scholarly journals MxB Is Not Responsible for the Blocking of HIV-1 Infection Observed in Alpha Interferon-Treated Cells

2015 ◽  
Vol 90 (6) ◽  
pp. 3056-3064 ◽  
Author(s):  
Silvana Opp ◽  
Daniel A. S. A. Vieira ◽  
Bianca Schulte ◽  
Sumit K. Chanda ◽  
Felipe Diaz-Griffero
Keyword(s):  
Immune System ◽  
Human Cells ◽  
Alpha Interferon ◽  
Restriction Factor ◽  
Viral Capsid ◽  
Restriction Factors ◽  
Number Of Genes ◽  
Hiv 1 ◽  
In Cells

ABSTRACTMxB restricts HIV-1 infection by directly interacting with the HIV-1 core, which is made of viral capsid; however, the contribution of MxB to the HIV-1 restriction observed in alpha interferon (IFN-α)-treated human cells is unknown. To understand this contribution, we used HIV-1 bearing the G208R capsid mutant (HIV-1-G208R), which overcomes the restriction imposed by cells expressing MxB. Here we showed that the reason why MxB does not block HIV-1-G208R is that MxB does not interact with HIV-1 cores bearing the mutation G208R. To understand whether MxB contributes to the HIV-1 restriction imposed by IFN-α-treated human cells, we challenged IFN-α-treated cells with HIV-G208R and found that MxB does not contribute to the restriction imposed by IFN-α-treated cells. To more directly test the contribution of MxB, we challenged IFN-α-treated human cells that are knocked out for the expression of MxB with HIV-1. These experiments suggested that MxB does not contribute to the HIV-1 restriction observed in IFN-α-treated human cells.IMPORTANCEMxB is a restriction factor that blocks HIV-1 infection in human cells. Although it has been postulated that MxB is the factor that blocks HIV-1 infection in IFN-α-treated cells, this is a hard concept to grasp due to the great number of genes that are induced by IFN-α in cells from the immune system. The work presented here elegantly demonstrates that MxB has minimal or no contribution to the ability of IFN-α-treated human cells to block HIV-1 infection. Furthermore, this work suggests the presence of novel restriction factors in IFN-α-treated human cells that block HIV-1 infection.

scholarly journals HIV envelope tail truncation confers resistance to SERINC5 restriction

2021 ◽  
Vol 118 (21) ◽  
pp. e2101450118
Author(s):  
Tafhima Haider ◽  
Xenia Snetkov ◽  
Clare Jolly
Keyword(s):  
T Cells ◽  
Envelope Glycoprotein ◽  
Cytoplasmic Tail ◽  
Restriction Factor ◽  
Viral Fusion ◽  
Restriction Factors ◽  
Complete Resistance ◽  
Hiv Envelope ◽  
Hiv 1

SERINC5 is a potent lentiviral restriction factor that gets incorporated into nascent virions and inhibits viral fusion and infectivity. The envelope glycoprotein (Env) is a key determinant for SERINC restriction, but many aspects of this relationship remain incompletely understood, and the mechanism of SERINC5 restriction remains unresolved. Here, we have used mutants of HIV-1 and HIV-2 to show that truncation of the Env cytoplasmic tail (ΔCT) confers complete resistance of both viruses to SERINC5 and SERINC3 restriction. Critically, fusion of HIV-1 ΔCT virus was not inhibited by SERINC5 incorporation into virions, providing a mechanism to explain how EnvCT truncation allows escape from restriction. Neutralization and inhibitor assays showed ΔCT viruses have an altered Env conformation and fusion kinetics, suggesting that EnvCT truncation dysregulates the processivity of entry, in turn allowing Env to escape targeting by SERINC5. Furthermore, HIV-1 and HIV-2 ΔCT viruses were also resistant to IFITMs, another entry-targeting family of restriction factors. Notably, while the EnvCT is essential for Env incorporation into HIV-1 virions and spreading infection in T cells, HIV-2 does not require the EnvCT. Here, we reveal a mechanism by which human lentiviruses can evade two potent Env-targeting restriction factors but show key differences in the capacity of HIV-1 and HIV-2 to exploit this. Taken together, this study provides insights into the interplay between HIV and entry-targeting restriction factors, revealing viral plasticity toward mechanisms of escape and a key role for the long lentiviral EnvCT in regulating these processes.

scholarly journals Antiviral Activity and Adaptive Evolution of Avian Tetherins

2020 ◽  
Vol 94 (12) ◽  
Author(s):  
Veronika Krchlíková ◽  
Helena Fábryová ◽  
Tomáš Hron ◽  
Janet M. Young ◽  
Anna Koslová ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Recent Work ◽  
Avian Species ◽  
Domestic Chicken ◽  
Restriction Factor ◽  
Restriction Factors ◽  
Zoonotic Infections ◽  
Avian Viruses ◽  
Avian Sarcoma ◽  
Hiv 1

ABSTRACT Tetherin/BST-2 is an antiviral protein that blocks the release of enveloped viral particles by linking them to the membrane of producing cells. At first, BST-2 genes were described only in humans and other mammals. Recent work identified BST-2 orthologs in nonmammalian vertebrates, including birds. Here, we identify the BST-2 sequence in domestic chicken (Gallus gallus) for the first time and demonstrate its activity against avian sarcoma and leukosis virus (ASLV). We generated a BST-2 knockout in chicken cells and showed that BST-2 is a major determinant of an interferon-induced block of ASLV release. Ectopic expression of chicken BST-2 blocks the release of ASLV in chicken cells and of human immunodeficiency virus type 1 (HIV-1) in human cells. Using metabolic labeling and pulse-chase analysis of HIV-1 Gag proteins, we verified that chicken BST-2 blocks the virus at the release stage. Furthermore, we describe BST-2 orthologs in multiple avian species from 12 avian orders. Previously, some of these species were reported to lack BST-2, highlighting the difficulty of identifying sequences of this extremely variable gene. We analyzed BST-2 genes in the avian orders Galliformes and Passeriformes and showed that they evolve under positive selection. This indicates that avian BST-2 is involved in host-virus evolutionary arms races and suggests that BST-2 antagonists exist in some avian viruses. In summary, we show that chicken BST-2 has the potential to act as a restriction factor against ASLV. Characterizing the interaction of avian BST-2 with avian viruses is important in understanding innate antiviral defenses in birds. IMPORTANCE Birds are important hosts of viruses that have the potential to cause zoonotic infections in humans. However, only a few antiviral genes (called viral restriction factors) have been described in birds, mostly because birds lack counterparts of highly studied mammalian restriction factors. Tetherin/BST-2 is a restriction factor, originally described in humans, that blocks the release of newly formed virus particles from infected cells. Recent work identified BST-2 in nonmammalian vertebrate species, including birds. Here, we report the BST-2 sequence in domestic chicken and describe its antiviral activity against a prototypical avian retrovirus, avian sarcoma and leukosis virus (ASLV). We also identify BST-2 genes in multiple avian species and show that they evolve rapidly in birds, which is an important indication of their relevance for antiviral defense. Analysis of avian BST-2 genes will shed light on defense mechanisms against avian viral pathogens.

scholarly journals The Evolutionary Histories of Antiretroviral Proteins SERINC3 and SERINC5 Do Not Support an Evolutionary Arms Race in Primates

2016 ◽  
Vol 90 (18) ◽  
pp. 8085-8089 ◽  
Author(s):  
Ben Murrell ◽  
Thomas Vollbrecht ◽  
John Guatelli ◽  
Joel O. Wertheim
Keyword(s):  
Viral Infections ◽  
Arms Race ◽  
Restriction Factor ◽  
Restriction Factors ◽  
Arms Races ◽  
Host Restriction ◽  
Host Restriction Factor ◽  
Novel Host ◽  
Evolutionary Arms Race ◽  
Hiv 1

ABSTRACTMolecular evolutionary arms races between viruses and their hosts are important drivers of adaptation. These Red Queen dynamics have been frequently observed in primate retroviruses and their antagonists, host restriction factor genes, such as APOBEC3F/G, TRIM5-α, SAMHD1, and BST-2. Host restriction factors have experienced some of the most intense and pervasive adaptive evolution documented in primates. Recently, two novel host factors, SERINC3 and SERINC5, were identified as the targets of HIV-1 Nef, a protein crucial for the optimal infectivity of virus particles. Here, we compared the evolutionary fingerprints of SERINC3 and SERINC5 to those of other primate restriction factors and to a set of other genes with diverse functions. SERINC genes evolved in a manner distinct from the canonical arms race dynamics seen in the other restriction factors. Despite their antiviral activity against HIV-1 and other retroviruses, SERINC3 and SERINC5 have a relatively uneventful evolutionary history in primates.IMPORTANCERestriction factors are host proteins that block viral infection and replication. Many viruses, like HIV-1 and related retroviruses, evolved accessory proteins to counteract these restriction factors. The importance of these interactions is evidenced by the intense adaptive selection pressures that dominate the evolutionary histories of both the host and viral genes involved in this so-called arms race. The dynamics of these arms races can point to mechanisms by which these viral infections can be prevented. Two human genes, SERINC3 and SERINC5, were recently identified as targets of an HIV-1 accessory protein important for viral infectivity. Unexpectedly, we found that these SERINC genes, unlike other host restriction factor genes, show no evidence of a recent evolutionary arms race with viral pathogens.

scholarly journals TRIM34 acts with TRIM5 to restrict HIV and SIV capsids

2019 ◽  
Author(s):  
Molly Ohainle ◽  
Kyusik Kim ◽  
Sevnur Keceli ◽  
Abby Felton ◽  
Ed Campbell ◽  
...  
Keyword(s):  
Host Cell ◽  
Critical Role ◽  
Restriction Factor ◽  
Target Cells ◽  
Restriction Factors ◽  
Host Proteins ◽  
Hiv Replication ◽  
Cytoplasmic Bodies ◽  
Host Cell Factors ◽  
Hiv 1

AbstractThe HIV-1 capsid protein makes up the core of the virion and plays a critical role in early steps of HIV replication. Due to its exposure in the cytoplasm after entry, HIV capsid is a target for host cell factors that act directly to block infection such as TRIM5 and MxB. Several host proteins also play a role in facilitating infection, including in the protection of HIV-1 capsid from recognition by host cell restriction factors. Through an unbiased screening approach, called HIV-CRISPR, we show that the Cyclophilin A-binding deficient P90A HIV-1 capsid mutant becomes highly-sensitized to TRIM5alpha restriction in IFN-treated cells. Further, the CPSF6-binding deficient, N74D HIV-1 capsid mutant is sensitive to restriction mediated by human TRIM34, a close paralog of the well-characterized HIV restriction factor TRIM5. This restriction occurs at the step of reverse transcription, is independent of interferon stimulation and limits HIV-1 infection in key target cells of HIV infection including CD4+ T cells and monocyte-derived dendritic cells. TRIM34 restriction requires TRIM5alpha as knockout or knockdown of TRIM5alpha results in a loss of antiviral activity. TRIM34 can also restrict some SIV capsids. Through immunofluorescence studies, we show that TRIM34 and TRIM5alpha colocalize to cytoplasmic bodies and are more frequently observed to be associated with infecting N74D capsids than with WT capsids. Our results identify TRIM34 as an HIV-1 CA-targeting restriction factor and highlight the potential role for heteromultimeric TRIM interactions in contributing restriction of HIV-1 infection in human cells.

scholarly journals Editing of the Human TRIM5 Gene to Introduce Mutations with the Potential to Inhibit HIV-1

2017 ◽  
Author(s):  
Caroline Dufour ◽  
Alix Claudel ◽  
Nicolas Joubarne ◽  
Natacha Merindol ◽  
Tara Maisonnet ◽  
...  
Keyword(s):  
Cell Line ◽  
Type I Interferon ◽  
Human Cells ◽  
Restriction Factor ◽  
Type I ◽  
Dna Transfection ◽  
Homology Directed Repair ◽  
Cell Clones ◽  
Overall Efficiency ◽  
Hiv 1

ABSTRACTThe type I interferon (IFN-I)-inducible human restriction factor TRIM5α inhibits the infection of human cells by specific nonhuman retroviruses, such as N-MLV and EIAV, but does not generally target HIV-1. However, the introduction of two aminoacid substitutions, R332G and R355G, in the human TRIM5α (huTRIM5α) domain responsible for retroviral capsid recognition leads to efficient HIV-1 restriction. Using a DNA transfection-based CRISPR-Cas9 genome editing protocol, we successfully mutated TRIM5 to its HIV-1-restrictive version by homology-directed repair (HDR) in HEK293T cells. Nine clones bearing at least one HDR-edited TRIM5 allele containing both mutations were isolated (5.6% overall efficiency), whereas another one contained only the R332G mutation. Of concern, several of these HDR-edited clones contained on-target undesired mutations, and none had all the alleles corrected. We observed a lack of HIV-1 restriction in the cell clones generated, even when cells were stimulated with IFN-I prior to infection. This, however, was partly explained by the unexpectedly low potential for TRIM5α-mediated restriction activity in this cell line. Our study demonstrates the feasibility of editing the TRIM5 gene to in human cells and identifies the main challenges to be addressed in order to use this approach to confer protection from HIV-1.

scholarly journals Contribution of MxB Oligomerization to HIV-1 Capsid Binding and Restriction

2015 ◽  
Vol 89 (6) ◽  
pp. 3285-3294 ◽  
Author(s):  
Cindy Buffone ◽  
Bianca Schulte ◽  
Silvana Opp ◽  
Felipe Diaz-Griffero
Keyword(s):  
T Cells ◽  
Structure Function ◽  
Capsid Protein ◽  
Reverse Transcription ◽  
Tertiary Structure ◽  
Alpha Interferon ◽  
Restriction Factor ◽  
Current Structure ◽  
Modeled Structure ◽  
Hiv 1

ABSTRACTThe alpha interferon (IFN-α)-inducible restriction factor myxovirus B (MxB) blocks HIV-1 infection after reverse transcription but prior to integration. MxB binds to the HIV-1 core, which is composed of capsid protein, and this interaction leads to inhibition of the uncoating process of HIV-1. Previous studies suggested that HIV-1 restriction by MxB requires binding to capsid. This work tests the hypothesis that MxB oligomerization is important for the ability of MxB to bind to the HIV-1 core. For this purpose, we modeled the structure of MxB using the published tertiary structure of MxA. The modeled structure of MxB guided our mutagenic studies and led to the discovery of several MxB variants that lose the capacity to oligomerize. In agreement with our hypothesis, MxB variants that lost the oligomerization capacity also lost the ability to bind to the HIV-1 core. MxB variants deficient for oligomerization were not able to block HIV-1 infection. Overall, our work showed that oligomerization is required for the ability of MxB to bind to the HIV-1 core and block HIV-1 infection.IMPORTANCEMxB is a novel restriction factor that blocks infection of HIV-1. MxB is inducible by IFN-α, particularly in T cells. The current work studies the oligomerization determinants of MxB and carefully explores the contribution of oligomerization to capsid binding and restriction. This work takes advantage of the current structure of MxA and models the structure of MxB, which is used to guide structure-function studies. This work leads to the conclusion that MxB oligomerization is important for HIV-1 capsid binding and restriction.

scholarly journals APOBEC3C Tandem Domain Proteins Create Super Restriction Factors against HIV-1

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Mollie M. McDonnell ◽  
Kate H. D. Crawford ◽  
Adam S. Dingens ◽  
Jesse D. Bloom ◽  
Michael Emerman
Keyword(s):  
Antiviral Activity ◽  
Innate Immune System ◽  
Cytidine Deaminase ◽  
Innate Immune ◽  
Restriction Factor ◽  
Restriction Factors ◽  
Domain Protein ◽  
Antiviral Proteins ◽  
Deaminase Domain ◽  
Hiv 1

ABSTRACT Humans encode proteins, called restriction factors, that inhibit replication of viruses such as HIV-1. The members of one family of antiviral proteins, apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3 (APOBEC3; shortened here to A3), act by deaminating cytidines to uridines during the reverse transcription reaction of HIV-1. The A3 locus encodes seven genes, named A3A to A3H. These genes have either one or two cytidine deaminase domains, and several of these A3s potently restrict HIV-1. A3C, which has only a single cytidine deaminase domain, however, inhibits HIV-1 only very weakly. We tested novel double domain protein combinations by genetically linking two A3C genes to make a synthetic tandem domain protein. This protein created a “super restriction factor” that had more potent antiviral activity than the native A3C protein, which correlated with increased packaging into virions. Furthermore, disabling one of the active sites of the synthetic tandem domain protein resulted in an even greater increase in the antiviral activity—recapitulating a similar evolution seen in A3F and A3G (double domain A3s that use only a single catalytically active deaminase domain). These A3C tandem domain proteins do not have an increase in mutational activity but instead inhibit formation of reverse transcription products, which correlates with their ability to form large higher-order complexes in cells. Finally, the A3C-A3C super restriction factor largely escaped antagonism by the HIV-1 viral protein Vif. IMPORTANCE As a part of the innate immune system, humans encode proteins that inhibit viruses such as HIV-1. These broadly acting antiviral proteins do not protect humans from viral infections because viruses encode proteins that antagonize the host antiviral proteins to evade the innate immune system. One such example of a host antiviral protein is APOBEC3C (A3C), which weakly inhibits HIV-1. Here, we show that we can improve the antiviral activity of A3C by duplicating the DNA sequence to create a synthetic tandem domain and, furthermore, that the proteins thus generated are relatively resistant to the viral antagonist Vif. Together, these data give insights about how nature has evolved a defense against viral pathogens such as HIV.

scholarly journals Gene knockout shows that PML (TRIM19) does not restrict the early stages of HIV-1 infection in human cell lines

2017 ◽  
Author(s):  
Nasser Masroori ◽  
Pearl Cherry ◽  
Natacha Merindol ◽  
Jia-xin Li ◽  
Caroline Dufour ◽  
...  
Keyword(s):  
Cell Lines ◽  
Human Cell ◽  
Gene Knockout ◽  
Human Cells ◽  
Restriction Factor ◽  
Type I ◽  
Human Cell Lines ◽  
Early Stages ◽  
Human T Cell ◽  
Hiv 1

AbstractThe PML (promyelocytic leukemia) protein is a member of the TRIM family, a large group of proteins that show high diversity in functions but possess a common tripartite motif giving the family its name. We and others recently reported that both murine PML (mPML) and human PML (hPML) strongly restrict the early stages of infection by HIV-1 and other lentiviruses when expressed in mouse embryonic fibroblasts (MEFs). This restriction activity was found to contribute to the type I interferon (IFN-I)-mediated inhibition of HIV-1 in MEFs. Additionally, PML caused transcriptional repression of the HIV-1 promoter in MEFs. By contrast, the modulation of the early stages of HIV-1 infection of human cells by PML has been investigated by RNAi with unclear results. In order to conclusively determine whether PML restricts HIV-1 or not in human cells, we used CRISPR-Cas9 to knock out its gene in epithelial, lymphoid and monocytic human cell lines. Infection challenges showed that PML knockout had no effect on the permissiveness of these cells to HIV-1 infection. IFN-I treatments inhibited HIV-1 equally whether PML was expressed or not. Over-expression of individual hPML isoforms, or of mPML, in a human T cell line did not restrict HIV-1. The presence of PML was not required for the restriction of nonhuman retroviruses by TRIM5α was inhibited by arsenic trioxide through a PML-independent mechanism. We conclude that PML is not a restriction factor for HIV-1 in human cell lines representing diverse lineages.ImportancePML is involved in innate immune mechanisms against both DNA and RNA viruses. Although the mechanism by which PML inhibits highly divergent viruses is unclear, it was recently found that it can increase the transcription of interferon-stimulated genes (ISGs). However, whether human PML inhibits HIV-1 has been debated. Here we provide unambiguous, knockout-based evidence that PML does not restrict the early post-entry stages of HIV-1 infection in a variety of human cell types and does not participate in the inhibition of HIV-1 by IFN-I. Although this study does not exclude the possibility of other mechanisms by which PML may interfere with HIV-1, we nonetheless demonstrate that PML does not generally act as an HIV-1 restriction factor in human cells and that its presence is not required for IFN-I to stimulate the expression of anti-HIV-1 genes. These results contribute to uncovering the landscape of HIV-1 inhibition by ISGs in human cells.

scholarly journals Gene Knockout Shows That PML (TRIM19) Does Not Restrict the Early Stages of HIV-1 Infection in Human Cell Lines

mSphere ◽  
2017 ◽  
Vol 2 (3) ◽  
Author(s):  
Nasser Masroori ◽  
Pearl Cherry ◽  
Natacha Merindol ◽  
Jia-xin Li ◽  
Caroline Dufour ◽  
...  
Keyword(s):  
Cell Lines ◽  
Human Cell ◽  
Gene Knockout ◽  
Human Cells ◽  
Restriction Factor ◽  
Type I ◽  
Human Cell Lines ◽  
Early Stages ◽  
Human T Cell ◽  
Hiv 1

ABSTRACTThe PML (promyelocytic leukemia) protein is a member of the TRIM family, a large group of proteins that show high diversity in functions but possess a common tripartite motif giving the family its name. We and others recently reported that both murine PML (mPML) and human PML (hPML) strongly restrict the early stages of infection by HIV-1 and other lentiviruses when expressed in mouse embryonic fibroblasts (MEFs). This restriction activity was found to contribute to the type I interferon (IFN-I)-mediated inhibition of HIV-1 in MEFs. Additionally, PML caused transcriptional repression of the HIV-1 promoter in MEFs. In contrast, the modulation of the early stages of HIV-1 infection of human cells by PML has been investigated by RNA interference, with unclear results. In order to conclusively determine whether PML restricts HIV-1 or not in human cells, we used the clustered regularly interspaced short palindromic repeat with Cas9 (CRISPR-Cas9) system to knock out its gene in epithelial, lymphoid, and monocytic human cell lines. Infection challenges showed that PML knockout had no effect on the permissiveness of these cells to HIV-1 infection. IFN-I treatments inhibited HIV-1 equally whether PML was expressed or not. Overexpression of individual hPML isoforms, or of mPML, in a human T cell line did not restrict HIV-1. The presence of PML was not required for the restriction of nonhuman retroviruses by TRIM5α (another human TRIM protein), and TRIM5α was inhibited by arsenic trioxide through a PML-independent mechanism. We conclude that PML is not a restriction factor for HIV-1 in human cell lines representing diverse lineages.IMPORTANCEPML is involved in innate immune mechanisms against both DNA and RNA viruses. Although the mechanism by which PML inhibits highly divergent viruses is unclear, it was recently found that it can increase the transcription of interferon-stimulated genes (ISGs). However, whether human PML inhibits HIV-1 has been debated. Here we provide unambiguous, knockout-based evidence that PML does not restrict the early postentry stages of HIV-1 infection in a variety of human cell types and does not participate in the inhibition of HIV-1 by IFN-I. Although this study does not exclude the possibility of other mechanisms by which PML may interfere with HIV-1, we nonetheless demonstrate that PML does not generally act as an HIV-1 restriction factor in human cells and that its presence is not required for IFN-I to stimulate the expression of anti-HIV-1 genes. These results contribute to uncovering the landscape of HIV-1 inhibition by ISGs in human cells.

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