1
|
Staudacher AH, Li Y, Liapis V, Brown MP. The RNA-binding protein La/SSB associates with radiation-induced DNA double-strand breaks in lung cancer cell lines. Cancer Rep (Hoboken) 2022; 5:e1543. [PMID: 34636174 PMCID: PMC9351668 DOI: 10.1002/cnr2.1543] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 07/13/2021] [Accepted: 08/06/2021] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Platinum-based chemotherapy and radiotherapy are standard treatments for non-small cell lung cancer, which is the commonest, most lethal cancer worldwide. As a marker of treatment-induced cancer cell death, we have developed a radiodiagnostic imaging antibody, which binds to La/SSB. La/SSB is an essential, ubiquitous ribonuclear protein, which is over expressed in cancer and plays a role in resistance to cancer therapies. AIM In this study, we examined radiation-induced DNA double strand breaks (DSB) in lung cancer cell lines and examined whether La/SSB associated with these DSB. METHOD Three lung cancer lines (A549, H460 and LL2) were irradiated with different X-ray doses or X-radiated with a 5 Gy dose and examined at different time-points post-irradiation for DNA DSB in the form of γ-H2AX and Rad51 foci. Using fluorescence microscopy, we examined whether La/SSB and γ-H2AX co-localise and performed proximity ligation assay (PLA) and co-immunoprecipitation to confirm the interaction of these proteins. RESULTS We found that the radio-resistant A549 cell line compared to the radio-sensitive H460 cell line showed faster resolution of radiation-induced γ-H2AX foci over time. Conversely, we found more co-localised γ-H2AX and La/SSB foci by PLA in irradiated A549 cells. CONCLUSION The co-localisation of La/SSB with radiation-induced DNA breaks suggests a role of La/SSB in DNA repair, however further experimentation is required to validate this.
Collapse
Affiliation(s)
- Alexander H. Staudacher
- Translational Oncology Laboratory, Centre for Cancer BiologySA Pathology and University of South AustraliaAdelaideSouth Australia5000Australia
- School of MedicineUniversity of AdelaideAdelaideSouth Australia5000Australia
| | - Yanrui Li
- Translational Oncology Laboratory, Centre for Cancer BiologySA Pathology and University of South AustraliaAdelaideSouth Australia5000Australia
| | - Vasilios Liapis
- Translational Oncology Laboratory, Centre for Cancer BiologySA Pathology and University of South AustraliaAdelaideSouth Australia5000Australia
| | - Michael P. Brown
- Translational Oncology Laboratory, Centre for Cancer BiologySA Pathology and University of South AustraliaAdelaideSouth Australia5000Australia
- School of MedicineUniversity of AdelaideAdelaideSouth Australia5000Australia
- Cancer Clinical Trials UnitRoyal Adelaide HospitalAdelaideSouth Australia5000Australia
| |
Collapse
|
2
|
Berndt N, Bippes CC, Michalk I, Bartsch T, Arndt C, Puentes-Cala E, Soto JA, Loureiro LR, Kegler A, Bachmann D, Gross JK, Gross T, Kurien BT, Scofield RH, Farris AD, James JA, Bergmann R, Schmitz M, Feldmann A, Bachmann MP. And Yet It Moves: Oxidation of the Nuclear Autoantigen La/SS-B Is the Driving Force for Nucleo-Cytoplasmic Shuttling. Int J Mol Sci 2021; 22:9699. [PMID: 34575862 PMCID: PMC8470643 DOI: 10.3390/ijms22189699] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 09/02/2021] [Accepted: 09/03/2021] [Indexed: 01/10/2023] Open
Abstract
Decades ago, we and many other groups showed a nucleo-cytoplasmic translocation of La protein in cultured cells. This shuttling of La protein was seen after UV irradiation, virus infections, hydrogen peroxide exposure and the Fenton reaction based on iron or copper ions. All of these conditions are somehow related to oxidative stress. Unfortunately, these harsh conditions could also cause an artificial release of La protein. Even until today, the shuttling and the cytoplasmic function of La/SS-B is controversially discussed. Moreover, the driving mechanism for the shuttling of La protein remains unclear. Recently, we showed that La protein undergoes redox-dependent conformational changes. Moreover, we developed anti-La monoclonal antibodies (anti-La mAbs), which are specific for either the reduced form of La protein or the oxidized form. Using these tools, here we show that redox-dependent conformational changes are the driving force for the shuttling of La protein. Moreover, we show that translocation of La protein to the cytoplasm can be triggered in a ligand/receptor-dependent manner under physiological conditions. We show that ligands of toll-like receptors lead to a redox-dependent shuttling of La protein. The shuttling of La protein depends on the redox status of the respective cell type. Endothelial cells are usually resistant to the shuttling of La protein, while dendritic cells are highly sensitive. However, the deprivation of intracellular reducing agents in endothelial cells makes endothelial cells sensitive to a redox-dependent shuttling of La protein.
Collapse
Affiliation(s)
- Nicole Berndt
- Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany; (N.B.); (T.B.); (C.A.); (E.P.-C.); (J.A.S.); (L.R.L.); (A.K.); (R.B.); (A.F.)
| | - Claudia C. Bippes
- Institute of Immunology, Medical Faculty Carl Gustav Carus Dresden, Technische Universität Dresden, 01307 Dresden, Germany; (C.C.B.); (I.M.); (M.S.)
| | - Irene Michalk
- Institute of Immunology, Medical Faculty Carl Gustav Carus Dresden, Technische Universität Dresden, 01307 Dresden, Germany; (C.C.B.); (I.M.); (M.S.)
| | - Tabea Bartsch
- Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany; (N.B.); (T.B.); (C.A.); (E.P.-C.); (J.A.S.); (L.R.L.); (A.K.); (R.B.); (A.F.)
| | - Claudia Arndt
- Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany; (N.B.); (T.B.); (C.A.); (E.P.-C.); (J.A.S.); (L.R.L.); (A.K.); (R.B.); (A.F.)
| | - Edinson Puentes-Cala
- Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany; (N.B.); (T.B.); (C.A.); (E.P.-C.); (J.A.S.); (L.R.L.); (A.K.); (R.B.); (A.F.)
- Corporación para la Investigación de la Corrosión (CIC), Piedecuesta 681011, Colombia
| | - Javier Andrés Soto
- Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany; (N.B.); (T.B.); (C.A.); (E.P.-C.); (J.A.S.); (L.R.L.); (A.K.); (R.B.); (A.F.)
- Instituto de Investigación Masira, Facultad de Ciencias Médicas y de la Salud, Universidad de Santander, Cúcuta 540001, Colombia
| | - Liliana R. Loureiro
- Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany; (N.B.); (T.B.); (C.A.); (E.P.-C.); (J.A.S.); (L.R.L.); (A.K.); (R.B.); (A.F.)
| | - Alexandra Kegler
- Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany; (N.B.); (T.B.); (C.A.); (E.P.-C.); (J.A.S.); (L.R.L.); (A.K.); (R.B.); (A.F.)
| | - Dominik Bachmann
- Tumor Immunology, University Cancer Center (UCC), University Hospital Carl Gustav Carus Technische Universität Dresden, 01307 Dresden, Germany;
| | - Joanne K. Gross
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (J.K.G.); (T.G.); (B.T.K.); (R.H.S.); (A.D.F.); (J.A.J.)
| | - Tim Gross
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (J.K.G.); (T.G.); (B.T.K.); (R.H.S.); (A.D.F.); (J.A.J.)
| | - Biji T. Kurien
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (J.K.G.); (T.G.); (B.T.K.); (R.H.S.); (A.D.F.); (J.A.J.)
| | - R. Hal Scofield
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (J.K.G.); (T.G.); (B.T.K.); (R.H.S.); (A.D.F.); (J.A.J.)
| | - A. Darise Farris
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (J.K.G.); (T.G.); (B.T.K.); (R.H.S.); (A.D.F.); (J.A.J.)
| | - Judith A. James
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (J.K.G.); (T.G.); (B.T.K.); (R.H.S.); (A.D.F.); (J.A.J.)
| | - Ralf Bergmann
- Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany; (N.B.); (T.B.); (C.A.); (E.P.-C.); (J.A.S.); (L.R.L.); (A.K.); (R.B.); (A.F.)
- Department of Biophysics and Radiobiology, Semmelweis University, 1094 Budapest, Hungary
| | - Marc Schmitz
- Institute of Immunology, Medical Faculty Carl Gustav Carus Dresden, Technische Universität Dresden, 01307 Dresden, Germany; (C.C.B.); (I.M.); (M.S.)
- National Center for Tumor Diseases (NCT), 03128 Dresden, Germany
| | - Anja Feldmann
- Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany; (N.B.); (T.B.); (C.A.); (E.P.-C.); (J.A.S.); (L.R.L.); (A.K.); (R.B.); (A.F.)
| | - Michael P. Bachmann
- Department of Radioimmunology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany; (N.B.); (T.B.); (C.A.); (E.P.-C.); (J.A.S.); (L.R.L.); (A.K.); (R.B.); (A.F.)
- Institute of Immunology, Medical Faculty Carl Gustav Carus Dresden, Technische Universität Dresden, 01307 Dresden, Germany; (C.C.B.); (I.M.); (M.S.)
- National Center for Tumor Diseases (NCT), 03128 Dresden, Germany
| |
Collapse
|
3
|
Translational regulation in pathogenic and beneficial plant-microbe interactions. Biochem J 2021; 478:2775-2788. [PMID: 34297042 DOI: 10.1042/bcj20210066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 07/01/2021] [Accepted: 07/02/2021] [Indexed: 11/17/2022]
Abstract
Plants are surrounded by a vast diversity of microorganisms. Limiting pathogenic microorganisms is crucial for plant survival. On the other hand, the interaction of plants with beneficial microorganisms promotes their growth or allows them to overcome nutrient deficiencies. Balancing the number and nature of these interactions is crucial for plant growth and development, and thus, for crop productivity in agriculture. Plants use sophisticated mechanisms to recognize pathogenic and beneficial microorganisms and genetic programs related to immunity or symbiosis. Although most research has focused on characterizing changes in the transcriptome during plant-microbe interactions, the application of techniques such as Translating Ribosome Affinity Purification (TRAP) and Ribosome profiling allowed examining the dynamic association of RNAs to the translational machinery, highlighting the importance of the translational level of control of gene expression in both pathogenic and beneficial interactions. These studies revealed that the transcriptional and the translational responses are not always correlated, and that translational control operates at cell-specific level. In addition, translational control is governed by cis-elements present in the 5'mRNA leader of regulated mRNAs, e.g. upstream open reading frames (uORFs) and sequence-specific motifs. In this review, we summarize and discuss the recent advances made in the field of translational control during pathogenic and beneficial plant-microbe interactions.
Collapse
|
4
|
Bayfield MA, Vinayak J, Kerkhofs K, Mansouri-Noori F. La proteins couple use of sequence-specific and non-specific binding modes to engage RNA substrates. RNA Biol 2021; 18:168-177. [PMID: 30777481 PMCID: PMC7928037 DOI: 10.1080/15476286.2019.1582955] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 02/05/2019] [Accepted: 02/05/2019] [Indexed: 12/31/2022] Open
Abstract
La shuttles between the nucleus and cytoplasm where it binds nascent RNA polymerase III (pol III) transcripts and mRNAs, respectively. La protects the 3' end of pol III transcribed RNA precursors, such as pre-tRNAs, through the use of a well-characterized UUU-3'OH binding mode. La proteins are also RNA chaperones, and La-dependent RNA chaperone activity is hypothesized to promote pre-tRNA maturation and translation at cellular and viral internal ribosome entry sites via binding sites distinct from those used for UUU-3'OH recognition. Since the publication of La-UUU-3'OH co-crystal structures, biochemical and genetic experiments have expanded our understanding of how La proteins use UUU-3'OH-independent binding modes to make sequence-independent contacts that can increase affinity for ligands and promote RNA remodeling. Other recent work has also expanded our understanding of how La binds mRNAs through contacts to the poly(A) tail. In this review, we focus on advances in the study of La protein-RNA complex surfaces beyond the description of the La-UUU-3'OH binding mode. We highlight recent advances in the functions of expected canonical nucleic acid interaction surfaces, a heightened appreciation of disordered C-terminal regions, and the nature of sequence-independent RNA determinants in La-RNA target binding. We further discuss how these RNA binding modes may have relevance to the function of the La-related proteins.
Collapse
Affiliation(s)
- Mark A. Bayfield
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Jyotsna Vinayak
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Kyra Kerkhofs
- Department of Biology, York University, Toronto, Ontario, Canada
| | | |
Collapse
|
5
|
Al-Ashtal HA, Rubottom CM, Leeper TC, Berman AJ. The LARP1 La-Module recognizes both ends of TOP mRNAs. RNA Biol 2021; 18:248-258. [PMID: 31601159 PMCID: PMC7927982 DOI: 10.1080/15476286.2019.1669404] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 08/22/2019] [Accepted: 09/12/2019] [Indexed: 12/11/2022] Open
Abstract
La-Related Protein 1 (LARP1) is an RNA-binding protein that regulates the stability and translation of mRNAs encoding the translation machinery, including ribosomal proteins and translation factors. These mRNAs are characterized by a 5'-terminal oligopyrimidine (TOP) motif that coordinates their temporal and stoichiometric expression. While LARP1 represses TOP mRNA translation via the C-terminal DM15 region, the role of the N-terminal La-Module in the recognition and translational regulation of TOP mRNAs remains elusive. Herein we show that the LARP1 La-Module also binds TOP motifs, although in a cap-independent manner. We also demonstrate that it recognizes poly(A) RNA. Further, our data reveal that the LARP1 La-Module can simultaneously engage TOP motifs and poly(A) RNA. These results evoke an intriguing molecular mechanism whereby LARP1 could regulate translation and stabilization of TOP transcripts.
Collapse
Affiliation(s)
- Hiba A. Al-Ashtal
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Courtney M. Rubottom
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Thomas C. Leeper
- Department of Chemistry & Biochemistry, Kennesaw State University, Kennesaw, GA, USA
| | - Andrea J. Berman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| |
Collapse
|
6
|
Abstract
RNA-binding proteins are important regulators of RNA metabolism and are of critical importance in all steps of the gene expression cascade. The role of aberrantly expressed RBPs in human disease is an exciting research field and the potential application of RBPs as a therapeutic target or a diagnostic marker represents a fast-growing area of research.Aberrant overexpression of the human RNA-binding protein La has been found in various cancer entities including lung, cervical, head and neck, and chronic myelogenous leukaemia. Cancer-associated La protein supports tumour-promoting processes such as proliferation, mobility, invasiveness and tumour growth. Moreover, the La protein maintains the survival of cancer cells by supporting an anti-apoptotic state that may cause resistance to chemotherapeutic therapy.The human La protein represents a multifunctional post-translationally modified RNA-binding protein with RNA chaperone activity that promotes processing of non-coding precursor RNAs but also stimulates the translation of selective messenger RNAs encoding tumour-promoting and anti-apoptotic factors. In our model, La facilitates the expression of those factors and helps cancer cells to cope with cellular stress. In contrast to oncogenes, able to initiate tumorigenesis, we postulate that the aberrantly elevated expression of the human La protein contributes to the non-oncogenic addiction of cancer cells. In this review, we summarize the current understanding about the implications of the RNA-binding protein La in cancer progression and therapeutic resistance. The concept of exploiting the RBP La as a cancer drug target will be discussed.
Collapse
Affiliation(s)
- Gunhild Sommer
- Department for Pediatric Hematology, Oncology and Stem Cell Transplantation, University Hospital Regensburg, Regensburg, Germany
| | - Tilman Heise
- Department for Pediatric Hematology, Oncology and Stem Cell Transplantation, University Hospital Regensburg, Regensburg, Germany
| |
Collapse
|
7
|
Jaud M, Philippe C, Di Bella D, Tang W, Pyronnet S, Laurell H, Mazzolini L, Rouault-Pierre K, Touriol C. Translational Regulations in Response to Endoplasmic Reticulum Stress in Cancers. Cells 2020; 9:cells9030540. [PMID: 32111004 PMCID: PMC7140484 DOI: 10.3390/cells9030540] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/18/2020] [Accepted: 02/24/2020] [Indexed: 12/20/2022] Open
Abstract
During carcinogenesis, almost all the biological processes are modified in one way or another. Among these biological processes affected, anomalies in protein synthesis are common in cancers. Indeed, cancer cells are subjected to a wide range of stresses, which include physical injuries, hypoxia, nutrient starvation, as well as mitotic, oxidative or genotoxic stresses. All of these stresses will cause the accumulation of unfolded proteins in the Endoplasmic Reticulum (ER), which is a major organelle that is involved in protein synthesis, preservation of cellular homeostasis, and adaptation to unfavourable environment. The accumulation of unfolded proteins in the endoplasmic reticulum causes stress triggering an unfolded protein response in order to promote cell survival or to induce apoptosis in case of chronic stress. Transcription and also translational reprogramming are tightly controlled during the unfolded protein response to ensure selective gene expression. The majority of stresses, including ER stress, induce firstly a decrease in global protein synthesis accompanied by the induction of alternative mechanisms for initiating the translation of mRNA, later followed by a translational recovery. After a presentation of ER stress and the UPR response, we will briefly present the different modes of translation initiation, then address the specific translational regulatory mechanisms acting during reticulum stress in cancers and highlight the importance of translational control by ER stress in tumours.
Collapse
Affiliation(s)
- Manon Jaud
- Inserm UMR1037, CRCT (Cancer Research Center of Toulouse), F-31037 Toulouse, France; (M.J.); (S.P.); (L.M.)
- Université Toulouse III Paul-Sabatier, F-31000 Toulouse, France;
| | - Céline Philippe
- Barts Cancer Institute, Queen Mary University of London, London E1 4NS, UK; (C.P.); (D.D.B.); (W.T.); (K.R.-P.)
| | - Doriana Di Bella
- Barts Cancer Institute, Queen Mary University of London, London E1 4NS, UK; (C.P.); (D.D.B.); (W.T.); (K.R.-P.)
| | - Weiwei Tang
- Barts Cancer Institute, Queen Mary University of London, London E1 4NS, UK; (C.P.); (D.D.B.); (W.T.); (K.R.-P.)
| | - Stéphane Pyronnet
- Inserm UMR1037, CRCT (Cancer Research Center of Toulouse), F-31037 Toulouse, France; (M.J.); (S.P.); (L.M.)
- Université Toulouse III Paul-Sabatier, F-31000 Toulouse, France;
| | - Henrik Laurell
- Université Toulouse III Paul-Sabatier, F-31000 Toulouse, France;
- Inserm UMR1048, I2MC (Institut des Maladies Métaboliques et Cardiovasculaires), BP 84225, CEDEX 04, 31 432 Toulouse, France
| | - Laurent Mazzolini
- Inserm UMR1037, CRCT (Cancer Research Center of Toulouse), F-31037 Toulouse, France; (M.J.); (S.P.); (L.M.)
- CNRS ERL5294, CRCT, F-31037 Toulouse, France
| | - Kevin Rouault-Pierre
- Barts Cancer Institute, Queen Mary University of London, London E1 4NS, UK; (C.P.); (D.D.B.); (W.T.); (K.R.-P.)
| | - Christian Touriol
- Inserm UMR1037, CRCT (Cancer Research Center of Toulouse), F-31037 Toulouse, France; (M.J.); (S.P.); (L.M.)
- Université Toulouse III Paul-Sabatier, F-31000 Toulouse, France;
- Correspondence:
| |
Collapse
|
8
|
Cho H, Cho HS, Hwang I. Emerging roles of RNA-binding proteins in plant development. CURRENT OPINION IN PLANT BIOLOGY 2019; 51:51-57. [PMID: 31071564 DOI: 10.1016/j.pbi.2019.03.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 03/27/2019] [Accepted: 03/30/2019] [Indexed: 05/22/2023]
Abstract
RNA-binding proteins (RBPs) influence the fate of target RNAs via direct interactions. During transcription, RBPs and interacting partners are recruited to and modify transcripts, after which they may also participate in critical steps to generate functional RNA. RBP-RNA interactions govern post-transcriptional processing of RNA, consequently regulating gene expression in a spatio-temporal manner. In plants, an increasing number of proteins have been classified as RBPs, many of which have been shown to function as key players in diverse developmental processes. However, a comprehensive understanding of how RBPs function, which RNAs are targeted, and where RBP-RNA interactions occur within plant cells is lacking. Here, we discuss recent findings in the field and newly defined roles for RBPs in plant growth and development. We also describe the mechanistic effects of RBPs on target RNA metabolism and translation.
Collapse
Affiliation(s)
- Hyunwoo Cho
- Department of Industrial Plant Science and Technology, College of Agricultural, Life and Environmental Sciences, Chungbuk National University, Cheongju 2864, Republic of Korea
| | - Hyun Seob Cho
- Department of Life Sciences, POSTECH Biotech Center, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Ildoo Hwang
- Department of Life Sciences, POSTECH Biotech Center, Pohang University of Science and Technology, Pohang 37673, Republic of Korea.
| |
Collapse
|
9
|
Vinayak J, Marrella SA, Hussain RH, Rozenfeld L, Solomon K, Bayfield MA. Human La binds mRNAs through contacts to the poly(A) tail. Nucleic Acids Res 2019; 46:4228-4240. [PMID: 29447394 PMCID: PMC5934636 DOI: 10.1093/nar/gky090] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 01/31/2018] [Indexed: 12/31/2022] Open
Abstract
In addition to a role in the processing of nascent RNA polymerase III transcripts, La proteins are also associated with promoting cap-independent translation from the internal ribosome entry sites of numerous cellular and viral coding RNAs. La binding to RNA polymerase III transcripts via their common UUU-3’OH motif is well characterized, but the mechanism of La binding to coding RNAs is poorly understood. Using electromobility shift assays and cross-linking immunoprecipitation, we show that in addition to a sequence specific UUU-3’OH binding mode, human La exhibits a sequence specific and length dependent poly(A) binding mode. We demonstrate that this poly(A) binding mode uses the canonical nucleic acid interaction winged helix face of the eponymous La motif, previously shown to be vacant during uridylate binding. We also show that cytoplasmic, but not nuclear La, engages poly(A) RNA in human cells, that La entry into polysomes utilizes the poly(A) binding mode, and that La promotion of translation from the cyclin D1 internal ribosome entry site occurs in competition with cytoplasmic poly(A) binding protein (PABP). Our data are consistent with human La functioning in translation through contacts to the poly(A) tail.
Collapse
Affiliation(s)
- Jyotsna Vinayak
- Department of Biology, York University, 4700 Keele St., Life Science Building #327E, Toronto, ON M3J 1P3, Canada
| | - Stefano A Marrella
- Department of Biology, York University, 4700 Keele St., Life Science Building #327E, Toronto, ON M3J 1P3, Canada
| | - Rawaa H Hussain
- Department of Biology, York University, 4700 Keele St., Life Science Building #327E, Toronto, ON M3J 1P3, Canada
| | - Leonid Rozenfeld
- Department of Biology, York University, 4700 Keele St., Life Science Building #327E, Toronto, ON M3J 1P3, Canada
| | - Karine Solomon
- Department of Biology, York University, 4700 Keele St., Life Science Building #327E, Toronto, ON M3J 1P3, Canada
| | - Mark A Bayfield
- Department of Biology, York University, 4700 Keele St., Life Science Building #327E, Toronto, ON M3J 1P3, Canada
| |
Collapse
|
10
|
Kwan T, Thompson SR. Noncanonical Translation Initiation in Eukaryotes. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a032672. [PMID: 29959190 DOI: 10.1101/cshperspect.a032672] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The vast majority of eukaryotic messenger RNAs (mRNAs) initiate translation through a canonical, cap-dependent mechanism requiring a free 5' end and 5' cap and several initiation factors to form a translationally active ribosome. Stresses such as hypoxia, apoptosis, starvation, and viral infection down-regulate cap-dependent translation during which alternative mechanisms of translation initiation prevail to express proteins required to cope with the stress, or to produce viral proteins. The diversity of noncanonical initiation mechanisms encompasses a broad range of strategies and cellular cofactors. Herein, we provide an overview and, whenever possible, a mechanistic understanding of the various noncanonical mechanisms of initiation used by cells and viruses. Despite many unanswered questions, recent advances have propelled our understanding of the scope, diversity, and mechanisms of alternative initiation.
Collapse
Affiliation(s)
- Thaddaeus Kwan
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Sunnie R Thompson
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| |
Collapse
|
11
|
Shrivastava R, Drory-Retwitzer M, Shapira M. Nutritional stress targets LeishIF4E-3 to storage granules that contain RNA and ribosome components in Leishmania. PLoS Negl Trop Dis 2019; 13:e0007237. [PMID: 30870425 PMCID: PMC6435199 DOI: 10.1371/journal.pntd.0007237] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Revised: 03/26/2019] [Accepted: 02/12/2019] [Indexed: 12/02/2022] Open
Abstract
Leishmania parasites lack pathways for de novo purine biosynthesis. The depletion of purines induces differentiation into virulent metacyclic forms. In vitro, the parasites can survive prolonged periods of purine withdrawal changing their morphology to long and slender cells with an extended flagellum, and decreasing their translation rates. Reduced translation leads to the appearance of discrete granules that contain LeishIF4E-3, one of the six eIF4E paralogs encoded by the Leishmania genome. We hypothesize that each is responsible for a different function during the life cycle. LeishIF4E-3 is a weak cap-binding protein paralog, but its involvement in translation under normal conditions cannot be excluded. However, in response to nutritional stress, LeishIF4E-3 concentrates in specific cytoplasmic granules. LeishIF4E-3 granulation can be induced by the independent elimination of purines, amino acids and glucose. As these granules contain mature mRNAs, we propose that these bodies store inactive transcripts until recovery from stress occurs. In attempt to examine the content of the nutritional stress-induced granules, they were concentrated over sucrose gradients and further pulled-down by targeting in vivo tagged LeishIF4E-3. Proteomic analysis highlighted granule enrichment with multiple ribosomal proteins, suggesting that ribosome particles are abundant in these foci, as expected in case of translation inhibition. RNA-binding proteins, RNA helicases and metabolic enzymes were also enriched in the granules, whereas no degradation enzymes or P-body markers were detected. The starvation-induced LeishIF4E-3-containing granules, therefore, appear to store stalled ribosomes and ribosomal subunits, along with their associated mRNAs. Following nutritional stress, LeishIF4E-3 becomes phosphorylated at position S75, located in its less-conserved N-terminal extension. The ability of the S75A mutant to form granules was reduced, indicating that cellular signaling regulates LeishIF4E-3 function. Cells respond to cellular stress by decreasing protein translation, to prevent the formation of partially folded or misfolded new polypeptides whose accumulation can be detrimental to living cells. Under such conditions, the cells benefit from storing inactive mRNAs and stalled ribosomal particles, to maintain their availability once conditions improve; dedicated granules offer a solution for such storage. Leishmania parasites are exposed to a variety of stress conditions as a natural part of their life cycle, including the nutritional stress that the parasites experience within the gut of the sandfly. Thus, Leishmania and related trypanosomatids serve as a good model system to investigate RNA fate during different stress conditions. Various granules appear in Leishmania and related organisms in response to different stress conditions. Here, we investigated how nutritional stress, in particular elimination of purines, induced the formation of granules that harbor a specific cap-binding protein, LeishIF4E-3. The starvation-induced LeishIF4E-3 containing granules consist of a variety of ribosomal proteins, along with RNA-binding proteins and mature mRNAs. We thus propose that Leishmania modulates the assembly of LeishIF4E-3-containing granules for transient storage of stalled ribosomal particles and inactive mRNAs. Following renewal of nutrient availability, as occurs during the parasite’s life cycle, the granules disappear. Although their fate is yet unclear, they could be recycled in the cell. Unlike other granules described in trypanosomes, the LeishIF4E-3-containing granules did not contain RNA degradation enzymes, suggesting that their function is mainly for storage until conditions improve.
Collapse
Affiliation(s)
- Rohit Shrivastava
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Matan Drory-Retwitzer
- Department of Computer Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Michal Shapira
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- * E-mail:
| |
Collapse
|
12
|
Godet AC, David F, Hantelys F, Tatin F, Lacazette E, Garmy-Susini B, Prats AC. IRES Trans-Acting Factors, Key Actors of the Stress Response. Int J Mol Sci 2019; 20:ijms20040924. [PMID: 30791615 PMCID: PMC6412753 DOI: 10.3390/ijms20040924] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Revised: 02/12/2019] [Accepted: 02/14/2019] [Indexed: 12/16/2022] Open
Abstract
The cellular stress response corresponds to the molecular changes that a cell undergoes in response to various environmental stimuli. It induces drastic changes in the regulation of gene expression at transcriptional and posttranscriptional levels. Actually, translation is strongly affected with a blockade of the classical cap-dependent mechanism, whereas alternative mechanisms are activated to support the translation of specific mRNAs. A major mechanism involved in stress-activated translation is the internal ribosome entry site (IRES)-driven initiation. IRESs, first discovered in viral mRNAs, are present in cellular mRNAs coding for master regulators of cell responses, whose expression must be tightly controlled. IRESs allow the translation of these mRNAs in response to different stresses, including DNA damage, amino-acid starvation, hypoxia or endoplasmic reticulum stress, as well as to physiological stimuli such as cell differentiation or synapse network formation. Most IRESs are regulated by IRES trans-acting factor (ITAFs), exerting their action by at least nine different mechanisms. This review presents the history of viral and cellular IRES discovery as well as an update of the reported ITAFs regulating cellular mRNA translation and of their different mechanisms of action. The impact of ITAFs on the coordinated expression of mRNA families and consequences in cell physiology and diseases are also highlighted.
Collapse
Affiliation(s)
- Anne-Claire Godet
- UMR 1048-I2MC, Inserm, Université de Toulouse, UT3, 31432 Toulouse cedex 4, France.
| | - Florian David
- UMR 1048-I2MC, Inserm, Université de Toulouse, UT3, 31432 Toulouse cedex 4, France.
| | - Fransky Hantelys
- UMR 1048-I2MC, Inserm, Université de Toulouse, UT3, 31432 Toulouse cedex 4, France.
| | - Florence Tatin
- UMR 1048-I2MC, Inserm, Université de Toulouse, UT3, 31432 Toulouse cedex 4, France.
| | - Eric Lacazette
- UMR 1048-I2MC, Inserm, Université de Toulouse, UT3, 31432 Toulouse cedex 4, France.
| | - Barbara Garmy-Susini
- UMR 1048-I2MC, Inserm, Université de Toulouse, UT3, 31432 Toulouse cedex 4, France.
| | - Anne-Catherine Prats
- UMR 1048-I2MC, Inserm, Université de Toulouse, UT3, 31432 Toulouse cedex 4, France.
| |
Collapse
|
13
|
Marrella SA, Brown KA, Mansouri-Noori F, Porat J, Wilson DJ, Bayfield MA. An interdomain bridge influences RNA binding of the human La protein. J Biol Chem 2018; 294:1529-1540. [PMID: 30530494 DOI: 10.1074/jbc.ra118.003995] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 11/20/2018] [Indexed: 12/15/2022] Open
Abstract
La proteins are RNA chaperones that perform various functions depending on distinct RNA-binding modes and their subcellular localization. In the nucleus, they help process UUU-3'OH-tailed nascent RNA polymerase III transcripts, such as pre-tRNAs, whereas in the cytoplasm they contribute to translation of poly(A)-tailed mRNAs. La accumulation in the nucleus and cytoplasm is controlled by several trafficking elements, including a canonical nuclear localization signal in the extreme C terminus and a nuclear retention element (NRE) in the RNA recognition motif 2 (RRM2) domain. Previous findings indicate that cytoplasmic export of La due to mutation of the NRE can be suppressed by mutations in RRM1, but the mechanism by which the RRM1 and RRM2 domains functionally cooperate is poorly understood. In this work, we use electromobility shift assays (EMSA) to show that mutations in the NRE and RRM1 affect binding of human La to pre-tRNAs but not UUU-3'OH or poly(A) sequences, and we present compensatory mutagenesis data supporting a direct interaction between the RRM1 and RRM2 domains. Moreover, we use collision-induced unfolding and time-resolved hydrogen-deuterium exchange MS analyses to study the conformational dynamics that occur when this interaction is intact or disrupted. Our results suggest that the intracellular distribution of La may be linked to its RNA-binding modes and provide the first evidence for a direct protein-protein interdomain interaction in La proteins.
Collapse
Affiliation(s)
- Stefano A Marrella
- Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada; Centres for Research in Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
| | - Kerene A Brown
- Centres for Research in Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada; Department of Chemistry, York University, Toronto, Ontario M3J 1P3, Canada; Research in Mass Spectrometry, York University, Toronto, Ontario M3J 1P3, Canada
| | - Farnaz Mansouri-Noori
- Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada; Centres for Research in Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
| | - Jennifer Porat
- Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada; Centres for Research in Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada
| | - Derek J Wilson
- Centres for Research in Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada; Department of Chemistry, York University, Toronto, Ontario M3J 1P3, Canada; Research in Mass Spectrometry, York University, Toronto, Ontario M3J 1P3, Canada.
| | - Mark A Bayfield
- Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada; Centres for Research in Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada.
| |
Collapse
|
14
|
Iwata Y, Iida T, Matsunami T, Yamada Y, Mishiba KI, Ogawa T, Kurata T, Koizumi N. Constitutive BiP protein accumulation in Arabidopsis mutants defective in a gene encoding chloroplast-resident stearoyl-acyl carrier protein desaturase. Genes Cells 2018; 23:456-465. [PMID: 29688606 DOI: 10.1111/gtc.12585] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 03/19/2018] [Indexed: 01/11/2023]
Abstract
The unfolded protein response (UPR) occurs when protein folding and maturation are disturbed in the endoplasmic reticulum (ER). During the UPR, a number of genes including those encoding ER-resident molecular chaperones are induced. In Arabidopsis, BiP3 has been used as a UPR marker gene whose expression is strongly induced in response to ER stress. In this study, we mutagenized Arabidopsis plants expressing β-glucuronidase (GUS) gene under the control of BiP3 promoter and isolated a mutant that exhibits strong GUS activity without treatment with ER stress inducers. By whole genome sequencing, we identified a causal gene in the mutant as SUPPRESSOR OF SALICYLIC ACID INSENSITIVITY2 (SSI2), which encodes stearoyl-acyl carrier protein desaturase that converts stearic acids to oleic acids in the chloroplasts. In addition to GUS proteins, the ssi2 mutant accumulates endogenous BiP3 proteins without treatment by any stress reagents. Interestingly, although the degree of endogenous BiP3 protein accumulation in the ssi2 mutant was comparable to that in wild-type plants treated with the ER stress inducer tunicamycin, much less BiP3 transcripts were detected in the ssi2 mutant compared to tunicamycin-treated wild-type plants. Our finding suggests a genetic link between fatty acid metabolism in the chloroplasts and ER functions.
Collapse
Affiliation(s)
- Yuji Iwata
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Tsukasa Iida
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Toshihiro Matsunami
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Yu Yamada
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Kei-Ichiro Mishiba
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Takumi Ogawa
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Tetsuya Kurata
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan
| | - Nozomu Koizumi
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan
| |
Collapse
|
15
|
The La protein counteracts cisplatin-induced cell death by stimulating protein synthesis of anti-apoptotic factor Bcl2. Oncotarget 2018; 7:29664-76. [PMID: 27105491 PMCID: PMC5045424 DOI: 10.18632/oncotarget.8819] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 03/28/2016] [Indexed: 02/06/2023] Open
Abstract
Up-regulation of anti-apoptotic factors is a critical mechanism of cancer cell resistance and often counteracts the success of chemotherapeutic treatment. Herein, we identified the cancer-associated RNA-binding protein La as novel factor contributing to cisplatin resistance. Our data demonstrate that depletion of the RNA-binding protein La in head and neck squamous cell carcinoma cells (HNSCC) increases the sensitivity toward cisplatin-induced cell death paralleled by reduced expression of the anti-apoptotic factor Bcl2. Furthermore, it is shown that transient expression of Bcl2 in La-depleted cells protects against cisplatin-induced cell death. By dissecting the underlying mechanism we report herein, that the La protein is required for Bcl2 protein synthesis in cisplatin-treated cells. The RNA chaperone La binds in close proximity to the authentic translation start site and unwinds a secondary structure embedding the authentic AUG. Altogether, our data support a novel model, whereby cancer-associated La protein contributes to cisplatin resistance by stimulating the translation of anti-apoptotic factor Bcl2 in HNSCC cells.
Collapse
|
16
|
Maraia RJ, Mattijssen S, Cruz-Gallardo I, Conte MR. The La and related RNA-binding proteins (LARPs): structures, functions, and evolving perspectives. WILEY INTERDISCIPLINARY REVIEWS. RNA 2017; 8:10.1002/wrna.1430. [PMID: 28782243 PMCID: PMC5647580 DOI: 10.1002/wrna.1430] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 05/12/2017] [Accepted: 05/15/2017] [Indexed: 01/02/2023]
Abstract
La was first identified as a polypeptide component of ribonucleic protein complexes targeted by antibodies in autoimmune patients and is now known to be a eukaryote cell-ubiquitous protein. Structure and function studies have shown that La binds to a common terminal motif, UUU-3'-OH, of nascent RNA polymerase III (RNAP III) transcripts and protects them from exonucleolytic decay. For precursor-tRNAs, the most diverse and abundant of these transcripts, La also functions as an RNA chaperone that helps to prevent their misfolding. Related to this, we review evidence that suggests that La and its link to RNAP III were significant in the great expansions of the tRNAomes that occurred in eukaryotes. Four families of La-related proteins (LARPs) emerged during eukaryotic evolution with specialized functions. We provide an overview of the high-resolution structural biology of La and LARPs. LARP7 family members most closely resemble La but function with a single RNAP III nuclear transcript, 7SK, or telomerase RNA. A cytoplasmic isoform of La protein as well as LARPs 6, 4, and 1 function in mRNA metabolism and translation in distinct but similar ways, sometimes with the poly(A)-binding protein, and in some cases by direct binding to poly(A)-RNA. New structures of LARP domains, some complexed with RNA, provide novel insights into the functional versatility of these proteins. We also consider LARPs in relation to ancestral La protein and potential retention of links to specific RNA-related pathways. One such link may be tRNA surveillance and codon usage by LARP-associated mRNAs. WIREs RNA 2017, 8:e1430. doi: 10.1002/wrna.1430 For further resources related to this article, please visit the WIREs website.
Collapse
Affiliation(s)
- Richard J. Maraia
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD USA
- Commissioned Corps, U.S. Public Health Service, Rockville, MD USA
| | - Sandy Mattijssen
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD USA
| | - Isabel Cruz-Gallardo
- Randall Division of Cell and Molecular Biophysics, King's College London, Guy's Campus, London, UK
| | - Maria R. Conte
- Randall Division of Cell and Molecular Biophysics, King's College London, Guy's Campus, London, UK
| |
Collapse
|
17
|
Pan J, Tong S, Tang J. Alteration of microRNA profiles by a novel inhibitor of human La protein in HBV-transformed human hepatoma cells. J Med Virol 2017; 90:255-262. [PMID: 28885699 PMCID: PMC5763324 DOI: 10.1002/jmv.24941] [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] [Received: 06/03/2017] [Accepted: 08/23/2017] [Indexed: 12/22/2022]
Abstract
A pyrazolopyridine HBSC11 was previously identified as a novel inhibitor of human La protein with anti‐hepatitis B virus (HBV) activity. However, the underlying mechanism(s) of HBV inhibition by HBSC11 remains unclear. This study aimed to examine the regulation of microRNA (miRNA) by HBSC11 in HBV‐transformed human hepatoma HepG2.2.15 cells using microarray and quantitative real‐time PCR. Target genes of the differentially expressed miRNAs were predicted and subjected to bioinformatics analysis. Results showed that HBSC11 significantly upregulated the expression of miR‐3912‐5p, miR‐6793‐5p, and miR‐7159‐5p in HepG2.2.15 cells. Target genes of the three miRNAs were mainly involved in the regulation of nucleic acid‐templated transcription, negative regulation of gene expression, nucleic acid binding transcription factor activity and regulation of phosphorylation. In addition, target genes were enriched in certain regulatory pathways related to HBV infection and HBV‐associated disease progression, such as the transforming growth factor (TGF)‐β, Wnt, and p53 signaling. Our study demonstrates the involvement of miR‐3912‐5p, miR‐6793‐5p, and miR‐7159‐5p and the potential modulation of specific pathways (TGF‐β, Wnt, and p53 signaling) in HBSC11‐mediated inhibition of HBV replication. This study provides insight into the molecular mechanism of the action of HBSC11 against HBV infection and will support the development of antiviral drugs targeting La protein.
Collapse
Affiliation(s)
- Jiaqian Pan
- Department of Clinical Pharmacy, Shanghai General Hospital of Nanjing Medical University, Shanghai, China.,Department of Clinical Pharmacy, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shuangmei Tong
- Department of Clinical Pharmacy, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jing Tang
- Department of Clinical Pharmacy, Shanghai General Hospital of Nanjing Medical University, Shanghai, China.,Department of Clinical Pharmacy, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| |
Collapse
|
18
|
Merchante C, Stepanova AN, Alonso JM. Translation regulation in plants: an interesting past, an exciting present and a promising future. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 90:628-653. [PMID: 28244193 DOI: 10.1111/tpj.13520] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 02/17/2017] [Accepted: 02/21/2017] [Indexed: 05/19/2023]
Abstract
Changes in gene expression are at the core of most biological processes, from cell differentiation to organ development, including the adaptation of the whole organism to the ever-changing environment. Although the central role of transcriptional regulation is solidly established and the general mechanisms involved in this type of regulation are relatively well understood, it is clear that regulation at a translational level also plays an essential role in modulating gene expression. Despite the large number of examples illustrating the critical role played by translational regulation in determining the expression levels of a gene, our understanding of the molecular mechanisms behind such types of regulation has been slow to emerge. With the recent development of high-throughput approaches to map and quantify different critical parameters affecting translation, such as RNA structure, protein-RNA interactions and ribosome occupancy at the genome level, a renewed enthusiasm toward studying translation regulation is warranted. The use of these new powerful technologies in well-established and uncharacterized translation-dependent processes holds the promise to decipher the likely complex and diverse, but also fascinating, mechanisms behind the regulation of translation.
Collapse
Affiliation(s)
- Catharina Merchante
- Departamento de Biologia Molecular y Bioquimica, Universidad de Malaga-Instituto de Hortofruticultura Subtropical y Mediterranea, IHSM-UMA-CSIC, Malaga, Andalucía, Spain
| | - Anna N Stepanova
- Department of Plant and Microbial Biology, Genetics Graduate Program, North Carolina State University, Raleigh, NC, 27607, USA
| | - Jose M Alonso
- Department of Plant and Microbial Biology, Genetics Graduate Program, North Carolina State University, Raleigh, NC, 27607, USA
| |
Collapse
|
19
|
Casas C. GRP78 at the Centre of the Stage in Cancer and Neuroprotection. Front Neurosci 2017; 11:177. [PMID: 28424579 PMCID: PMC5380735 DOI: 10.3389/fnins.2017.00177] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 03/17/2017] [Indexed: 12/21/2022] Open
Abstract
The 78-kDa glucose-regulated protein GRP78, also known as BiP and HSP5a, is a multifunctional protein with activities far beyond its well-known role in the unfolded protein response (UPR) which is activated after endoplasmic reticulum (ER) stress in the cells. Most of these newly discovered activities depend on its position within the cell. GRP78 is located mainly in the ER, but it has also been observed in the cytoplasm, the mitochondria, the nucleus, the plasma membrane, and secreted, although it is dedicated mostly to engage endogenous cytoprotective processes. Hence, GRP78 may control either UPR and macroautophagy or may activated phosphatidylinositol 3-kinase (PI3K)/AKT pro-survival pathways. GRP78 influences how tumor cells survive, proliferate, and develop chemoresistance. In neurodegeneration, endogenous mechanisms of neuroprotection are frequently insufficient or dysregulated. Lessons from tumor biology may give us clues about how boosting endogenous neuroprotective mechanisms in age-related neurodegeneration. Herein, the functions of GRP78 are revealed at the center of the stage of apparently opposite sites of the same coin regarding cytoprotection: neurodegeneration and cancer. The goal is to give a comprehensive and critical review that may serve to guide future experiments to identify interventions that will enhance neuroprotection.
Collapse
Affiliation(s)
- Caty Casas
- Department of Cell Biology, Physiology and Immunology, Institut de Neurociències, Universitat Autònoma de BarcelonaBarcelona, Spain
| |
Collapse
|
20
|
Brown KA, Sharifi S, Hussain R, Donaldson L, Bayfield MA, Wilson DJ. Distinct Dynamic Modes Enable the Engagement of Dissimilar Ligands in a Promiscuous Atypical RNA Recognition Motif. Biochemistry 2016; 55:7141-7150. [PMID: 27959512 DOI: 10.1021/acs.biochem.6b00995] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Conformational dynamics play a critical role in ligand binding, often conferring divergent activities and specificities even in species with highly similar ground-state structures. Here, we employ time-resolved electrospray ionization hydrogen-deuterium exchange (TRESI-HDX) to characterize the changes in dynamics that accompany oligonucleotide binding in the atypical RNA recognition motif (RRM2) in the C-terminal domain (CTD) of human La protein. Using this approach, which is uniquely capable of probing changes in the structure and dynamics of weakly ordered regions of proteins, we reveal that binding of RRM2 to a model 23-mer single-stranded RNA and binding of RRM2 to structured IRES domain IV of the hepatitis C viral (HCV) RNA are driven by fundamentally different dynamic processes. In particular, binding of the single-stranded RNA induces helical "unwinding" in a region of the CTD previously hypothesized to play an important role in La and La-related protein-associated RNA remodeling, while the same region becomes less dynamic upon engagement with the double-stranded HCV RNA. Binding of double-stranded RNA also involves less penetration into the RRM2 binding pocket and more engagement with the unstructured C-terminus of the La CTD. The complementarity between TRESI-HDX and Δδ nuclear magnetic resonance measurements for ligand binding analysis is also explored.
Collapse
Affiliation(s)
- Kerene A Brown
- Department of Chemistry, York University , Toronto, ON M3J 1P3, Canada
- Centre for Research in Mass Spectrometry, York University , Toronto, ON M3J 1P3, Canada
| | - Samel Sharifi
- Department of Biology, York University , Toronto, ON M3J 1P3, Canada
| | - Rawaa Hussain
- Department of Biology, York University , Toronto, ON M3J 1P3, Canada
| | - Logan Donaldson
- Department of Biology, York University , Toronto, ON M3J 1P3, Canada
| | - Mark A Bayfield
- Department of Biology, York University , Toronto, ON M3J 1P3, Canada
- Centre for Research in Biomolecular Interactions, York University , Toronto, ON M3J 1P3, Canada
| | - Derek J Wilson
- Department of Chemistry, York University , Toronto, ON M3J 1P3, Canada
- Centre for Research in Mass Spectrometry, York University , Toronto, ON M3J 1P3, Canada
- Centre for Research in Biomolecular Interactions, York University , Toronto, ON M3J 1P3, Canada
| |
Collapse
|
21
|
Vincent HA, Ziehr B, Moorman NJ. Human Cytomegalovirus Strategies to Maintain and Promote mRNA Translation. Viruses 2016; 8:97. [PMID: 27089357 PMCID: PMC4848592 DOI: 10.3390/v8040097] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 03/25/2016] [Accepted: 03/31/2016] [Indexed: 02/02/2023] Open
Abstract
mRNA translation requires the ordered assembly of translation initiation factors and ribosomal subunits on a transcript. Host signaling pathways regulate each step in this process to match levels of protein synthesis to environmental cues. In response to infection, cells activate multiple defenses that limit viral protein synthesis, which viruses must counteract to successfully replicate. Human cytomegalovirus (HCMV) inhibits host defenses that limit viral protein expression and manipulates host signaling pathways to promote the expression of both host and viral proteins necessary for virus replication. Here we review key regulatory steps in mRNA translation, and the strategies used by HCMV to maintain protein synthesis in infected cells.
Collapse
Affiliation(s)
- Heather A Vincent
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Benjamin Ziehr
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Nathaniel J Moorman
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| |
Collapse
|
22
|
Stavraka C, Blagden S. The La-Related Proteins, a Family with Connections to Cancer. Biomolecules 2015; 5:2701-22. [PMID: 26501340 PMCID: PMC4693254 DOI: 10.3390/biom5042701] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 09/21/2015] [Accepted: 10/07/2015] [Indexed: 01/09/2023] Open
Abstract
The evolutionarily-conserved La-related protein (LARP) family currently comprises Genuine La, LARP1, LARP1b, LARP4, LARP4b, LARP6 and LARP7. Emerging evidence suggests each LARP has a distinct role in transcription and/or mRNA translation that is attributable to subtle sequence variations within their La modules and specific C-terminal domains. As emerging research uncovers the function of each LARP, it is evident that La, LARP1, LARP6, LARP7 and possibly LARP4a and 4b are dysregulated in cancer. Of these, LARP1 is the first to be demonstrated to drive oncogenesis. Here, we review the role of each LARP and the evidence linking it to malignancy. We discuss a future strategy of targeting members of this protein family as cancer therapy.
Collapse
Affiliation(s)
- Chara Stavraka
- Ovarian Cancer Research Centre, Institute for Reproductive and Developmental Biology, Imperial College, Du Cane Road, London W12 0HS, UK.
| | - Sarah Blagden
- Ovarian Cancer Research Centre, Institute for Reproductive and Developmental Biology, Imperial College, Du Cane Road, London W12 0HS, UK.
- Department of Oncology, University of Oxford, Churchill Hospital, Old Road, Oxford OX3 7LE, UK.
| |
Collapse
|
23
|
Cui Y, Rao S, Chang B, Wang X, Zhang K, Hou X, Zhu X, Wu H, Tian Z, Zhao Z, Yang C, Huang T. AtLa1 protein initiates IRES-dependent translation of WUSCHEL mRNA and regulates the stem cell homeostasis of Arabidopsis in response to environmental hazards. PLANT, CELL & ENVIRONMENT 2015; 38:2098-2114. [PMID: 25764476 DOI: 10.1111/pce.12535] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2014] [Revised: 03/01/2015] [Accepted: 03/02/2015] [Indexed: 06/04/2023]
Abstract
Plant stem cells are hypersensitive to environmental hazards throughout their life cycle, but the mechanism by which plants safeguard stem cell homeostasis in response to environmental hazards is largely unknown. The homeodomain transcription factor WUSCHEL (WUS) protein maintains the stem cell pool in the shoot apical meristem of Arabidopsis. Here, we demonstrate that the translation of WUS mRNA is directed by an internal ribosomal entry site (IRES) located in the 5'-untranslated region. The AtLa1 protein, an RNA-binding factor, binds to the 5'-untranslated region and initiates the IRES-dependent translation of WUS mRNA. Knockdown of AtLa1 expression represses the WUS IRES-dependent translation and leads to the arrest of growth and development. The AtLa1 protein is mainly located in the nucleoplasm. However, environmental hazards promote the nuclear-to-cytoplasmic translocation of the AtLa1 protein, which further enhances the IRES-dependent translation of WUS mRNA. Genetic evidence indicates that the WUS protein increases the tolerance of the shoot apical meristem to environmental hazards. Based on these results, we conclude that the stem cell niche in Arabidopsis copes with environmental hazards by enhancing the IRES-dependent translation of WUS mRNA under the control of the AtLa1 protein.
Collapse
Affiliation(s)
- Yuchao Cui
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Fujian, 361102, China
| | - Shaofei Rao
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Fujian, 361102, China
| | - Beibei Chang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Fujian, 361102, China
| | - Xiaoshuang Wang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Fujian, 361102, China
| | - Kaidian Zhang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Fujian, 361102, China
| | - Xueliang Hou
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Fujian, 361102, China
| | - Xueyi Zhu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Fujian, 361102, China
| | - Haijun Wu
- School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Zhaoxia Tian
- School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Zhong Zhao
- School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Chengwei Yang
- Guangdong Key Laboratory of Biotechnology for Plant Development, College of Life Science, South China Normal University, Guangzhou, 510631, China
| | - Tao Huang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Fujian, 361102, China
| |
Collapse
|
24
|
Kuehnert J, Sommer G, Zierk AW, Fedarovich A, Brock A, Fedarovich D, Heise T. Novel RNA chaperone domain of RNA-binding protein La is regulated by AKT phosphorylation. Nucleic Acids Res 2015; 43:581-94. [PMID: 25520193 PMCID: PMC4288197 DOI: 10.1093/nar/gku1309] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Revised: 12/02/2014] [Accepted: 12/04/2014] [Indexed: 01/13/2023] Open
Abstract
The cellular function of the cancer-associated RNA-binding protein La has been linked to translation of viral and cellular mRNAs. Recently, we have shown that the human La protein stimulates IRES-mediated translation of the cooperative oncogene CCND1 in cervical cancer cells. However, there is little known about the underlying molecular mechanism by which La stimulates CCND1 IRES-mediated translation, and we propose that its RNA chaperone activity is required. Herein, we show that La binds close to the CCND1 start codon and demonstrate that La's RNA chaperone activity can change the folding of its binding site. We map the RNA chaperone domain (RCD) within the C-terminal region of La in close proximity to a novel AKT phosphorylation site (T389). Phosphorylation at T389 by AKT-1 strongly impairs its RNA chaperone activity. Furthermore, we demonstrate that the RCD as well as T389 is required to stimulate CCND1 IRES-mediated translation in cells. In summary, we provide a model whereby a novel interplay between RNA-binding, RNA chaperoning and AKT phosphorylation of La protein regulates CCND1 IRES-mediated translation.
Collapse
Affiliation(s)
- Julia Kuehnert
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Gunhild Sommer
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Avery W Zierk
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Alena Fedarovich
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Alexander Brock
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Dzmitry Fedarovich
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Tilman Heise
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| |
Collapse
|
25
|
Jiang X, Kanda T, Wu S, Nakamoto S, Saito K, Shirasawa H, Kiyohara T, Ishii K, Wakita T, Okamoto H, Yokosuka O. Suppression of La antigen exerts potential antiviral effects against hepatitis A virus. PLoS One 2014; 9:e101993. [PMID: 24999657 PMCID: PMC4084951 DOI: 10.1371/journal.pone.0101993] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 06/12/2014] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Despite the development and availability of hepatitis A virus (HAV) vaccine, HAV infection is still a major cause of acute hepatitis that occasionally leads to fatal liver disease. HAV internal ribosomal entry-site (IRES) is one of the attractive targets of antiviral agents against HAV. The aim of the present study is to evaluate the impact of La, one of the cellular proteins, on HAV IRES-mediated translation and HAV replication. METHODS AND FINDINGS We investigated the therapeutic feasibility of siRNAs specific for cellular cofactors for HAV IRES-mediated translation in cell culture. It was revealed that siRNA against La could inhibit HAV IRES activities as well as HAV subgenomic replication. We also found that the Janus kinase (JAK) inhibitors SD-1029 and AG490, which reduce La expression, could inhibit HAV IRES activities as well as HAV replication. CONCLUSIONS Inhibition of La by siRNAs and chemical agents could lead to the efficient inhibition of HAV IRES-mediated translation and HAV replication in cell culture models. La might play important roles in HAV replication and is being exploited as one of the therapeutic targets of host-targeting antivirals.
Collapse
Affiliation(s)
- Xia Jiang
- Department of Gastroenterology and Nephrology, Chiba University, Graduate School of Medicine, Chiba, Japan
| | - Tatsuo Kanda
- Department of Gastroenterology and Nephrology, Chiba University, Graduate School of Medicine, Chiba, Japan
| | - Shuang Wu
- Department of Gastroenterology and Nephrology, Chiba University, Graduate School of Medicine, Chiba, Japan
| | - Shingo Nakamoto
- Department of Molecular Virology, Chiba University, Graduate School of Medicine, Chiba, Japan
| | - Kengo Saito
- Department of Molecular Virology, Chiba University, Graduate School of Medicine, Chiba, Japan
| | - Hiroshi Shirasawa
- Department of Molecular Virology, Chiba University, Graduate School of Medicine, Chiba, Japan
| | - Tomoko Kiyohara
- Department of Virology II, National Institute of Infectious Diseases, Musashimurayama, Japan
| | - Koji Ishii
- Department of Virology II, National Institute of Infectious Diseases, Musashimurayama, Japan
| | - Takaji Wakita
- Department of Virology II, National Institute of Infectious Diseases, Musashimurayama, Japan
| | - Hiroaki Okamoto
- Division of Virology, Department of Infection and Immunity, Jichi Medical University School of Medicine, Shimotsuke, Japan
| | - Osamu Yokosuka
- Department of Gastroenterology and Nephrology, Chiba University, Graduate School of Medicine, Chiba, Japan
| |
Collapse
|
26
|
Chan SW. Establishment of chronic hepatitis C virus infection: Translational evasion of oxidative defence. World J Gastroenterol 2014; 20:2785-2800. [PMID: 24659872 PMCID: PMC3961964 DOI: 10.3748/wjg.v20.i11.2785] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 12/03/2013] [Accepted: 01/15/2014] [Indexed: 02/06/2023] Open
Abstract
Hepatitis C virus (HCV) causes a clinically important disease affecting 3% of the world population. HCV is a single-stranded, positive-sense RNA virus belonging to the genus Hepacivirus within the Flaviviridae family. The virus establishes a chronic infection in the face of an active host oxidative defence, thus adaptation to oxidative stress is key to virus survival. Being a small RNA virus with a limited genomic capacity, we speculate that HCV deploys a different strategy to evade host oxidative defence. Instead of counteracting oxidative stress, it utilizes oxidative stress to facilitate its own survival. Translation is the first step in the replication of a plus strand RNA virus so it would make sense if the virus can exploit the host oxidative defence in facilitating this very first step. This is particularly true when HCV utilizes an internal ribosome entry site element in translation, which is distinctive from that of cap-dependent translation of the vast majority of cellular genes, thus allowing selective translation of genes under conditions when global protein synthesis is compromised. Indeed, we were the first to show that HCV translation was stimulated by an important pro-oxidant-hydrogen peroxide in hepatocytes, suggesting that HCV is able to adapt to and utilize the host anti-viral response to facilitate its own translation thus allowing the virus to thrive under oxidative stress condition to establish chronicity. Understanding how HCV translation is regulated under oxidative stress condition will advance our knowledge on how HCV establishes chronicity. As chronicity is the initiator step in disease progression this will eventually lead to a better understanding of pathogenicity, which is particularly relevant to the development of anti-virals and improved treatments of HCV patients using anti-oxidants.
Collapse
|
27
|
Human La protein interaction with GCAC near the initiator AUG enhances hepatitis C Virus RNA replication by promoting linkage between 5' and 3' untranslated regions. J Virol 2013; 87:6713-26. [PMID: 23552417 DOI: 10.1128/jvi.00525-13] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Human La protein has been implicated in facilitating the internal initiation of translation as well as replication of hepatitis C virus (HCV) RNA. Previously, we demonstrated that La interacts with the HCV internal ribosome entry site (IRES) around the GCAC motif near the initiator AUG within stem-loop IV by its RNA recognition motif (RRM) (residues 112 to 184) and influences HCV translation. In this study, we have deciphered the role of this interaction in HCV replication in a hepatocellular carcinoma cell culture system. We incorporated mutation of the GCAC motif in an HCV monocistronic subgenomic replicon and a pJFH1 construct which altered the binding of La and checked HCV RNA replication by reverse transcriptase PCR (RT-PCR). The mutation drastically affected HCV replication. Furthermore, to address whether the decrease in replication is a consequence of translation inhibition or not, we incorporated the same mutation into a bicistronic replicon and observed a substantial decrease in HCV RNA levels. Interestingly, La overexpression rescued this inhibition of replication. More importantly, we observed that the mutation reduced the association between La and NS5B. The effect of the GCAC mutation on the translation-to-replication switch, which is regulated by the interplay between NS3 and La, was further investigated. Additionally, our analyses of point mutations in the GCAC motif revealed distinct roles of each nucleotide in HCV replication and translation. Finally, we showed that a specific interaction of the GCAC motif with human La protein is crucial for linking 5' and 3' ends of the HCV genome. Taken together, our results demonstrate the mechanism of regulation of HCV replication by interaction of the cis-acting element GCAC within the HCV IRES with human La protein.
Collapse
|
28
|
Petz M, Them NCC, Huber H, Mikulits W. PDGF enhances IRES-mediated translation of Laminin B1 by cytoplasmic accumulation of La during epithelial to mesenchymal transition. Nucleic Acids Res 2012; 40:9738-49. [PMID: 22904067 PMCID: PMC3479205 DOI: 10.1093/nar/gks760] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The extracellular matrix protein Laminin B1 (LamB1) regulates tumor cell migration and invasion. Carcinoma cells acquire invasive properties by epithelial to mesenchymal transition (EMT), which is a fundamental step in dissemination of metastatic cells from the primary tumor. Recently, we showed that enhanced translation of LamB1 upon EMT of malignant hepatocytes is mediated by an internal ribosome entry site (IRES). We demonstrated that the IRES transacting factor La binds the minimal IRES motif and positively modulates IRES activity of LamB1. Here, we show that platelet-derived growth factor (PDGF) enhances IRES activity of LamB1 by the increasing cytoplasmic localization of La during EMT. Accordingly, cells expressing dominant negative PDGF receptor display reduced cytoplasmic accumulation of La and show no elevation of IRES activity or endogenous LamB1 levels after stimulation with PDGF. Furthermore, La-mediated regulation of LamB1 IRES activity predominantly depends on MAPK/ERK signaling downstream of PDGF. Notably, LamB1 expression is not significantly downregulated by the impairment of the translation initiation factor eIF4E. In vivo, knockdown of La associated with decreased LamB1 expression and reduced tumor growth. Together, these data suggest that PDGF is required for the cytoplasmic accumulation of La that triggers IRES-dependent translation of LamB1 during EMT.
Collapse
Affiliation(s)
- Michaela Petz
- Department of Medicine I, Institute of Cancer Research, Comprehensive Cancer Center Vienna, Medical University of Vienna, Borschkegasse 8a, 1090 Vienna, Austria
| | | | | | | |
Collapse
|
29
|
Zhang J, Dinh TN, Kappeler K, Tsaprailis G, Chen QM. La autoantigen mediates oxidant induced de novo Nrf2 protein translation. Mol Cell Proteomics 2012; 11:M111.015032. [PMID: 22207702 PMCID: PMC3433904 DOI: 10.1074/mcp.m111.015032] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 12/25/2011] [Indexed: 01/20/2023] Open
Abstract
Nrf2 gene encodes a transcription factor that regulates the expression of a cluster of antioxidant and detoxification genes. Recent works from our laboratory indicate that oxidative stress causes rapid de novo synthesis of Nrf2 protein. We have found that 5' Untranslated Region (5'UTR) of Nrf2 allows the mRNA to undergo an Internal Ribosomal Entry Site (IRES) mediated protein translation. Using liquid chromatography tandem MS, we have discovered that La/SSB protein bound to Nrf2 5'UTR in response to oxidative stress. In vitro RNA binding and in vivo ribonucleoprotein immunoprecipitation showed H(2)O(2) dose and time dependent increases of La/SSB binding to Nrf2 5'UTR. La/SSB protein translocated from the nuclei to cytoplasm and distributed in the perinuclear space in cells treated with H(2)O(2). Isolation of ribosomal fractions indicated that oxidants caused an association of La/SSB with ribosomes. Physical interaction of La/SSB with representative proteins from the small or large subunits of ribosomes was found to increase in cells responding to H(2)O(2) treatment. Knocking down La/SSB gene with siRNA prevented Nrf2 protein elevation or Nrf2 5'UTR activation by oxidants. In contrast, overexpression of La/SSB gene was able to enhance Nrf2 5'UTR activation and Nrf2 protein increase. Our data suggest that oxidants cause nuclear export of La/SSB protein and subsequent association of La/SSB with Nrf2 5'UTR and ribosomes. These events contribute to de novo Nrf2 protein translation because of oxidative stress.
Collapse
Affiliation(s)
- Jack Zhang
- From the ‡Department of Pharmacology, University of Arizona, College of Medicine, 1501 N. Campbell Ave, Tucson, Arizona 85724
| | - Thai Nho Dinh
- From the ‡Department of Pharmacology, University of Arizona, College of Medicine, 1501 N. Campbell Ave, Tucson, Arizona 85724
| | - Kyle Kappeler
- From the ‡Department of Pharmacology, University of Arizona, College of Medicine, 1501 N. Campbell Ave, Tucson, Arizona 85724
| | - George Tsaprailis
- §Center for Toxicology, College of Pharmacy, 1703 E. Mabel St Tucson, Arizona 85721
| | - Qin M. Chen
- From the ‡Department of Pharmacology, University of Arizona, College of Medicine, 1501 N. Campbell Ave, Tucson, Arizona 85724
| |
Collapse
|
30
|
Versatility of RNA-Binding Proteins in Cancer. Comp Funct Genomics 2012; 2012:178525. [PMID: 22666083 PMCID: PMC3359819 DOI: 10.1155/2012/178525] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 02/28/2012] [Indexed: 01/22/2023] Open
Abstract
Posttranscriptional gene regulation is a rapid and efficient process to adjust the proteome of a cell to a changing environment. RNA-binding proteins (RBPs) are the master regulators of mRNA processing and translation and are often aberrantly expressed in cancer. In addition to well-studied transcription factors, RBPs are emerging as fundamental players in tumor development. RBPs and their mRNA targets form a complex network that plays a crucial role in tumorigenesis. This paper describes mechanisms by which RBPs influence the expression of well-known oncogenes, focusing on precise examples that illustrate the versatility of RBPs in posttranscriptional control of cancer development. RBPs appeared very early in evolution, and new RNA-binding domains and combinations of them were generated in more complex organisms. The identification of RBPs, their mRNA targets, and their mechanism of action have provided novel potential targets for cancer therapy.
Collapse
|
31
|
The 3'-terminal hexamer sequence of classical swine fever virus RNA plays a role in negatively regulating the IRES-mediated translation. PLoS One 2012; 7:e33764. [PMID: 22432046 PMCID: PMC3303849 DOI: 10.1371/journal.pone.0033764] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 02/17/2012] [Indexed: 12/14/2022] Open
Abstract
The 3′ untranslated region (UTR) is usually involved in the switch of the translation and replication for a positive-sense RNA virus. To understand the 3′ UTR involved in an internal ribosome entry site (IRES)-mediated translation in Classical swine fever virus (CSFV), we first confirmed the predicted secondary structure (designated as SLI, SLII, SLIII, and SLIV) by enzymatic probing. Using a reporter assay in which the luciferase expression is under the control of CSFV 5′ and 3′ UTRs, we found that the 3′ UTR harbors the positive and negative regulatory elements for translational control. Unlike other stem loops, SLI acts as a repressor for expression of the reporter gene. The negative cis-acting element in SLI is further mapped to the very 3′-end hexamer CGGCCC sequence. Further, the CSFV IRES-mediated translation can be enhanced by the heterologous 3′-ends such as the poly(A) or the 3′ UTR of Hepatitis C virus (HCV). Interestingly, such an enhancement was repressed by flanking this hexamer to the end of poly(A) or HCV 3′ UTR. After sequence comparison and alignment, we have found that this hexamer sequence could hypothetically base pair with the sequence in the IRES IIId1, the 40 S ribosomal subunit binding site for the translational initiation, located at the 5′ UTR. In conclusion, we have found that the 3′-end terminal sequence can play a role in regulating the translation of CSFV.
Collapse
|
32
|
Petz M, Them N, Huber H, Beug H, Mikulits W. La enhances IRES-mediated translation of laminin B1 during malignant epithelial to mesenchymal transition. Nucleic Acids Res 2012; 40:290-302. [PMID: 21896617 PMCID: PMC3245933 DOI: 10.1093/nar/gkr717] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 07/26/2011] [Accepted: 08/21/2011] [Indexed: 12/13/2022] Open
Abstract
The majority of transcripts that harbor an internal ribosome entry site (IRES) are involved in cancer development via corresponding proteins. A crucial event in tumor progression referred to as epithelial to mesenchymal transition (EMT) allows carcinoma cells to acquire invasive properties. The translational activation of the extracellular matrix component laminin B1 (LamB1) during EMT has been recently reported suggesting an IRES-mediated mechanism. In this study, the IRES activity of LamB1 was determined by independent bicistronic reporter assays. Strong evidences exclude an impact of cryptic promoter or splice sites on IRES-driven translation of LamB1. Furthermore, no other LamB1 mRNA species arising from alternative transcription start sites or polyadenylation signals were detected that account for its translational control. Mapping of the LamB1 5'-untranslated region (UTR) revealed the minimal LamB1 IRES motif between -293 and -1 upstream of the start codon. Notably, RNA affinity purification showed that the La protein interacts with the LamB1 IRES. This interaction and its regulation during EMT were confirmed by ribonucleoprotein immunoprecipitation. In addition, La was able to positively modulate LamB1 IRES translation. In summary, these data indicate that the LamB1 IRES is activated by binding to La which leads to translational upregulation during hepatocellular EMT.
Collapse
Affiliation(s)
- Michaela Petz
- Department of Medicine I, Division: Institute of Cancer Research, Comprehensive Cancer Center Vienna, Medical University of Vienna, Borschkegasse 8a, 1090 Vienna and Institute for Animal Breeding and Genetics, University of Veterinary Medicine I, Veterinärplatz 1, 1210 Vienna, Austria
| | - Nicole Them
- Department of Medicine I, Division: Institute of Cancer Research, Comprehensive Cancer Center Vienna, Medical University of Vienna, Borschkegasse 8a, 1090 Vienna and Institute for Animal Breeding and Genetics, University of Veterinary Medicine I, Veterinärplatz 1, 1210 Vienna, Austria
| | - Heidemarie Huber
- Department of Medicine I, Division: Institute of Cancer Research, Comprehensive Cancer Center Vienna, Medical University of Vienna, Borschkegasse 8a, 1090 Vienna and Institute for Animal Breeding and Genetics, University of Veterinary Medicine I, Veterinärplatz 1, 1210 Vienna, Austria
| | - Hartmut Beug
- Department of Medicine I, Division: Institute of Cancer Research, Comprehensive Cancer Center Vienna, Medical University of Vienna, Borschkegasse 8a, 1090 Vienna and Institute for Animal Breeding and Genetics, University of Veterinary Medicine I, Veterinärplatz 1, 1210 Vienna, Austria
| | - Wolfgang Mikulits
- Department of Medicine I, Division: Institute of Cancer Research, Comprehensive Cancer Center Vienna, Medical University of Vienna, Borschkegasse 8a, 1090 Vienna and Institute for Animal Breeding and Genetics, University of Veterinary Medicine I, Veterinärplatz 1, 1210 Vienna, Austria
| |
Collapse
|
33
|
Inoue Y, Sato H, Fujita K, Tsukiyama-Kohara K, Yoneda M, Kai C. Selective translation of the measles virus nucleocapsid mRNA by la protein. Front Microbiol 2011; 2:173. [PMID: 22007186 PMCID: PMC3188812 DOI: 10.3389/fmicb.2011.00173] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Accepted: 08/02/2011] [Indexed: 02/05/2023] Open
Abstract
Measles, caused by measles virus (MeV) infection, is the leading cause of death in children because of secondary infections attributable to MeV-induced immune suppression. Recently, we have shown that wild-type MeVs induce the suppression of protein synthesis in host cells (referred to as “shutoff”) and that viral mRNAs are preferentially translated under shutoff conditions in infected cells. To determine the mechanism behind the preferential translation of viral mRNA, we focused on the 5′ untranslated region (UTR) of nucleocapsid (N) mRNA. The La/SSB autoantigen (La) was found to specifically bind to an N-5′UTR probe. Recombinant La enhanced the translation of luciferase mRNA containing the N-5′UTR (N-fLuc), and RNA interference of La suppressed N-fLuc translation. Furthermore, recombinant MeV lacking the La-binding motif in the N-5′UTR displayed delayed viral protein synthesis and growth kinetics at an early phase of infection. These results suggest that La induced predominant translation of N mRNA via binding to its 5′UTR under shutoff conditions. This is the first report on a cellular factor that specifically regulates paramyxovirus mRNA translation.
Collapse
Affiliation(s)
- Yoshihisa Inoue
- Laboratory Animal Research Center, Institute of Medical Science, The University of Tokyo Tokyo, Japan
| | | | | | | | | | | |
Collapse
|
34
|
Shi-Chen Ou D, Lee SB, Chu CS, Chang LH, Chung BC, Juan LJ. Transcriptional activation of endoplasmic reticulum chaperone GRP78 by HCMV IE1-72 protein. Cell Res 2011; 21:642-53. [PMID: 21221131 PMCID: PMC3203653 DOI: 10.1038/cr.2011.10] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Glucose-regulated protein 78 (GRP78), a key regulator of endoplasmic reticulum (ER) stress, facilitates cancer cell growth and viral replication. The mechanism leading to grp78 gene activation during viral infection is largely unknown. In this study, we show that the immediate-early 1 (IE1-72) protein of the human cytomegalovirus (HCMV) is essential for HCMV-mediated GRP78 activation. IE1-72 upregulated grp78 gene expression depending on the ATP-binding site, the zinc-finger domain and the putative leucine-zipper motif of IE1-72, as well as the ER stress response elements (ERSEs) on the grp78 promoter. The purified IE1-72 protein bound to the CCAAT box within ERSE in vitro, whereas deletion mutants of IE1-72 deficient in grp78 promoter stimulation failed to do so. Moreover, IE1-72 binding to the grp78 promoter in infected cells accompanied the recruitment of TATA box-binding protein-associated factor 1 (TAF1), a histone acetyltransferase, and the increased level of acetylated histone H4, an indicator of active-state chromatin. These results provide evidence that HCMV IE1-72 activates grp78 gene expression through direct promoter binding and modulation of the local chromatin structure, indicating an active viral mechanism of cellular chaperone induction for viral growth.
Collapse
Affiliation(s)
- Derick Shi-Chen Ou
- Institute of Molecular and Cellular Biology, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu 300
- Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 115
| | - Sung-Bau Lee
- Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 115
| | - Chi-Shuen Chu
- Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 115
| | - Liang-Hao Chang
- Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 115
| | - Bon-chu Chung
- Institute of Molecular and Cellular Biology, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu 300
- Institute of Molecular Biology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 115
- Tel: +886-2-2789-9215; Fax: +886-2-27826085
E-mail:
| | - Li-Jung Juan
- Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 115
- Institute of Molecular Medicine, National Taiwan University, No.7, Chung San South Road, Taipei 100
- Tel: +886-2-27871234; Fax: +886-2-27898811
E-mail:
| |
Collapse
|
35
|
Garlapati S, Saraiya AA, Wang CC. A La autoantigen homologue is required for the internal ribosome entry site mediated translation of giardiavirus. PLoS One 2011; 6:e18263. [PMID: 21479239 PMCID: PMC3066225 DOI: 10.1371/journal.pone.0018263] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Accepted: 02/28/2011] [Indexed: 12/11/2022] Open
Abstract
Translation of Giardiavirus (GLV) mRNA is initiated at an internal ribosome entry site (IRES) in the viral transcript. The IRES localizes to a downstream portion of 5′ untranslated region (UTR) and a part of the early downstream coding region of the transcript. Recent studies indicated that the IRES does not require a pre-initiation complex to initiate translation but may directly recruit the small ribosome subunit with the help of a number of trans-activating protein factors. A La autoantigen homologue in the viral host Giardia lamblia, GlLa, was proposed as one of the potential trans-activating factors based on its specific binding to GLV-IRES in vitro. In this study, we further elucidated the functional role of GlLa in GLV-IRES mediated translation in Giardia by knocking down GlLa with antisense morpholino oligo, which resulted in a reduction of GLV-IRES activity by 40%. An over-expression of GlLa in Giardia moderately stimulated GLV-IRES activity by 20%. A yeast inhibitory RNA (IRNA), known to bind mammalian and yeast La autoantigen and inhibit Poliovirus and Hepatitis C virus IRES activities in vitro and in vivo, was also found to bind to GlLa protein in vitro and inhibited GLV-IRES function in vivo. The C-terminal domain of La autoantigen interferes with the dimerization of La and inhibits its function. An over-expression of the C-terminal domain (200–348aa) of GlLa in Giardia showed a dominant-negative effect on GLV-IRES activity, suggesting a potential inhibition of GlLa dimerization. HA tagged GlLa protein was detected mainly in the cytoplasm of Giardia, thus supporting a primary role of GlLa in translation initiation in Giardiavirus.
Collapse
Affiliation(s)
- Srinivas Garlapati
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Ashesh A. Saraiya
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Ching C. Wang
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
| |
Collapse
|
36
|
Sommer G, Dittmann J, Kuehnert J, Reumann K, Schwartz PE, Will H, Coulter BL, Smith MT, Heise T. The RNA-binding protein La contributes to cell proliferation and CCND1 expression. Oncogene 2011; 30:434-44. [PMID: 20856207 DOI: 10.1038/onc.2010.425] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 07/22/2010] [Accepted: 08/10/2010] [Indexed: 11/08/2022]
Abstract
The La protein is an essential RNA-binding protein implicated in different aspects of RNA metabolism. Herein, we report that small interfering (siRNA)-mediated La depletion reduces cell proliferation of different cell lines concomitant with a reduction in cyclin D1 (CCND1) protein. To exclude off-target effects we demonstrate that exogenous La expression in La-depleted cells restores cell proliferation and CCND1 protein levels. In contrast, proliferation of immortalized CCND1 knockout cells is not affected by La depletion, supporting a functional coherence between La, CCND1 and proliferation. Furthermore, we document by reversible in vivo crosslinking and ribonucleoprotein (RNP) immunoprecipitation an association of the La protein with CCND1 messengerRNA and that CCND1 internal ribosome entry site (IRES)-dependent translation is modulated by La protein level within the cell. In addition, we show elevated La protein expression in cervical cancer tissue and its correlation with aberrant CCND1 protein levels in cervical tumor tissue lysates. In conclusion, this study establishes a role of La in cell proliferation and CCND1 expression and demonstrates for the first time an overexpression of the RNA-binding protein La in solid tumors.
Collapse
Affiliation(s)
- G Sommer
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Human cytomegalovirus induces the endoplasmic reticulum chaperone BiP through increased transcription and activation of translation by using the BiP internal ribosome entry site. J Virol 2010; 84:11479-86. [PMID: 20739513 DOI: 10.1128/jvi.01330-10] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The endoplasmic reticulum (ER) chaperone BiP (immunoglobulin binding protein) plays a major role in the control of the unfolded protein response. We have previously shown that BiP levels are dramatically increased during human cytomegalovirus (HCMV) infection, where BiP performs unique roles in viral assembly and egress. We show that BiP mRNA levels increase during infection due to activation of the BiP promoter by the major immediate-early (MIE) proteins. The BiP promoter, like other ER stress-activated promoters, contains endoplasmic reticulum stress elements (ERSEs), which are activated by unfolded protein response (UPR)-induced transcription factors. However, these elements are not needed for MIE protein-mediated transcriptional activation; thus, a virus-specific transcriptional activation mechanism is used. Transcriptional activation results in only a 3- to 4-fold increase in BiP mRNA, suggesting that additional mechanisms for BiP production are utilized. The BiP mRNA contains an internal ribosome entry site (IRES) which increases the level of BiP mRNA translation. We show that utilization of the BiP IRES is dramatically increased in HCMV-infected cells. Utilization of the BiP IRES can be activated by the La autoantigen, also called Sjögren's syndrome antigen B (SSB). We show that SSB/La levels are significantly increased during HCMV infection, and SSB/La depletion causes the loss of BiP IRES utilization and lowers endogenous BiP levels in infected cells. Our data show that BiP levels increase in HCMV-infected cells through the combination of increased BiP gene transcription mediated by the MIE proteins and increased BiP mRNA translation due to SSB/La-induced utilization of the BiP IRES.
Collapse
|
38
|
Bayfield MA, Yang R, Maraia RJ. Conserved and divergent features of the structure and function of La and La-related proteins (LARPs). BIOCHIMICA ET BIOPHYSICA ACTA 2010; 1799:365-78. [PMID: 20138158 PMCID: PMC2860065 DOI: 10.1016/j.bbagrm.2010.01.011] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 01/08/2010] [Accepted: 01/27/2010] [Indexed: 12/19/2022]
Abstract
Genuine La proteins contain two RNA binding motifs, a La motif (LAM) followed by a RNA recognition motif (RRM), arranged in a unique way to bind RNA. These proteins interact with an extensive variety of cellular RNAs and exhibit activities in two broad categories: i) to promote the metabolism of nascent pol III transcripts, including precursor-tRNAs, by binding to their common, UUU-3'OH containing ends, and ii) to modulate the translation of certain mRNAs involving an unknown binding mechanism. Characterization of several La-RNA crystal structures as well as biochemical studies reveal insight into their unique two-motif domain architecture and how the LAM recognizes UUU-3'OH while the RRM binds other parts of a pre-tRNA. Recent studies of members of distinct families of conserved La-related proteins (LARPs) indicate that some of these harbor activity related to genuine La proteins, suggesting that their UUU-3'OH binding mode has been appropriated for the assembly and regulation of a specific snRNP (e.g., 7SK snRNP assembly by hLARP7/PIP7S). Analyses of other LARP family members suggest more diverged RNA binding modes and specialization for cytoplasmic mRNA-related functions. Thus it appears that while genuine La proteins exhibit broad general involvement in both snRNA-related and mRNA-related functions, different LARP families may have evolved specialized activities in either snRNA or mRNA-related functions. In this review, we summarize recent progress that has led to greater understanding of the structure and function of La proteins and their roles in tRNA processing and RNP assembly dynamics, as well as progress on the different LARPs.
Collapse
Affiliation(s)
- Mark A Bayfield
- Department of Biology, York University, Toronto, ON, Canada.
| | | | | |
Collapse
|
39
|
Exon junction complex enhances translation of spliced mRNAs at multiple steps. Biochem Biophys Res Commun 2009; 384:334-40. [PMID: 19409878 DOI: 10.1016/j.bbrc.2009.04.123] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Accepted: 04/24/2009] [Indexed: 11/23/2022]
Abstract
Translation of spliced mRNAs is enhanced by exon junction complex (EJC), which is deposited on mRNAs as a result of splicing. Although this phenomenon itself is well known, the underlying molecular mechanism remains poorly understood. Here we show, using siRNAs against Y14 and eIF4AIII and spliced or intronless constructs that contain different types of internal ribosome entry sites (IRESes), that Y14 and eIF4AIII increase translation of spliced mRNAs before and after formation of the 80S ribosome complex, respectively. These results suggest that EJC modulates translation of spliced mRNA at multiple steps.
Collapse
|
40
|
Bousquet-Antonelli C, Deragon JM. A comprehensive analysis of the La-motif protein superfamily. RNA (NEW YORK, N.Y.) 2009; 15:750-64. [PMID: 19299548 PMCID: PMC2673062 DOI: 10.1261/rna.1478709] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 01/22/2009] [Indexed: 05/24/2023]
Abstract
The extremely well-conserved La motif (LAM), in synergy with the immediately following RNA recognition motif (RRM), allows direct binding of the (genuine) La autoantigen to RNA polymerase III primary transcripts. This motif is not only found on La homologs, but also on La-related proteins (LARPs) of unrelated function. LARPs are widely found amongst eukaryotes and, although poorly characterized, appear to be RNA-binding proteins fulfilling crucial cellular functions. We searched the fully sequenced genomes of 83 eukaryotic species scattered along the tree of life for the presence of LAM-containing proteins. We observed that these proteins are absent from archaea and present in all eukaryotes (except protists from the Plasmodium genus), strongly suggesting that the LAM is an ancestral motif that emerged early after the archaea-eukarya radiation. A complete evolutionary and structural analysis of these proteins resulted in their classification into five families: the genuine La homologs and four LARP families. Unexpectedly, in each family a conserved domain representing either a classical RRM or an RRM-like motif immediately follows the LAM of most proteins. An evolutionary analysis of the LAM-RRM/RRM-L regions shows that these motifs co-evolved and should be used as a single entity to define the functional region of interaction of LARPs with their substrates. We also found two extremely well conserved motifs, named LSA and DM15, shared by LARP6 and LARP1 family members, respectively. We suggest that members of the same family are functional homologs and/or share a common molecular mode of action on different RNA baits.
Collapse
|
41
|
The hnRNA-binding proteins hnRNP L and PTB are required for efficient translation of the Cat-1 arginine/lysine transporter mRNA during amino acid starvation. Mol Cell Biol 2009; 29:2899-912. [PMID: 19273590 DOI: 10.1128/mcb.01774-08] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The response to amino acid starvation involves the global decrease of protein synthesis and an increase in the translation of some mRNAs that contain an internal ribosome entry site (IRES). It was previously shown that translation of the mRNA for the arginine/lysine amino acid transporter Cat-1 increases during amino acid starvation via a mechanism that utilizes an IRES in the 5' untranslated region of the Cat-1 mRNA. It is shown here that polypyrimidine tract binding protein (PTB) and an hnRNA binding protein, heterogeneous nuclear ribonucleoprotein L (hnRNP L), promote the efficient translation of Cat-1 mRNA during amino acid starvation. Association of both proteins with Cat-1 mRNA increased during starvation with kinetics that paralleled that of IRES activation, although the levels and subcellular distribution of the proteins were unchanged. The sequence CUUUCU within the Cat-1 IRES was important for PTB binding and for the induction of translation during amino acid starvation. Binding of hnRNP L to the IRES or the Cat-1 mRNA in vivo was independent of PTB binding but was not sufficient to increase IRES activity or Cat-1 mRNA translation during amino acid starvation. In contrast, binding of PTB to the Cat-1 mRNA in vivo required hnRNP L. A wider role of hnRNP L in mRNA translation was suggested by the decrease of global protein synthesis in cells with reduced hnRNP L levels. It is proposed that PTB and hnRNP L are positive regulators of Cat-1 mRNA translation via the IRES under stress conditions that cause a global decrease of protein synthesis.
Collapse
|
42
|
Brenet F, Socci ND, Sonenberg N, Holland EC. Akt phosphorylation of La regulates specific mRNA translation in glial progenitors. Oncogene 2009; 28:128-39. [PMID: 18836485 DOI: 10.1038/onc.2008.376] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 08/19/2008] [Accepted: 08/22/2008] [Indexed: 11/09/2022]
Abstract
The Akt signaling pathway activity increases as normal tissue progresses to malignant transformation, and regulates the translation of specific messenger RNAs (mRNAs) through multiple mechanisms. We have identified one such mechanism of Akt-dependent translation control as involving the lupus autoantigen La. La is an RNA-associated protein that contains multiple trafficking elements to support the interaction with RNAs in different subcellular locations. We show here that the La protein is a direct target of the serine/threonine protein kinase Akt on threonine 301, and La nuclear export in mouse glial progenitors, as well as its association with polysomes is modulated by Akt activity. Using a functional approach to determine the network of genes affected by La in the cytoplasm by microarray analysis of polysome-bound mRNAs, we found that La binds 34% of the polysome bound mRNAs and regulates the expression of a specific pool of mRNAs under KRas/Akt activation. Therefore, La appears to be an important contributor to Akt-mediated translational regulation of these transcripts in murine glial cells.
Collapse
Affiliation(s)
- F Brenet
- Department of Cancer Biology and Genetics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
| | | | | | | |
Collapse
|
43
|
Cecconi D, Zamò A, Bianchi E, Parisi A, Barbi S, Milli A, Rinalducci S, Rosenwald A, Hartmann E, Zolla L, Chilosi M. Signal transduction pathways of mantle cell lymphoma: A phosphoproteome-based study. Proteomics 2008; 8:4495-506. [DOI: 10.1002/pmic.200800080] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
44
|
Ul-Hussain M, Dermietzel R, Zoidl G. Characterization of the internal IRES element of the zebrafish connexin55.5 reveals functional implication of the polypyrimidine tract binding protein. BMC Mol Biol 2008; 9:92. [PMID: 18947383 PMCID: PMC2579433 DOI: 10.1186/1471-2199-9-92] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Accepted: 10/23/2008] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Connexin55.5 (Cx55.5) is a gap junction protein with horizontal cell-restricted expression in zebrafish accumulating at dendritic sites within the receptor-horizontal cell complex in form of hemichannels where light-dependent plasticity occurs. This connexin is the first example of a gap junction protein processed to form two protein isoforms from a monocistronic message by an IRES mediated process. The nuclear occurrence of a carboxy-terminal fragment of this protein provides evidence that this gap junction protein may participate in a putative cytoplasmic to nuclear signal transfer. RESULTS We characterized the IRES element of Cx55.5 in terms of sequence elements necessary for its activity and protein factor(s), which may play a role for its function. Two stretches of polypyrimidine tracts designated PPT1 and PPT2 which influence the IRES activity of this neuronal gap junction protein were identified. Selective deletion of PPT1 results in an appreciable decrease of the IRES activity, while the deletion of PPT2 results in a complete loss. RNA-EMSA and UV-cross linking experiments showed that protein complexes bind to this IRES element, of which the polypyrimidine tract binding protein (PTB) was identified as one of the interacting partners with influence on IRES activity. These results indicate that PTB conveys a role in the regulation of the IRES activity of Cx55.5. CONCLUSION Our findings indicate that the activity of the IRES element of the neuronal gap junction protein Cx55.5 is subject of regulation through flanking polypyrimidine tracts, and that the non-canonical trans-activation factor PTB plays an essential role in this process. This observation is of considerable importance and may provide initial insight into molecular-functional relationships of electrical coupling in horizontal cells.
Collapse
Affiliation(s)
- Mahboob Ul-Hussain
- Department of Neuroanatomy and Molecular Brain Research, Ruhr-University Bochum, Bochum, Germany.
| | | | | |
Collapse
|
45
|
Iron increases translation initiation directed by internal ribosome entry site of hepatitis C virus. Virus Genes 2008; 37:154-60. [PMID: 18566883 DOI: 10.1007/s11262-008-0250-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Accepted: 06/05/2008] [Indexed: 12/21/2022]
Abstract
Although increased liver iron in individuals with chronic hepatitis C virus (HCV) is associated with a poor response to interferon therapy, the underlying molecular mechanisms are poorly understood. In this study, we show that iron enhances the translation initiation mediated by the internal ribosome entry site (IRES) of HCV. We also demonstrate by UV cross-linking analysis that specific cellular proteins bind to HCV 5' untranslated region (5' UTR) in an iron-dependent manner. Notably, p85 and p110 are competed out for their binding to HCV 5' UTR when excess amounts of iron-responsive element (IRE) competitor RNAs are treated. This indicates that at least these two factors are common proteins for binding to HCV 5' UTR and IRE. Our results, taken together, suggest that intracellular iron modulates the iron sensing pathway and HCV IRES-dependent translation by changing the binding affinities of the common cellular factors to IRE and HCV IRES, respectively. As a consequence, the coordinated regulation of gene expression by intracellular iron could provide favorable conditions for HCV proliferation.
Collapse
|
46
|
Identification of novel posttranscriptional targets of the BCR/ABL oncoprotein by ribonomics: requirement of E2F3 for BCR/ABL leukemogenesis. Blood 2007; 111:816-28. [PMID: 17925491 DOI: 10.1182/blood-2007-05-090472] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several RNA binding proteins (RBPs) have been implicated in the progression of chronic myelogenous leukemia (CML) from the indolent chronic phase to the aggressively fatal blast crisis. In the latter phase, expression and function of specific RBPs are aberrantly regulated at transcriptional or posttranslational levels by the constitutive kinase activity of the BCR/ABL oncoprotein. As a result, altered expression/function of RBPs leads to increased resistance to apoptotic stimuli, enhanced survival, growth advantage, and differentiation arrest of CD34+ progenitors from patients in CML blast crisis. Here, we identify the mRNAs bound to the hnRNP-A1, hnRNP-E2, hnRNP-K, and La/SSB RBPs in BCR/ABLtransformed myeloid cells. Interestingly, we found that the mRNA encoding the transcription factor E2F3 associates to hnRNP-A1 through a conserved binding site located in the E2F3 3' untranslated region (UTR). E2F3 levels were up-regulated in CML-BCCD34+ in a BCR/ABL kinase- and hnRNP-A1 shuttling-dependent manner. Moreover, by using shRNA-mediated E2F3 knock-down and BCR/ABL-transduced lineage-negative bone marrow cells from E2F3+/+ and E2F3-/- mice, we show that E2F3 expression is important for BCR/ABL clonogenic activity and in vivo leukemogenic potential. Thus, the complexity of the mRNA/RBP network, together with the discovery of E2F3 as an hnRNP-A1-regulated factor, outlines the relevant role played by RBPs in posttranscriptional regulation of CML development and progression.
Collapse
|
47
|
van Niekerk EA, Willis DE, Chang JH, Reumann K, Heise T, Twiss JL. Sumoylation in axons triggers retrograde transport of the RNA-binding protein La. Proc Natl Acad Sci U S A 2007; 104:12913-8. [PMID: 17646655 PMCID: PMC1937566 DOI: 10.1073/pnas.0611562104] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
A surprisingly large population of mRNAs has been shown to localize to sensory axons, but few RNA-binding proteins have been detected in these axons. These axonal mRNAs include several potential binding targets for the La RNA chaperone protein. La is transported into axonal processes in both culture and peripheral nerve. Interestingly, La is posttranslationally modified in sensory neurons by sumoylation. In axons, small ubiquitin-like modifying polypeptides (SUMO)-La interacts with dynein, whereas native La interacts with kinesin. Lysine 41 is required for sumoylation, and sumoylation-incompetent La(K41R) shows only anterograde transport, whereas WT La shows both anterograde and retrograde transport in axons. Thus, sumoylation of La determines the directionality of its transport within the axonal compartment, with SUMO-La likely recycling to the cell body.
Collapse
Affiliation(s)
- Erna A. van Niekerk
- *Department of Biological Sciences, University of Delaware, Newark, DE 19713
| | - Dianna E. Willis
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, DE 19803
| | - Jay H. Chang
- Neural Development and Plasticity Section, Laboratory of Cellular and Synaptic Neurophysiology, National Institute of Child Health and Human Development–National Institutes of Health, Bethesda, MD 20892
| | - Kerstin Reumann
- Heinrich Pette Institute for Experimental Virology and Immunology, University of Hamburg, D-20251 Hamburg, Germany; and
| | - Tilman Heise
- Heinrich Pette Institute for Experimental Virology and Immunology, University of Hamburg, D-20251 Hamburg, Germany; and
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425
| | - Jeffery L. Twiss
- *Department of Biological Sciences, University of Delaware, Newark, DE 19713
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, DE 19803
- To whom correspondence should be addressed. E-mail:
| |
Collapse
|
48
|
Fleurdépine S, Deragon JM, Devic M, Guilleminot J, Bousquet-Antonelli C. A bona fide La protein is required for embryogenesis in Arabidopsis thaliana. Nucleic Acids Res 2007; 35:3306-21. [PMID: 17459889 PMCID: PMC1904278 DOI: 10.1093/nar/gkm200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 03/21/2007] [Accepted: 03/21/2007] [Indexed: 01/28/2023] Open
Abstract
Searches in the Arabidopsis thaliana genome using the La motif as query revealed the presence of eight La or La-like proteins. Using structural and phylogenetic criteria, we identified two putative genuine La proteins (At32 and At79) and showed that both are expressed throughout plant development but at different levels and under different regulatory conditions. At32, but not At79, restores Saccharomyces cerevisiae La nuclear functions in non-coding RNAs biogenesis and is able to bind to plant 3'-UUU-OH RNAs. We conclude that these La nuclear functions are conserved in Arabidopsis and supported by At32, which we renamed as AtLa1. Consistently, AtLa1 is predominantly localized to the plant nucleoplasm and was also detected in the nucleolar cavity. The inactivation of AtLa1 in Arabidopsis leads to an embryonic-lethal phenotype with deficient embryos arrested at early globular stage of development. In addition, mutant embryonic cells display a nucleolar hypertrophy suggesting that AtLa1 is required for normal ribosome biogenesis. The identification of two distantly related proteins with all structural characteristics of genuine La proteins suggests that these factors evolved to a certain level of specialization in plants. This unprecedented situation provides a unique opportunity to dissect the very different aspects of this crucial cellular activity.
Collapse
Affiliation(s)
- Sophie Fleurdépine
- CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France
| | - Jean-Marc Deragon
- CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France
| | - Martine Devic
- CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France
| | - Jocelyne Guilleminot
- CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France
| | - Cécile Bousquet-Antonelli
- CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France
| |
Collapse
|
49
|
Kamrud KI, Custer M, Dudek JM, Owens G, Alterson KD, Lee JS, Groebner JL, Smith JF. Alphavirus replicon approach to promoterless analysis of IRES elements. Virology 2007; 360:376-87. [PMID: 17156813 PMCID: PMC1885372 DOI: 10.1016/j.virol.2006.10.049] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2006] [Revised: 08/30/2006] [Accepted: 10/30/2006] [Indexed: 02/05/2023]
Abstract
Here we describe a system for promoterless analysis of putative internal ribosome entry site (IRES) elements using an alphavirus (family Togaviridae) replicon vector. The system uses the alphavirus subgenomic promoter to produce transcripts that, when modified to contain a spacer region upstream of an IRES element, allow analysis of cap-independent translation of genes of interest (GOI). If the IRES element is removed, translation of the subgenomic transcript can be reduced >95% compared to the same transcript containing a functional IRES element. Alphavirus replicons, used in this manner, offer an alternative to standard dicistronic DNA vectors or in vitro translation systems currently used to analyze putative IRES elements. In addition, protein expression levels varied depending on the spacer element located upstream of each IRES. The ability to modulate the level of expression from alphavirus vectors should extend the utility of these vectors in vaccine development.
Collapse
Affiliation(s)
- K I Kamrud
- AlphaVax, Inc., 2 Triangle Drive, Research Triangle Park, NC 27709-0307, USA.
| | | | | | | | | | | | | | | |
Collapse
|
50
|
Lewis SM, Veyrier A, Hosszu Ungureanu N, Bonnal S, Vagner S, Holcik M. Subcellular relocalization of a trans-acting factor regulates XIAP IRES-dependent translation. Mol Biol Cell 2007; 18:1302-11. [PMID: 17287399 PMCID: PMC1838995 DOI: 10.1091/mbc.e06-06-0515] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Revised: 01/19/2007] [Accepted: 01/31/2007] [Indexed: 01/15/2023] Open
Abstract
Translation of the X-linked inhibitor of apoptosis (XIAP) proceeds by internal ribosome entry site (IRES)-mediated initiation, a process that is physiologically important because XIAP expression is essential for cell survival under conditions of compromised cap-dependent translation, such as cellular stress. The regulation of internal initiation requires the interaction of IRES trans-acting factors (ITAFs) with the IRES element. We used RNA-affinity chromatography to identify XIAP ITAFs and isolated the heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1). We find that hnRNP A1 interacts with XIAP IRES RNA both in vitro and in vivo and that hnRNP A1 negatively regulates XIAP IRES activity. Moreover, XIAP IRES-dependent translation is significantly reduced when hnRNP A1 accumulates in the cytoplasm. Osmotic shock, a cellular stress that causes cytoplasmic accumulation of hnRNP A1, also leads to a decrease in XIAP levels that is abrogated by knockdown of hnRNP A1 expression. These results suggest that the subcellular localization of hnRNP A1 is an important determinant of its ability to negatively regulate XIAP IRES activity, suggesting that the subcellular distribution of ITAFs plays a critical role in regulating IRES-dependent translation. Our findings demonstrate that cytoplasmic hnRNP A1 is a negative regulator of XIAP IRES-dependent translation, indicating a novel function for the cytoplasmic form of this protein.
Collapse
Affiliation(s)
- Stephen M. Lewis
- *Apoptosis Research Centre, Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, K1H 8L1, Canada
| | - Anne Veyrier
- INSERM U563, Toulouse, F-31000, France
- Institut Claudius Régaud, Toulouse, F-31052, France; and
- Université Toulouse III Paul Sabatier, Toulouse, F-31000, France
| | - Nicoleta Hosszu Ungureanu
- *Apoptosis Research Centre, Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, K1H 8L1, Canada
| | - Sophie Bonnal
- INSERM U563, Toulouse, F-31000, France
- Institut Claudius Régaud, Toulouse, F-31052, France; and
- Université Toulouse III Paul Sabatier, Toulouse, F-31000, France
| | - Stéphan Vagner
- INSERM U563, Toulouse, F-31000, France
- Institut Claudius Régaud, Toulouse, F-31052, France; and
- Université Toulouse III Paul Sabatier, Toulouse, F-31000, France
| | - Martin Holcik
- *Apoptosis Research Centre, Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, K1H 8L1, Canada
| |
Collapse
|