Structural basis ofDeerpox virus-mediated inhibition of apoptosis

2015 ◽  
Vol 71 (8) ◽  
pp. 1593-1603 ◽  
Author(s):  
Denis R. Burton ◽  
Sofia Caria ◽  
Bevan Marshall ◽  
Michele Barry ◽  
Marc Kvansakul
Keyword(s):  
Structural Analysis ◽  
Ligand Binding ◽  
Structural Basis ◽  
Inhibitor Of Apoptosis ◽  
Defence Mechanism ◽  
Partial Obstruction ◽  
Host Cell Apoptosis ◽  
Infected Cells ◽  
Binding Groove ◽  
Innate Defence

Apoptosis is a key innate defence mechanism to eliminate virally infected cells. To counteract premature host-cell apoptosis, poxviruses have evolved numerous molecular strategies, including the use of Bcl-2 proteins, to ensure their own survival. Here, it is reported that theDeerpox virusinhibitor of apoptosis, DPV022, only engages a highly restricted set of death-inducing Bcl-2 proteins, including Bim, Bax and Bak, with modest affinities. Structural analysis reveals that DPV022 adopts a Bcl-2 fold with a dimeric domain-swapped topology and binds pro-death Bcl-2 proteinsviatwo conserved ligand-binding grooves found on opposite sides of the dimer. Structures of DPV022 bound to Bim, Bak and Bax BH3 domains reveal that a partial obstruction of the binding groove is likely to be responsible for the modest affinities of DPV022 for BH3 domains. These findings reveal that domain-swapped dimeric Bcl-2 folds are not unusual and may be found more widely in viruses. Furthermore, the modest affinities of DPV022 for pro-death Bcl-2 proteins suggest that two distinct classes of anti-apoptotic viral Bcl-2 proteins exist: those that are monomeric and tightly bind a range of death-inducing Bcl-2 proteins, and others such as DPV022 that are dimeric and only bind a very limited number of death-inducing Bcl-2 proteins with modest affinities.

scholarly journals Ancient and conserved functional interplay between Bcl-2 family proteins in the mitochondrial pathway of apoptosis

2020 ◽  
Vol 6 (40) ◽  
pp. eabc4149 ◽  
Author(s):  
Nikolay Popgeorgiev ◽  
Jaison D Sa ◽  
Lea Jabbour ◽  
Suresh Banjara ◽  
Trang Thi Minh Nguyen ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ligand Binding ◽  
Cancer Cells ◽  
Mitochondrial Pathway ◽  
Structural Basis ◽  
Mitochondrial Outer Membrane ◽  
Chemotherapy Treatment ◽  
Trichoplax Adhaerens ◽  
Binding Groove

In metazoans, Bcl-2 family proteins are major regulators of mitochondrially mediated apoptosis; however, their evolution remains poorly understood. Here, we describe the molecular characterization of the four members of the Bcl-2 family in the most primitive metazoan, Trichoplax adhaerens. All four trBcl-2 homologs are multimotif Bcl-2 group, with trBcl-2L1 and trBcl-2L2 being highly divergent antiapoptotic Bcl-2 members, whereas trBcl-2L3 and trBcl-2L4 are homologs of proapoptotic Bax and Bak, respectively. trBax expression permeabilizes the mitochondrial outer membrane, while trBak operates as a BH3-only sensitizer repressing antiapoptotic activities of trBcl-2L1 and trBcl-2L2. The crystal structure of a trBcl-2L2:trBak BH3 complex reveals that trBcl-2L2 uses the canonical Bcl-2 ligand binding groove to sequester trBak BH3, indicating that the structural basis for apoptosis control is conserved from T. adhaerens to mammals. Finally, we demonstrate that both trBax and trBak BH3 peptides bind selectively to human Bcl-2 homologs to sensitize cancer cells to chemotherapy treatment.

scholarly journals Structural insight into tanapoxvirus mediated inhibition of apoptosis

2020 ◽  
Author(s):  
Chathura D. Suraweera ◽  
Mohd Ishtiaq Anasir ◽  
Srishti Chugh ◽  
Airah Javorsky ◽  
Rachael E. Impey ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Host Cell ◽  
Inhibitory Protein ◽  
Double Stranded Dna ◽  
Host Cell Apoptosis ◽  
Mechanistic Basis ◽  
Binding Groove ◽  
Multicellular Organisms ◽  
Oligomeric Forms ◽  
Insight Into

AbstractPremature programmed cell death or apoptosis of cells is a strategy utilized by multicellular organisms to counter microbial threats. Tanapoxvirus (TANV) is a large double-stranded DNA virus belonging to the poxviridae that causes mild Monkeypox-like infections in humans and primates. TANV encodes for a putative apoptosis inhibitory protein 16L. We show that TANV16L is able to bind to a range of peptides spanning the BH3 motif of human pro-apoptotic Bcl-2 proteins, and is able to counter growth arrest of yeast induced by human Bak and Bax. We then determined the crystal structures of TANV16L bound to three identified interactors, Bax, Bim and Puma BH3. TANV16L adopts a globular Bcl-2 fold comprising 7 α-helices, and utilizes the canonical Bcl-2 binding groove to engage pro-apoptotic host cell Bcl-2 proteins. Unexpectedly, TANV16L is able to adopt both a monomeric as well as a domain-swapped dimeric topology where the α1 helix from one protomer is swapped into a neighbouring unit. Despite adopting two different oligomeric forms, the canonical ligand binding groove in TANV16L remains unchanged from monomer to domain-swapped dimer. Our results provide a structural and mechanistic basis for tanapoxvirus mediated inhibition of host cell apoptosis, and reveal the capacity of Bcl-2 proteins to adopt differential oligomeric states whilst maintaining the canonical ligand binding groove in an unchanged state.

scholarly journals Structural Investigation of Orf Virus Bcl-2 Homolog ORFV125 Interactions with BH3-Motifs from BH3-Only Proteins Puma and Hrk

Viruses ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1374
Author(s):  
Chathura D. Suraweera ◽  
Mark G. Hinds ◽  
Marc Kvansakul
Keyword(s):  
Cell Death ◽  
Structural Investigation ◽  
Potent Inhibitor ◽  
Host Cells ◽  
Orf Virus ◽  
Structural Basis ◽  
Signalling Pathways ◽  
Ionic Interaction ◽  
Host Cell Apoptosis ◽  
Binding Groove

Numerous viruses have evolved sophisticated countermeasures to hijack the early programmed cell death of host cells in response to infection, including the use of proteins homologous in sequence or structure to Bcl-2. Orf virus, a member of the parapoxviridae, encodes for the Bcl-2 homolog ORFV125, a potent inhibitor of Bcl-2-mediated apoptosis in the host. ORFV125 acts by directly engaging host proapoptotic Bcl-2 proteins including Bak and Bax as well as the BH3-only proteins Hrk and Puma. Here, we determined the crystal structures of ORFV125 bound to the BH3 motif of proapoptotic proteins Puma and Hrk. The structures reveal that ORFV125 engages proapoptotic BH3 motif peptides using the canonical ligand binding groove. An Arg located in the structurally equivalent BH1 region of ORFV125 forms an ionic interaction with the conserved Asp in the BH3 motif in a manner that mimics the canonical ionic interaction seen in host Bcl-2:BH3 motif complexes. These findings provide a structural basis for Orf virus-mediated inhibition of host cell apoptosis and reveal the flexibility of virus encoded Bcl-2 proteins to mimic key interactions from endogenous host signalling pathways.

scholarly journals Crystal structures of the sheeppoxvirus encoded inhibitor of apoptosis SPPV14 bound to Hrk and Bax BH3 peptides

2020 ◽  
Author(s):  
Chathura D. Suraweera ◽  
Denis R. Burton ◽  
Mark G. Hinds ◽  
Marc Kvansakul
Keyword(s):  
Crystal Structures ◽  
Viral Infections ◽  
Structural Basis ◽  
Ionic Interaction ◽  
Apoptosis Inhibition ◽  
Programmed Death ◽  
Infected Cells ◽  
Binding Groove ◽  
Almost All ◽  
Multicellular Organisms

AbstractProgrammed death of infected cells is used by multicellular organisms to counter viral infections. Sheeppoxvirus encodes for SPPV14, a potent inhibitor of Bcl-2 mediated apoptosis. We reveal the structural basis of apoptosis inhibition by determining crystal structures of SPPV14 bound to BH3 motifs of proapoptotic Bax and Hrk. The structures show that SPPV14 engages BH3 peptides using the canonical ligand binding groove. Unexpectedly, Arg84 from SPPV14 forms an ionic interaction with the conserved Asp in the BH3 motif in a manner that replaces the canonical ionic interaction seen in almost all host Bcl-2:BH3 motif complexes. These results reveal the flexibility of virus encoded Bcl-2 proteins to mimic key interactions from endogenous host signalling pathways to retain BH3-binding and pro-survival functionality.

scholarly journals Crystal structures of ORFV125 provide insight into orf virus-mediated inhibition of apoptosis

2020 ◽  
Vol 477 (23) ◽  
pp. 4527-4541 ◽  
Author(s):  
Chathura D. Suraweera ◽  
Mark G. Hinds ◽  
Marc Kvansakul
Keyword(s):  
Host Cell ◽  
Crystal Structures ◽  
B Cell Lymphoma ◽  
Orf Virus ◽  
Structural Basis ◽  
Inhibitory Protein ◽  
Affinity Ligand ◽  
Host Cell Apoptosis ◽  
Mechanistic Basis ◽  
Binding Groove

Premature apoptosis of cells is a strategy utilized by multicellular organisms to counter microbial threats. Orf virus (ORFV) is a large double-stranded DNA virus belonging to the poxviridae. ORFV encodes for an apoptosis inhibitory protein ORFV125 homologous to B-cell lymphoma 2 or Bcl-2 family proteins, which has been shown to inhibit host cell encoded pro-apoptotic Bcl-2 proteins. However, the structural basis of apoptosis inhibition by ORFV125 remains to be clarified. We show that ORFV125 is able to bind to a range of peptides spanning the BH3 motif of human pro-apoptotic Bcl-2 proteins including Bax, Bak, Puma and Hrk with modest to weak affinity. We then determined the crystal structures of ORFV125 alone as well as bound to the highest affinity ligand Bax BH3 motif. ORFV125 adopts a globular Bcl-2 fold comprising 7 α-helices, and utilizes the canonical Bcl-2 binding groove to engage pro-apoptotic host cell Bcl-2 proteins. In contrast with a previously predicted structure, ORFV125 adopts a domain-swapped dimeric topology, where the α1 helix from one protomer is swapped into a neighbouring unit. Furthermore, ORFV125 differs from the conserved architecture of the Bcl-2 binding groove and instead of α3 helix forming one of the binding groove walls, ORFV125 utilizes an extended α2 helix that comprises the equivalent region of helix α3. This results in a subtle variation of previously observed dimeric Bcl-2 architectures in other poxvirus and human encoded Bcl-2 proteins. Overall, our results provide a structural and mechanistic basis for orf virus-mediated inhibition of host cell apoptosis.

scholarly journals Poxviral Strategies to Overcome Host Cell Apoptosis

Pathogens ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 6
Author(s):  
Chathura D. Suraweera ◽  
Mark G. Hinds ◽  
Marc Kvansakul
Keyword(s):  
Viral Infections ◽  
B Cell Lymphoma ◽  
Intrinsic Apoptosis ◽  
Host Cell Apoptosis ◽  
Successful Infection ◽  
Infected Cells ◽  
Host Virus Interactions ◽  
Almost All ◽  
Virus Interactions ◽  
Multicellular Organisms

Apoptosis is a form of cellular suicide initiated either via extracellular (extrinsic apoptosis) or intracellular (intrinsic apoptosis) cues. This form of programmed cell death plays a crucial role in development and tissue homeostasis in multicellular organisms and its dysregulation is an underlying cause for many diseases. Intrinsic apoptosis is regulated by members of the evolutionarily conserved B-cell lymphoma-2 (Bcl-2) family, a family that consists of pro- and anti-apoptotic members. Bcl-2 genes have also been assimilated by numerous viruses including pox viruses, in particular the sub-family of chordopoxviridae, a group of viruses known to infect almost all vertebrates. The viral Bcl-2 proteins are virulence factors and aid the evasion of host immune defenses by mimicking the activity of their cellular counterparts. Viral Bcl-2 genes have proved essential for the survival of virus infected cells and structural studies have shown that though they often share very little sequence identity with their cellular counterparts, they have near-identical 3D structures. However, their mechanisms of action are varied. In this review, we examine the structural biology, molecular interactions, and detailed mechanism of action of poxvirus encoded apoptosis inhibitors and how they impact on host–virus interactions to ultimately enable successful infection and propagation of viral infections.

scholarly journals Identification of fidelity-governing factors in human recombinases DMC1 and RAD51 from cryo-EM structures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shih-Chi Luo ◽  
Hsin-Yi Yeh ◽  
Wei-Hsuan Lan ◽  
Yi-Min Wu ◽  
Cheng-Han Yang ◽  
...  
Keyword(s):  
Functional Analysis ◽  
Structural Analysis ◽  
Md Simulation ◽  
Structural Basis ◽  
High Fidelity ◽  
Dna Dynamics ◽  
Genomic Integrity ◽  
Mismatched Dna ◽  
Dna Backbone ◽  
Loop 2

AbstractBoth high-fidelity and mismatch-tolerant recombination, catalyzed by RAD51 and DMC1 recombinases, respectively, are indispensable for genomic integrity. Here, we use cryo-EM, MD simulation and functional analysis to elucidate the structural basis for the mismatch tolerance of DMC1. Structural analysis of DMC1 presynaptic and postsynaptic complexes suggested that the lineage-specific Loop 1 Gln244 (Met243 in RAD51) may help stabilize DNA backbone, whereas Loop 2 Pro274 and Gly275 (Val273/Asp274 in RAD51) may provide an open “triplet gate” for mismatch tolerance. In support, DMC1-Q244M displayed marked increase in DNA dynamics, leading to unobservable DNA map. MD simulation showed highly dispersive mismatched DNA ensemble in RAD51 but well-converged DNA in DMC1 and RAD51-V273P/D274G. Replacing Loop 1 or Loop 2 residues in DMC1 with RAD51 counterparts enhanced DMC1 fidelity, while reciprocal mutations in RAD51 attenuated its fidelity. Our results show that three Loop 1/Loop 2 residues jointly enact contrasting fidelities of DNA recombinases.

scholarly journals Structural analysis of the human SYCE2–TEX12 complex provides molecular insights into synaptonemal complex assembly

Open Biology ◽  
2012 ◽  
Vol 2 (7) ◽  
pp. 120099 ◽  
Author(s):  
Owen R. Davies ◽  
Joseph D. Maman ◽  
Luca Pellegrini
Keyword(s):  
Structural Analysis ◽  
Synaptonemal Complex ◽  
Recurrent Miscarriage ◽  
Central Element ◽  
Biological Data ◽  
Structural Basis ◽  
Structural Framework ◽  
Chromosome Synapsis ◽  
Heterotypic Interactions ◽  
Physical Features

The successful completion of meiosis is essential for all sexually reproducing organisms. The synaptonemal complex (SC) is a large proteinaceous structure that holds together homologous chromosomes during meiosis, providing the structural framework for meiotic recombination and crossover formation. Errors in SC formation are associated with infertility, recurrent miscarriage and aneuploidy. The current lack of molecular information about the dynamic process of SC assembly severely restricts our understanding of its function in meiosis. Here, we provide the first biochemical and structural analysis of an SC protein component and propose a structural basis for its function in SC assembly. We show that human SC proteins SYCE2 and TEX12 form a highly stable, constitutive complex, and define the regions responsible for their homotypic and heterotypic interactions. Biophysical analysis reveals that the SYCE2–TEX12 complex is an equimolar hetero-octamer, formed from the association of an SYCE2 tetramer and two TEX12 dimers. Electron microscopy shows that biochemically reconstituted SYCE2–TEX12 complexes assemble spontaneously into filamentous structures that resemble the known physical features of the SC central element (CE). Our findings can be combined with existing biological data in a model of chromosome synapsis driven by growth of SYCE2–TEX12 higher-order structures within the CE of the SC.

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