumour kinase, SRMS is highly expressed in most breast cancers compared to normal mammary cell lines and tissues. We generated a series of SRMS point and deletion mutants and assessed enzymatic activity, subcellular localization and substrate recognition. We report for the first time that ectopically-expressed SRMS is constitutively active and that its N-terminal region regulates the enzymatic activity of the protein. Finally, we present evidence indicating that docking protein 1 is a direct substrate of SRMS. Our data demonstrate that, unlike members of the Src family, the enzymatic activity of SRMS is regulated by the intramolecular interactions involving the N-terminus of the enzyme and that docking protein 1 is a bona fide substrate of SRMS.
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Affiliation(s)
- Raghuveera K Goel
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Saskatoon, Canada
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Liao WT, Liu JL, Wang ZG, Cui YM, Shi L, Li TT, Zhao XH, Chen XT, Ding YQ, Song LB. High expression level and nuclear localization of Sam68 are associated with progression and poor prognosis in colorectal cancer. BMC Gastroenterol 2013; 13:126. [PMID: 23937454 PMCID: PMC3751151 DOI: 10.1186/1471-230x-13-126] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Accepted: 08/02/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Src-associated in mitosis (Sam68; 68 kDa) has been implicated in the oncogenesis and progression of several human cancers. The aim of this study was to investigate the clinicopathologic significance of Sam68 expression and its subcellular localization in colorectal cancer (CRC). METHODS Sam68 expression was examined in CRC cell lines, nine matched CRC tissues and adjacent noncancerous tissues using reverse transcription (RT)-PCR, quantitative RT-PCR and Western blotting. Sam68 protein expression and localization were determined in 224 paraffin-embedded archived CRC samples using immunohistochemistry. Statistical analyses were applied to evaluate the clinicopathologic significance. RESULTS Sam68 was upregulated in CRC cell lines and CRC, as compared with normal tissues; high Sam68 expression was detected in 120/224 (53.6%) of the CRC tissues. High Sam68 expression correlated significantly with poor differentiation (P = 0.033), advanced T stage (P < 0.001), N stage (P = 0.023) and distant metastasis (P = 0.033). Sam68 nuclear localization correlated significantly with poor differentiation (P = 0.002) and T stage (P =0.021). Patients with high Sam68 expression or Sam68 nuclear localization had poorer overall survival than patients with low Sam68 expression or Sam68 cytoplasmic localization. Patients with high Sam68 expression had a higher risk of recurrence than those with low Sam68 expression. CONCLUSIONS Overexpression of Sam68 correlated highly with cancer progression and poor differentiation in CRC. High Sam68 expression and Sam68 nuclear localization were associated with poorer overall survival.
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Ehrmann I, Dalgliesh C, Liu Y, Danilenko M, Crosier M, Overman L, Arthur HM, Lindsay S, Clowry GJ, Venables JP, Fort P, Elliott DJ. The tissue-specific RNA binding protein T-STAR controls regional splicing patterns of neurexin pre-mRNAs in the brain. PLoS Genet 2013; 9:e1003474. [PMID: 23637638 PMCID: PMC3636136 DOI: 10.1371/journal.pgen.1003474] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 03/07/2013] [Indexed: 11/18/2022] Open
Abstract
The RNA binding protein T-STAR was created following a gene triplication 520-610 million years ago, which also produced its two parologs Sam68 and SLM-1. Here we have created a T-STAR null mouse to identify the endogenous functions of this RNA binding protein. Mice null for T-STAR developed normally and were fertile, surprisingly, given the high expression of T-STAR in the testis and the brain, and the known infertility and pleiotropic defects of Sam68 null mice. Using a transcriptome-wide search for splicing targets in the adult brain, we identified T-STAR protein as a potent splicing repressor of the alternatively spliced segment 4 (AS4) exons from each of the Neurexin1-3 genes, and exon 23 of the Stxbp5l gene. T-STAR protein was most highly concentrated in forebrain-derived structures like the hippocampus, which also showed maximal Neurexin1-3 AS4 splicing repression. In the absence of endogenous T-STAR protein, Nrxn1-3 AS4 splicing repression dramatically decreased, despite physiological co-expression of Sam68. In transfected cells Neurexin3 AS4 alternative splicing was regulated by either T-STAR or Sam68 proteins. In contrast, Neurexin2 AS4 splicing was only regulated by T-STAR, through a UWAA-rich response element immediately downstream of the regulated exon conserved since the radiation of bony vertebrates. The AS4 exons in the Nrxn1 and Nrxn3 genes were also associated with distinct patterns of conserved UWAA repeats. Consistent with an ancient mechanism of splicing control, human T-STAR protein was able to repress splicing inclusion of the zebrafish Nrxn3 AS4 exon. Although Neurexin1-3 and Stxbp5l encode critical synaptic proteins, T-STAR null mice had no detectable spatial memory deficits, despite an almost complete absence of AS4 splicing repression in the hippocampus. Our work identifies T-STAR as an ancient and potent tissue-specific splicing regulator that uses a concentration-dependent mechanism to co-ordinately regulate regional splicing patterns of the Neurexin1-3 AS4 exons in the mouse brain.
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Affiliation(s)
- Ingrid Ehrmann
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Caroline Dalgliesh
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Yilei Liu
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Marina Danilenko
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Moira Crosier
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Lynn Overman
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Helen M. Arthur
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Susan Lindsay
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Gavin J. Clowry
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Julian P. Venables
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Philippe Fort
- Universités Montpellier 2 et 1, UMR 5237, Centre de Recherche de Biochimie Macromoléculaire, CNRS, Montpellier, France
| | - David J. Elliott
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
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Locatelli A, Lofgren KA, Daniel AR, Castro NE, Lange CA. Mechanisms of HGF/Met signaling to Brk and Sam68 in breast cancer progression. Discov Oncol 2012; 3:14-25. [PMID: 22124844 DOI: 10.1007/s12672-011-0097-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Signal transduction pathways downstream of receptor tyrosine kinases (RTKs) are often deregulated during oncogenesis, tumor progression, and metastasis. In particular, the peptide growth factor hormone, hepatocyte growth factor (HGF), and its specific receptor, Met tyrosine kinase, regulate cancer cell migration, thereby conferring an aggressive phenotype (Nakamura et al., J Clin Invest 106(12):1511-1519, 2000; Huh et al., Proc Natl Acad Sci U S A 101:4477-4482, 2004). Additionally, overexpression of Met is associated with enhanced invasiveness of breast cancer cells (Edakuni et al., Pathol Int 51(3):172-178, 2001; Jin et al., Cancer 79(4):749-760, 1997; Tuck et al., Am J Pathol 148(1):225-232, 1996). Here, we review the regulation of recently identified novel downstream mediators of HGF/Met signaling, Breast tumor kinase (Brk/PTK6), and Src-associated substrate during mitosis of 68 kDa (Sam68), and discuss their relevance to mechanisms of breast cancer progression.
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Affiliation(s)
- Alessia Locatelli
- Department of Medicine, Division of Hematology, Oncology and Transplantation, University of Minnesota, Minneapolis, 55455, USA
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45
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Asbach B, Ludwig C, Saksela K, Wagner R. Comprehensive analysis of interactions between the Src-associated protein in mitosis of 68 kDa and the human Src-homology 3 proteome. PLoS One 2012; 7:e38540. [PMID: 22745667 PMCID: PMC3379994 DOI: 10.1371/journal.pone.0038540] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 05/07/2012] [Indexed: 11/19/2022] Open
Abstract
The protein Sam68 is involved in many cellular processes such as cell-cycle regulation, RNA metabolism, or signal transduction. Sam68 comprises a central RNA-binding domain flanked by unstructured tails containing docking sites for signalling proteins including seven proline-rich sequences (denoted P0 to P6) as potential SH3-domain binding motifs. To comprehensively assess Sam68-SH3-interactions, we applied a phage-display screening of a library containing all approx. 300 human SH3 domains. Thereby we identified five new (from intersectin 2, the osteoclast stimulating factor OSF, nephrocystin, sorting nexin 9, and CIN85) and seven already known high-confidence Sam68-ligands (mainly from the Src-kinase family), as well as several lower-affinity binders. Interaction of the high-affinity Sam68-binders was confirmed in independent assays in vitro (phage-ELISA, GST-pull-down) and in vivo (FACS-based FRET-analysis with CFP- and YFP-tagged proteins). Fine-mapping analyses with peptides established P0, P3, P4, and P5 as exclusive docking-sites for SH3 domains, which showed varying preferences for these motifs. Mutational analyses identified individual residues within the proline-rich motifs being crucial for the interactions. Based on these data, we generated a Sam68-mutant incapable of interacting with SH3 domains any more, as subsequently demonstrated by FRET-analyses. In conclusion, we present a thorough characterization of Sam68's interplay with the SH3 proteome. The observed interaction between Sam68 and OSF complements the known Sam68-Src and OSF-Src interactions. Thus, we propose, that Sam68 functions as a classical scaffold protein in this context, assembling components of an osteoclast-specific signalling pathway.
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Affiliation(s)
- Benedikt Asbach
- Institute of Medical Microbiology and Hygiene, University of Regensburg, Regensburg, Germany
| | - Christine Ludwig
- Institute of Medical Microbiology and Hygiene, University of Regensburg, Regensburg, Germany
| | - Kalle Saksela
- Department of Virology, Haartman Institute, University of Helsinki, Helsinki, Finland
| | - Ralf Wagner
- Institute of Medical Microbiology and Hygiene, University of Regensburg, Regensburg, Germany
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Abstract
Interference with stress granule (SG) accumulation is gaining increased appreciation as a common strategy used by diverse viruses to facilitate their replication and to cope with translational arrest. Here, we examined the impact of infection by herpes simplex virus 2 (HSV-2) on SG accumulation by monitoring the localization of the SG components T cell internal antigen 1 (TIA-1), Ras-GTPase-activating SH3-domain-binding protein (G3BP), and poly(A)-binding protein (PABP). Our results indicate that SGs do not accumulate in HSV-2-infected cells and that HSV-2 can interfere with arsenite-induced SG accumulation early after infection. Surprisingly, SG accumulation was inhibited despite increased phosphorylation of eukaryotic translation initiation factor 2α (eIF2α), implying that HSV-2 encodes previously unrecognized activities designed to maintain translation initiation downstream of eIF2α. SG accumulation was not inhibited in HSV-2-infected cells treated with pateamine A, an inducer that works independently of eIF2α phosphorylation. The SGs that accumulated following pateamine A treatment of infected cells contained G3BP and PABP but were largely devoid of TIA-1. We also identified novel nuclear structures containing TIA-1 that form late in infection. These structures contain the RNA binding protein 68-kDa Src-associated in mitosis (Sam68) and were noticeably absent in infected cells treated with inhibitors of viral DNA replication, suggesting that they arise as a result of late events in the virus replicative cycle.
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Lawrence P, Schafer EA, Rieder E. The nuclear protein Sam68 is cleaved by the FMDV 3C protease redistributing Sam68 to the cytoplasm during FMDV infection of host cells. Virology 2012; 425:40-52. [PMID: 22280896 DOI: 10.1016/j.virol.2011.12.019] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 11/23/2011] [Accepted: 12/31/2011] [Indexed: 01/28/2023]
Abstract
Picornavirus infection can lead to disruption of nuclear pore traffic, shut-off of cell translation machinery, and cleavage of proteins involved in cellular signal transduction and the innate response to infection. Here, we demonstrated that the FMDV 3C(pro) induced the cleavage of nuclear RNA-binding protein Sam68 C-terminus containing the nuclear localization sequence (NLS). Consequently, it stimulated the redistribution of Sam68 to the cytoplasm. The siRNA knockdown of Sam68 resulted in a 1000-fold reduction in viral titers, which prompted us to study the effect of Sam68 on FMDV post-entry events. Interestingly, Sam68 interacts with the internal ribosomal entry site within the 5' non-translated region of the FMDV genome, and Sam68 knockdown decreased FMDV IRES-driven activity in vitro suggesting that it could modulate translation of the viral genome. The results uncover a novel role for Sam68 in the context of picornaviruses and the proteolysis of a new cellular target of the FMDV 3C(pro).
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Affiliation(s)
- Paul Lawrence
- Foreign Animal Disease Research Unit, United States Department of Agriculture, Agricultural Research Service, Plum Island Animal Disease Center, Greenport, NY 11944, USA
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48
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Sam68 interacts with IRS1. Biochem Pharmacol 2011; 83:78-87. [PMID: 22005517 DOI: 10.1016/j.bcp.2011.09.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 09/26/2011] [Accepted: 09/28/2011] [Indexed: 12/18/2022]
Abstract
Sam68 (Src associated in mitosis) is a RNA binding protein that links cellular signaling to RNA processing. In previous studies we found that insulin promotes Sam68 relocalization in the cytoplasm allowing Sam68 to associate with p85PI3K, Grb2, GAP and probably the insulin receptor (IR), modulating insulin action positively. In the present work, we wanted to define the role of Sam68 in the first stages of IR signaling. Both BRET and co-immunoprecipitation assays have been used for the study of Sam68 binding to IR, IRS1 and p85-PI3K. BRET saturation experiments indicated, for the first time, that Sam68 associates with IRS1 in basal condition. To map the region of Sam68 implicated in the interaction with IRS1, different Sam68 mutants deleted in the proline-rich domains were used. The deletion of P0, P1 and P2 proline rich domains in N-terminus as well as P4 and P5 in C-terminus of Sam68 increased BRET(50), thus indicating that the affinity of Sam68 for IRS1 is lower when these domains are missing. Moreover, in IR-transfected HEK-293 cells, BRET saturation experiment indicated that insulin increases the affinity between Sam68-Rluc and IRS1-YFP. In conclusion, our data indicate that Sam68 interacts with IRS-1 in basal conditions, and insulin increases the affinity between these two partners.
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49
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Mao YS, Zhang B, Spector DL. Biogenesis and function of nuclear bodies. Trends Genet 2011; 27:295-306. [PMID: 21680045 DOI: 10.1016/j.tig.2011.05.006] [Citation(s) in RCA: 500] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2011] [Revised: 05/10/2011] [Accepted: 05/11/2011] [Indexed: 12/17/2022]
Abstract
Nuclear bodies including nucleoli, Cajal bodies, nuclear speckles, Polycomb bodies, and paraspeckles are membraneless subnuclear organelles. They are present at steady-state and dynamically respond to basic physiological processes as well as to various forms of stress, altered metabolic conditions and alterations in cellular signaling. The formation of a specific nuclear body has been suggested to follow a stochastic or ordered assembly model. In addition, a seeding mechanism has been proposed to assemble, maintain, and regulate particular nuclear bodies. In coordination with noncoding RNAs, chromatin modifiers and other machineries, various nuclear bodies have been shown to sequester and modify proteins, process RNAs and assemble ribonucleoprotein complexes, as well as epigenetically regulate gene expression. Understanding the functional relationships between the 3D organization of the genome and nuclear bodies is essential to fully uncover the regulation of gene expression and its implications for human disease.
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Affiliation(s)
- Yuntao S Mao
- Cold Spring Harbor Laboratory, One Bungtown Road, Cold Spring Harbor, NY 11724, USA
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50
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Locatelli A, Lange CA. Met receptors induce Sam68-dependent cell migration by activation of alternate extracellular signal-regulated kinase family members. J Biol Chem 2011; 286:21062-72. [PMID: 21489997 DOI: 10.1074/jbc.m110.211409] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The hepatocyte growth factor (HGF)/Met receptor signaling pathway is deregulated in diverse human malignancies and plays a central role in oncogenesis, tumor progression, and invasive cancer growth. Similarly, altered expression and splicing (i.e. inclusion of variant exon 5, "v5") of the cell adhesion marker, CD44, is associated with advanced cancer phenotypes. We sought to further understand how HGF regulates CD44v5 expression. Immortalized nontumorigenic keratinocyte (HaCaT) cells abundantly express both Met receptors and CD44v5 transmembrane glycoproteins. HGF stimulated CD44v5 protein expression and HaCaT cell migration; these events required activation of the ERK1/2 MAPK module and Sam68, a protein involved in RNA processing, splicing, and v5 inclusion. Similar to HaCaT cells, highly migratory MDA-MB-231 breast cancer cells also required Sam68 expression for HGF-induced migration. However, MDA-MB-231 cell migration occurred independently of ERK1/2 and CD44v5 expression and instead required ERK5 signaling to Sam68. Phospho-mutant, but not WT-Sam68, blocked HGF-induced cell migration in both cell types; MDA-MB-435 cells behaved similarly. These results suggest that Sam68 acts as a convergence point for ERK signaling to cell migration; blockade of phospho-Sam68 may provide a new avenue for therapeutic inhibition of metastatic cancers.
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Affiliation(s)
- Alessia Locatelli
- Department of Medicine (Division of Hematology, Oncology, and Transplantation), Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455, USA
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