VP35

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0003723 RNA binding	IEA GO_REF:0000043	MODIFY	Summary: VP35 binds RNA, but the activity that is actually characterised is duplex-specific: the C-terminal IID binds dsRNA and explicitly does not bind single-stranded RNA. Reason: The keyword mapping gives the correct branch but stops one level above the evidence. Cardenas et al. showed binding to poly(rI).poly(rC), poly(rA).poly(rU) and in vitro-transcribed EBOV dsRNAs but not to ssRNA or dsDNA (PMID:16698997), and the IID structures (PDB 3L29, 3L25-3L28) confirm a dsRNA-binding interface. GO:0003725 double-stranded RNA binding is an is_a descendant of GO:0003723 and is what the assays support, so this is a refinement rather than a correction. Proposed replacements: double-stranded RNA binding Supporting Evidence: PMID:16698997 VP35 interacted specifically with poly(rI) · poly(rC), poly(rA) · poly(rU), or in vitro-transcribed dsRNAs derived from EBOV sequences, and not with single-stranded RNAs (ssRNAs) or double-stranded DNA file:EBOZM/VP35/VP35-uniprot.txt DOMAIN: The interferon inhibitory domain (IID) binds dsRNA
GO:0005515 protein binding	IPI PMID:19153231 Ebola virus protein VP35 impairs the function of interferon ...	MODIFY	Summary: The interaction with host IKBKE/IKKepsilon is real, but bare protein binding is uninformative; the paper supports an inhibitory activity against this kinase. Reason: Prins et al. co-immunoprecipitated VP35 with IKKepsilon, mapped the interaction to the kinase domain, showed that VP35 displaces IKKepsilon from IRF-3, IRF-7 and IPS-1, and showed that VP35 suppresses the IRF-3-directed kinase activity present in IKKepsilon-expressing lysates (PMID:19153231). That is a protein kinase inhibitor activity, which is the informative replacement for GO:0005515 under the protein-binding policy. Removal of the generic term does not imply the interaction is false. Proposed replacements: protein kinase inhibitor activity Supporting Evidence: PMID:19153231 Coimmunoprecipitation experiments now demonstrate physical interactions of VP35 with IKKepsilon and TBK-1 PMID:19153231 These data suggest that VP35 exerts its IFN-antagonist function, at least in part, by blocking necessary interactions between the kinases IKKepsilon and TBK-1 and their normal interaction partners, including their substrates, IRF-3 and IRF-7.
GO:0005515 protein binding	IPI PMID:19153231 Ebola virus protein VP35 impairs the function of interferon ...	MODIFY	Summary: Same experiment, TBK1 as the partner: the informative function is inhibition of this IRF-activating kinase, not generic binding. Reason: TBK1 was co-immunoprecipitated with VP35 alongside IKKepsilon, and VP35 blocks IFN-beta promoter activation driven by either kinase (PMID:19153231). As for the IKBKE row, GO:0005515 carries no functional information and is replaced by protein kinase inhibitor activity. Proposed replacements: protein kinase inhibitor activity Supporting Evidence: PMID:19153231 Coimmunoprecipitation experiments now demonstrate physical interactions of VP35 with IKKepsilon and TBK-1
GO:0005515 protein binding	IPI PMID:21987769 DRBP76 associates with Ebola virus VP35 and suppresses viral...	MODIFY	Summary: VP35-NP binding; the informative molecular function is sequestration of NP monomers, which is independently annotated to VP35 from PMID:25865894. Reason: Bare protein binding is uninformative. The VP35-NP interaction has a characterised molecular consequence: the N-terminal NPBP peptide binds NP with high affinity, prevents NP oligomerization and releases RNA from NP-RNA complexes (PMID:25865894), i.e. it holds NP in an inactive, unpolymerised state. GO:0140313 molecular sequestering activity is therefore the evidence-backed replacement and is already present on other rows of this review. Removing the generic term does not question the interaction. Proposed replacements: molecular sequestering activity Supporting Evidence: PMID:25865894 We identify an intrinsically disordered peptide derived from EBOV VP35 (NPBP, residues 20-48) that binds NP with high affinity and specificity, inhibits NP oligomerization, and releases RNA from NP-RNA complexes in vitro.
GO:0005515 protein binding	IPI PMID:21987769 DRBP76 associates with Ebola virus VP35 and suppresses viral...	REMOVE	Summary: Interaction with host DRBP76/ILF3, a restriction factor that acts on VP35 rather than a target of a VP35 activity; the generic term is uninformative and no specific VP35 function is supported. Reason: The directionality here runs host to virus: DRBP76 overexpression impairs the EBOV transcription/replication complex and the authors conclude it exerts an anti-EBOV function (PMID:21987769). So this interaction records something a host protein does to VP35, and licenses no molecular function for VP35. Per the protein-binding policy a bare GO:0005515 row with no informative replacement is removed as uninformative; this says nothing against the reported interaction, which IntAct records independently. Supporting Evidence: PMID:21987769 Overexpression of DRBP76 did not alter the ability of VP35 to inhibit type I IFN production but did impair the function of the EBOV transcription/replication complex. PMID:21987769 These data suggest that DRBP76, via its association with VP35, exerts an anti-EBOV function.
GO:0005515 protein binding	IPI PMID:23870315 Mutual antagonism between the Ebola virus VP35 protein and t...	MODIFY	Summary: VP35 binds host PRKRA/PACT and strips it off RIG-I; the informative function is sequestration of PACT, not generic binding. Reason: Luthra et al. showed that VP35 inhibits PACT-induced RIG-I ATPase activity dose-dependently and that wild-type VP35, but not PACT-binding mutants, disrupts the PACT-RIG-I interaction (PMID:23870315). Binding that removes a cofactor from its activating partner is molecular sequestering activity, which replaces the uninformative GO:0005515. Proposed replacements: molecular sequestering activity Supporting Evidence: PMID:23870315 Here, we show that EBOV VP35 inhibits PACT-induced RIG-I ATPase activity in a dose-dependent manner. The interaction of PACT with RIG-I is disrupted by wild-type VP35, but not by VP35 mutants that are unable to bind PACT.
GO:0005515 protein binding	IPI PMID:23870315 Mutual antagonism between the Ebola virus VP35 protein and t...	MODIFY	Summary: VP35-NP binding again; replaced by the characterised NP-sequestering activity. Reason: As for the other NP rows, the generic term carries no functional information while the molecular consequence of VP35-NP binding is documented: NPBP occludes the NP surfaces needed for NP-NP and NP-RNA contacts, holding NP monomeric and RNA-free (PMID:25865894). Proposed replacements: molecular sequestering activity Supporting Evidence: PMID:25865894 Our results also show that the VP35 NPBP binding relieves NP oligomerization and NP-RNA binding by interacting with two distinct regions within NP that are important for viral RNA synthesis.
GO:0005515 protein binding	IPI PMID:25865894 An Intrinsically Disordered Peptide from Ebola Virus VP35 Co...	MODIFY	Summary: The NP interaction from the paper that defined its molecular consequence; the specific activity, molecular sequestering, is annotated from the same reference on separate rows. Reason: This row duplicates, at the uninformative GO:0005515 level, the very interaction whose mechanism PMID:25865894 established. The specific term GO:0140313 is already annotated from this reference (EXP and IPI rows), so the generic row should be replaced by it rather than kept. Proposed replacements: molecular sequestering activity Supporting Evidence: PMID:25865894 We identify an intrinsically disordered peptide derived from EBOV VP35 (NPBP, residues 20-48) that binds NP with high affinity and specificity, inhibits NP oligomerization, and releases RNA from NP-RNA complexes in vitro.
GO:0010629 negative regulation of gene expression	IDA PMID:12829834 The Ebola virus VP35 protein inhibits activation of interfer...	MODIFY	Summary: CACAO row. Basler et al. showed that VP35 expression blocks virus-induced activation of host IRF3-responsive promoters (ISG54-CAT, ISG56-luciferase, IFN-alpha4-CAT) in Vero and 293T cells, and blocks IRF-3 phosphorylation, dimerization and nuclear translocation. Host gene expression is indeed reduced, but a root-level regulation-of-gene-expression term discards everything the experiment established. Reason: What the paper actually measures is the interferon-induction arm of innate immunity: reporter promoters that IRF-3 drives, plus native-gel dimerization and 32P-labelling of IRF-3 (Figs 1-4). The claim is sound, so this is not an over-annotation; it is the wrong granularity. For a virus protein the informative class is the symbiont-interaction branch, and the mechanism identified -- loss of virus-induced IRF-3 phosphorylation, with no effect on the constitutively active IRF-3 5D mutant -- is exactly GO:0039548. The CACAO term matched the observation (less host gene expression) rather than the process the observation was reporting on. Proposed replacements: symbiont-mediated suppression of host cytoplasmic pattern recognition receptor signaling pathway via inhibition of IRF3 activity Supporting Evidence: PMID:12829834 VP35 blocks virus-induced IRF-3 phosphorylation and subsequent IRF-3 dimerization and nuclear translocation. PMID:12829834 Expression of the influenza virus NS1 protein or the VP35 protein of Ebola virus Zaire dramatically decreased the activation of either reporter gene (Fig. 1A and B).
GO:0019013 viral nucleocapsid	IDA PMID:12191476 The assembly of Ebola virus nucleocapsid requires virion-ass...	ACCEPT	Summary: CACAO row, and a well-chosen one. Huang et al. showed by transmission electron microscopy that co-expression of NP, VP35 and VP24 in 293T cells is sufficient for spontaneous nucleocapsid assembly, together with a specific biochemical interaction among the three proteins. Later in situ cryo-electron tomography placed VP35 in the nucleocapsid's outer layer. Reason: The CACAO term matches the assay: nucleocapsid-like structures were visualised by TEM and VP35 is one of only three proteins needed to make them. Our cached copy of this 2002 paper is abstract-only and the GONUTS wiki was offline when checked, so the student's figure-level evidence could not be inspected -- but the claim does not depend on it. UniProt curates VP35 as part of the nucleocapsid outer layer from the 2024 cryo-ET structures (PubMed:39293445, PDB 8USN/8UST), so the structural membership, not merely a requirement for assembly, is independently established. Core: VP35 is both a structural nucleocapsid protein and the polymerase cofactor acting on that structure. Supporting Evidence: PMID:12191476 Expression of the nucleoprotein (NP) and virion-associated proteins VP35 and VP24 led to spontaneous assembly of nucleocapsids in transfected 293T cells by transmission electron microscopy. file:EBOZM/VP35/VP35-uniprot.txt Part of the external layer of the nucleocapsid, likely tethering the nucleocapsid to the matrix and membrane
GO:0019079 viral genome replication	IDA PMID:25865894 An Intrinsically Disordered Peptide from Ebola Virus VP35 Co...	ACCEPT	Summary: VP35 is an essential cofactor of the filoviral RNA-dependent RNA polymerase, and the VP35-NP interface characterised here controls the switch between RNA-bound and free NP, i.e. between genome replication and encapsidation. Minigenome assays in this paper read out VP35-dependent RNA synthesis directly. Reason: One of the two core functions. VP35 is one of four proteins required for filoviral genome RNA synthesis, it bridges polymerase L to the NP-encapsidated template, and the NPBP/NP structure shows how it keeps newly made NP competent for the template-loading step. Supporting Evidence: PMID:25865894 Our results also show that the VP35 NPBP binding relieves NP oligomerization and NP-RNA binding by interacting with two distinct regions within NP that are important for viral RNA synthesis. file:EBOZM/VP35/VP35-uniprot.txt VP35-NP interaction controls the switch between RNA-bound NP and free NP and thus the switch between genome replication and genome packaging into the nucleocapsid
GO:0019083 viral transcription	IDA PMID:25865894 An Intrinsically Disordered Peptide from Ebola Virus VP35 Co...	ACCEPT	Summary: The same polymerase cofactor role, on the transcription side. VP35 is one of the four proteins essential for transcription of the EBOV genome, and the NPBP-NP interface is required for the minigenome reporter activity measured in this paper. Reason: Core. Independent of this paper, VP35 is an obligate subunit of the transcribing polymerase complex: it tethers the catalytic L protein to the nucleocapsid and is one of NP, L, VP35, VP30 (PMID:23493393); the cryo-EM L-VP35 structure (PubMed:40164610) shows the bridging arrangement. Supporting Evidence: PMID:23493393 For transcription of the viral genome four viral proteins are essential: the nucleoprotein NP, the polymerase L, the polymerase cofactor VP35, and VP30. PMID:23493393 The enzymatically active part of the viral polymerase L is bound to the nucleocapsid by interaction with the polymerase cofactor VP35
GO:0030430 host cell cytoplasm	EXP PMID:23493393 Phosphorylation of Ebola virus VP30 influences the compositi...	ACCEPT	Summary: Immunofluorescence in this paper shows VP35 diffusely distributed through the cytoplasm of transfected cells. Reason: Correct and functionally meaningful: filoviral transcription and replication occur in the cytoplasm, so this is where VP35's polymerase cofactor activity acts. The observation is incidental in this paper (the diffuse distribution defeated the authors' attempted colocalization analysis) but it is a direct observation, and it agrees with PMID:28679761 and with the curated UniProt subcellular location. Supporting Evidence: PMID:23493393 both VP30 and VP35 are diffusely distributed in the cytoplasm preventing colocalization analyses
GO:0030430 host cell cytoplasm	EXP PMID:28679761 The Host E3-Ubiquitin Ligase TRIM6 Ubiquitinates the Ebola V...	ACCEPT	Summary: Confocal imaging shows VP35 in a diffuse, slightly granular cytoplasmic pattern, with recruitment into TRIM6 cytoplasmic bodies on co-expression. Reason: Direct imaging evidence agreeing with the other localization rows. Two independent papers and the curated UniProt location support it, so this is not a single-assay localization call. Supporting Evidence: PMID:28679761 In contrast, VP35 showed a diffuse, slightly granular cytoplasmic localization, and in some cases it localized in apparent inclusion bodies
GO:0030430 host cell cytoplasm	IEA GO_REF:0000044	ACCEPT	Summary: Keyword/subcellular-location mapping of the curated UniProt location, which itself rests on the two EXP references above. Reason: The electronic mapping reproduces a curated, experimentally grounded location (ECO:0000269 on PubMed:23493393 and PubMed:28679761) and is at the right granularity: there is no evidence placing VP35 in a specific cytoplasmic sub-compartment beyond transient recruitment to inclusion bodies and TRIM6 bodies. Supporting Evidence: file:EBOZM/VP35/VP35-uniprot.txt SUBCELLULAR LOCATION: Virion. Host cytoplasm
GO:0033235 positive regulation of protein sumoylation	IMP PMID:19557165 Ebola Zaire virus blocks type I interferon production by exp...	KEEP AS NON CORE	Summary: CACAO row, and the term matches the assay closely. Chang et al. found VP35 in a yeast two-hybrid screen with Ubc9 and PIAS1, showed VP35 binds PIAS1 and IRF7, and then showed in SUMOylation assays (Fig. 7) that VP35 raises PIAS1-mediated SUMO3 conjugation of IRF7 above PIAS1 alone, and raises it dose-dependently even without PIAS1; wild-type but not conjugation-defective SUMO3 gave the shifted bands. Reason: Well supported and at a useful level of granularity: VP35 is explicitly not itself a SUMO ligase, so a positive-regulation term rather than a ligase activity is the right call, and that distinction is one the annotation gets right. It is kept as non-core because it is one narrower arm of VP35's interferon antagonism, rests on a single paper using overexpression in 293T cells, and is downstream of the dsRNA-sequestration and IRF3-kinase mechanisms that account for most of the IFN-antagonist phenotype. The IRF7-directed consequence is separately annotated as GO:0039557. Supporting Evidence: PMID:19557165 VP35, while not itself a SUMO ligase, increased PIAS1-mediated SUMOylation of IRF7, and repressed Ifn transcription. PMID:19557165 Importantly, in the presence of both PIAS1 and VP35, the levels of SUMO conjugated IRF7 were significantly greater than those expressing PIAS1 alone.
GO:0039502 symbiont-mediated suppression of host type I interferon-mediated signaling pathway	IMP PMID:16698997 Ebola virus VP35 protein binds double-stranded RNA and inhib...	MODIFY	Summary: CACAO row, and the one clear error in the set. Cardenas et al. showed that VP35 binds dsRNA (poly(rI).poly(rC) beads; R312A and K309A mutants impaired) and that VP35 blocks IRF-3 activation induced by RIG-I overexpression, i.e. it suppresses the pathway that induces type I interferon. GO:0039502 is about the type I interferon-mediated signalling pathway itself -- the receptor-proximal JAK/STAT response to secreted IFN -- which is a different arm. Reason: The companion paper from the same laboratory tested the arm this term names and found VP35 inactive on it: neither Zaire nor Reston VP35 could inhibit IFN-beta-induced ISG54 or ISG56 promoter activation (PMID:12829834, Fig. 1C and D). In Ebola virus it is VP24, not VP35, that blocks the cellular response to exogenous IFN, via karyopherin alpha1 and STAT1/STAT2 nuclear accumulation (PMID:19557165). So the annotation is on the wrong side of the interferon circuit. This is a MODIFY, not a REMOVE: the underlying claim -- VP35 suppresses the host type I interferon system -- is right, and the mutant-based experiments the student cited support the induction-side terms instead. GO:0039540 covers the RIG-I step the paper assays directly; GO:0039548 covers the IRF3 endpoint, which is the readout used throughout. Proposed replacements: symbiont-mediated suppression of host cytoplasmic pattern recognition receptor signaling pathway via inhibition of RIG-I activity symbiont-mediated suppression of host cytoplasmic pattern recognition receptor signaling pathway via inhibition of IRF3 activity Supporting Evidence: PMID:16698997 These experiments indicate that VP35 blocks activation of IRF-3 induced by overexpression of RIG-I, a cellular helicase recently implicated in the activation of IRF-3 by either virus or dsRNA. PMID:12829834 Neither the Zaire or Reston VP35 proteins were able to inhibit IFN-β-induced activation of the ISG54 or the ISG56 promoters (Fig. 1C and D). PMID:19557165 VP24 inhibits the cellular response to exogenous IFN by interacting with karyopherin α1, preventing the nuclear accumulation of tyrosine-phosphorylated Stat1 and Stat2
GO:0039505 symbiont-mediated suppression of host antigen processing and presentation of peptide antigen via MHC class II	IMP PMID:19828757 The VP35 protein of Ebola virus impairs dendritic cell matur...	MARK AS OVER ANNOTATED	Summary: CACAO row. Jin et al. expressed VP35 in mouse bone-marrow-derived dendritic cells (HSV vector and retroviral transduction) and found that, unlike the empty vector, VP35 prevented virus- and LPS-induced up-regulation of MHC class II, CD40, CD80 and CD86 by FACS (Figs 2, 4, 6), suppressed IL-6, IL-12, TNF-alpha and IFN-alpha/beta, and reduced the DCs' capacity to activate CD4+ T cells (Fig. 5). Reason: MHC class II here is one of four surface markers read out by flow cytometry as an index of dendritic-cell maturation; nothing in the paper assays antigen processing, peptide loading, invariant-chain handling, MHC-II trafficking or presentation of a defined antigen. The CD4+ T-cell readout uses allogeneic naive T cells, which measures the DCs' overall stimulatory capacity rather than processing and presentation of a peptide antigen. The effect is also partly indirect, since exogenous type I IFN partially reverses it, placing the MHC-II change downstream of the interferon blockade that is VP35's documented activity. The claim is not invented -- surface MHC class II really is reduced -- so this is marked as over-annotated rather than removed, and the demonstrated endpoint, loss of adaptive priming, is captured by the GO:0039504 replacement proposed on the GO:0052562 row from this same paper. A classic phenotype-read-as-process annotation: the term names a mechanism the assay cannot see. Supporting Evidence: PMID:19828757 When expressed in mouse immature DCs, Ebola virus VP35 prevents virus-stimulated expression of CD40, CD80, CD86 and major histocompatibility complex class II. PMID:19828757 Addition of type I IFN to mouse DCs only partially reverses the inhibitory effects of VP35.
GO:0039557 symbiont-mediated suppression of host cytoplasmic pattern recognition receptor signaling pathway via inhibition of IRF7 activity	IEA GO_REF:0000043	KEEP AS NON CORE	Summary: Keyword mapping of a curated, experimentally supported statement: VP35 binds IRF7 and raises its PIAS1-dependent SUMOylation, repressing interferon transcription. Reason: The keyword rests on ECO:0000269\|PubMed:19557165 in the UniProt FUNCTION block, not on an unvetted prediction, and VP35 also impairs IKKepsilon-IRF-7 association (PMID:19153231), so the IRF7 claim is sound. It is non-core because the dominant, mutationally mapped IFN-antagonist mechanisms run through dsRNA sequestration and the IRF3-activating kinases; IRF7 inhibition is the narrower, plasmacytoid-DC-weighted arm, supported by one study. Supporting Evidence: file:EBOZM/VP35/VP35-uniprot.txt Increases PIAS1-mediated SUMOylation of IRF7, thereby repressing interferon transcription (PubMed:19557165) PMID:19557165 VP35, while not itself a SUMO ligase, increased PIAS1-mediated SUMOylation of IRF7, and repressed Ifn transcription.
GO:0039580 symbiont-mediated suppression of host PKR/eIFalpha signaling	EXP PMID:22238300 Characterization of the RNA silencing suppression activity o...	KEEP AS NON CORE	Summary: VP35 antagonises the dsRNA-activated kinase PKR/EIF2AK2. PKR antagonism was assayed for wild-type and mutant VP35 in this paper, and the primary demonstration is in PubMed:17065211, curated by UniProt. Reason: The claim is sound and specific. It is kept as non-core because PKR antagonism is a separable, narrower activity than the IRF3-directed interferon-induction blockade: in this paper PKR antagonism did not track with the RNA-silencing-suppression phenotype, and in Jin et al. the N-terminal region required for PKR inhibition, not the dsRNA-binding motif, was what the DC phenotype needed. Our cached copy of PMID:22238300 is abstract-only, so the figure-level PKR data could not be inspected; the abstract states the assay was done, and the independent UniProt-curated statement carries the claim. Supporting Evidence: PMID:22238300 Analysis of mutant proteins demonstrated that reporter activity in RSS assays did not correlate with their ability to antagonize double-stranded RNA (dsRNA)-activated protein kinase R (PKR) or bind siRNA. file:EBOZM/VP35/VP35-uniprot.txt Also inhibits the antiviral effect mediated by the host interferon-induced, double-stranded RNA-activated protein kinase EIF2AK2/PKR (PubMed:17065211)
GO:0039722 symbiont-mediated suppression of host toll-like receptor signaling pathway	IEA GO_REF:0000043	KEEP AS NON CORE	Summary: Supported experimentally, though by a phenotypic route: VP35 transduced into mouse DCs suppressed LPS-induced (TLR4-dependent) CD80, CD86, IL-6, IL-12 and IFN-beta induction, and the deletion mutant dN190 did not. Reason: The keyword mapping is not merely predictive here: PMID:19828757 Fig. 6 shows suppression of a TLR4 agonist response, with a loss-of-function mutant control. But no step of the TLR signalling cascade was assayed directly, and the authors themselves say the inhibition cannot be explained solely by IRF3 inactivation and may involve an unidentified target, so this is kept as a real but peripheral and mechanistically open activity rather than a core function. Supporting Evidence: PMID:19828757 These results suggested that VP35 is able to suppress DC maturation induced by TLR4 signalling. PMID:19828757 Moreover, VP35 perturbs mouse DC functions induced by lipopolysaccharide, an agonist of Toll-like receptor 4.
GO:0039723 symbiont-mediated suppression of host cytoplasmic pattern recognition receptor signaling pathway via inhibition of TBK1 activity	IEA GO_REF:0000043	ACCEPT	Summary: Keyword mapping of a curated experimental finding: VP35 interacts with TBK1 and blocks IFN-beta promoter activation driven by it. Reason: Core. This is one of the two mutationally and biochemically mapped mechanisms of VP35 interferon antagonism, and the keyword rests on ECO:0000269\|PubMed:19153231 rather than on an unvetted prediction. The term is at the right granularity: the named kinase was the one assayed. Supporting Evidence: PMID:19153231 Coimmunoprecipitation experiments now demonstrate physical interactions of VP35 with IKKepsilon and TBK-1 file:EBOZM/VP35/VP35-uniprot.txt Interacts with host IKBKE and TBK1; the interactions lead to inhibition of cellular antiviral response by blocking necessary interactions of IKBKE and TBK1 with their substrate IRF3
GO:0039724 symbiont-mediated suppression of host cytoplasmic pattern recognition receptor signaling pathway via inhibition of IKBKE activity	IEA GO_REF:0000043	ACCEPT	Summary: The IKKepsilon counterpart, with the most direct evidence of the two: VP35 is itself phosphorylated by IKKepsilon, displaces IRF-3, IRF-7 and IPS-1 from it, and suppresses the IRF-3-directed kinase activity of IKKepsilon-containing lysates. Reason: Core, same mechanism as the TBK1 row and supported by the same ECO:0000269 curated statement. The granularity is right and the interaction is reciprocal enough to be well evidenced (the kinase phosphorylates VP35 in vitro). Supporting Evidence: PMID:19153231 These data suggest that VP35 exerts its IFN-antagonist function, at least in part, by blocking necessary interactions between the kinases IKKepsilon and TBK-1 and their normal interaction partners, including their substrates, IRF-3 and IRF-7. file:EBOZM/VP35/VP35-uniprot.txt PTM: Phosphorylated by host IKBKE (PubMed:19153231)
GO:0052031 symbiont-mediated perturbation of host defense response	IEA GO_REF:0000043	TOO GENERAL	Summary: True of VP35 but at the top of the host-interaction branch: it is an ancestor of every other immune-evasion term in this review. Reason: GO:0052031 is an ancestor of GO:0052170, GO:0039723 and GO:0039724, all accepted here, so it is already entailed and adds no information. The claim is not in doubt -- the two source keywords (viral immunoevasion, interferon antiviral system evasion) are both correct for VP35.
GO:0052170 symbiont-mediated suppression of host innate immune response	IDA PMID:12829834 The Ebola virus VP35 protein inhibits activation of interfer...	ACCEPT	Summary: CACAO row, and a good one. Basler et al. showed directly that VP35 expression blocks virus-induced activation of IRF3-responsive promoters, blocks IRF-3 phosphorylation, dimerization and nuclear translocation, and does not block the constitutively active IRF-3 5D mutant; EBOV infection itself likewise failed to activate ISG54 or drive IRF-3 nuclear accumulation. Reason: The term matches what the paper shows and sits at a useful pathway level rather than being a root term: the innate immune response is the process being suppressed, and the suppression is direct (VP35 expression alone, with NP as a negative control). Core: interferon antagonism is one of VP35's two principal functions. The mechanism-level refinement (GO:0039548, IRF3 inhibition) is introduced through the GO:0010629 row from this same paper, so the pathway-level term is retained alongside it rather than replaced. Supporting Evidence: PMID:12829834 VP35 blocks virus-induced IRF-3 phosphorylation and subsequent IRF-3 dimerization and nuclear translocation. PMID:12829834 That expression of VP35 was unable to inhibit the function of IRF-3 5D, which does not need to be phosphorylated to stimulate gene expression, argues strongly for a model whereby VP35 functions specifically by blocking IRF-3 phosphorylation.
GO:0052170 symbiont-mediated suppression of host innate immune response	IEA GO_REF:0000043	ACCEPT	Summary: Keyword mapping of the same claim as the IDA row above, from KW-1090 (inhibition of host innate immune response by virus). Reason: Reinforces the experimentally grounded row rather than duplicating it wastefully, and the keyword is backed by the curated FUNCTION statements citing PubMed:11027311, PubMed:12829834 and PubMed:23870315. Same claim, same action. Supporting Evidence: file:EBOZM/VP35/VP35-uniprot.txt Plays an essential role in viral RNA synthesis and also a role in suppressing innate immune signaling
GO:0052562 symbiont-mediated suppression of host immune response	IDA PMID:19828757 The VP35 protein of Ebola virus impairs dendritic cell matur...	MODIFY	Summary: CACAO row from the dendritic-cell paper. What that paper adds to the VP35 literature is the adaptive end of the story: VP35-expressing DCs failed to raise CD44 and CD69 or to lower CD62L on allogeneic naive CD4+ T cells, failed to elicit IFN-gamma from them, and instead increased IL-10 (Fig. 5). The term chosen is the generic parent of the whole immune-suppression branch. Reason: Correct but less specific than the evidence supports, which is a MODIFY rather than a KEEP: GO:0039504 symbiont-mediated suppression of host adaptive immune response is an is_a descendant of GO:0052562 and is exactly what the T-cell priming experiments demonstrate, while the innate side of GO:0052562 is already carried by the accepted GO:0052170 rows. The effect is partly IFN-mediated and therefore partly indirect, but the failure of DCs to prime CD4+ T cells is measured directly here with a loss-of-function mutant (dN190) control, so attributing adaptive suppression to VP35 is not a phenotype-at-a-distance inference. Proposed replacements: symbiont-mediated suppression of host adaptive immune response Supporting Evidence: PMID:19828757 We conclude from these experiments that the VP35 protein attenuates the capacity of DCs to stimulate CD4 + T-cell activation. PMID:19828757 Deletion of the amino terminus abolishes its activity, whereas a mutation in the RNA binding motif has no effect.
GO:0060965 negative regulation of miRNA-mediated gene silencing	IDA PMID:22238300 Characterization of the RNA silencing suppression activity o...	KEEP AS NON CORE	Summary: CACAO row, and the abstract states the supporting assay explicitly: a reporter carrying microRNA target sequences showed that prior expression of wild-type VP35 blocked establishment of microRNA silencing in mammalian cells. VP35 CTD fusions also bound siRNA. Reason: The term matches the assay, which is unusual precision for a host-process term applied to a viral protein, and RNA-silencing suppression is independently established for VP35 (PMID:21228243, via TRBP and PACT binding to Dicer partners). It is non-core for two reasons: the authors caution that part of the mammalian reporter signal is non-specific translational enhancement rather than silencing suppression, and the symbiont-branch equivalent GO:0140533 states the same activity in the host-interaction framing better suited to a virus protein. Our cached copy is abstract-only and the GONUTS wiki was offline when checked, so the student's figure-level evidence could not be inspected; the abstract carries the claim on its own. Supporting Evidence: PMID:22238300 A reporter gene containing specific microRNA target sequences was used to demonstrate that prior expression of wild-type VP35 was able to block establishment of microRNA silencing in mammalian cells. PMID:22238300 The results suggest that enhanced reporter activity in the presence of VP35 is a composite of nonspecific translational enhancement and silencing suppression.
GO:0140313 molecular sequestering activity	EXP PMID:25865894 An Intrinsically Disordered Peptide from Ebola Virus VP35 Co...	ACCEPT	Summary: The VP35 NPBP peptide binds NP with high affinity and specificity, prevents NP oligomerization, and releases RNA from pre-formed NP-RNA complexes; size-exclusion chromatography showed NPBP-bound NP behaves as a 1:1 heterodimer instead of eluting at the void volume. Reason: This is the molecular-function description of one of VP35's two core activities. Binding a partner so as to prevent it from oligomerising and from engaging its RNA substrate is precisely molecular sequestering activity, and the 3.7 A NPBP/NP structure (PDB 4YPI) shows the occluded surfaces. It is also the mechanistic basis of the chaperone role UniProt curates for VP35 toward NP monomers. Supporting Evidence: PMID:25865894 We identify an intrinsically disordered peptide derived from EBOV VP35 (NPBP, residues 20-48) that binds NP with high affinity and specificity, inhibits NP oligomerization, and releases RNA from NP-RNA complexes in vitro. PMID:25865894 In contrast to previous results for the peptide-free NP proteins (Figure 1B–C), which eluted at the V0, all NPBP-bound NP proteins eluted at a volume consistent with a well-behaved heterodimer (one molecule of NP and one NPBP molecule) (Figure 6C), indicating that NPBP interaction also prevents oligomerization.
GO:0140313 molecular sequestering activity	IPI PMID:25865894 An Intrinsically Disordered Peptide from Ebola Virus VP35 Co...	ACCEPT	Summary: The same activity with the sequestered partner named: NP (P18272). Reason: Core, and the partner-resolved form of the row above. Naming NP is what makes the annotation useful, since the sequestration is substrate-specific and is the switch controlling whether NP is free or RNA-bound. Supporting Evidence: PMID:25865894 Our results also show that the VP35 NPBP binding relieves NP oligomerization and NP-RNA binding by interacting with two distinct regions within NP that are important for viral RNA synthesis. file:EBOZM/VP35/VP35-uniprot.txt Serves as nucleoprotein/NP monomer chaperone prior to the formation of the large oligomeric RNA-bound complexes
GO:0140533 symbiont-mediated suppression of host RNAi-mediated antiviral immune response	IDA PMID:22238300 Characterization of the RNA silencing suppression activity o...	KEEP AS NON CORE	Summary: VP35 is an RNA silencing suppressor: it blocked establishment of microRNA-directed silencing in mammalian cells, and showed potent suppressor activity in plant silencing assays where mutant activities tracked RNA binding. Reason: Sound and in the right branch for a viral protein. Non-core because most of the specific suppressor activity in mammalian cells was found to be RNA-binding-independent and attributed to protein sequestration within silencing complexes, so the activity is real but mechanistically secondary to the dsRNA-sequestration and kinase-inhibition arms; and because antiviral RNAi is of debated importance in mammalian cells, which is why the authors turned to plants. Supporting Evidence: PMID:22238300 VP35 was shown to possess potent plant RSS activity, and the activities of mutant proteins correlated strongly, but not exclusively, with RNA binding ability. PMID:22238300 Moreover, most of the specific RSS activity in mammalian cells is RNA binding independent, consistent with VP35's proposed role in sequestering one or more silencing complex proteins.
GO:0140533 symbiont-mediated suppression of host RNAi-mediated antiviral immune response	IMP PMID:21228243 Ebolavirus proteins suppress the effects of small interferin...	KEEP AS NON CORE	Summary: Independent support for the same claim with a mechanism: a screen of all EBOV proteins identified VP35 (with VP30 and VP40) as a suppressor of RNA silencing, and VP35 was shown to bind the Dicer partners TRBP and PACT in an siRNA-independent manner and without effects on interferon. Reason: Same claim as the IDA row, so the same action; the two reinforce each other and the TRBP/PACT mechanism is what UniProt curates for this activity. Our cached copy is abstract-only, so the figure-level data could not be inspected, but the abstract states the result for VP35 directly and the interaction partners are corroborated by PMID:23870315 for PACT. Supporting Evidence: PMID:21228243 VP35 directly interacts with Dicer partners TRBP and PACT in an siRNA-independent fashion and in the absence of effects on interferon (IFN). file:EBOZM/VP35/VP35-uniprot.txt Interacts with host TARBP2/TRBP and PRKRA/PACT; these interactions prevent TARBP2 and PRKRA binding to DICER1 and thus allows the virus to counteract host RNA silencing

Gene Description

Existing Annotations Review

Core Functions

Sequesters newly synthesized nucleoprotein NP as an RNA-free monomer through its N-terminal intrinsically disordered NP-binding peptide (residues 20-48), occluding the NP surfaces required for NP-NP and NP-RNA contacts and thereby setting the switch between free NP and template-bound NP.

Acts as the polymerase cofactor of the filoviral RNA-dependent RNA polymerase, oligomerizing through its coiled-coil domain and bridging the catalytic L protein to the NP-encapsidated genome within cytoplasmic nucleocapsids, so that viral transcription and genome replication can proceed.

Binds and sequesters cytoplasmic double-stranded RNA through its C-terminal interferon inhibitory domain, shielding viral replication intermediates from the pattern-recognition receptor RIG-I and additionally displacing the RIG-I activator PRKRA/PACT, so that interferon induction is not triggered.

Binds the IRF3-activating kinases IKBKE/IKKepsilon and TBK1 and blocks their engagement of their substrates IRF3 and IRF7, preventing virus-induced IRF3 phosphorylation, dimerization and nuclear translocation and hence type I interferon gene induction.

References

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Suggested Experiments

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Notes

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