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Shao J, Pan T, Wang J, Tang T, Li Y, Jia X, Lai S. MiR-208b Regulates Rabbit Preadipocyte Proliferation and Differentiation. Genes (Basel) 2021; 12:genes12060890. [PMID: 34207778 PMCID: PMC8228405 DOI: 10.3390/genes12060890] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 06/03/2021] [Accepted: 06/03/2021] [Indexed: 01/13/2023] Open
Abstract
microRNAs (miRNAs) play an important role in gene regulation in animals by pairing with target gene mRNA. Many miRNAs are differentially expressed in the adipose tissue, often with conserved expression. In our study, we found that miR-208b expression was observed differently in the preadipocyte differentiation model. When miR-208b was overexpressed in the preadipocyte differentiation model, the overexpressed group displayed higher expression of PPARγ and FABP4—the markers of preadipocyte differentiation. Oil Red O staining revealed that the count of lipid droplets was increased in the overexpressed group. When the expression of miR-208b was inhibited, the above indicators showed an opposite trend. Moreover, results from both 5-ethynyl-2′-deoxyuridine (EDU) and cell counting kit (CCK) analysis showed that miR-208b promoted the proliferation of preadipocyte. Expression of gene CSNK2A2, a direct miR-208b target, was downregulated in the overexpressed group, providing a possible link to multiple signal pathways. Overall, our data indicate that miR-208b play a positive regulatory effect on the proliferation and differentiation of rabbit preadipocyte.
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Affiliation(s)
- Jiahao Shao
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China; (J.S.); (J.W.); (T.T.); (Y.L.); (X.J.)
| | - Ting Pan
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China;
| | - Jie Wang
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China; (J.S.); (J.W.); (T.T.); (Y.L.); (X.J.)
| | - Tao Tang
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China; (J.S.); (J.W.); (T.T.); (Y.L.); (X.J.)
| | - Yanhong Li
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China; (J.S.); (J.W.); (T.T.); (Y.L.); (X.J.)
| | - Xianbo Jia
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China; (J.S.); (J.W.); (T.T.); (Y.L.); (X.J.)
| | - Songjia Lai
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China; (J.S.); (J.W.); (T.T.); (Y.L.); (X.J.)
- Correspondence:
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Imai S, Kumar P, Hellen CUT, D'Souza VM, Wagner G. An accurately preorganized IRES RNA structure enables eIF4G capture for initiation of viral translation. Nat Struct Mol Biol 2016; 23:859-64. [PMID: 27525590 DOI: 10.1038/nsmb.3280] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 07/21/2016] [Indexed: 02/06/2023]
Abstract
Many viruses bypass canonical cap-dependent translation in host cells by using internal ribosomal entry sites (IRESs) in their transcripts; IRESs hijack initiation factors for the assembly of initiation complexes. However, it is currently unknown how IRES RNAs recognize initiation factors that have no endogenous RNA binding partners; in a prominent example, the IRES of encephalomyocarditis virus (EMCV) interacts with the HEAT-1 domain of eukaryotic initiation factor 4G (eIF4G). Here we report the solution structure of the J-K region of this IRES and show that its stems are precisely organized to position protein-recognition bulges. This multisite interaction mechanism operates on an all-or-nothing principle in which all domains are required. This preorganization is accomplished by an 'adjuster module': a pentaloop motif that acts as a dual-sided docking station for base-pair receptors. Because subtle changes in the orientation abrogate protein capture, our study highlights how a viral RNA acquires affinity for a target protein.
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Affiliation(s)
- Shunsuke Imai
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Parimal Kumar
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York, USA
| | | | - Victoria M D'Souza
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
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Leen EN, Sorgeloos F, Correia S, Chaudhry Y, Cannac F, Pastore C, Xu Y, Graham SC, Matthews SJ, Goodfellow IG, Curry S. A Conserved Interaction between a C-Terminal Motif in Norovirus VPg and the HEAT-1 Domain of eIF4G Is Essential for Translation Initiation. PLoS Pathog 2016; 12:e1005379. [PMID: 26734730 PMCID: PMC4703368 DOI: 10.1371/journal.ppat.1005379] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 12/10/2015] [Indexed: 11/28/2022] Open
Abstract
Translation initiation is a critical early step in the replication cycle of the positive-sense, single-stranded RNA genome of noroviruses, a major cause of gastroenteritis in humans. Norovirus RNA, which has neither a 5´ m7G cap nor an internal ribosome entry site (IRES), adopts an unusual mechanism to initiate protein synthesis that relies on interactions between the VPg protein covalently attached to the 5´-end of the viral RNA and eukaryotic initiation factors (eIFs) in the host cell. For murine norovirus (MNV) we previously showed that VPg binds to the middle fragment of eIF4G (4GM; residues 652–1132). Here we have used pull-down assays, fluorescence anisotropy, and isothermal titration calorimetry (ITC) to demonstrate that a stretch of ~20 amino acids at the C terminus of MNV VPg mediates direct and specific binding to the HEAT-1 domain within the 4GM fragment of eIF4G. Our analysis further reveals that the MNV C terminus binds to eIF4G HEAT-1 via a motif that is conserved in all known noroviruses. Fine mutagenic mapping suggests that the MNV VPg C terminus may interact with eIF4G in a helical conformation. NMR spectroscopy was used to define the VPg binding site on eIF4G HEAT-1, which was confirmed by mutagenesis and binding assays. We have found that this site is non-overlapping with the binding site for eIF4A on eIF4G HEAT-1 by demonstrating that norovirus VPg can form ternary VPg-eIF4G-eIF4A complexes. The functional significance of the VPg-eIF4G interaction was shown by the ability of fusion proteins containing the C-terminal peptide of MNV VPg to inhibit in vitro translation of norovirus RNA but not cap- or IRES-dependent translation. These observations define important structural details of a functional interaction between norovirus VPg and eIF4G and reveal a binding interface that might be exploited as a target for antiviral therapy. Norovirus infections cause acute gastroenteritis and are a growing worldwide problem in human health. A critical early step in infection is translation of the viral RNA genome to produce the proteins needed to assemble new virus particles. In mouse noroviruses (MNV), which provide a useful model for studying human noroviruses, the VPg protein attached to the viral RNA is essential for this process because it interacts with a cellular protein, eIF4G, that is normally involved in initiating protein synthesis from the messenger RNA of host genes. We have used a variety of biochemical and biophysical experiments to measure how well MNV VPg binds to eIF4G and to identify the parts of both proteins that are involved in this interaction. We show that a sequence of about 20 amino acids at one end of MNV VPg–the C terminus– allows it to bind to a well-defined domain within eIF4G (called HEAT-1), and that it may adopt a helical structure when doing so. Our data suggest that this interaction is common to all noroviruses, including types that infect humans. We have also shown that the MNV VPg C-terminal peptide can inhibit norovirus protein synthesis, which raises the possibility that the VPg-eIF4G interaction could be targeted in the design of antiviral drugs.
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Affiliation(s)
- Eoin N Leen
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Frédéric Sorgeloos
- Division of Virology, Department of Pathology, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Samantha Correia
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Yasmin Chaudhry
- Division of Virology, Department of Pathology, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Fabien Cannac
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Chiara Pastore
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Yingqi Xu
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Stephen C Graham
- Division of Virology, Department of Pathology, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Stephen J Matthews
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Ian G Goodfellow
- Division of Virology, Department of Pathology, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Stephen Curry
- Department of Life Sciences, Imperial College London, London, United Kingdom
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Akabayov SR, Akabayov B, Wagner G. Human translation initiation factor eIF4G1 possesses a low-affinity ATP binding site facing the ATP-binding cleft of eIF4A in the eIF4G/eIF4A complex. Biochemistry 2014; 53:6422-5. [PMID: 25255371 PMCID: PMC4204880 DOI: 10.1021/bi500600m] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Eukaryotic
translation initiation factor 4G (eIF4G) plays a crucial
role in translation initiation, serving as a scaffolding protein binding
several other initiation factors, other proteins, and RNA. Binding
of eIF4G to the ATP-dependent RNA helicase eukaryotic translation
initiation factor 4A (eIF4A) enhances the activity of eIF4A in solution
and in crowded environments. Previously, this activity enhancement
was solely attributed to eIF4G, conferring a closed, active conformation
upon eIF4A. Here we show that eIF4G contains a low-affinity binding
site at the entrance to the ATP-binding cleft on eIF4A, suggesting
that regulation of the local ATP concentration may be an additional
reason for the enhancement in activity.
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Affiliation(s)
- Sabine R Akabayov
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School , Longwood Avenue, Boston, Massachusetts 02115, United States
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Akabayov SR, Akabayov B, Richardson CC, Wagner G. Molecular crowding enhanced ATPase activity of the RNA helicase eIF4A correlates with compaction of its quaternary structure and association with eIF4G. J Am Chem Soc 2013; 135:10040-7. [PMID: 23767688 DOI: 10.1021/ja404404h] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Enzymatic reactions occur in a crowded and confined environment in vivo, containing proteins, RNA and DNA. Previous reports have shown that interactions between macromolecules, and reactions rates differ significantly between crowded environments and dilute buffers. However, the direct effect of crowding on the level of high-resolution structures of macromolecules has not been extensively analyzed and is not well understood. Here we analyze the effect of macromolecular crowding on structure and function of the human translation initiation factors eIF4A, a two-domain DEAD-Box helicase, the HEAT-1 domain of eIF4G, and their complex. We find that crowding enhances the ATPase activity of eIF4A, which correlates with a shift to a more compact structure as revealed with small-angle X-ray scattering. However, the individual domains of eIF4A, or the eIF4G-HEAT-1 domain alone show little structural changes due to crowding except for flexible regions. Thus, the effect of macromolecular crowding on activity and structure need to be taken into account when evaluating enzyme activities and structures of multidomain proteins, proteins with flexible regions, or protein complexes obtained by X-ray crystallography, NMR, or other structural methods.
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Affiliation(s)
- Sabine R Akabayov
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA
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