Dataset Information

The ebola virus interferon antagonist VP24 directly binds STAT1 and has a novel, pyramidal fold.

ABSTRACT: Ebolaviruses cause hemorrhagic fever with up to 90% lethality and in fatal cases, are characterized by early suppression of the host innate immune system. One of the proteins likely responsible for this effect is VP24. VP24 is known to antagonize interferon signaling by binding host karyopherin ? proteins, thereby preventing them from transporting the tyrosine-phosphorylated transcription factor STAT1 to the nucleus. Here, we report that VP24 binds STAT1 directly, suggesting that VP24 can suppress at least two distinct branches of the interferon pathway. Here, we also report the first crystal structures of VP24, derived from different species of ebolavirus that are pathogenic (Sudan) and nonpathogenic to humans (Reston). These structures reveal that VP24 has a novel, pyramidal fold. A site on a particular face of the pyramid exhibits reduced solvent exchange when in complex with STAT1. This site is above two highly conserved pockets in VP24 that contain key residues previously implicated in virulence. These crystal structures and accompanying biochemical analysis map differences between pathogenic and nonpathogenic viruses, offer templates for drug design, and provide the three-dimensional framework necessary for biological dissection of the many functions of VP24 in the virus life cycle.

SUBMITTER: Zhang AP

PROVIDER: S-EPMC3285596 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

The ebola virus interferon antagonist VP24 directly binds STAT1 and has a novel, pyramidal fold.

Zhang Adrianna P P AP Bornholdt Zachary A ZA Liu Tong T Abelson Dafna M DM Lee David E DE Li Sheng S Woods Virgil L VL Saphire Erica Ollmann EO

PLoS pathogens 20120223 2

Ebolaviruses cause hemorrhagic fever with up to 90% lethality and in fatal cases, are characterized by early suppression of the host innate immune system. One of the proteins likely responsible for this effect is VP24. VP24 is known to antagonize interferon signaling by binding host karyopherin α proteins, thereby preventing them from transporting the tyrosine-phosphorylated transcription factor STAT1 to the nucleus. Here, we report that VP24 binds STAT1 directly, suggesting that VP24 can suppre ...[more]

PMID: 22383882

Similar Datasets

Project description:Some viruses take advantage of conjugation of ubiquitin or ubiquitin-like proteins to enhance their own replication. One example is Ebola virus, which has evolved strategies to utilize these modification pathways to regulate the viral proteins VP40 and VP35 and to counteract the host defenses. Here, we show a novel mechanism by which Ebola virus exploits the ubiquitin and SUMO pathways. Our data reveal that minor matrix protein VP24 of Ebola virus is a bona fide SUMO target. Analysis of a SUMOylation-defective VP24 mutant revealed a reduced ability to block the type I interferon (IFN) pathway and to inhibit IFN-mediated STAT1 nuclear translocation, exhibiting a weaker interaction with karyopherin 5 and significantly diminished stability. Using glutathione S-transferase (GST) pulldown assay, we found that VP24 also interacts with SUMO in a noncovalent manner through a SIM domain. Mutation of the SIM domain in VP24 resulted in a complete inability of the protein to downmodulate the IFN pathway and in the monoubiquitination of the protein. We identified SUMO deubiquitinating enzyme ubiquitin-specific-processing protease 7 (USP7) as an interactor and a negative modulator of VP24 ubiquitination. Finally, we show that mutation of one ubiquitination site in VP24 potentiates the IFN modulatory activity of the viral protein and its ability to block IFN-mediated STAT1 nuclear translocation, pointing to the ubiquitination of VP24 as a negative modulator of the VP24 activity. Altogether, these results indicate that SUMO interacts with VP24 and promotes its USP7-mediated deubiquitination, playing a key role in the interference with the innate immune response mediated by the viral protein.IMPORTANCE The Ebola virus VP24 protein plays a critical role in escape of the virus from the host innate immune response. Therefore, deciphering the molecular mechanisms modulating VP24 activity may be useful to identify potential targets amenable to therapeutics. Here, we identify the cellular proteins USP7, SUMO, and ubiquitin as novel interactors and regulators of VP24. These interactions may represent novel potential targets to design new antivirals with the ability to modulate Ebola virus replication.

Project description:Ebola virus (EBOV) protein VP24 carries out at least two critical functions. It promotes condensation of viral nucleocapsids, which is crucial for infectious virus production, and it suppresses interferon (IFN) signaling, which requires interaction with the NPI-1 subfamily of importin-α (IMPA) nuclear transport proteins. Interestingly, over-expressed IMPA leads to VP24 nuclear accumulation and a carboxy-terminus nuclear export signal (NES) has been reported, suggesting that VP24 may undergo nuclear trafficking. For the first time, we demonstrate that NPI-1 IMPA overexpression leads to the nuclear accumulation of VP24 during EBOV infection. To assess the functional impact of nuclear trafficking, we generated tetracistronic minigenomes encoding VP24 nuclear import and/or export signal mutants. The minigenomes, which also encode Renilla luciferase and viral proteins VP40 and GP, were used to generate transcription and replication competent virus-like particles (trVLPs) that can be used to assess EBOV RNA synthesis, gene expression, entry and viral particle production. With this system, we confirmed that NES or IMPA binding site mutations altered VP24 nuclear localization, demonstrating functional trafficking signals. While these mutations minimally affected transcription and replication, the trVLPs exhibited impaired infectivity and formation of shortened nucleocapsids for the IMPA binding mutant. For the NES mutants, infectivity was reduced approximately 1000-fold. The NES mutant could still suppress IFN signaling but failed to promote nucleocapsid formation. To determine whether VP24 nuclear export is required for infectivity, the residues surrounding the wildtype NES were mutated to alanine or the VP24 NES was replaced with the Protein Kinase A Inhibitor NES. While nuclear export remained intact for these mutants, infectivity was severely impaired. These data demonstrate that VP24 undergoes nuclear trafficking and illuminates a separate and critical role for the NES and surrounding sequences in infectivity and nucleocapsid assembly.

Dataset Information

The ebola virus interferon antagonist VP24 directly binds STAT1 and has a novel, pyramidal fold.

Publications

The ebola virus interferon antagonist VP24 directly binds STAT1 and has a novel, pyramidal fold.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets