151
|
eIF4E3 acts as a tumor suppressor by utilizing an atypical mode of methyl-7-guanosine cap recognition. Proc Natl Acad Sci U S A 2013; 110:3877-82. [PMID: 23431134 DOI: 10.1073/pnas.1216862110] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recognition of the methyl-7-guanosine (m(7)G) cap structure on mRNA is an essential feature of mRNA metabolism and thus gene expression. Eukaryotic translation initiation factor 4E (eIF4E) promotes translation, mRNA export, proliferation, and oncogenic transformation dependent on this cap-binding activity. eIF4E-cap recognition is mediated via complementary charge interactions of the positively charged m(7)G cap between the negative π-electron clouds from two aromatic residues. Here, we demonstrate that a variant subfamily, eIF4E3, specifically binds the m(7)G cap in the absence of an aromatic sandwich, using instead a different spatial arrangement of residues to provide the necessary electrostatic and van der Waals contacts. Contacts are much more extensive between eIF4E3-cap than other family members. Structural analyses of other cap-binding proteins indicate this recognition mode is atypical. We demonstrate that eIF4E3 relies on this cap-binding activity to act as a tumor suppressor, competing with the growth-promoting functions of eIF4E. In fact, reduced eIF4E3 in high eIF4E cancers suggests that eIF4E3 underlies a clinically relevant inhibitory mechanism that is lost in some malignancies. Taken together, there is more structural plasticity in cap recognition than previously thought, and this is physiologically relevant.
Collapse
|
152
|
Klein BY, Tamir H, Hirschberg DL, Glickstein SB, Welch MG. Oxytocin modulates mTORC1 pathway in the gut. Biochem Biophys Res Commun 2013; 432:466-71. [PMID: 23410756 DOI: 10.1016/j.bbrc.2013.01.121] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 01/29/2013] [Indexed: 12/12/2022]
Abstract
Our recent findings of a weaning-related pattern of oxytocin (OT) and OT receptor (OTR) expression in the rat enteric nervous system and in villus-crypt enterocytes, together with the known high level and stability of OT in breast milk support that OT may play a role in gut function and development. We previously described a biphasic dose-response of the PI3K/Akt pathway in gut cells treated with OT. Activation peaked at 62.5 nM OT (30 min) and coincided with OTR internalization. Here we use automated Western blotting to further explore OT-elicited changes in Akt and pAkt(T308), as well as in downstream substrates p70 S6 kinase-1 (S6K1) and eIF-4E binding protein 1 (4E-BP1). Relative to fresh growth medium (FGM) alone, our results showed OT in FGM reduced the abundance and phosphorylation of S6K1 and the phosphorylation of 4E-BP1, both substrates of mammalian target of rapamycin complex 1 (mTORC1). Phosphorylation of mTORC1 regulator, Raptor(S792), was increased by high and low OT concentrations, with predicted inhibitory effects on mTORC1. OT thus downregulates anabolic effects induced by FGM activity catalyzed by mTORC1. OT is a regulator of the PI3K/Akt/mTORC1 pathway in Caco2BB cells and may modulate translation in gut cells.
Collapse
Affiliation(s)
- Benjamin Y Klein
- Department of Pathology & Cell Biology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
| | | | | | | | | |
Collapse
|
153
|
Garvie CW. Solution-based approach to study binding to the eIF4E cap-binding site using CD spectroscopy. Anal Biochem 2012; 434:166-71. [PMID: 23219983 DOI: 10.1016/j.ab.2012.11.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 11/21/2012] [Accepted: 11/26/2012] [Indexed: 01/04/2023]
Abstract
The eukaryotic initiation factor 4E (eIF4E) is the key component of the translational initiation complex that recruits mRNA by binding to a unique "cap" structure located at the 5' end of the mRNA. Overexpression of eIF4E has been implicated in the development of cancer, potentially as a result of increasing the cellular levels of proteins involved in processes that include proliferation and regulation of apoptosis. As a result, the cap-binding site of eIF4E has become a target for the development of anti-cancer therapeutics. The structure of eIF4E bound to the cap mimic 7-methyl-GDP revealed that two tryptophans from different loops in eIF4E sandwiched the 7-methylguanine group between them. This interaction gives rise to a strong exciton coupling signal between the two tryptophans that can be visualized by CD spectroscopy. eIF4E is a challenging protein to work with because of a propensity to aggregate under conditions used in biophysical techniques. CD spectroscopy provides a gentle, solution-based approach to study binding to the cap-binding site of eIF4E. Evidence is provided that the exciton coupling signal can be used to both qualitatively and quantitatively analyze the binding of cap analogs to eIF4E.
Collapse
Affiliation(s)
- Colin W Garvie
- Discovery Technology, Hoffmann-La Roche Inc., 340 Kingsland Street, Nutley, NJ 07110, USA.
| |
Collapse
|
154
|
Mahadevi AS, Sastry GN. Cation-π interaction: its role and relevance in chemistry, biology, and material science. Chem Rev 2012; 113:2100-38. [PMID: 23145968 DOI: 10.1021/cr300222d] [Citation(s) in RCA: 728] [Impact Index Per Article: 60.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- A Subha Mahadevi
- Molecular Modeling Group, CSIR-Indian Institute of Chemical Technology Tarnaka, Hyderabad 500 607, Andhra Pradesh, India
| | | |
Collapse
|
155
|
Wypijewska A, Bojarska E, Lukaszewicz M, Stepinski J, Jemielity J, Davis RE, Darzynkiewicz E. 7-methylguanosine diphosphate (m(7)GDP) is not hydrolyzed but strongly bound by decapping scavenger (DcpS) enzymes and potently inhibits their activity. Biochemistry 2012; 51:8003-13. [PMID: 22985415 DOI: 10.1021/bi300781g] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Decapping scavenger (DcpS) enzymes catalyze the cleavage of a residual cap structure following 3' → 5' mRNA decay. Some previous studies suggested that both m(7)GpppG and m(7)GDP were substrates for DcpS hydrolysis. Herein, we show that mononucleoside diphosphates, m(7)GDP (7-methylguanosine diphosphate) and m(3)(2,2,7)GDP (2,2,7-trimethylguanosine diphosphate), resulting from mRNA decapping by the Dcp1/2 complex in the 5' → 3' mRNA decay, are not degraded by recombinant DcpS proteins (human, nematode, and yeast). Furthermore, whereas mononucleoside diphosphates (m(7)GDP and m(3)(2,2,7)GDP) are not hydrolyzed by DcpS, mononucleoside triphosphates (m(7)GTP and m(3)(2,2,7)GTP) are, demonstrating the importance of a triphosphate chain for DcpS hydrolytic activity. m(7)GTP and m(3)(2,2,7)GTP are cleaved at a slower rate than their corresponding dinucleotides (m(7)GpppG and m(3)(2,2,7)GpppG, respectively), indicating an involvement of the second nucleoside for efficient DcpS-mediated digestion. Although DcpS enzymes cannot hydrolyze m(7)GDP, they have a high binding affinity for m(7)GDP and m(7)GDP potently inhibits DcpS hydrolysis of m(7)GpppG, suggesting that m(7)GDP may function as an efficient DcpS inhibitor. Our data have important implications for the regulatory role of m(7)GDP in mRNA metabolic pathways due to its possible interactions with different cap-binding proteins, such as DcpS or eIF4E.
Collapse
Affiliation(s)
- Anna Wypijewska
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw 02-089, Poland
| | | | | | | | | | | | | |
Collapse
|
156
|
Wang YJ, Wang JF, Ping J, Yu Y, Wang Y, Lian P, Li X, Li YX, Hao P. Computational studies on the substrate interactions of influenza A virus PB2 subunit. PLoS One 2012; 7:e44079. [PMID: 22957044 PMCID: PMC3434214 DOI: 10.1371/journal.pone.0044079] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Accepted: 07/30/2012] [Indexed: 12/28/2022] Open
Abstract
Influenza virus, which spreads around the world in seasonal epidemics and leads to large numbers of deaths every year, has several ribonucleoproteins in the central core of the viral particle. These viral ribonucleoproteins can specifically bind the conserved 3' and 5' caps of the viral RNAs with responsibility for replication and transcription of the viral RNA in the nucleus of infected cells. A fundamental question of most importance is that how the cap-binding proteins in the influenza virus discriminates between capped RNAs and non-capped ones. To get an answer, we performed molecular dynamics simulations and free energy calculations on the influenza A virus PB2 subunit, an important component of the RNP complexes, with a cap analog m7GTP. Our calculations showed that some key residues in the active site, such as Arg355, His357, Glu361 as well as Gln406, could offer significant hydrogen bonding and hydrophobic interactions with the guanine ring of the cap analog m7GTP to form an aromatic sandwich mechanism for the cap recognition and positioning in the active site. Subsequently, we applied this idea to a virtual screening procedure and identified 5 potential candidates that might be inhibitors against the PB2 subunit. Interestingly, 2 candidates Cpd1 and Cpd2 have been already reported to have inhibitory activities to the influenza virus cap-binding proteins. Further calculation also showed that they had comparatively higher binding affinities to the PB2 subunit than that of m7GTP. We believed that our findings could give an atomic insight into the deeper understanding of the cap recognition and binding mechanism, providing useful information for searching or designing novel drugs against influenza viruses.
Collapse
Affiliation(s)
- Ya-Jun Wang
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Jiao Tong University, Shanghai, China
| | - Jing-Fang Wang
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Jiao Tong University, Shanghai, China
- Shanghai Center for Bioinformation and Technology, Shanghai, China
| | - Jie Ping
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Jiao Tong University, Shanghai, China
| | - Yao Yu
- Shanghai Center for Bioinformation and Technology, Shanghai, China
- Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Ying Wang
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Jiao Tong University, Shanghai, China
| | - Peng Lian
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Jiao Tong University, Shanghai, China
| | - Xuan Li
- Shanghai Center for Bioinformation and Technology, Shanghai, China
- Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Yi-Xue Li
- Shanghai Center for Bioinformation and Technology, Shanghai, China
- Bioinformatics Center, Key Laboratory of Systems Biology, Chinese Academy of Sciences, Shanghai, China
| | - Pei Hao
- Shanghai Center for Bioinformation and Technology, Shanghai, China
- Institute of Pasteur, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| |
Collapse
|
157
|
Kinkelin K, Veith K, Grünwald M, Bono F. Crystal structure of a minimal eIF4E-Cup complex reveals a general mechanism of eIF4E regulation in translational repression. RNA (NEW YORK, N.Y.) 2012; 18:1624-34. [PMID: 22832024 PMCID: PMC3425778 DOI: 10.1261/rna.033639.112] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Cup is an eIF4E-binding protein (4E-BP) that plays a central role in translational regulation of localized mRNAs during early Drosophila development. In particular, Cup is required for repressing translation of the maternally contributed oskar, nanos, and gurken mRNAs, all of which are essential for embryonic body axis determination. Here, we present the 2.8 Å resolution crystal structure of a minimal eIF4E-Cup assembly, consisting of the interacting regions of the two proteins. In the structure, two separate segments of Cup contact two orthogonal faces of eIF4E. The eIF4E-binding consensus motif of Cup (YXXXXLΦ) binds the convex side of eIF4E similarly to the consensus of other eIF4E-binding proteins, such as 4E-BPs and eIF4G. The second, noncanonical, eIF4E-binding site of Cup binds laterally and perpendicularly to the eIF4E β-sheet. Mutations of Cup at this binding site were shown to reduce binding to eIF4E and to promote the destabilization of the associated mRNA. Comparison with the binding mode of eIF4G to eIF4E suggests that Cup and eIF4G binding would be mutually exclusive at both binding sites. This shows how a common molecular surface of eIF4E might recognize different proteins acting at different times in the same pathway. The structure provides insight into the mechanism by which Cup disrupts eIF4E-eIF4G interaction and has broader implications for understanding the role of 4E-BPs in translational regulation.
Collapse
Affiliation(s)
- Kerstin Kinkelin
- Max-Planck-Institute for Developmental Biology, 71076 Tübingen, Germany
| | - Katharina Veith
- Max-Planck-Institute for Developmental Biology, 71076 Tübingen, Germany
| | - Marlene Grünwald
- Max-Planck-Institute for Developmental Biology, 71076 Tübingen, Germany
| | - Fulvia Bono
- Max-Planck-Institute for Developmental Biology, 71076 Tübingen, Germany
- Corresponding authorE-mail
| |
Collapse
|
158
|
Piecyk K, Davis RE, Jankowska-Anyszka M. Synthesis of ¹³C- and ¹⁴C-labeled dinucleotide mRNA cap analogues for structural and biochemical studies. Bioorg Med Chem Lett 2012; 22:4391-5. [PMID: 22658555 PMCID: PMC3652009 DOI: 10.1016/j.bmcl.2012.04.120] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 04/26/2012] [Accepted: 04/29/2012] [Indexed: 12/13/2022]
Abstract
Herein we describe the first simple and short method for specific labeling of mono- and trimethylated dinucleotide mRNA cap analogues with (13)C and (14)C isotopes. The labels were introduced within the cap structures either at the N7 for monomethylguanosine cap or N7 and N2 position for trimethylguanosine cap. The compounds designed for structural and biochemical studies will be useful tools for better understanding the role of the mRNA cap structures in pre-mRNA splicing, nucleocytoplasmic transport, translation initiation and mRNA degradation.
Collapse
Affiliation(s)
- Karolina Piecyk
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
| | - Richard E. Davis
- Department of Biochemistry and Molecular Genetics, University of Colorado, School of Medicine, Aurora, CO 80045, USA
| | | |
Collapse
|
159
|
Kore AR, Shanmugasundaram M, Charles I. An efficient synthesis of highly functionalized dinucleotide cap analogs. Tetrahedron Lett 2012. [DOI: 10.1016/j.tetlet.2012.04.133] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
160
|
Szczepaniak SA, Zuberek J, Darzynkiewicz E, Kufel J, Jemielity J. Affinity resins containing enzymatically resistant mRNA cap analogs--a new tool for the analysis of cap-binding proteins. RNA (NEW YORK, N.Y.) 2012; 18:1421-32. [PMID: 22589334 PMCID: PMC3383972 DOI: 10.1261/rna.032078.111] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 04/12/2012] [Indexed: 05/21/2023]
Abstract
Cap-binding proteins have been routinely isolated using m⁷GTP-Sepharose; however, this resin is inefficient for proteins such as DcpS (scavenger decapping enzyme), which interacts not only with the 7-methylguanosine, but also with the second cap base. In addition, DcpS purification may be hindered by the reduced resin capacity due to the ability of DcpS to hydrolyze m⁷GTP. Here, we report the synthesis of new affinity resins, m⁷GpCH₂pp- and m⁷GpCH₂ppA-Sepharoses, with attached cap analogs resistant to hydrolysis by DcpS. Biochemical tests showed that these matrices, as well as a hydrolyzable m⁷GpppA-Sepharose, bind recombinant mouse eIF4E²⁸⁻²¹⁷ specifically and at high capacity. In addition, purification of cap-binding proteins from yeast extracts confirmed the presence of all expected cap-binding proteins, including DcpS in the case of m⁷GpCH₂pp- and m⁷GpCH₂ppA-Sepharoses. In contrast, binding studies in vitro demonstrated that recombinant human DcpS efficiently bound only m⁷GpCH₂ppA-Sepharose. Our data prove the applicability of these novel resins, especially m⁷GpCH₂ppA-Sepharose, in biochemical studies such as the isolation and identification of cap-binding proteins from different organisms.
Collapse
Affiliation(s)
- Sylwia Anna Szczepaniak
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-089 Warsaw, Poland
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, 02-106 Warsaw, Poland
- College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, University of Warsaw, 02-089 Warsaw, Poland
| | - Joanna Zuberek
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-089 Warsaw, Poland
| | - Edward Darzynkiewicz
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-089 Warsaw, Poland
| | - Joanna Kufel
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, 02-106 Warsaw, Poland
| | - Jacek Jemielity
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-089 Warsaw, Poland
| |
Collapse
|
161
|
Diversity of Eukaryotic Translational Initiation Factor eIF4E in Protists. Comp Funct Genomics 2012; 2012:134839. [PMID: 22778692 PMCID: PMC3388326 DOI: 10.1155/2012/134839] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 04/09/2012] [Indexed: 01/01/2023] Open
Abstract
The greatest diversity of eukaryotic species is within the microbial eukaryotes, the protists, with plants and fungi/metazoa representing just two of the estimated seventy five lineages of eukaryotes. Protists are a diverse group characterized by unusual genome features and a wide range of genome sizes from 8.2 Mb in the apicomplexan parasite Babesia bovis to 112,000-220,050 Mb in the dinoflagellate Prorocentrum micans. Protists possess numerous cellular, molecular and biochemical traits not observed in “text-book” model organisms. These features challenge some of the concepts and assumptions about the regulation of gene expression in eukaryotes. Like multicellular eukaryotes, many protists encode multiple eIF4Es, but few functional studies have been undertaken except in parasitic species. An earlier phylogenetic analysis of protist eIF4Es indicated that they cannot be grouped within the three classes that describe eIF4E family members from multicellular organisms. Many more protist sequences are now available from which three clades can be recognized that are distinct from the plant/fungi/metazoan classes. Understanding of the protist eIF4Es will be facilitated as more sequences become available particularly for the under-represented opisthokonts and amoebozoa. Similarly, a better understanding of eIF4Es within each clade will develop as more functional studies of protist eIF4Es are completed.
Collapse
|
162
|
Kowalska J, Osowniak A, Zuberek J, Jemielity J. Synthesis of nucleoside phosphosulfates. Bioorg Med Chem Lett 2012; 22:3661-4. [PMID: 22572581 DOI: 10.1016/j.bmcl.2012.04.039] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 04/04/2012] [Accepted: 04/07/2012] [Indexed: 11/25/2022]
Abstract
We describe an efficient and scalable procedure for the chemical synthesis of nucleoside 5'-phosphosulfates (NPS) from nucleoside 5'-phosphorimidazolides and sulfate bis(tributylammonium) salt. Using this method we obtained various NPS with yields ranging from 70-90%, including adenosine 5'-phosphosulfate (APS) and 2',3'-cyclic precursor of 3'-phosphoadenosine 5'-phosphosulfate (PAPS), which are the key intermediates in the assimilation and metabolism of sulfur in all living organisms.
Collapse
Affiliation(s)
- Joanna Kowalska
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland
| | | | | | | |
Collapse
|
163
|
Chen X, Kopecky DJ, Mihalic J, Jeffries S, Min X, Heath J, Deignan J, Lai S, Fu Z, Guimaraes C, Shen S, Li S, Johnstone S, Thibault S, Xu H, Cardozo M, Shen W, Walker N, Kayser F, Wang Z. Structure-guided design, synthesis, and evaluation of guanine-derived inhibitors of the eIF4E mRNA-cap interaction. J Med Chem 2012; 55:3837-51. [PMID: 22458568 DOI: 10.1021/jm300037x] [Citation(s) in RCA: 167] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The eukaryotic initiation factor 4E (eIF4E) plays a central role in the initiation of gene translation and subsequent protein synthesis by binding the 5' terminal mRNA cap structure. We designed and synthesized a series of novel compounds that display potent binding affinity against eIF4E despite their lack of a ribose moiety, phosphate, and positive charge as present in m7-GMP. The biochemical activity of compound 33 is 95 nM for eIF4E in an SPA binding assay. More importantly, the compound has an IC(50) of 2.5 μM for inhibiting cap-dependent mRNA translation in a rabbit reticular cell extract assay (RRL-IVT). This series of potent, truncated analogues could serve as a promising new starting point toward the design of neutral eIF4E inhibitors with physicochemical properties suitable for cellular activity assessment.
Collapse
Affiliation(s)
- Xiaoqi Chen
- Department of Chemistry Research & Discovery, Amgen Inc., 1120 Veterans Boulevard, South San Francisco, California 94080, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
164
|
Jia Y, Polunovsky V, Bitterman PB, Wagner CR. Cap-dependent translation initiation factor eIF4E: an emerging anticancer drug target. Med Res Rev 2012; 32:786-814. [PMID: 22495651 PMCID: PMC7168506 DOI: 10.1002/med.21260] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cancer cells tend to be more highly dependent on cap‐dependent translation than normal tissues. Thus, proteins involved in the initiation of cap‐dependent translation have emerged as potential anti‐cancer drug targets. Cap‐dependent translation is initiated by the binding of the factor eIF4E to the cap domain of mRNA. Detailed x‐ray crystal and NMR structures are available for eIF4E in association with cap‐analogs, as well as domains of other initiation factors. This review will summarize efforts to design potential antagonist of eIF4E that could be used as new pharmacological tools and anti‐cancer agents and. Insights drawn from these studies should aid in the design of future inhibitors of eIF4E dependent translation initiation. © 2012 Wiley Periodicals, Inc. Med Res Rev., 32, No. 4, 786‐814, 2012
Collapse
Affiliation(s)
- Yan Jia
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | | | | | | |
Collapse
|
165
|
Abstract
A defining feature of many cancers is deregulated translational control. Typically, this occurs at the level of recruitment of the 40S ribosomes to the 5'-cap of cellular messenger RNAs (mRNAs), the rate-limiting step of protein synthesis, which is controlled by the heterotrimeric eukaryotic initiation complex eIF4F. Thus, eIF4F in particular, and translation initiation in general, represent an exploitable vulnerability and unique opportunity for therapeutic intervention in many transformed cells. In this article, we discuss the development, mode of action and biological activity of a number of small-molecule inhibitors that interrupt PI3K/mTOR signaling control of eIF4F assembly, as well as compounds that more directly block eIF4F activity.
Collapse
Affiliation(s)
- Abba Malina
- Department of Biochemistry and McGill University, Montréal, Québec H3G 1Y6, Canada
| | | | | |
Collapse
|
166
|
Visco C, Perrera C, Thieffine S, Sirtori FR, D'Alessio R, Magnaghi P. Development of biochemical assays for the identification of eIF4E-specific inhibitors. ACTA ACUST UNITED AC 2012; 17:581-92. [PMID: 22392810 DOI: 10.1177/1087057112438554] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Control of mRNA translation plays a critical role in cell growth, proliferation, and differentiation and is tightly regulated by AKT and RAS oncogenic pathways. A key player in the regulation of this process is the mRNA 5' cap-binding protein, eukaryotic translation initiation factor 4E (eIF4E). eIF4E contributes to malignancy by selectively enabling the translation of a limited pool of mRNAs that generally encode key proteins involved in cell cycle progression, angiogenesis, and metastasis. Several data indicate that the inhibition of eIF4E in tumor cell lines and xenograft models impairs tumor growth and induces apoptosis; eIF4E, therefore, can be considered a valuable target for cancer therapy. Targeting the cap-binding pocket of eIF4E should represent a way to inhibit all the eIF4E cellular functions. We present here the development and validation of different biochemical assays based on fluorescence polarization and surface plasmon resonance techniques. These assays could support high-throughput screening, further refinement, and characterization of eIF4E inhibitors, as well as selectivity assessment against CBP80/CBP20, the other major cap-binding complex of eukaryotic cells, overall providing a robust roadmap for development of eIF4E-specific inhibitors.
Collapse
Affiliation(s)
- Carlo Visco
- Biotechnology Department, Nerviano Medical Sciences, Nerviano (MI), Italy
| | | | | | | | | | | |
Collapse
|
167
|
Rydzik AM, Kulis M, Lukaszewicz M, Kowalska J, Zuberek J, Darzynkiewicz ZM, Darzynkiewicz E, Jemielity J. Synthesis and properties of mRNA cap analogs containing imidodiphosphate moiety--fairly mimicking natural cap structure, yet resistant to enzymatic hydrolysis. Bioorg Med Chem 2012; 20:1699-710. [PMID: 22316555 DOI: 10.1016/j.bmc.2012.01.013] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Revised: 01/04/2012] [Accepted: 01/09/2012] [Indexed: 11/19/2022]
Abstract
We describe synthesis and properties of eight dinucleotide mRNA 5' cap analogs containing imidodiphosphate moiety within 5',5'-tri- or tetraphosphate bridge (NH-analogs). The compounds were obtained by coupling an appropriate nucleoside 5'-imidodiphosphate with nucleotide P-imidazolide mediated by divalent metal chloride in anhydrous DMF. To evaluate the novel compounds as tools for studying cap-dependent processes, we determined their binding affinities for eukaryotic translation initiation factor 4E, susceptibilities to decapping pyrophosphatase DcpS and, for non-hydrolysable analogs, binding affinities to this enzyme. The results indicate that the O to NH substitution in selected positions of oligophosphate bridge ensures resistance to enzymatic decapping and suggest that interactions of NH-analogs with cap binding proteins fairly mimic interactions of unmodified parent compounds. Finally, we identified NH-analogs as potent inhibitors of cap-dependent translation in cell free system, and evaluated their utility as reagents for obtaining 5' capped mRNAs in vitro to be rather moderate.
Collapse
Affiliation(s)
- Anna M Rydzik
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Zwirki i Wigury 93, Warsaw, Poland
| | | | | | | | | | | | | | | |
Collapse
|
168
|
Siddiqui N, Tempel W, Nedyalkova L, Volpon L, Wernimont AK, Osborne MJ, Park HW, Borden KLB. Structural insights into the allosteric effects of 4EBP1 on the eukaryotic translation initiation factor eIF4E. J Mol Biol 2011; 415:781-92. [PMID: 22178476 DOI: 10.1016/j.jmb.2011.12.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Revised: 11/25/2011] [Accepted: 12/01/2011] [Indexed: 01/11/2023]
Abstract
The eukaryotic translation initiation factor eIF4E plays key roles in cap-dependent translation and mRNA export. These functions rely on binding the 7-methyl-guanosine moiety (5'cap) on the 5'-end of all mRNAs. eIF4E is regulated by proteins such as eIF4G and eIF4E binding proteins (4EBPs) that bind the dorsal surface of eIF4E, distal to the cap binding site, and modulate cap binding activity. Both proteins increase the affinity of eIF4E for 5'cap. Our understanding of the allosteric effects and structural underpinnings of 4EBP1 or eIF4G binding can be advanced by obtaining structural data on cap-free eIF4E bound to one of these proteins. Here, we report the crystal structure of apo-eIF4E and cap-free eIF4E in complex with a 4EBP1 peptide. We also monitored 4EBP1 binding to cap-free eIF4E in solution using NMR. Together, these studies suggest that 4EBP1 transforms eIF4E into a cap-receptive state. NMR methods were also used to compare the allosteric routes activated by 4EBP1, eIF4G, and the arenavirus Z protein, a negative regulator of cap binding. We observed chemical shift perturbation at the dorsal binding site leading to alterations in the core of the protein, which were ultimately communicated to the unoccupied cap binding site of eIF4E. There were notable similarities between the routes taken by 4EBP1 and eIF4G and differences from the negative regulator Z. Thus, binding of 4EBP1 or eIF4G allosterically drives alterations throughout the protein that increase the affinity of eIF4E for the 5'cap.
Collapse
Affiliation(s)
- Nadeem Siddiqui
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, Canada H3T 1J4
| | | | | | | | | | | | | | | |
Collapse
|
169
|
Landeras-Bueno S, Jorba N, Pérez-Cidoncha M, Ortín J. The splicing factor proline-glutamine rich (SFPQ/PSF) is involved in influenza virus transcription. PLoS Pathog 2011; 7:e1002397. [PMID: 22114566 PMCID: PMC3219729 DOI: 10.1371/journal.ppat.1002397] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Accepted: 10/10/2011] [Indexed: 01/15/2023] Open
Abstract
The influenza A virus RNA polymerase is a heterotrimeric complex responsible for viral genome transcription and replication in the nucleus of infected cells. We recently carried out a proteomic analysis of purified polymerase expressed in human cells and identified a number of polymerase-associated cellular proteins. Here we characterise the role of one such host factors, SFPQ/PSF, during virus infection. Down-regulation of SFPQ/PSF by silencing with two independent siRNAs reduced the virus yield by 2–5 log in low-multiplicity infections, while the replication of unrelated viruses as VSV or Adenovirus was almost unaffected. As the SFPQ/PSF protein is frequently associated to NonO/p54, we tested the potential implication of the latter in influenza virus replication. However, down-regulation of NonO/p54 by silencing with two independent siRNAs did not affect virus yields. Down-regulation of SFPQ/PSF by siRNA silencing led to a reduction and delay of influenza virus gene expression. Immunofluorescence analyses showed a good correlation between SFPQ/PSF and NP levels in infected cells. Analysis of virus RNA accumulation in silenced cells showed that production of mRNA, cRNA and vRNA is reduced by more than 5-fold but splicing is not affected. Likewise, the accumulation of viral mRNA in cicloheximide-treated cells was reduced by 3-fold. In contrast, down-regulation of SFPQ/PSF in a recombinant virus replicon system indicated that, while the accumulation of viral mRNA is reduced by 5-fold, vRNA levels are slightly increased. In vitro transcription of recombinant RNPs generated in SFPQ/PSF-silenced cells indicated a 4–5-fold reduction in polyadenylation but no alteration in cap snatching. These results indicate that SFPQ/PSF is a host factor essential for influenza virus transcription that increases the efficiency of viral mRNA polyadenylation and open the possibility to develop new antivirals targeting the accumulation of primary transcripts, a very early step during infection. The influenza A viruses cause annual epidemics and occasional pandemics of respiratory infections that may be life threatening. The viral genome contains 8 RNA molecules forming ribonucleoproteins that replicate and transcribe in the nucleus of infected cells. Influenza viruses are intracellular parasites that need the host cell machinery to replicate. To better understand this virus-cell interplay we purified the viral RNA polymerase expressed in human cells and identified several specifically associated cellular proteins. Here we characterise the role of one of them, the proline-glutamine rich splicing factor (SFPQ/PSF). Down-regulation of SFPQ/PSF indicated that it is essential for virus multiplication. Specifically, the accumulation of messenger and genomic virus-specific RNAs was reduced by SFPQ/PSF silencing in infected cells. Furthermore, transcription of parental ribonucleoproteins was affected by SFPQ/PSF down-regulation. The consequences of silencing SFPQ/PSF on the transcription and replication of a viral recombinant replicon indicated that it is required for virus transcription but not for virus RNA replication. In vitro transcription experiments indicated that SFPQ/PSF increases the efficiency of virus mRNA polyadenylation. This is the first description of a cellular factor essential for influenza virus transcription and opens the possibility to identify inhibitors that target this host-virus interaction and block virus gene expression.
Collapse
Affiliation(s)
- Sara Landeras-Bueno
- Centro Nacional de Biotecnología (CSIC), Campus de Cantoblanco, Madrid, Spain
- CIBER de Enfermedades Respiratorias, ISCIII, Bunyola, Mallorca, Spain
| | - Núria Jorba
- Centro Nacional de Biotecnología (CSIC), Campus de Cantoblanco, Madrid, Spain
- CIBER de Enfermedades Respiratorias, ISCIII, Bunyola, Mallorca, Spain
| | - Maite Pérez-Cidoncha
- Centro Nacional de Biotecnología (CSIC), Campus de Cantoblanco, Madrid, Spain
- CIBER de Enfermedades Respiratorias, ISCIII, Bunyola, Mallorca, Spain
| | - Juan Ortín
- Centro Nacional de Biotecnología (CSIC), Campus de Cantoblanco, Madrid, Spain
- CIBER de Enfermedades Respiratorias, ISCIII, Bunyola, Mallorca, Spain
- * E-mail:
| |
Collapse
|
170
|
Kruse S, Zhong S, Bodi Z, Button J, Alcocer MJC, Hayes CJ, Fray R. A novel synthesis and detection method for cap-associated adenosine modifications in mouse mRNA. Sci Rep 2011; 1:126. [PMID: 22355643 PMCID: PMC3216607 DOI: 10.1038/srep00126] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 10/07/2011] [Indexed: 11/17/2022] Open
Abstract
A method is described for the detection of certain nucleotide modifications adjacent to the 5' 7-methyl guanosine cap of mRNAs from individual genes. The method quantitatively measures the relative abundance of 2'-O-methyl and N6,2'-O-dimethyladenosine, two of the most common modifications. In order to identify and quantitatify the amounts of N6,2'-O-dimethyladenosine, a novel method for the synthesis of modified adenosine phosphoramidites was developed. This method is a one step synthesis and the product can directly be used for the production of N6,2'-O-dimethyladenosine containing RNA oligonucleotides. The nature of the cap-adjacent nucleotides were shown to be characteristic for mRNAs from individual genes transcribed in liver and testis.
Collapse
Affiliation(s)
- Susanne Kruse
- School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | | | | | | | | | | | | |
Collapse
|
171
|
Liu W, Jankowska-Anyszka M, Piecyk K, Dickson L, Wallace A, Niedzwiecka A, Stepinski J, Stolarski R, Darzynkiewicz E, Kieft J, Zhao R, Jones DNM, Davis RE. Structural basis for nematode eIF4E binding an m(2,2,7)G-Cap and its implications for translation initiation. Nucleic Acids Res 2011; 39:8820-32. [PMID: 21965542 PMCID: PMC3203607 DOI: 10.1093/nar/gkr650] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Metazoan spliced leader (SL) trans-splicing generates mRNAs with an m2,2,7G-cap and a common downstream SL RNA sequence. The mechanism for eIF4E binding an m2,2,7G-cap is unknown. Here, we describe the first structure of an eIF4E with an m2,2,7G-cap and compare it to the cognate m7G-eIF4E complex. These structures and Nuclear Magnetic Resonance (NMR) data indicate that the nematode Ascaris suum eIF4E binds the two different caps in a similar manner except for the loss of a single hydrogen bond on binding the m2,2,7G-cap. Nematode and mammalian eIF4E both have a low affinity for m2,2,7G-cap compared with the m7G-cap. Nematode eIF4E binding to the m7G-cap, m2,2,7G-cap and the m2,2,7G-SL 22-nt RNA leads to distinct eIF4E conformational changes. Additional interactions occur between Ascaris eIF4E and the SL on binding the m2,2,7G-SL. We propose interactions between Ascaris eIF4E and the SL impact eIF4G and contribute to translation initiation, whereas these interactions do not occur when only the m2,2,7G-cap is present. These data have implications for the contribution of 5′-UTRs in mRNA translation and the function of different eIF4E isoforms.
Collapse
Affiliation(s)
- Weizhi Liu
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
172
|
Wang Z, Parisien M, Scheets K, Miller WA. The cap-binding translation initiation factor, eIF4E, binds a pseudoknot in a viral cap-independent translation element. Structure 2011; 19:868-80. [PMID: 21645857 DOI: 10.1016/j.str.2011.03.013] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2011] [Revised: 03/11/2011] [Accepted: 03/13/2011] [Indexed: 01/15/2023]
Abstract
Eukaryotic initiation factor eIF4E performs a key early step in translation by specifically recognizing the m⁷GpppN cap structure at the 5' end of cellular mRNAs. Many viral mRNAs lack a 5' cap and thus bypass eIF4E. In contrast, we reported a cap-independent translation element (PTE) in Pea enation mosaic virus RNA2 that binds and requires eIF4E for translation initiation. To understand how this uncapped RNA is bound tightly by eIF4E, we employ SHAPE probing, phylogenetic comparisons with new PTEs discovered in panico- and carmoviruses, footprinting of the eIF4E binding site, and 3D RNA modeling using NAST, MC-Fold, and MC-Sym to predict a compact, 3D structure of the RNA. We propose that the cap-binding pocket of eIF4E clamps around a pseudoknot, placing a highly SHAPE-reactive guanosine in the pocket in place of the normal m⁷GpppN cap. This reveals a new mechanism of mRNA recognition by eIF4E.
Collapse
Affiliation(s)
- Zhaohui Wang
- Plant Pathology Department, and Biochemistry, Biophysics, and Molecular Biology Department, Iowa State University, Ames, IA 50011, USA
| | | | | | | |
Collapse
|
173
|
Geiss BJ, Stahla-Beek HJ, Hannah AM, Gari HH, Henderson BR, Saeedi BJ, Keenan SM. A high-throughput screening assay for the identification of flavivirus NS5 capping enzyme GTP-binding inhibitors: implications for antiviral drug development. ACTA ACUST UNITED AC 2011; 16:852-61. [PMID: 21788392 DOI: 10.1177/1087057111412183] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
There are no effective antivirals currently available for the treatment of flavivirus infection in humans. As such, the identification and characterization of novel drug target sites are critical to developing new classes of antiviral drugs. The flavivirus NS5 N-terminal capping enzyme (CE) is vital for the formation of the viral RNA cap structure, which directs viral polyprotein translation and stabilizes the 5' end of the viral genome. The structure of the flavivirus CE has been solved, and a detailed understanding of the CE-guanosine triphosphate (GTP) and CE-RNA cap interactions is available. Because of the essential nature of the interaction for viral replication, disrupting CE-GTP binding is an attractive approach for drug development. The authors have previously developed a robust assay for monitoring CE-GTP binding in real time. They adapted this assay for high-throughput screening and performed a pilot screen of 46 323 commercially available compounds. A number of small-molecule inhibitors capable of displacing a fluorescently labeled GTP in vitro were identified, and a second functional assay was developed to identify false positives. The results presented indicate that the flavivirus CE cap-binding site is a valuable new target site for antiviral drug discovery and should be further exploited for broad-spectrum anti-flaviviral drug development.
Collapse
Affiliation(s)
- Brian J Geiss
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
| | | | | | | | | | | | | |
Collapse
|
174
|
Jankowska-Anyszka M, Piecyk K, Šamonina-Kosicka J. Synthesis of a new class of ribose functionalized dinucleotide cap analogues for biophysical studies on interaction of cap-binding proteins with the 5' end of mRNA. Org Biomol Chem 2011; 9:5564-72. [PMID: 21701749 DOI: 10.1039/c1ob05425b] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
mRNAs of primitive eukaryotes such as Caenorhabditis elegans and Ascaris summ possess two different caps at their 5' terminus. They have either a typical cap which consists of 7-methylguanosine linked via a 5',5'-triphosphate bridge to the first transcribed nucleotide (MMG cap) or an atypical hypermethylated form with two additional methyl groups at the N2 position (TMG cap). Studies on interaction between the 5' end of mRNA and proteins that specifically recognize its structure have been carried out for several years and they often require chemically modified cap analogues. Here, we present the synthesis of five novel dinucleotide MMG and TMG cap analogues designed for binding studies using biophysical methods such as electron spin resonance (ESR) and surface plasmon resonance (SPR). New analogues were prepared by derivatization of the 2',3'-cis diol of the second nucleotide in the cap structure with levulinic acid, and coupling of the obtained acetal through its carboxylic group with 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino TEMPO), ethylenediamine (EDA) or (+)-biotinyl-3,6,9-trioxaundecanediamine (amine-PEO(3)-biotin).
Collapse
|
175
|
Kiraga-Motoszko K, Niedzwiecka A, Modrak-Wojcik A, Stepinski J, Darzynkiewicz E, Stolarski R. Thermodynamics of molecular recognition of mRNA 5' cap by yeast eukaryotic initiation factor 4E. J Phys Chem B 2011; 115:8746-54. [PMID: 21650456 DOI: 10.1021/jp2012039] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular mechanisms underlying the recognition of the mRNA 5' terminal structure called "cap" by the eukaryotic initiation factor 4E (eIF4E) are crucial for cap-dependent translation. To gain a deeper insight into how the yeast eIF4E interacts with the cap structure, isothermal titration calorimetry and the van't Hoff analysis based on intrinsic protein fluorescence quenching upon titration with a series of chemical cap analogs were performed, providing a consistent thermodynamic description of the binding process in solution. Equilibrium association constants together with thermodynamic parameters revealed similarities and differences between yeast and mammalian eIF4Es. The yeast eIF4E complex formation was enthalpy-driven and entropy-opposed for each cap analog at 293 K. A nontrivial isothermal enthalpy–entropy compensation was found, described by a compensation temperature, T(c) = 411 ± 18 K. For a low affinity analog, 7-methylguanosine monophosphate, a heat capacity change was detected, ΔC(p)° = +5.2 ± 1.3 kJ·mol(-1)·K(-1). The charge-related interactions involving the 5′-5′ triphosphate bridge of the cap and basic amino acid side chains at the yeast eIF4E cap-binding site were significantly weaker (by ΔΔH°(vH) of about +10 kJ·mol(-1)) than those for the mammalian homologues, suggesting their optimization during the evolution.
Collapse
Affiliation(s)
- Katarzyna Kiraga-Motoszko
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-089 Warsaw, Poland
| | | | | | | | | | | |
Collapse
|
176
|
Biosensor-based small molecule fragment screening with biolayer interferometry. J Comput Aided Mol Des 2011; 25:669-76. [DOI: 10.1007/s10822-011-9439-8] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 05/18/2011] [Indexed: 12/11/2022]
|
177
|
Recognition of cap structure by influenza B virus RNA polymerase is less dependent on the methyl residue than recognition by influenza A virus polymerase. J Virol 2011; 85:7504-12. [PMID: 21593178 DOI: 10.1128/jvi.02375-10] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cap-dependent endonuclease activity of the influenza virus RNA-dependent RNA polymerase cleaves host mRNAs to produce capped RNA fragments for primers to initiate viral mRNA synthesis. The influenza A virus (FluA) cap-dependent endonuclease preferentially recognizes the cap1 structure (m(7)GpppNm). However, little is known about the substrate specificity of the influenza B virus (FluB) endonuclease. Here, we determined the substrate specificity of the FluB polymerase using purified viral RNPs and (32)P-labeled polyribonucleotides containing a variety of cap structures (m(7)GpppGm, m(7)GpppG, and GpppG). We found that the FluA polymerase cleaves m(7)G-capped RNAs preferentially. In contrast, the FluB polymerase could efficiently cleave not only m(7)G-capped RNAs but also unmethylated GpppG-RNAs. To identify a key amino acid(s) related to the cap recognition specificity of the PB2 subunit, the transcription activity of FluB polymerases containing mutated cap-binding domains was examined by use of a minireplicon assay system. In the case of FluA PB2, Phe323, His357, and Phe404, which stack the m(7)GTP, and Glu361 and Lys376, which make hydrogen bonds with a guanine base, were essential for the transcription activity. In contrast, in the case of FluB PB2, the stacking interaction of Trp359 with a guanine base and putative hydrogen bonds using Gln325 and Glu363 were enough for the transcription activity. Taking these results together with the result for the cap-binding activity, we propose that the cap recognition pocket of FluB PB2 does not have the specificity for m(7)G-cap structures and thus is more flexible to accept various cap structures than FluA PB2.
Collapse
|
178
|
Su W, Slepenkov S, Grudzien-Nogalska E, Kowalska J, Kulis M, Zuberek J, Lukaszewicz M, Darzynkiewicz E, Jemielity J, Rhoads RE. Translation, stability, and resistance to decapping of mRNAs containing caps substituted in the triphosphate chain with BH3, Se, and NH. RNA (NEW YORK, N.Y.) 2011; 17:978-88. [PMID: 21447710 PMCID: PMC3078746 DOI: 10.1261/rna.2430711] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2010] [Accepted: 02/15/2011] [Indexed: 05/23/2023]
Abstract
Decapping is an essential step in multiple pathways of mRNA degradation. Previously, we synthesized mRNAs containing caps that were resistant to decapping, both to dissect the various pathways for mRNA degradation and to stabilize mRNA for more sustained protein expression. mRNAs containing an α-β CH(2) group are resistant to in vitro cleavage by the decapping enzyme hDcp2 but poorly translated. mRNAs containing an S substitution at the β-phosphate are well translated but only partially resistant to hDcp2. We now describe seven new cap analogs substituted at the β-phosphate with BH(3) or Se, or substituted at either the α-β or β-γ O with NH. The analogs differ in affinity for eIF4E and efficiency of in vitro incorporation into mRNA by T7 RNA polymerase. Luciferase mRNAs capped with these analogs differ in resistance to hDcp2 hydrolysis in vitro, translational efficiency in rabbit reticulocyte lysate and in HeLa cells, and stability in HeLa cells. Whereas mRNAs capped with m(2)(7,2'-O)Gpp(S)pG were previously found to have the most favorable properties of translational efficiency and stability in mammalian cells, mRNAs capped with m(7)Gpp(BH3)pm(7)G are translated with the same efficiency but are more stable. Interestingly, some mRNAs exhibit a lag of up to 60 min before undergoing first-order decay (t(1/2) ≅ 25 min). Only mRNAs that are efficiently capped, resistant to decapping in vitro, and actively translated have long lag phases.
Collapse
Affiliation(s)
- Wei Su
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130-3932, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
179
|
Kore AR, Shanmugasundaram M, Barta TJ. Synthesis and substrate validation of cap analogs containing 7-deazaguanosine moiety by RNA polymerase. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2011; 29:821-30. [PMID: 21128169 DOI: 10.1080/15257770.2010.529860] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
An efficient synthesis of new cap analogs containing 7-deazaguanosine moiety such as m(7)G[5']ppp[5'](7-deaza)G and m₂(7,3'O)G[5']ppp[5'](7-deaza)G is described. The biological substrate validation of these new cap analogs is evaluated with respect to its capping efficiency and in vitro T7 RNA polymerase transcription using standard cap m⁷G[5']ppp[5']G as a control. The capping efficiency and HPLC data reveal that these new analogs are not the substrate for T7 RNA polymerase or SP6 RNA polymerase. The present study highlights the importance of the presence of nitrogen atom at N7-position of the guanosine moiety for the polymerase recognition.
Collapse
Affiliation(s)
- Anilkumar R Kore
- Life Technologies Corporation, Bioorganic Chemistry Division, 2130 Woodward Street, Austin, TX 78744-1832, USA.
| | | | | |
Collapse
|
180
|
Martin F, Barends S, Jaeger S, Schaeffer L, Prongidi-Fix L, Eriani G. Cap-assisted internal initiation of translation of histone H4. Mol Cell 2011; 41:197-209. [PMID: 21255730 DOI: 10.1016/j.molcel.2010.12.019] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Revised: 09/08/2010] [Accepted: 11/10/2010] [Indexed: 11/30/2022]
Abstract
In eukaryotes, a crucial step of translation initiation is the binding of the multifactor complex eIF4F to the 5' end of the mRNA, a prerequisite to recruitment of the activated small ribosomal 43S particle. Histone H4 mRNAs have short 5'UTRs, which do not conform to the conventional scanning-initiation model. Here we show that the ORF of histone mRNA contains two structural elements critical for translation initiation. One of the two structures binds eIF4E without the need of the cap. Ribosomal 43S particles become tethered to this site and directly loaded in the vicinity of the AUG. The other structure, 19 nucleotides downstream of the initiation codon, forms a three-way helix junction, which sequesters the m(7)G cap. This element facilitates direct positioning of the ribosome on the cognate start codon. This unusual translation initiation mode might be considered as a hybrid mechanism between the canonical and the IRES-driven translation initiation process.
Collapse
Affiliation(s)
- Franck Martin
- Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, Institut de Biologie Moléculaire et Cellulaire, 15 rue René Descartes, 67084 Strasbourg CEDEX, France
| | | | | | | | | | | |
Collapse
|
181
|
Ashby JA, Stevenson CEM, Jarvis GE, Lawson DM, Maule AJ. Structure-based mutational analysis of eIF4E in relation to sbm1 resistance to pea seed-borne mosaic virus in pea. PLoS One 2011; 6:e15873. [PMID: 21283665 PMCID: PMC3025909 DOI: 10.1371/journal.pone.0015873] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Accepted: 11/26/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Pea encodes eukaryotic translation initiation factor eIF4E (eIF4E(S)), which supports the multiplication of Pea seed-borne mosaic virus (PSbMV). In common with hosts for other potyviruses, some pea lines contain a recessive allele (sbm1) encoding a mutant eIF4E (eIF4E(R)) that fails to interact functionally with the PSbMV avirulence protein, VPg, giving genetic resistance to infection. METHODOLOGY/PRINCIPAL FINDINGS To study structure-function relationships between pea eIF4E and PSbMV VPg, we obtained an X-ray structure for eIF4E(S) bound to m(7)GTP. The crystallographic asymmetric unit contained eight independent copies of the protein, providing insights into the structurally conserved and flexible regions of eIF4E. To assess indirectly the importance of key residues in binding to VPg and/or m(7)GTP, an extensive range of point mutants in eIF4E was tested for their ability to complement PSbMV multiplication in resistant pea tissues and for complementation of protein translation, and hence growth, in an eIF4E-defective yeast strain conditionally dependent upon ectopic expression of eIF4E. The mutants also dissected individual contributions from polymorphisms present in eIF4E(R) and compared the impact of individual residues altered in orthologous resistance alleles from other crop species. The data showed that essential resistance determinants in eIF4E differed for different viruses although the critical region involved (possibly in VPg-binding) was conserved and partially overlapped with the m(7)GTP-binding region. This overlap resulted in coupled inhibition of virus multiplication and translation in the majority of cases, although the existence of a few mutants that uncoupled the two processes supported the view that the specific role of eIF4E in potyvirus infection may not be restricted to translation. CONCLUSIONS/SIGNIFICANCE The work describes the most extensive structural analysis of eIF4E in relation to potyvirus resistance. In addition to defining functional domains within the eIF4E structure, we identified eIF4E alleles with the potential to convey novel virus resistance phenotypes.
Collapse
Affiliation(s)
- Jamie A. Ashby
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | | | - Gavin E. Jarvis
- School of Pharmacy, Queen's University Belfast, Belfast, United Kingdom
| | - David M. Lawson
- John Innes Centre, Norwich Research Park, Norwich, United Kingdom
| | - Andrew J. Maule
- John Innes Centre, Norwich Research Park, Norwich, United Kingdom
| |
Collapse
|
182
|
Antosiewicz JM, Shugar D. Poisson–Boltzmann continuum-solvation models: applications to pH-dependent properties of biomolecules. MOLECULAR BIOSYSTEMS 2011; 7:2923-49. [DOI: 10.1039/c1mb05170a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
|
183
|
Gosselin P, Oulhen N, Jam M, Ronzca J, Cormier P, Czjzek M, Cosson B. The translational repressor 4E-BP called to order by eIF4E: new structural insights by SAXS. Nucleic Acids Res 2010; 39:3496-503. [PMID: 21183464 PMCID: PMC3082885 DOI: 10.1093/nar/gkq1306] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
eIF4E binding protein (4E-BP) inhibits translation of capped mRNA by binding to the initiation factor eIF4E and is known to be mostly or completely unstructured in both free and bound states. Using small angle X-ray scattering (SAXS), we report here the analysis of 4E-BP structure in solution, which reveals that while 4E-BP is intrinsically disordered in the free state, it undergoes a dramatic compaction in the bound state. Our results demonstrate that 4E-BP and eIF4E form a ‘fuzzy complex’, challenging current visions of eIF4E/4E-BP complex regulation.
Collapse
Affiliation(s)
- Pauline Gosselin
- UPMC Univ Paris 06, UMR 7150, Mer et Santé, Equipe Traduction Cycle Cellulaire et Développement, Station Biologique de Roscoff, 29680 Roscoff, France.
| | | | | | | | | | | | | |
Collapse
|
184
|
Topisirovic I, Svitkin YV, Sonenberg N, Shatkin AJ. Cap and cap-binding proteins in the control of gene expression. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 2:277-98. [PMID: 21957010 DOI: 10.1002/wrna.52] [Citation(s) in RCA: 280] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The 5' mRNA cap structure is essential for efficient gene expression from yeast to human. It plays a critical role in all aspects of the life cycle of an mRNA molecule. Capping occurs co-transcriptionally on the nascent pre-mRNA as it emerges from the RNA exit channel of RNA polymerase II. The cap structure protects mRNAs from degradation by exonucleases and promotes transcription, polyadenylation, splicing, and nuclear export of mRNA and U-rich, capped snRNAs. In addition, the cap structure is required for the optimal translation of the vast majority of cellular mRNAs, and it also plays a prominent role in the expression of eukaryotic, viral, and parasite mRNAs. Cap-binding proteins specifically bind to the cap structure and mediate its functions in the cell. Two major cellular cap-binding proteins have been described to date: eukaryotic translation initiation factor 4E (eIF4E) in the cytoplasm and nuclear cap binding complex (nCBC), a nuclear complex consisting of a cap-binding subunit cap-binding protein 20 (CBP 20) and an auxiliary protein cap-binding protein 80 (CBP 80). nCBC plays an important role in various aspects of nuclear mRNA metabolism such as pre-mRNA splicing and nuclear export, whereas eIF4E acts primarily as a facilitator of mRNA translation. In this review, we highlight recent findings on the role of the cap structure and cap-binding proteins in the regulation of gene expression. We also describe emerging regulatory pathways that control mRNA capping and cap-binding proteins in the cell.
Collapse
Affiliation(s)
- Ivan Topisirovic
- Department of Biochemistry and Goodman Cancer Centre, McGill University, Montréal, QC, Canada
| | | | | | | |
Collapse
|
185
|
Ayuso MI, Hernández-Jiménez M, Martín ME, Salinas M, Alcázar A. New hierarchical phosphorylation pathway of the translational repressor eIF4E-binding protein 1 (4E-BP1) in ischemia-reperfusion stress. J Biol Chem 2010; 285:34355-63. [PMID: 20736160 PMCID: PMC2966049 DOI: 10.1074/jbc.m110.135103] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Eukaryotic initiation factor (eIF) 4E-binding protein 1 (4E-BP1) is a translational repressor that is characterized by its capacity to bind specifically to eIF4E and inhibit its interaction with eIF4G. Phosphorylation of 4E-BP1 regulates eIF4E availability, and therefore, cap-dependent translation, in cell stress. This study reports a physiological study of 4E-BP1 regulation by phosphorylation using control conditions and a stress-induced translational repression condition, ischemia-reperfusion (IR) stress, in brain tissue. In control conditions, 4E-BP1 was found in four phosphorylation states that were detected by two-dimensional gel electrophoresis and Western blotting, which corresponded to Thr69-phosphorylated alone, Thr69- and Thr36/Thr45-phosphorylated, all these plus Ser64 phosphorylation, and dephosphorylation of the sites analyzed. In control or IR conditions, no Thr36/Thr45 phosphorylation alone was detected without Thr69 phosphorylation, and neither was Ser64 phosphorylation without Thr36/Thr45/Thr69 phosphorylation detected. Ischemic stress induced 4E-BP1 dephosphorylation at Thr69, Thr36/Thr45, and Ser64 residues, with 4E-BP1 remaining phosphorylated at Thr69 alone or dephosphorylated. In the subsequent reperfusion, 4E-BP1 phosphorylation was induced at Thr36/Thr45 and Ser64, in addition to Thr69. Changes in 4E-BP1 phosphorylation after IR were according to those found for Akt and mammalian target of rapamycin (mTOR) kinases. These results demonstrate a new hierarchical phosphorylation for 4E-BP1 regulation in which Thr69 is phosphorylated first followed by Thr36/Thr45 phosphorylation, and Ser64 is phosphorylated last. Thr69 phosphorylation alone allows binding to eIF4E, and subsequent Thr36/Thr45 phosphorylation was sufficient to dissociate 4E-BP1 from eIF4E, which led to eIF4E-4G interaction. These data help to elucidate the physiological role of 4E-BP1 phosphorylation in controlling protein synthesis.
Collapse
Affiliation(s)
- María I Ayuso
- Department of Investigation, Hospital Ramón y Cajal, 28034 Madrid, Spain
| | | | | | | | | |
Collapse
|
186
|
May ER, Armen RS, Mannan AM, Brooks CL. The flexible C-terminal arm of the Lassa arenavirus Z-protein mediates interactions with multiple binding partners. Proteins 2010; 78:2251-64. [PMID: 20544962 PMCID: PMC2933069 DOI: 10.1002/prot.22738] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The arenavirus genome encodes for a Z-protein, which contains a RING domain that coordinates two zinc ions, and has been identified as having several functional roles at various stages of the virus life cycle. Z-protein binds to multiple host proteins and has been directly implicated in the promotion of viral budding, repression of mRNA translation, and apoptosis of infected cells. Using homology models of the Z-protein from Lassa strain arenavirus, replica exchange molecular dynamics (MD) was used to refine the structures, which were then subsequently clustered. Population-weighted ensembles of low-energy cluster representatives were predicted based upon optimal agreement of the chemical shifts computed with the SPARTA program with the experimental NMR chemical shifts. A member of the refined ensemble was identified to be a potential binder of budding factor Tsg101 based on its correspondence to the structure of the HIV-1 Gag late domain when bound to Tsg101. Members of these ensembles were docked against the crystal structure of human eIF4E translation initiation factor. Two plausible binding modes emerged based upon their agreement with experimental observation, favorable interaction energies and stability during MD trajectories. Mutations to Z are proposed that would either inhibit both binding mechanisms or selectively inhibit only one mode. The C-terminal domain conformation of the most populated member of the representative ensemble shielded protein-binding recognition motifs for Tsg101 and eIF4E and represents the most populated state free in solution. We propose that C-terminal flexibility is key for mediating the different functional states of the Z-protein.
Collapse
Affiliation(s)
- Eric R. May
- Department of Chemistry and Program in Biophysics, 930 N. University Ave, University of Michigan, Ann Arbor, MI 48109
| | - Roger S. Armen
- Department of Chemistry and Program in Biophysics, 930 N. University Ave, University of Michigan, Ann Arbor, MI 48109
| | - Aristotle M. Mannan
- Department of Chemistry and Program in Biophysics, 930 N. University Ave, University of Michigan, Ann Arbor, MI 48109
| | - Charles L. Brooks
- Department of Chemistry and Program in Biophysics, 930 N. University Ave, University of Michigan, Ann Arbor, MI 48109
| |
Collapse
|
187
|
Ruszczyńska-Bartnik K, Maciejczyk M, Stolarski R. Dynamical insight into Caenorhabditis elegans eIF4E recognition specificity for mono-and trimethylated structures of mRNA 5' cap. J Mol Model 2010; 17:727-37. [PMID: 20535623 PMCID: PMC3076583 DOI: 10.1007/s00894-010-0773-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Accepted: 05/06/2010] [Indexed: 12/01/2022]
Abstract
Specific recognition and binding of the ribonucleic acid 5′ termini (mRNA 5′ cap) by the eukaryotic translation initiation factor 4E (eIF4E) is a key, rate limiting step in translation initiation. Contrary to mammalian and yeast eIF4Es that discriminate in favor of 7-methylguanosine cap, three out of five eIF4E isoforms from the nematode Caenorhabditis elegans as well as eIF4Es from the parasites Schistosome mansoni and Ascaris suum, exhibit dual binding specificity for both 7-methylguanosine-and N2,N2,7-trimethylguanosine cap. To address the problem of the differences in the mechanism of the cap recognition by those highly homologic proteins, we carried out molecular dynamics simulations in water of three factors, IFE-3 and IFE-5 isoforms from C. elegans and murine eIF4E, in the apo form as well as in the complexes with 7-methyl-GDP and N2,N2,7-trimethyl-GDP. The results clearly pointed to a dynamical mechanism of discrimination between each type of the cap, viz. differences in mobility of the loops located at the entrance into the protein binding pockets during the cap association and dissociation. Additionally, our data showed that the hydrogen bond involving the N2-amino group of 7-methylguanosine and the carboxylate of glutamic acid was not stable. The dynamic mechanism proposed here differs from a typical, static one in that the differences in the protein-ligand binding specificity cannot be ascribed to formation and/or disruption of well defined stabilizing contacts.
Collapse
Affiliation(s)
- Katarzyna Ruszczyńska-Bartnik
- Nuclear Magnetic Resonance Laboratory, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | | | | |
Collapse
|
188
|
Guimarães CRW, Kopecky DJ, Mihalic J, Shen S, Jeffries S, Thibault ST, Chen X, Walker N, Cardozo M. Thermodynamic analysis of mRNA cap binding by the human initiation factor eIF4E via free energy perturbations. J Am Chem Soc 2010; 131:18139-46. [PMID: 19924990 DOI: 10.1021/ja9064359] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Eukaryotic mRNAs are appended at the 5' end, with the 7-methylguanosine cap linked by a 5'-5'-triphosphate bridge to the first transcribed nucleoside (m7GpppX). Initiation of cap-dependent translation of mRNA requires direct interaction between the cap structure and the eukaryotic translation initiation factor eIF4E. Biophysical studies of the association between eIF4E and various cap analogs have demonstrated that m(7)GTP binds to the protein ca. -5.0 kcal/mol more favorably than unmethylated GTP. In this work, a thermodynamic analysis of the binding process between eIF4E and several cap analogs has been conducted using Monte Carlo (MC) simulations in conjunction with free energy perturbation (FEP) calculations. To address the role of the 7-methyl group in the eIF4E/m7GpppX cap interaction, binding free energies have been computed for m(7)GTP, GTP, protonated GTP at N(7), the 7-methyldeazaguanosine 5'-triphosphate (m(7)DTP), and 7-deazaguanosine 5'-triphosphate (DTP) cap analogs. The MC/FEP simulations for the GTP-->m(7)DTP transformation demonstrate that half of the binding free energy gain of m(7)GTP with respect to GTP can be attributed to favorable van der Waals interactions with Trp166 and reduced desolvation penalty due to the N(7) methyl group. The methyl group both eliminates the desolvation penalty of the N(7) atom upon binding and creates a larger cavity within the solvent that further facilitates the desolvation step. Analysis of the pair m(7)GTP-m(7)DTP suggests that the remaining gain in affinity is related to the positive charge created on the guanine moiety due to the N(7) methylation. The charge provides favorable cation-pi interactions with Trp56 and Trp102 and decreases the negative molecular charge, which helps the transfer from the solvent, a more polar environment, to the protein.
Collapse
Affiliation(s)
- Cristiano R W Guimarães
- Department of Molecular Structure, Amgen, Inc., 1120 Veterans Boulevard, South San Francisco, California 94080, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
189
|
|
190
|
Casanova E, Priego EM, Jimeno ML, Aguado L, Negri A, Gago F, Camarasa MJ, Pérez-Pérez MJ. Intramolecular Cation−π Interactions As the Driving Force To Restrict the Conformation of Certain Nucleosides. J Org Chem 2010; 75:1974-81. [DOI: 10.1021/jo902677s] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Elena Casanova
- Instituto de Química Médica (CSIC), Juan de la Cierva 3, E-28006 Madrid, Spain
| | - Eva-María Priego
- Instituto de Química Médica (CSIC), Juan de la Cierva 3, E-28006 Madrid, Spain
| | - María-Luisa Jimeno
- Centro de Química Orgánica Lora-Tamayo (CSIC), Juan de la Cierva 3, E-28006 Madrid, Spain
| | - Leire Aguado
- Instituto de Química Médica (CSIC), Juan de la Cierva 3, E-28006 Madrid, Spain
| | - Ana Negri
- Departamento de Farmacología, Universidad de Alcalá, Alcalá de Henares, E-28871 Madrid, Spain
| | - Federico Gago
- Departamento de Farmacología, Universidad de Alcalá, Alcalá de Henares, E-28871 Madrid, Spain
| | - María-José Camarasa
- Instituto de Química Médica (CSIC), Juan de la Cierva 3, E-28006 Madrid, Spain
| | | |
Collapse
|
191
|
Kowalska J, Lukaszewicz M, Zuberek J, Darzynkiewicz E, Jemielity J. Phosphoroselenoate dinucleotides for modification of mRNA 5' end. Chembiochem 2010; 10:2469-73. [PMID: 19739194 DOI: 10.1002/cbic.200900522] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Joanna Kowalska
- Division of Biophysics, Institute of Experimental Physics, Department of Physics, University of Warsaw, Zwirki i Wigury 93, 02-089 Warsaw, Poland
| | | | | | | | | |
Collapse
|
192
|
Mir MA, Sheema S, Haseeb A, Haque A. Hantavirus nucleocapsid protein has distinct m7G cap- and RNA-binding sites. J Biol Chem 2010; 285:11357-68. [PMID: 20164193 DOI: 10.1074/jbc.m110.102459] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Hantaviruses, members of the Bunyaviridae family, are emerging category A pathogens that carry three negative stranded RNA molecules as their genome. Hantavirus nucleocapsid protein (N) is encoded by the smallest S segment genomic RNA (viral RNA). N specifically binds mRNA caps and requires four nucleotides adjacent to the cap for high affinity binding. We show that the N peptide has distinct cap- and RNA-binding sites that independently interact with mRNA cap and viral genomic RNA, respectively. In addition, N can simultaneously bind with both mRNA cap and vRNA. N undergoes distinct conformational changes after binding with either mRNA cap or vRNA or both mRNA cap and vRNA simultaneously. Hantavirus RNA-dependent RNA polymerase (RdRp) uses a capped RNA primer for transcription initiation. The capped RNA primer is generated from host cell mRNA by the cap-snatching mechanism and is supposed to anneal with the 3' terminus of vRNA template during transcription initiation by single G-C base pairing. We show that the capped RNA primer binds at the cap-binding site and induces a conformational change in N. The conformationally altered N with a capped primer loaded at the cap-binding site specifically binds the conserved 3' nine nucleotides of vRNA and assists the bound primer to anneal at the 3' terminus. We suggest that the cap-binding site of N, in conjunction with RdRp, plays a key role during the transcription and replication initiation of vRNA genome.
Collapse
Affiliation(s)
- Mohammad A Mir
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, Kansas 66103, USA.
| | | | | | | |
Collapse
|
193
|
Khan MA, Yumak H, Goss DJ. Kinetic mechanism for the binding of eIF4F and tobacco Etch virus internal ribosome entry site rna: effects of eIF4B and poly(A)-binding protein. J Biol Chem 2010; 284:35461-70. [PMID: 19858189 DOI: 10.1074/jbc.m109.038463] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The wheat germ eukaryotic translation initiation factor (eIF) 4F binds tightly to the mRNA internal ribosome entry site (IRES) of tobacco etch virus (TEV) to promote translation initiation. When eIF4F is limiting, TEV is preferentially translated compared with host cell mRNA. To gain insight into the dynamic process of protein synthesis initiation and the mechanism of binding, the kinetics of eIF4F binding to TEV IRES were examined. The association rate constant (k(on)) and dissociation rate constant (k(off)) for eIF4F binding to IRES were 59 +/- 2.1 micro s(-1) and 12.9 +/- 0.3 s(-1), respectively, comparable with the rates for capped RNA. Binding of eIF4E or eIF4F to the cap of mRNA is the rate-limiting step for initiation of cap-dependent protein synthesis. The concentration dependence of the reactions suggested a simple one-step association mechanism. However, the association rate was reduced more than 10-fold when KCl concentration was increased from 50 to 300 mm, whereas the dissociation rate constant was increased 2-fold. The addition of eIF4B and poly(A)-binding protein enhanced the association rate of eIF4F approximately 3-fold. These results suggest a mechanism where eIF4F initially binds electrostatically, followed by a conformational change to further stabilize binding. Poly(A)-binding protein and eIF4B mainly affect the eIF4F/TEV association rate. These results demonstrate the first direct kinetic measurements of translation initiation factor binding to an IRES.
Collapse
Affiliation(s)
- Mateen A Khan
- Department of Chemistry and Biochemistry, Hunter College and Graduate Center of the City University of New York, New York, New York 10065, USA
| | | | | |
Collapse
|
194
|
Moraes KCM. RNA surveillance: molecular approaches in transcript quality control and their implications in clinical diseases. Mol Med 2010; 16:53-68. [PMID: 19829759 PMCID: PMC2761007 DOI: 10.2119/molmed.2009.00026] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Accepted: 10/06/2009] [Indexed: 11/06/2022] Open
Abstract
Production of mature mRNAs that encode functional proteins involves highly complex pathways of synthesis, processing and surveillance. At numerous steps during the maturation process, the mRNA transcript undergoes scrutiny by cellular quality control machinery. This extensive RNA surveillance ensures that only correctly processed mature mRNAs are translated and precludes production of aberrant transcripts that could encode mutant or possibly deleterious proteins. Recent advances in elucidating the molecular mechanisms of mRNA processing have demonstrated the existence of an integrated network of events, and have revealed that a variety of human diseases are caused by disturbances in the well-coordinated molecular equilibrium of these events. From a medical perspective, both loss and gain of function are relevant, and a considerable number of different diseases exemplify the importance of the mechanistic function of RNA surveillance in a cell. Here, mechanistic hallmarks of mRNA processing steps are reviewed, highlighting the medical relevance of their deregulation and how the understanding of such mechanisms can contribute to the development of therapeutic strategies.
Collapse
Affiliation(s)
- Karen C M Moraes
- Molecular Biology Laboratory, IP&D, Universidade do Vale do Paraíba, São José dos Campos, São Paulo, CEP-12244-000, Brazil.
| |
Collapse
|
195
|
Benarroch D, Jankowska-Anyszka M, Stepinski J, Darzynkiewicz E, Shuman S. Cap analog substrates reveal three clades of cap guanine-N2 methyltransferases with distinct methyl acceptor specificities. RNA (NEW YORK, N.Y.) 2010; 16:211-20. [PMID: 19926722 PMCID: PMC2802030 DOI: 10.1261/rna.1872110] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The Tgs proteins are structurally homologous AdoMet-dependent eukaryal enzymes that methylate the N2 atom of 7-methyl guanosine nucleotides. They have an imputed role in the synthesis of the 2,2,7-trimethylguanosine (TMG) RNA cap. Here we exploit a collection of cap-like substrates to probe the repertoire of three exemplary Tgs enzymes, from mammalian, protozoan, and viral sources, respectively. We find that human Tgs (hTgs1) is a bona fide TMG synthase adept at two separable transmethylation steps: (1) conversion of m(7)G to m(2,7)G, and (2) conversion of m(2,7)G to m(2,2,7)G. hTgs1 is unable to methylate G or m(2)G, signifying that both steps require an m(7)G cap. hTgs1 utilizes a broad range of m(7)G nucleotides, including mono-, di-, tri-, and tetraphosphate derivatives as well as cap dinucleotides with triphosphate or tetraphosphate bridges. In contrast, Giardia lamblia Tgs (GlaTgs2) exemplifies a different clade of guanine-N2 methyltransferase that synthesizes only a dimethylguanosine (DMG) cap structure and cannot per se convert DMG to TMG under any conditions tested. Methylation of benzyl(7)G and ethyl(7)G nucleotides by hTgs1 and GlaTgs2 underscored the importance of guanine N7 alkylation in providing a key pi-cation interaction in the methyl acceptor site. Mimivirus Tgs (MimiTgs) shares with the Giardia homolog the ability to catalyze only a single round of methyl addition at guanine-N2, but is distinguished by its capacity for guanine-N2 methylation in the absence of prior N7 methylation. The relaxed cap specificity of MimiTgs is revealed at alkaline pH. Our findings highlight both stark and subtle differences in acceptor specificity and reaction outcomes among Tgs family members.
Collapse
Affiliation(s)
- Delphine Benarroch
- Molecular Biology Program, Sloan-Kettering Institute, New York, New York 10065, USA
| | | | | | | | | |
Collapse
|
196
|
Cao Q, Padmanabhan K, Richter JD. Pumilio 2 controls translation by competing with eIF4E for 7-methyl guanosine cap recognition. RNA (NEW YORK, N.Y.) 2010; 16:221-7. [PMID: 19933321 PMCID: PMC2802031 DOI: 10.1261/rna.1884610] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Pumilio 2 (Pum2) interacts with the 3' UTR-containing pumilio binding element (PBE) of RINGO/SPY mRNA to repress translation in Xenopus oocytes. Here, we show that Pum2 also binds directly to the 5' 7mG cap structure; in so doing, it precludes eIF4E from binding the cap. Using deletion analysis, we have mapped the cap interaction domain of Pum2 to the amino terminus of the protein and identified a conserved tryptophan residue that mediates this specific interaction. Reporter mRNA-based assays demonstrate that Pum2 requires the conserved tryptophan to repress translation in injected Xenopus oocytes. Thus, in addition to its suggested role in regulating poly(A) tail length and mRNA stability, our results suggest that vertebrate Pumilio can repress translation by blocking the assembly of the essential initiation complex on the cap.
Collapse
Affiliation(s)
- Quiping Cao
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | | | | |
Collapse
|
197
|
Strenkowska M, Kowalska J, Lukaszewicz M, Zuberek J, Su W, Rhoads RE, Darzynkiewicz E, Jemielity J. Towards mRNA with superior translational activity: synthesis and properties of ARCA tetraphosphates with single phosphorothioate modifications. NEW J CHEM 2010; 34:993-1007. [PMID: 20711517 PMCID: PMC2918917 DOI: 10.1039/b9nj00644c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We describe the chemical synthesis and preliminary biophysical and biochemical characterization of a series of mRNA 5' end (cap) analogs designed as reagents for obtaining mRNA molecules with augmented translation efficiency and stability in vivo and as useful tools to study mRNA metabolism. The analogs share three structural features: (i) 5',5'- bridge elongated to tetraphosphate to increase their affinity to translation initiation factor eIF4E (ii) a single phosphorothioate modification at either the α, β, γ or δ-position of the tetraphosphate to decrease their susceptibility to enzymatic degradation and/or to modulate their interaction with specific proteins and (iii) a 2'-O-methyl group in the ribose of 7-methylguanosine, characteristic to Anti-Reverse Cap Analogs (ARCAs), which are incorporated into mRNA during in vitro transcription exclusively in the correct orientation. The dinucleotides bearing modified tetraphosphate bridge were synthesized by ZnCl(2) mediated coupling between two mononucleotide subunits with isolated yields of 30-65%. The preliminary biochemical results show that mRNAs capped with new analogs are 2.5-4.5 more efficiently translated in a cell free system than m(7)GpppG-capped mRNAs, which makes them promising candidates for RNA-based therapeutic applications such as gene therapy and anti-cancer vaccines.
Collapse
Affiliation(s)
- Malwina Strenkowska
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland. Fax: 48 22 5540771; Tel: 48 22 5540774
| | - Joanna Kowalska
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland. Fax: 48 22 5540771; Tel: 48 22 5540774
| | - Maciej Lukaszewicz
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland. Fax: 48 22 5540771; Tel: 48 22 5540774
| | - Joanna Zuberek
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland. Fax: 48 22 5540771; Tel: 48 22 5540774
| | - Wei Su
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA 71130-3932, USA
| | - Robert E. Rhoads
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA 71130-3932, USA
| | - Edward Darzynkiewicz
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland. Fax: 48 22 5540771; Tel: 48 22 5540774
| | - Jacek Jemielity
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland. Fax: 48 22 5540771; Tel: 48 22 5540774
| |
Collapse
|
198
|
Jemielity J, Kowalska J, Rydzik AM, Darzynkiewicz E. Synthetic mRNA cap analogs with a modified triphosphate bridge – synthesis, applications and prospects. NEW J CHEM 2010. [DOI: 10.1039/c0nj00041h] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
199
|
Jia Y, Chiu TL, Amin EA, Polunovsky V, Bitterman PB, Wagner CR. Design, synthesis and evaluation of analogs of initiation factor 4E (eIF4E) cap-binding antagonist Bn7-GMP. Eur J Med Chem 2009; 45:1304-13. [PMID: 20060622 DOI: 10.1016/j.ejmech.2009.11.054] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Revised: 11/17/2009] [Accepted: 11/27/2009] [Indexed: 01/19/2023]
Abstract
Aberrant regulation of cap-dependent translation has been frequently observed in the development of cancer. Association of the cap-binding protein eIF4E with N(7)-methylated guanosine capped mRNA is the rate limiting step governing translation initiation; and therefore represents an attractive process for cancer drug discovery. Previously, replacement of the 7-Me group of the Me(7)-guanosine monophosphate with a benzyl group has been found to increase binding affinity to eIF4E. Recent X-ray crystallographic studies have revealed that the cap-binding pocket undergoes a unique structural change in order to accommodate the benzyl group. To explore the structure-activity relationships governing the affinity of N(7)-benzylated guanosine monophosphate (Bn(7)-GMP) for eIF4E, we virtually screened a library of 80 Bn(7)-GMP analogs utilizing CombiGlide as implemented in Schrodinger. A subset library of substituted Bn(7)-GMP analogs was synthesized and their dissociation constants (K(d)) were determined. Due to the poor correlation between docking/scoring results and experimental binding affinities, three-dimensional quantitative structure-activity relationship (3D-QSAR) calculations were performed. Two highly predictive and self-consistent CoMFA (comparative molecular field analysis) and CoMSIA (comparative molecular similarity indices analysis) models were derived and optimized. These models may be useful for the future design of eIF4E cap-binding antagonists.
Collapse
Affiliation(s)
- Yan Jia
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | | | | | | | | | | |
Collapse
|
200
|
Dias SM, Cerione RA, Wilson KF. Unloading RNAs in the cytoplasm: an "importin" task. Nucleus 2009; 1:139-43. [PMID: 21326945 DOI: 10.4161/nucl.1.2.10919] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Accepted: 12/02/2009] [Indexed: 11/19/2022] Open
Abstract
The nuclear cap-binding complex (CBC), a heterodimer comprised of a 20 kDa subunit (CBP20) and an 80 kDa regulatory subunit (CBP80), binds to nascent RNA polymerase II transcripts and is important throughout different aspects of RNA metabolism. In a recent publication, using a combination of X-ray crystallographic information, mutagenesis studies, small-angle scattering experiments, analytical ultracentrifugation and in vivo assays, we presented evidence that importin-α and importin-β, two nucleocytoplasmic transport proteins, play key roles in regulating the binding of capped RNA by the CBC in cells. A model for how complexes between CBC and the importins cycle in and out of the nucleus and direct the proper positional binding and release of capped RNA is presented here and is discussed in light of recent publications.
Collapse
Affiliation(s)
- Sandra Mg Dias
- Department of Molecular Medicine, College of Veterinary Medicine, Ithaca, NY, USA
| | | | | |
Collapse
|