scholarly journals The Influence of Envelope C-Terminus Amino Acid Composition on the Ratio of Cell-Free to Cell-Cell Transmission for Bovine Foamy Virus

Viruses ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 130 ◽  
Author(s):  
Suzhen Zhang ◽  
Xiaojuan Liu ◽  
Zhibin Liang ◽  
Tiejun Bing ◽  
Wentao Qiao ◽  
...  
Keyword(s):  
High Titer ◽  
Foamy Virus ◽  
Evolution System ◽  
Bovine Foamy Virus ◽  
C Terminus ◽  
Release Capacity ◽  
Cell Transmission ◽  
Extensive Cell ◽  
Original Cell

Foamy viruses (FVs) have extensive cell tropism in vitro, special replication features, and no clinical pathogenicity in naturally or experimentally infected animals, which distinguish them from orthoretroviruses. Among FVs, bovine foamy virus (BFV) has undetectable or extremely low levels of cell-free transmission in the supernatants of infected cells and mainly spreads by cell-to-cell transmission, which deters its use as a gene transfer vector. Here, using an in vitro virus evolution system, we successfully isolated high-titer cell-free BFV strains from the original cell-to-cell transmissible BFV3026 strain and further constructed an infectious cell-free BFV clone called pBS-BFV-Z1. Following sequence alignment with a cell-associated clone pBS-BFV-B, we identified a number of changes in the genome of pBS-BFV-Z1. Extensive mutagenesis analysis revealed that the C-terminus of envelope protein, especially the K898 residue, controls BFV cell-free transmission by enhancing cell-free virus entry but not the virus release capacity. Taken together, our data show the genetic determinants that regulate cell-to-cell and cell-free transmission of BFV.

scholarly journals Bovine Foamy Virus Transactivator BTas Interacts with Cellular RelB To Enhance Viral Transcription

2010 ◽  
Vol 84 (22) ◽  
pp. 11888-11897 ◽  
Author(s):  
Jian Wang ◽  
Juan Tan ◽  
Hongyan Guo ◽  
Qicheng Zhang ◽  
Rui Jia ◽  
...  
Keyword(s):  
Foamy Virus ◽  
Nuclear Factor Κb ◽  
Luciferase Reporter ◽  
Viral Transcription ◽  
Bovine Foamy Virus ◽  
Intracellular Parasites ◽  
Positive Feedback Circuit ◽  
Cellular Machinery

ABSTRACT Viruses are obligate intracellular parasites that depend on cellular machinery for their efficient transcription and replication. In a previous study we reported that bovine foamy virus (BFV) is able to activate the nuclear factor κB (NF-κB) pathway through the action of its transactivator BTas to enhance viral transcription. However, the mechanism used by NF-κB to enhance BFV transcription remains elusive. To address this question, we employed a yeast two-hybrid assay to screen for BTas-interacting proteins. We found that RelB, a member of NF-κB protein family, interacts with BTas. We confirmed the putative RelB-BTas interaction in vitro and in vivo and identified the protein regions responsible for the RelB-BTas interaction. Using a luciferase reporter assay, we next showed that RelB enhances BFV transcription (BTas-induced long terminal repeat [LTR] transactivation) and that this process requires both the localization of the RelB-BTas interaction in the nucleus and the Rel homology domain of RelB. The knockdown of the cellular endogenous RelB protein using small interfering RNA (siRNA) significantly attenuated BTas-induced LTR transcription. The results of chromatin immunoprecipitation (ChIP) analysis showed that endogenous RelB binds to the viral LTR in BFV-infected cells. Together, these results suggest that BFV engages the RelB protein as a cotransactivator of BTas to enhance viral transcription. In addition, our findings indicate that BFV infection upregulates cellular RelB expression through BTas-induced NF-κB activation. Thus, this study demonstrates the existence of a positive-feedback circuit in which BFV utilizes the host's NF-κB pathway through the RelB protein for efficient viral transcription.

scholarly journals Functional Analyses of Bovine Foamy Virus-Encoded miRNAs Reveal the Importance of a Defined miRNA for Virus Replication and Host–Virus Interaction

Viruses ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1250
Author(s):  
Wenhu Cao ◽  
Erik Stricker ◽  
Agnes Hotz-Wagenblatt ◽  
Anke Heit-Mondrzyk ◽  
Georgios Pougialis ◽  
...  
Keyword(s):  
Target Genes ◽  
Foamy Virus ◽  
Rna Polymerase Iii ◽  
Long Terminal Repeats ◽  
Bovine Foamy Virus ◽  
Host Interactions ◽  
Micro Rnas ◽  
Efficient Replication ◽  
Control Virus

In addition to regulatory or accessory proteins, some complex retroviruses gain a repertoire of micro-RNAs (miRNAs) to regulate and control virus–host interactions for efficient replication and spread. In particular, bovine and simian foamy viruses (BFV and SFV) have recently been shown to express a diverse set of RNA polymerase III-directed miRNAs, some with a unique primary miRNA double-hairpin, dumbbell-shaped structure not known in other viruses or organisms. While the mechanisms of expression and structural requirements have been studied, the functional importance of these miRNAs is still far from understood. Here, we describe the in silico identification of BFV miRNA targets and the subsequent experimental validation of bovine Ankyrin Repeat Domain 17 (ANKRD17) and Bax-interacting factor 1 (Bif1) target genes in vitro and, finally, the suppression of ANKRD17 downstream genes in the affected pathway. Deletion of the entire miRNA cassette in the non-coding part of the U3 region of the long terminal repeats attenuated replication of corresponding BFV mutants in bovine cells. This repression can be almost completely trans-complemented by the most abundant miRNA BF2-5p having the best scores for predicted and validated BFV miRNA target genes. Deletion of the miRNA cassette does not grossly affect particle release and overall particle composition.

scholarly journals Shared and cell type-specific adaptation strategies of Gag and Env yield high titer bovine foamy virus variants

2020 ◽  
Vol 82 ◽  
pp. 104287
Author(s):  
Qiuying Bao ◽  
Agnes Hotz-Wagenblatt ◽  
Matthew J. Betts ◽  
Michaela Hipp ◽  
Annette Hugo ◽  
...  
Keyword(s):  
High Titer ◽  
Foamy Virus ◽  
Adaptation Strategies ◽  
Cell Type ◽  
Bovine Foamy Virus ◽  
Specific Adaptation ◽  
Cell Type Specific

scholarly journals Application of Chimeric Feline Foamy Virus-Based Retroviral Vectors for the Induction of Antiviral Immunity in Cats

2003 ◽  
Vol 77 (14) ◽  
pp. 7830-7842 ◽  
Author(s):  
Astrid Schwantes ◽  
Uwe Truyen ◽  
Joachim Weikel ◽  
Christian Weiss ◽  
Martin Löchelt
Keyword(s):  
Cell Cultures ◽  
High Titer ◽  
Foamy Virus ◽  
Retroviral Vectors ◽  
Partial Protection ◽  
Humoral Immune ◽  
The Stability ◽  
Bet Protein ◽  
Hybrid Fusion

ABSTRACT In order to define the potential and applicability of replication-competent foamy virus-based vaccine vectors, recombinant feline foamy virus (FFV) vectors encoding defined segments of the feline calicivirus (FCV) capsid protein E domain were constructed. In cell cultures, these FFV-FCV vectors efficiently transduced and expressed a hybrid fusion protein consisting of the essential FFV Bet protein and the attached FCV E domains. The stability of the vectors in vitro was inversely correlated to the size of the heterologous insert. The deletion of a part of the FFV U3 sequence in these FFV-FCV vectors did not interfere with replication and titer in cell cultures but increased the genetic stability of the hybrid vectors. Selected chimeric vectors were injected into immunocompetent cats and persisted in the transduced host concomitant with a strong and specific humoral immune response against vector components. In a substantial number of cats, antibodies directed against the FCV E domain were induced by the FFV-FCV vectors, but no FCV-neutralizing activities were detectable in vitro. When the vaccinated cats were challenged with a high-titer FCV dose, sterile immunity was not induced by any of the hybrid FFV-FCV vectors. However, the FFV-FCV vector with a truncated U3 region of the long terminal repeat promoter significantly reduced the duration of FCV shedding after challenge and suppressed the appearance of FCV-specific ulcers. Possible mechanisms contributing to the partial protection will be discussed.

scholarly journals Role of the C Terminus of Foamy Virus Gag in RNA Packaging and Pol Expression

2004 ◽  
Vol 78 (17) ◽  
pp. 9423-9430 ◽  
Author(s):  
Carolyn R. Stenbak ◽  
Maxine L. Linial
Keyword(s):  
Foamy Virus ◽  
Nucleic Acid Binding ◽  
Rna Packaging ◽  
Binding Properties ◽  
Gag Protein ◽  
C Terminus ◽  
Foamy Viruses ◽  
The Matrix

ABSTRACT Foamy viruses (FV) are complex retroviruses that possess several unique features that distinguish them from all other retroviruses. FV Gag and Pol proteins are expressed independently of one another, and both proteins undergo single cleavage events. Thus, the mature FV Gag protein does not consist of the matrix, capsid, and nucleocapsid (NC) proteins found in orthoretroviruses, and the putative NC domain of FV Gag lacks the hallmark Cys-His motifs or I domains. As there is no Gag-Pol fusion protein, the mechanism of Pol packaging is different but unknown. FV RNA packaging is not well understood either. The C terminus of FV Gag has three glycine-arginine motifs (GR boxes), the first of which has been shown to have nucleic acid binding properties in vitro. The role of these GR boxes in RNA packaging and Pol packaging was investigated with a series of Gag C-terminal truncation mutants. GR box 1 was found to be the major determinant of RNA packaging, but all three GR boxes were required to achieve wild-type levels of RNA packaging. In addition, Pol was packaged in the absence of GR box 3, but GR boxes 1 and 2 were required for efficient Pol packaging. Interestingly, the Gag truncation mutants demonstrated decreased Pol expression levels as well as defects in Pol cleavage. Thus, the C terminus of FV Gag was found to be responsible for RNA packaging, as well as being involved in the expression, cleavage, and incorporation of the Pol protein.

scholarly journals Bovine Foamy Virus: Shared and Unique Molecular Features In Vitro and In Vivo

Viruses ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1084 ◽  
Author(s):  
Magdalena Materniak-Kornas ◽  
Juan Tan ◽  
Anke Heit-Mondrzyk ◽  
Agnes Hotz-Wagenblatt ◽  
Martin Löchelt
Keyword(s):  
Animal Studies ◽  
Foamy Virus ◽  
Companion Animals ◽  
Population Level ◽  
Medical Problems ◽  
Bovine Foamy Virus ◽  
Molecular Features ◽  
Unclear Etiology

The retroviral subfamily of Spumaretrovirinae consists of five genera of foamy (spuma) viruses (FVs) that are endemic in some mammalian hosts. Closely related species may be susceptible to the same or highly related FVs. FVs are not known to induce overt disease and thus do not pose medical problems to humans and livestock or companion animals. A robust lab animal model is not available or is a lab animal a natural host of a FV. Due to this, research is limited and often focused on the simian FVs with their well-established zoonotic potential. The authors of this review and their groups have conducted several studies on bovine FV (BFV) in the past with the intention of (i) exploring the risk of zoonotic infection via beef and raw cattle products, (ii) studying a co-factorial role of BFV in different cattle diseases with unclear etiology, (iii) exploring unique features of FV molecular biology and replication strategies in non-simian FVs, and (iv) conducting animal studies and functional virology in BFV-infected calves as a model for corresponding studies in primates or small lab animals. These studies gained new insights into FV-host interactions, mechanisms of gene expression, and transcriptional regulation, including miRNA biology, host-directed restriction of FV replication, spread and distribution in the infected animal, and at the population level. The current review attempts to summarize these findings in BFV and tries to connect them to findings from other FVs.

scholarly journals In Vitro Evolution of Bovine Foamy Virus Variants with Enhanced Cell-Free Virus Titers and Transmission

Viruses ◽  
2015 ◽  
Vol 7 (11) ◽  
pp. 5855-5874 ◽  
Author(s):  
Qiuying Bao ◽  
Michaela Hipp ◽  
Annette Hugo ◽  
Janet Lei ◽  
Yang Liu ◽  
...  
Keyword(s):  
Foamy Virus ◽  
Free Virus ◽  
In Vitro Evolution ◽  
Bovine Foamy Virus

Spastin Interacts with CRMP2 to Regulate Neurite Outgrowth by Controlling Microtubule Dynamics through Phosphorylation Modifications

2020 ◽  
Vol 19 ◽  
Author(s):  
Sumei Li ◽  
Jifeng Zhang ◽  
Jiaqi Zhang ◽  
Jiong Li ◽  
Longfei Cheng ◽  
...  
Keyword(s):  
Neurite Outgrowth ◽  
Hippocampal Neurons ◽  
Neuronal Development ◽  
Phosphorylation Site ◽  
Microtubule Dynamics ◽  
Microtubule Assembly ◽  
C Terminus ◽  
Mediator Protein ◽  
Branch Formation

Aims: Our work aims to revealing the underlying microtubule mechanism of neurites outgrowth during neuronal development, and also proposes a feasible intervention pathway for reconstructing neural network connections after nerve injury. Background: Microtubule polymerization and severing are the basis for the neurite outgrowth and branch formation. Collapsin response mediator protein 2 (CRMP2) regulates axonal growth and branching as a binding partner of the tubulin heterodimer to promote microtubule assembly. And spastin participates in the growth and regeneration of neurites by severing microtubules into small segments. However, how CRMP2 and spastin cooperate to regulate neurite outgrowth by controlling the microtubule dynamics needs to be elucidated. Objective: To explore whether neurite outgrowth was mediated by coordination of CRMP2 and spastin. Method: Hippocampal neurons were cultured in vitro in 24-well culture plates for 4 days before being used to perform the transfection. Calcium phosphate was used to transfect the CRMP2 and spastin constructs and their control into the neurons. An interaction between CRMP2 and spastin was examined by using pull down, CoIP and immunofluorescence colocalization assays. And immunostaining was also performed to determine the morphology of neurites. Result: We first demonstrated that CRMP2 interacted with spastin to promote the neurite outgrowth and branch formation. Furthermore, our results identified that phosphorylation modification failed to alter the binding affinities of CRMP2 for spastin, but inhibited their binding to microtubules. CRMP2 interacted with the MTBD domain of spastin via its C-terminus, and blocking the binding sites of them inhibited the outgrowth and branch formation of neurites. In addition, we confirmed one phosphorylation site S210 at spastin in hippocampal neurons and phosphorylation spastin at site S210 promoted the neurite outgrowth but not branch formation by remodeling microtubules. Conclusion: Taken together, our data demonstrated that the interaction of CRMP2 and spastin is required for neurite outgrowth and branch formation and their interaction is not regulated by their phosphorylation.

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