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Monté D, Lens Z, Dewitte F, Villeret V, Verger A. Assessment of machine-learning predictions for the Mediator complex subunit MED25 ACID domain interactions with transactivation domains. FEBS Lett 2024; 598:758-773. [PMID: 38436147 DOI: 10.1002/1873-3468.14837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 02/01/2024] [Accepted: 02/10/2024] [Indexed: 03/05/2024]
Abstract
The human Mediator complex subunit MED25 binds transactivation domains (TADs) present in various cellular and viral proteins using two binding interfaces, named H1 and H2, which are found on opposite sides of its ACID domain. Here, we use and compare deep learning methods to characterize human MED25-TAD interfaces and assess the predicted models to published experimental data. For the H1 interface, AlphaFold produces predictions with high-reliability scores that agree well with experimental data, while the H2 interface predictions appear inconsistent, preventing reliable binding modes. Despite these limitations, we experimentally assess the validity of MED25 interface predictions with the viral transcriptional activators Lana-1 and IE62. AlphaFold predictions also suggest the existence of a unique hydrophobic pocket for the Arabidopsis MED25 ACID domain.
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Affiliation(s)
- Didier Monté
- CNRS EMR 9002 Integrative Structural Biology, Inserm U 1167 - RID-AGE, Univ. Lille, CHU Lille, Institut Pasteur de Lille, France
| | - Zoé Lens
- CNRS EMR 9002 Integrative Structural Biology, Inserm U 1167 - RID-AGE, Univ. Lille, CHU Lille, Institut Pasteur de Lille, France
| | - Frédérique Dewitte
- CNRS EMR 9002 Integrative Structural Biology, Inserm U 1167 - RID-AGE, Univ. Lille, CHU Lille, Institut Pasteur de Lille, France
| | - Vincent Villeret
- CNRS EMR 9002 Integrative Structural Biology, Inserm U 1167 - RID-AGE, Univ. Lille, CHU Lille, Institut Pasteur de Lille, France
| | - Alexis Verger
- CNRS EMR 9002 Integrative Structural Biology, Inserm U 1167 - RID-AGE, Univ. Lille, CHU Lille, Institut Pasteur de Lille, France
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2
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Jeffery HM, Weinzierl ROJ. Multivalent and Bidirectional Binding of Transcriptional Transactivation Domains to the MED25 Coactivator. Biomolecules 2020; 10:biom10091205. [PMID: 32825095 PMCID: PMC7564715 DOI: 10.3390/biom10091205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 08/14/2020] [Accepted: 08/17/2020] [Indexed: 11/16/2022] Open
Abstract
The human mediator subunit MED25 acts as a coactivator that binds the transcriptional activation domains (TADs) present in various cellular and viral gene-specific transcription factors. Previous studies, including on NMR measurements and site-directed mutagenesis, have only yielded low-resolution models that are difficult to refine further by experimental means. Here, we apply computational molecular dynamics simulations to study the interactions of two different TADs from the human transcription factor ETV5 (ERM) and herpes virus VP16-H1 with MED25. Like other well-studied coactivator-TAD complexes, the interactions of these intrinsically disordered domains with the coactivator surface are temporary and highly dynamic (‘fuzzy’). Due to the fact that the MED25 TAD-binding region is organized as an elongated cleft, we specifically asked whether these TADs are capable of binding in either orientation and how this could be achieved structurally and energetically. The binding of both the ETV5 and VP16-TADs in either orientation appears to be possible but occurs in a conformationally distinct manner and utilizes different sets of hydrophobic residues present in the TADs to drive the interactions. We propose that MED25 and at least a subset of human TADs specifically evolved a redundant set of molecular interaction patterns to allow binding to particular coactivators without major prior spatial constraints.
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Affiliation(s)
- Heather M. Jeffery
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK;
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Robert O. J. Weinzierl
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK;
- Correspondence:
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Interferon Gamma Inhibits Varicella-Zoster Virus Replication in a Cell Line-Dependent Manner. J Virol 2019; 93:JVI.00257-19. [PMID: 30918075 DOI: 10.1128/jvi.00257-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 03/21/2019] [Indexed: 01/29/2023] Open
Abstract
The major immediate early 62 (IE62) protein of varicella-zoster virus (VZV) is delivered to newly infected cell nuclei, where it initiates VZV replication by transactivating viral immediate early (IE), early (E), and late (L) genes. Interferon gamma (IFN-γ) is a potent cytokine produced following primary VZV infection. Furthermore, VZV reactivation correlates with a decline in IFN-γ-producing immune cells. Our results showed that treatment with 20 ng/ml of IFN-γ completely reduced intracellular VZV yield in A549 lung epithelial cells, MRC-5 lung fibroblasts, and ARPE-19 retinal epithelial cells at 4 days post-VZV infection. However, IFN-γ reduced virus yield only 2-fold in MeWo melanoma cells compared to that of untreated cells. IFN-β significantly inhibited VZV replication in both ARPE-19 and MeWo cells. In luciferase assays with VZV open reading frame 61 (ORF61) promoter reporter plasmid, IFN-γ abrogated the transactivation activity of IE62 by 95%, 97%, and 89% in A549, ARPE-19, and MRC-5 cells, respectively. However, IFN-γ abrogated IE62's transactivation activity by 16% in MeWo cells, indicating that IFN-γ inhibits VZV replication as well as IE62-mediated transactivation in a cell line-dependent manner. The expression of VZV IE62 and ORF63 suppressed by IFN-γ was restored by JAK1 inhibitor treatment, indicating that the inhibition of VZV replication is mediated by JAK/STAT1 signaling. In the presence of IFN-γ, knockdown of interferon response factor 1 (IRF1) increased VZV replication. Ectopic expression of IRF1 reduced VZV yields 4,000-fold in MRC-5 and ARPE-19 cells but 3-fold in MeWo cells. These results suggest that IFN-γ blocks VZV replication by inhibiting IE62 function in a cell line-dependent manner.IMPORTANCE Our results showed that IFN-γ significantly inhibited VZV replication in a cell line-dependent manner. IFN-γ inhibited VZV gene expression after the immediate early stage of infection and abrogated IE62-mediated transactivation. These results suggest that IFN-γ blocks VZV replication by inhibiting IE62 function in a cell line-dependent manner. Understanding the mechanisms by which IFN-γ plays a role in VZV gene programming may be important in determining the tissue restriction of VZV.
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Structural Basis for the Interaction between p53 Transactivation Domain and the Mediator Subunit MED25. Molecules 2018; 23:molecules23102726. [PMID: 30360415 PMCID: PMC6222444 DOI: 10.3390/molecules23102726] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 10/17/2018] [Accepted: 10/20/2018] [Indexed: 01/21/2023] Open
Abstract
Eukaryotic transcription initiation is mediated by interactions between transcriptional activators and the mediator coactivator complex. Molecular interaction of p53 transcription factor with mediator complex subunit 25 (MED25) is essential for its target gene transcription. In this study, we characterized the molecular interaction between p53 transactivation domain (p53TAD) and activator interaction domain (ACID) of MED25 using nuclear magnetic resonance (NMR) spectroscopy. The NMR chemical shift perturbation and isothermal titration calorimetry (ITC) data showed that p53TAD interacted with MED25 ACID mainly through the p53TAD2 sequence motif. Taken together with the mutagenesis data, the refined structural model of MED25 ACID/p53TAD2 peptide complex showed that an amphipathic α-helix of p53TAD2 peptide bound an elongated hydrophobic groove of MED25 ACID. Furthermore, our results revealed the highly conserved mechanism of MED25 interaction with intrinsically unfolded acidic TADs from the transcriptional activators p53, ERM (Ets-related molecule), and herpes simplex virus protein 16 (VP16).
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Ko H, Lee GM, Shin OS, Song MJ, Lee CH, Kim YE, Ahn JH. Analysis of IE62 mutations found in Varicella-Zoster virus vaccine strains for transactivation activity. J Microbiol 2018; 56:441-448. [PMID: 29858833 DOI: 10.1007/s12275-018-8144-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/09/2018] [Accepted: 04/10/2018] [Indexed: 12/16/2022]
Abstract
Live attenuated vaccine strains have been developed for Varicella-Zoster virus (VZV). Compared to clinically isolated strains, the vaccine strains contain several non-synonymous mutations in open reading frames (ORFs) 0, 6, 31, 39, 55, 62, and 64. In particular, ORF62, encoding an immediate-early (IE) 62 protein that acts as a transactivator for viral gene expression, contains six non-synonymous mutations, but whether these mutations affect transactivation activity of IE62 is not understood. In this study, we investigated the role of non-synonymous vaccine-type mutations (M99T, S628G, R958G, V1197A, I1260V, and L1275S) of IE62 in Suduvax, a vaccine strain isolated in Korea, for transactivation activity. In reporter assays, Suduvax IE62 showed 2- to 4-fold lower transactivation activity toward ORF4, ORF28, ORF29, and ORF68 promoters than wild-type IE62. Introduction of individual M99T, S628G, R958G, or V1197A/I1260V/L1275S mutations into wild-type IE62 did not affect transactivation activity. However, the combination of M99T within the N-terminal Sp transcription factor binding region and V1197A/I1260V/L1275S within the C-terminal serine-enriched acidic domain (SEAD) significantly reduced the transactivation activity of IE62. The M99T/V1197A/I1260V/L1275S mutant IE62 did not show considerable alterations in intracellular distribution and Sp3 binding compared to wild-type IE62, suggesting that other alteration(s) may be responsible for the reduced transactivation activity. Collectively, our results suggest that acquisition of mutations in both Met 99 and the SEAD of IE62 is responsible for the reduced transactivation activity found in IE62 of the VZV vaccine strains and contributes to attenuation of the virus.
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Affiliation(s)
- Hyemin Ko
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Samsung Medical Center, Suwon, 16419, Republic of Korea
| | - Gwang Myeong Lee
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Samsung Medical Center, Suwon, 16419, Republic of Korea
| | - Ok Sarah Shin
- Department of Biomedical Sciences, College of Medicine, Korea University, Seoul, 08308, Republic of Korea
| | - Moon Jung Song
- Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 02841, Republic of Korea
| | - Chan Hee Lee
- Department of Microbiology, Chungbuk National University, Cheongju, 28644, Republic of Korea
| | - Young Eui Kim
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Samsung Medical Center, Suwon, 16419, Republic of Korea
| | - Jin-Hyun Ahn
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Samsung Medical Center, Suwon, 16419, Republic of Korea.
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Majima R, Shindoh K, Yamaguchi T, Inoue N. Characterization of a thienylcarboxamide derivative that inhibits the transactivation functions of cytomegalovirus IE2 and varicella zoster virus IE62. Antiviral Res 2017; 140:142-150. [PMID: 28161581 DOI: 10.1016/j.antiviral.2017.01.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 01/20/2017] [Accepted: 01/25/2017] [Indexed: 11/15/2022]
Abstract
Previously we established reporter cell lines for human cytomegalovirus (HCMV) and varicella zoster virus (VZV) and identified several antiviral compounds against these viruses using the reporter cells. In this study, we found that one of the identified anti-HCMV compounds, a thienylcarboxamide derivative (coded as 133G4), was effective against not only HCMV but also VZV. The following findings indicate that 133G4 inhibits the activation of early gene promoters by HCMV IE2 and VZV IE62: i) 133G4 decreased the expression of HCMV early and late genes but not that of HCMV IE1/IE2 in HCMV-infected cells, ii) 133G4 inhibited the activation of several HCMV early gene promoters of transiently-transfected plasmids in HCMV-infected cells, and iii) in transient transfection assays, 133G4 decreased the activation of HCMV (or VZV) early gene promoters by HCMV IE2 (or VZV IE62) in the absence of other viral protein expression. The inhibition of early gene activation was observed in the human and African green monkey cell lines but not in the rodent cell lines, and the compound was not effective against murine CMV. In addition, VZV IE62 activated HCMV early promoters, and 133G4 still inhibited such promoter activation. Therefore, we hypothesized that 133G4 targets a cellular factor used commonly in activation of human herpesvirus promoters and examined whether 133G4 affects the functions of cellular proteins USF1, TBP, Med25 and EAP, the involvement of which in VZV IE62-dependent viral gene activation has been well characterized. Our experimental results using one-hybrid and bimolecular fluorescence complementation assays demonstrated that 133G4 did not inhibit the recruitment of USF1 or TBP to their binding sites, nor inhibited the direct interactions of VZV IE62 with Med25 and EAP. Thus, 133G4 is a unique anti-VZV and -HCMV compound, which warrants further studies to find out its inhibitory mechanism.
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Affiliation(s)
- Ryuichi Majima
- Department of Microbiology and Immunology, Gifu Pharmaceutical University, Gifu, Japan
| | - Keiko Shindoh
- Department of Virology I, National Institute of Infectious Diseases, Tokyo, Japan; Department of Biosciences, Teikyo University of Science and Technology, Yamanashi, Japan
| | - Toyofumi Yamaguchi
- Department of Biosciences, Teikyo University of Science and Technology, Yamanashi, Japan
| | - Naoki Inoue
- Department of Microbiology and Immunology, Gifu Pharmaceutical University, Gifu, Japan; Department of Virology I, National Institute of Infectious Diseases, Tokyo, Japan.
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Karaz S, Courgeon M, Lepetit H, Bruno E, Pannone R, Tarallo A, Thouzé F, Kerner P, Vervoort M, Causeret F, Pierani A, D'Onofrio G. Neuronal fate specification by the Dbx1 transcription factor is linked to the evolutionary acquisition of a novel functional domain. EvoDevo 2016; 7:18. [PMID: 27525057 PMCID: PMC4983035 DOI: 10.1186/s13227-016-0055-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 07/27/2016] [Indexed: 12/18/2022] Open
Abstract
Background Dbx1 is a homeodomain transcription factor involved in neuronal fate specification belonging to a widely conserved family among bilaterians. In mammals, Dbx1 was proposed to act as a transcriptional repressor by interacting with the Groucho corepressors to allow the specification of neurons involved in essential biological functions such as locomotion or breathing. Results Sequence alignments of Dbx1 proteins from different species allowed us to identify two conserved domains related to the Groucho-dependent Engrailed repressor domain (RD), as well as a newly described domain composed of clusterized acidic residues at the C-terminus (Cter) which is present in tetrapods but also several invertebrates. Using a heterologous luciferase assay, we showed that the two putative repressor domains behave as such in a Groucho-dependent manner, whereas the Cter does not bear any intrinsic transcriptional activity. Consistently with in vitro data, we found that both RDs are involved in cell fate specification using in vivo electroporation experiments in the chick spinal cord. Surprisingly, we show that the Cter domain is required for Dbx1 function in vivo, acting as a modulator of its repressive activity and/or imparting specificity. Conclusion Our results strongly suggest that the presence of a Cter domain among tetrapods is essential for Dbx1 to regulate neuronal diversity and, in turn, nervous system complexity. Electronic supplementary material The online version of this article (doi:10.1186/s13227-016-0055-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sonia Karaz
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Maximilien Courgeon
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Hélène Lepetit
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Eugenia Bruno
- Dept. BEOM, Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Naples, Italy
| | - Raimondo Pannone
- Dept. BEOM, Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Naples, Italy
| | - Andrea Tarallo
- Dept. BEOM, Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Naples, Italy
| | - France Thouzé
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Pierre Kerner
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Michel Vervoort
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Frédéric Causeret
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Alessandra Pierani
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Giuseppe D'Onofrio
- Dept. BEOM, Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Naples, Italy
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Ku CC, Chang YH, Chien Y, Lee TL. Type I interferon inhibits varicella-zoster virus replication by interfering with the dynamic interaction between mediator and IE62 within replication compartments. Cell Biosci 2016; 6:21. [PMID: 26985360 PMCID: PMC4793741 DOI: 10.1186/s13578-016-0086-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 03/03/2016] [Indexed: 11/23/2022] Open
Abstract
Background Varicella-zoster virus (VZV) is the causative agent of varicella and zoster. The immediate-early protein, IE62 is the predominant VZ virion tegument protein, transactivating the expression of all kinetic classes of VZV genes. IE62 is localized to punctae that form DNA replication compartments in the nuclei of VZV infected cells. The morphological changes and the increase in the size of replication compartments that express IE62 are correlated with production of VZ virions. Mammalian Mediator serves as a coactivator of IE62 and functions by bridging DNA-binding transcription factors¸ RNA polymerase II (RNAP II) and their target DNAs for VZV replication. While VZV is highly sensitive to type I interferons (IFNs), how IFN-α inhibits early events during VZV replication is poorly understood. Results In this study, we performed in situ analysis to investigate the effects of IFN-α on the dynamic interactions of IE62 with the Mediator MED25 subunit and the RNAP II negative regulator cycle-dependent kinase 8 (CDK8) in VZV infected cells by confocal immunofluorescence. We found that in addition to dose-dependent inhibition of the yields of infectious virus by IFN treatment, IFN-α prominently impeded the development of large IE62+ nuclear compartments and significantly decreased transcription of VZV genes. Both the expression level and stable recruitment of MED25 to IE62+ replication compartments were inhibited by IFN-α. While IFN-α treatment upregulated CDK8 expression, redistribution and recruitment of CDK8 to IE62+ replication compartments in infected cells was not affected by VZV. Conclusion IFN-α exerts multiple inhibitory activities against virus infections. In this study, we provide visionary demonstration that continuous translocation of MED25 into VZV replication compartments ensures production of virions. IFN-α greatly impedes the formation of a stable complex between IE62 and the Mediator complex thereby suppresses VZV gene transcription. Our demonstration that IFN-α-induced antiviral effect against VZV infection is through inhibiting the reorganization of nuclear components uncovers a novel function of IFN-α. Targeting the interaction between IE62 and MED25 may offer a novel approach to the development of antiviral agents against VZV infection.
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Affiliation(s)
- Chia-Chi Ku
- Institute of Immunology, College of Medicine, National Taiwan University, No.1 Section 1 Jen-Ai Road, Taipei, Taiwan
| | - Yi-Hsuan Chang
- Institute of Immunology, College of Medicine, National Taiwan University, No.1 Section 1 Jen-Ai Road, Taipei, Taiwan
| | - Yun Chien
- Institute of Immunology, College of Medicine, National Taiwan University, No.1 Section 1 Jen-Ai Road, Taipei, Taiwan
| | - Tsung-Lin Lee
- Institute of Immunology, College of Medicine, National Taiwan University, No.1 Section 1 Jen-Ai Road, Taipei, Taiwan
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9
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Khalil MI, Che X, Sung P, Sommer MH, Hay J, Arvin AM. Mutational analysis of varicella-zoster virus (VZV) immediate early protein (IE62) subdomains and their importance in viral replication. Virology 2016; 492:82-91. [PMID: 26914506 DOI: 10.1016/j.virol.2016.02.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 01/30/2016] [Accepted: 02/14/2016] [Indexed: 12/29/2022]
Abstract
VZV IE62 is an essential, immediate-early, tegument protein and consists of five domains. We generated recombinant viruses carrying mutations in the first three IE62 domains and tested their influence on VZV replication kinetics. The mutations in domain I did not affect replication kinetics while domain II mutations, disrupting the DNA binding and dimerization domain (DBD), were lethal for VZV replication. Mutations in domain III of the nuclear localization signal (NLS) and the two phosphorylation sites S686A/S722A resulted in slower growth in early and late infection respectively and were associated with IE62 accumulation in the cytoplasm and nucleus respectively. This study mapped the functional domains of IE62 in context of viral infection, indicating that DNA binding and dimerization domain is essential for VZV replication. In addition, the correct localization of IE62, whether nuclear or cytoplasmic, at different points in the viral life cycle, is important for normal progression of VZV replication.
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Affiliation(s)
- Mohamed I Khalil
- Departments of Pediatrics and Microbiology & Immunology, Stan ford University School of Medicine, Stanford, CA, United States; Department of Molecular Biology, National Research Centre, El-Buhouth St., Cairo, Egypt.
| | - Xibing Che
- Departments of Pediatrics and Microbiology & Immunology, Stan ford University School of Medicine, Stanford, CA, United States
| | - Phillip Sung
- Departments of Pediatrics and Microbiology & Immunology, Stan ford University School of Medicine, Stanford, CA, United States
| | - Marvin H Sommer
- Departments of Pediatrics and Microbiology & Immunology, Stan ford University School of Medicine, Stanford, CA, United States
| | - John Hay
- Department of Microbiology and Immunology, School of Medicine and Biomedical Science, University at Buffalo, Buffalo, NY, United States
| | - Ann M Arvin
- Departments of Pediatrics and Microbiology & Immunology, Stan ford University School of Medicine, Stanford, CA, United States
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10
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Functional Characterization of the Serine-Rich Tract of Varicella-Zoster Virus IE62. J Virol 2015; 90:959-71. [PMID: 26537679 DOI: 10.1128/jvi.02096-15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 10/27/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The immediate early 62 protein (IE62) of varicella-zoster virus (VZV), a major viral trans-activator, initiates the virus life cycle and is a key component of pathogenesis. The IE62 possesses several domains essential for trans-activation, including an acidic trans-activation domain (TAD), a serine-rich tract (SRT), and binding domains for USF, TFIIB, and TATA box binding protein (TBP). Transient-transfection assays showed that the VZV IE62 lacking the SRT trans-activated the early VZV ORF61 promoter at only 16% of the level of the full-length IE62. When the SRT of IE62 was replaced with the SRT of equine herpesvirus 1 (EHV-1) IEP, its trans-activation activity was completely restored. Herpes simplex virus 1 (HSV-1) ICP4 that lacks a TAD very weakly (1.5-fold) trans-activated the ORF61 promoter. An IE62 TAD-ICP4 chimeric protein exhibited trans-activation ability (10.2-fold), indicating that the IE62 TAD functions with the SRT of HSV-1 ICP4 to trans-activate viral promoters. When the serine and acidic residues of the SRT were replaced with Ala, Leu, and Gly, trans-activation activities of the modified IE62 proteins IE62-SRTΔSe and IE62-SRTΔAc were reduced to 46% and 29% of wild-type activity, respectively. Bimolecular complementation assays showed that the TAD of IE62, EHV-1 IEP, and HSV-1 VP16 interacted with Mediator 25 in human melanoma MeWo cells. The SRT of IE62 interacted with the nucleolar-ribosomal protein EAP, which resulted in the formation of globular structures within the nucleus. These results suggest that the SRT plays an important role in VZV viral gene expression and replication. IMPORTANCE The immediate early 62 protein (IE62) of varicella-zoster virus (VZV) is a major viral trans-activator and is essential for viral growth. Our data show that the serine-rich tract (SRT) of VZV IE62, which is well conserved within the alphaherpesviruses, is needed for trans-activation mediated by the acidic trans-activation domain (TAD). The TADs of IE62, EHV-1 IEP, and HSV-1 VP16 interacted with cellular Mediator 25 in bimolecular complementation assays. The interaction of the IE62 SRT with nucleolar-ribosomal protein EAP resulted in the formation of globular structures within the nucleus. Understanding the mechanisms by which the TAD and SRT of IE62 contribute to the function of this essential regulatory protein is important in understanding the gene program of this human pathogen.
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Landrieu I, Verger A, Baert JL, Rucktooa P, Cantrelle FX, Dewitte F, Ferreira E, Lens Z, Villeret V, Monté D. Characterization of ERM transactivation domain binding to the ACID/PTOV domain of the Mediator subunit MED25. Nucleic Acids Res 2015; 43:7110-21. [PMID: 26130716 PMCID: PMC4538835 DOI: 10.1093/nar/gkv650] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 05/28/2015] [Indexed: 01/12/2023] Open
Abstract
The N-terminal acidic transactivation domain (TAD) of ERM/ETV5 (ERM38–68), a PEA3 group member of Ets-related transcription factors, directly interacts with the ACID/PTOV domain of the Mediator complex subunit MED25. Molecular details of this interaction were investigated using nuclear magnetic resonance (NMR) spectroscopy. The TAD is disordered in solution but has a propensity to adopt local transient secondary structure. We show that it folds upon binding to MED25 and that the resulting ERM–MED25 complex displays characteristics of a fuzzy complex. Mutational analysis further reveals that two aromatic residues in the ERM TAD (F47 and W57) are involved in the binding to MED25 and participate in the ability of ERM TAD to activate transcription. Mutation of a key residue Q451 in the VP16 H1 binding pocket of MED25 affects the binding of ERM. Furthermore, competition experiments show that ERM and VP16 H1 share a common binding interface on MED25. NMR data confirms the occupancy of this binding pocket by ERM TAD. Based on these experimental data, a structural model of a functional interaction is proposed. This study provides mechanistic insights into the Mediator–transactivator interactions.
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Affiliation(s)
- Isabelle Landrieu
- CNRS UMR 8576, Université de Lille, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
| | - Alexis Verger
- CNRS UMR 8576, Université de Lille, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
| | - Jean-Luc Baert
- CNRS UMR 8576, Université de Lille, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
| | - Prakash Rucktooa
- CNRS UMR 8576, Université de Lille, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
| | - François-Xavier Cantrelle
- CNRS UMR 8576, Université de Lille, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
| | - Frédérique Dewitte
- CNRS UMR 8576, Université de Lille, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
| | - Elisabeth Ferreira
- CNRS UMR 8576, Université de Lille, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
| | - Zoé Lens
- CNRS UMR 8576, Université de Lille, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
| | - Vincent Villeret
- CNRS UMR 8576, Université de Lille, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
| | - Didier Monté
- CNRS UMR 8576, Université de Lille, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
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12
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Kazan K, Lyons R. Intervention of Phytohormone Pathways by Pathogen Effectors. THE PLANT CELL 2014; 26:2285-2309. [PMID: 24920334 PMCID: PMC4114936 DOI: 10.1105/tpc.114.125419] [Citation(s) in RCA: 267] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 05/16/2014] [Accepted: 05/24/2014] [Indexed: 05/18/2023]
Abstract
The constant struggle between plants and microbes has driven the evolution of multiple defense strategies in the host as well as offense strategies in the pathogen. To defend themselves from pathogen attack, plants often rely on elaborate signaling networks regulated by phytohormones. In turn, pathogens have adopted innovative strategies to manipulate phytohormone-regulated defenses. Tactics frequently employed by plant pathogens involve hijacking, evading, or disrupting hormone signaling pathways and/or crosstalk. As reviewed here, this is achieved mechanistically via pathogen-derived molecules known as effectors, which target phytohormone receptors, transcriptional activators and repressors, and other components of phytohormone signaling in the host plant. Herbivores and sap-sucking insects employ obligate pathogens such as viruses, phytoplasma, or symbiotic bacteria to intervene with phytohormone-regulated defenses. Overall, an improved understanding of phytohormone intervention strategies employed by pests and pathogens during their interactions with plants will ultimately lead to the development of new crop protection strategies.
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Affiliation(s)
- Kemal Kazan
- Commonwealth Scientific and Industrial Research Organization (CSIRO) Plant Industry, Queensland Bioscience Precinct, Brisbane 4069, Queensland, Australia
| | - Rebecca Lyons
- Commonwealth Scientific and Industrial Research Organization (CSIRO) Plant Industry, Queensland Bioscience Precinct, Brisbane 4069, Queensland, Australia
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13
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Aguilar X, Blomberg J, Brännström K, Olofsson A, Schleucher J, Björklund S. Interaction studies of the human and Arabidopsis thaliana Med25-ACID proteins with the herpes simplex virus VP16- and plant-specific Dreb2a transcription factors. PLoS One 2014; 9:e98575. [PMID: 24874105 PMCID: PMC4038590 DOI: 10.1371/journal.pone.0098575] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 05/05/2014] [Indexed: 12/17/2022] Open
Abstract
Mediator is an evolutionary conserved multi-protein complex present in all eukaryotes. It functions as a transcriptional co-regulator by conveying signals from activators and repressors to the RNA polymerase II transcription machinery. The Arabidopsis thaliana Med25 (aMed25) ACtivation Interaction Domain (ACID) interacts with the Dreb2a activator which is involved in plant stress response pathways, while Human Med25-ACID (hMed25) interacts with the herpes simplex virus VP16 activator. Despite low sequence similarity, hMed25-ACID also interacts with the plant-specific Dreb2a transcriptional activator protein. We have used GST pull-down-, surface plasmon resonance-, isothermal titration calorimetry and NMR chemical shift experiments to characterize interactions between Dreb2a and VP16, with the hMed25 and aMed25-ACIDs. We found that VP16 interacts with aMed25-ACID with similar affinity as with hMed25-ACID and that the binding surface on aMed25-ACID overlaps with the binding site for Dreb2a. We also show that the Dreb2a interaction region in hMed25-ACID overlaps with the earlier reported VP16 binding site. In addition, we show that hMed25-ACID/Dreb2a and aMed25-ACID/Dreb2a display similar binding affinities but different binding energetics. Our results therefore indicate that interaction between transcriptional regulators and their target proteins in Mediator are less dependent on the primary sequences in the interaction domains but that these domains fold into similar structures upon interaction.
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Affiliation(s)
| | - Jeanette Blomberg
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | | | - Anders Olofsson
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Jürgen Schleucher
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Stefan Björklund
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
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14
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Khalil MI, Sommer M, Arvin A, Hay J, Ruyechan WT. Cellular transcription factor YY1 mediates the varicella-zoster virus (VZV) IE62 transcriptional activation. Virology 2014; 449:244-53. [PMID: 24418559 DOI: 10.1016/j.virol.2013.11.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 08/19/2013] [Accepted: 11/20/2013] [Indexed: 12/12/2022]
Abstract
Several cellular transcription factors have been shown to be involved in IE62-mediated activation. The YY1 cellular transcription factor has activating and repressive effects on gene transcription. Analysis of the VZV genome revealed 19 postulated YY1 binding sites located within putative promoters of 16 VZV genes. Electrophoretic mobility shift assays (EMSA) confirmed the binding of YY1 to ORF10, ORF28/29 and gI promoters and the mutation of these binding sites inhibited YY1 binding and the promoter activation by IE62 alone or following VZV infection. Mutation of the ORF28/29 YY1 site in the VZV genome displayed insignificant influence on virus growth in melanoma cells; but it inhibited the virus replication significantly at day 5 and 6 post infection in HELF cells. This work suggests a novel role for the cellular factor YY1 in VZV replication through the mediation of IE62 activation of viral gene expression.
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Affiliation(s)
- Mohamed I Khalil
- Departments of Pediatrics and Microbiology & Immunology, Stanford University School of Medicine, Stanford, CA 94305, United States; Department of Molecular Biology, National Research Center, Dokki, Cairo, Egypt.
| | - Marvin Sommer
- Departments of Pediatrics and Microbiology & Immunology, Stanford University School of Medicine, Stanford, CA 94305, United States
| | - Ann Arvin
- Departments of Pediatrics and Microbiology & Immunology, Stanford University School of Medicine, Stanford, CA 94305, United States
| | - John Hay
- Department of Microbiology and Immunology and the Witebsky Center for Microbial Pathogenesis and Immunology, University at Buffalo, Buffalo, NY, United States
| | - William T Ruyechan
- Department of Microbiology and Immunology and the Witebsky Center for Microbial Pathogenesis and Immunology, University at Buffalo, Buffalo, NY, United States
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15
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Ansari SA, Morse RH. Mechanisms of Mediator complex action in transcriptional activation. Cell Mol Life Sci 2013; 70:2743-56. [PMID: 23361037 PMCID: PMC11113466 DOI: 10.1007/s00018-013-1265-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 01/07/2013] [Accepted: 01/09/2013] [Indexed: 12/14/2022]
Abstract
Mediator is a large multisubunit complex that plays a central role in the regulation of RNA Pol II transcribed genes. Conserved in overall structure and function among eukaryotes, Mediator comprises 25-30 protein subunits that reside in four distinct modules, termed head, middle, tail, and CDK8/kinase. Different subunits of Mediator contact other transcriptional regulators including activators, co-activators, general transcription factors, subunits of RNA Pol II, and specifically modified histones, leading to the regulated expression of target genes. This review is focused on the interactions of specific Mediator subunits with diverse transcription regulators and how those interactions contribute to Mediator function in transcriptional activation.
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Affiliation(s)
- Suraiya A. Ansari
- Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, NY 12201–0509 USA
| | - Randall H. Morse
- Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, NY 12201–0509 USA
- Department of Biomedical Science, University at Albany School of Public Health, Albany, NY USA
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16
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Verger A, Baert JL, Verreman K, Dewitte F, Ferreira E, Lens Z, de Launoit Y, Villeret V, Monté D. The Mediator complex subunit MED25 is targeted by the N-terminal transactivation domain of the PEA3 group members. Nucleic Acids Res 2013; 41:4847-59. [PMID: 23531547 PMCID: PMC3643604 DOI: 10.1093/nar/gkt199] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
PEA3, ERM and ER81 belong to the PEA3 subfamily of Ets transcription factors and play important roles in a number of tissue-specific processes. Transcriptional activation by PEA3 subfamily factors requires their characteristic amino-terminal acidic transactivation domain (TAD). However, the cellular targets of this domain remain largely unknown. Using ERM as a prototype, we show that the minimal N-terminal TAD activates transcription by contacting the activator interacting domain (ACID)/Prostate tumor overexpressed protein 1 (PTOV) domain of the Mediator complex subunit MED25. We further show that depletion of MED25 disrupts the association of ERM with the Mediator in vitro. Small interfering RNA-mediated knockdown of MED25 as well as the overexpression of MED25-ACID and MED25-VWA domains efficiently inhibit the transcriptional activity of ERM. Moreover, mutations of amino acid residues that prevent binding of MED25 to ERM strongly reduce transactivation by ERM. Finally we show that siRNA depletion of MED25 diminishes PEA3-driven expression of MMP-1 and Mediator recruitment. In conclusion, this study identifies the PEA3 group members as the first human transcriptional factors that interact with the MED25 ACID/PTOV domain and establishes MED25 as a crucial transducer of their transactivation potential.
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Affiliation(s)
- Alexis Verger
- IRI USR 3078 CNRS, Parc CNRS de la Haute Borne, 50 avenue de Halley, B.P. 70478, 59658 Villeneuve d'Ascq Cedex, France
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17
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Abstract
Varicella zoster virus (VZV) is one of eight members of the Herpesviridae family for which humans are the primary host; it causes two distinct diseases, varicella (chickenpox) and zoster (shingles). Varicella results from primary infection, during which the virus establishes latency in sensory neurons, a characteristic of all members of the Alphaherpesvirinae subfamily. Zoster is caused by reactivation of latent virus, which typically occurs when cellular immunity is impaired. VZV is the first human herpesvirus for which a vaccine has been licensed. The vaccine preparation, v-Oka, is a live-attenuated virus stock produced by the classic method of tissue culture passage in animal and human cell lines. Over 90 million doses of the vaccine have been administered in countries worldwide, including the USA, where varicella morbidity and mortality has declined dramatically. Over the last decade, several laboratories have been committed to investigating the mechanism by which the Oka vaccine is attenuated. Mutations have accumulated across the genome of the vaccine during the attenuation process; however, studies of the contribution of these changes to vaccine attenuation have been hampered by the lack of a suitable animal model of VZV disease and by the heterogeneity that exists among the viral population within the vaccine preparation. Notwithstanding, a wealth of data has been generated using various laboratory methodologies. Studies of the vaccine virus in human xenografts implanted in severe combined immunodeficiency-hu mice, have enabled analyses of the replication dynamics of the vaccine in dorsal root ganglia, T lymphocytes and skin. In vitro assays have been used to investigate the effect of vaccine mutations on viral gene expression and sequence analysis of vaccine rash viruses has permitted investigations into spread of the vaccine virus in a human host. We present here a review of what has been learned thus far about the molecular and phenotypic characteristics of the Oka vaccine.
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MESH Headings
- Animals
- Chickenpox/immunology
- Chickenpox/prevention & control
- Chickenpox/virology
- Chickenpox Vaccine/administration & dosage
- Chickenpox Vaccine/genetics
- Chickenpox Vaccine/immunology
- Ganglia, Spinal/drug effects
- Ganglia, Spinal/immunology
- Ganglia, Spinal/pathology
- Ganglia, Spinal/virology
- Herpes Zoster/immunology
- Herpes Zoster/prevention & control
- Herpes Zoster/virology
- Herpesvirus 3, Human/drug effects
- Herpesvirus 3, Human/genetics
- Herpesvirus 3, Human/immunology
- Humans
- Immunity, Cellular
- Mice
- Mice, SCID
- Polymorphism, Single Nucleotide
- Sensory Receptor Cells/drug effects
- Sensory Receptor Cells/immunology
- Sensory Receptor Cells/pathology
- Sensory Receptor Cells/virology
- Skin/drug effects
- Skin/immunology
- Skin/pathology
- Skin/virology
- Transplantation, Heterologous/immunology
- Vaccines, Attenuated/administration & dosage
- Vaccines, Attenuated/genetics
- Vaccines, Attenuated/immunology
- Virus Activation/drug effects
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Affiliation(s)
- Mark Quinlivan
- Herpesvirus Team and National VZV Laboratory, MMRHLB, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
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18
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Kidd BN, Cahill DM, Manners JM, Schenk PM, Kazan K. Diverse roles of the Mediator complex in plants. Semin Cell Dev Biol 2011; 22:741-8. [DOI: 10.1016/j.semcdb.2011.07.012] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Accepted: 07/17/2011] [Indexed: 02/06/2023]
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19
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Kim SK, Kim S, Dai G, Zhang Y, Ahn BC, O'Callaghan DJ. Identification of functional domains of the IR2 protein of equine herpesvirus 1 required for inhibition of viral gene expression and replication. Virology 2011; 417:430-42. [PMID: 21794889 DOI: 10.1016/j.virol.2011.06.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Revised: 06/22/2011] [Accepted: 06/27/2011] [Indexed: 10/17/2022]
Abstract
The equine herpesvirus 1 (EHV-1) negative regulatory IR2 protein (IR2P), an early 1,165-amino acid (aa) truncated form of the 1487-aa immediate-early protein (IEP), lacks the trans-activation domain essential for IEP activation functions but retains domains for binding DNA, TFIIB, and TBP and the nuclear localization signal. IR2P mutants of the N-terminal region which lack either DNA-binding activity or TFIIB-binding activity were unable to down-regulate EHV-1 promoters. In EHV-1-infected cells expressing full-length IR2P, transcription and protein expression of viral regulatory IE, early EICP0, IR4, and UL5, and late ETIF genes were dramatically inhibited. Viral DNA levels were reduced to 2.1% of control infected cells, but were vey weakly affected in cells that express the N-terminal 706 residues of IR2P. These results suggest that IR2P function requires the two N-terminal domains for binding DNA and TFIIB as well as the C-terminal residues 707 to 1116 containing the TBP-binding domain.
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Affiliation(s)
- Seong K Kim
- Department of Microbiology and Immunology, and Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, Louisiana LA 71130-3932, USA.
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20
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Eletsky A, Ruyechan WT, Xiao R, Acton TB, Montelione GT, Szyperski T. Solution NMR structure of MED25(391-543) comprising the activator-interacting domain (ACID) of human mediator subunit 25. ACTA ACUST UNITED AC 2011; 12:159-66. [PMID: 21785987 DOI: 10.1007/s10969-011-9115-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 07/11/2011] [Indexed: 10/18/2022]
Abstract
The solution NMR structure of protein MED25(391-543), comprising the activator interacting domain (ACID) of subunit 25 of the human mediator, is presented along with the measurement of polypeptide backbone heteronuclear 15N-{1H} NOEs to identify fast internal motional modes. This domain interacts with the acidic transactivation domains of Herpes simplex type 1 (HSV-1) protein VP16 and the Varicella-zoster virus (VZV) major transactivator protein IE62, which initiate transcription of viral genes. The structure is similar to the β-barrel domains of the human protein Ku and the SPOC domain of human protein SHARP, and provides a starting point to understand the structural biology of initiation of HSV-1 and VZV gene activation. Homology models built for the two ACID domains of the prostate tumor overexpressed (PTOV1) protein using the structure of MED25(391-543) as a template suggest that differential biological activities of the ACID domains in MED25 and PTOV1 arise from modulation of quite similar protein-protein interactions by variable residues grouped around highly conserved charged surface areas.
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Affiliation(s)
- Alexander Eletsky
- Department of Chemistry, The State University of New York at Buffalo, Buffalo, NY 14260, USA
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21
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Structure of the VP16 transactivator target in the Mediator. Nat Struct Mol Biol 2011; 18:410-5. [PMID: 21378963 PMCID: PMC3076674 DOI: 10.1038/nsmb.1999] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Accepted: 12/03/2010] [Indexed: 11/09/2022]
Abstract
The human Activator-Recruited Cofactor (ARC)/Mediator co-activator complex interacts with many transcriptional activators and facilitates recruitment of RNA polymerase II to promote target gene transcription. The MED25 (ARC92) subunit is a critical target of the potent Herpes simplex 1 viral transcriptional activator VP16. Here, we determine the solution structure of the MED25 VP16-binding domain (VBD), and define its binding site for the N-terminal portion of the VP16 transactivation domain (TADn). A hydrophobic furrow, formed by a β-barrel and two α-helices in MED25 VBD, interacts tightly with VP16 TADn. Mutations in this furrow prevent binding of VP16 TAD to MED25 VBD and interfere with the ability of over-expressed MED25 VBD to inhibit VP16-dependent transcriptional activation in vivo. This detailed molecular understanding of transactivation by the benchmark activator VP16 could provide important insights into viral and cellular gene activation mechanisms.
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22
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Abstract
Varicella zoster virus (VZV) is the causative agent of chickenpox and shingles. During productive infection the complete VZV proteome consisting of some 68 unique gene products is expressed through interaction of a small number of viral transcriptional activators with the general transcription apparatus of the host cell. Recent work has shown that the major viral transactivator, commonly designated the IE62 protein, interacts with the human Mediator of transcription. This interaction requires direct contact between the MED25 subunit of Mediator and the acidic N-terminal transactivation domain of IE62. A second cellular factor, host cell factor-1, has been shown to be the common element in two mechanisms of activation of the promoter driving expression of the gene encoding IE62. Finally, the ubiquitous cellular transcription factors Sp1, Sp3, and YY1 have been shown to interact with sequences near the VZV origin of DNA replication and in the case of Sp1/Sp3 to influence replication efficiency.
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23
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NMR structure of the human Mediator MED25 ACID domain. J Struct Biol 2010; 174:245-51. [PMID: 20974256 DOI: 10.1016/j.jsb.2010.10.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 10/20/2010] [Accepted: 10/20/2010] [Indexed: 11/22/2022]
Abstract
MED25 (ARC92/ACID1) is a 747 residues subunit specific to higher eukaryote Mediator complex, an essential component of the RNA polymerase II general transcriptional machinery. MED25 is a target of the Herpes simplex virus transactivator protein VP16. MED25 interacts with VP16 through a central MED25 PTOV (Prostate tumour overexpressed)/ACID (Activator interacting domain) domain of unknown structure. As a first step towards understanding the mechanism of recruitment of transactivation domains by MED25, we report here the NMR structure of the MED25 ACID domain. The domain architecture consists of a closed β-barrel with seven strands (Β1-Β7) and three α-helices (H1-H3), an architecture showing similarities to that of the SPOC (Spen paralog and ortholog C-terminal domain) domain-like superfamily. Preliminary NMR chemical shift mapping showed that VP16 H2 (VP16C) interacts with MED25 ACID through one face of the β-barrel, defined by strands B4-B7-B6.
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24
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Role of the IE62 consensus binding site in transactivation by the varicella-zoster virus IE62 protein. J Virol 2010; 84:3767-79. [PMID: 20130051 DOI: 10.1128/jvi.02522-09] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The varicella-zoster virus (VZV) IE62 protein is the major transcriptional activator. IE62 is capable of associating with DNA both nonspecifically and in a sequence-specific manner via a consensus binding site (5'-ATCGT-3'). However, the function of the consensus site is poorly understood, since IE62 efficiently transactivates promoter elements lacking this sequence. In the work presented here, sequence analysis of the VZV genome revealed the presence of 245 IE62 consensus sites throughout the genome. Some 54 sites were found to be present within putative VZV promoters. Electrophoretic mobility shift assay (EMSA) experiments using an IE62 fragment containing the IE62 DNA-binding domain and duplex oligonucleotides that did or did not contain the IE62 consensus binding sequence yielded K(D) (equilibrium dissociation constant) values in the nanomolar range. Further, the IE62 DNA binding domain was shown to have a 5-fold-increased affinity for its consensus site compared to nonconsensus sequences. The effect of consensus site presence and position on IE62-mediated activation of native VZV and model promoters was examined using site-specific mutagenesis and transfection and superinfection reporter assays. In all promoters examined, the consensus sequence functioned as a distance-dependent repressive element. Protein recruitment assays utilizing the VZV gI promoter indicated that the presence of the consensus site increased the recruitment of IE62 but not Sp1. These data suggest a model where the IE62 consensus site functions to down-modulate IE62 activation, and interaction of IE62 with this sequence may result in loss or decrease of the ability of IE62 to recruit cellular factors needed for full promoter activation.
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