Interactions of Viral protein U (Vpu) with Cellular Factors

ABSTRACTEnterovirus 71 (EV71) recruits various cellular factors to assist in the replication and translation of its genome. Identification of the host factors involved in the EV71 life cycle not only will enable a better understanding of the infection mechanism but also has the potential to be of use in the development of antiviral therapeutics. In this study, we demonstrated that the cellular factor 68-kDa Src-associated protein in mitosis (Sam68) acts as an internal ribosome entry site (IRES)trans-acting factor (ITAF) that binds specifically to the EV71 5′ untranslated region (5′UTR). Interaction sites in both the viral IRES (stem-loops IV and V) and the heterogeneous nuclear ribonucleoprotein K homology (KH) domain of Sam68 protein were further mapped using an electrophoretic mobility shift assay (EMSA) and biotin RNA pulldown assay. More importantly, dual-luciferase (firefly) reporter analysis suggested that overexpression of Sam68 positively regulated IRES-dependent translation of virus proteins. In contrast, both IRES activity and viral protein translation significantly decreased in Sam68 knockdown cells compared with the negative-control cells treated with short hairpin RNA (shRNA). However, downregulation of Sam68 did not have a significant inhibitory effect on the accumulation of the EV71 genome. Moreover, Sam68 was redistributed from the nucleus to the cytoplasm and interacts with cellular factors, such as poly(rC)-binding protein 2 (PCBP2) and poly(A)-binding protein (PABP), during EV71 infection. The cytoplasmic relocalization of Sam68 in EV71-infected cells may be involved in the enhancement of EV71 IRES-mediated translation. Since Sam68 is known to be a RNA-binding protein, these results provide direct evidence that Sam68 is a novel ITAF that interacts with EV71 IRES and positively regulates viral protein translation.IMPORTANCEThe nuclear protein Sam68 is found as an additional new host factor that interacts with the EV71 IRES during infection and could potentially enhance the translation of virus protein. To our knowledge, this is the first report that describes Sam68 actively participating in the life cycle of EV71 at a molecular level. These studies will not only improve our understanding of the replication of EV71 but also have the potential for aiding in developing a therapeutic strategy against EV71 infection.

Download Full-text

Decreased, Deformed, Defective—How HIV-1 Vpu Targets Peroxisomes

mBio ◽

10.1128/mbio.00967-20 ◽

2020 ◽

Vol 11 (3) ◽

Cited By ~ 1

Author(s):

Kristina Hopfensperger ◽

Daniel Sauter

Keyword(s):

Gene Expression ◽

Viral Protein ◽

Eukaryotic Cells ◽

Peroxisome Biogenesis ◽

Cell Organelles ◽

Viral Pathogens ◽

Peroxisomal Biogenesis ◽

Downstream Effects ◽

Viral Protein U ◽

Hiv 1

ABSTRACT Peroxisomes are found in essentially all eukaryotic cells and have been described as important hubs in innate sensing and the induction of type III interferons upon viral infection. Nevertheless, it remains poorly investigated how viral pathogens modulate biogenesis or function of peroxisomes to evade innate sensing and restriction. In a recent study, Hobman and colleagues found that the accessory viral protein u (Vpu) of HIV-1 inhibits peroxisome activity by depleting cellular peroxisome pools. This depletion could be ascribed to a Vpu-dependent induction of four microRNAs (miRNAs) that suppress the expression of peroxisomal biogenesis factors PEX2, PEX7, PEX11B, and PEX13. Although the downstream effects on antiretroviral gene expression and HIV-1 replication remain to be determined, these findings provide important insights into peroxisome biogenesis and the modulation of cell organelles by HIV-1 Vpu.

Download Full-text

Molecular Dynamics Investigation of Membrane-Bound Bundles of the Channel-Forming Transmembrane Domain of Viral Protein U from the Human Immunodeficiency Virus HIV-1

Biophysical Journal ◽

10.1016/s0006-3495(02)73898-8 ◽

2002 ◽

Vol 83 (3) ◽

pp. 1259-1267 ◽

Cited By ~ 38

Author(s):

Carlos F. Lopez ◽

Mauricio Montal ◽

J. Kent Blasie ◽

Michael L. Klein ◽

Preston B. Moore

Keyword(s):

Molecular Dynamics ◽

Human Immunodeficiency Virus ◽

Viral Protein ◽

Transmembrane Domain ◽

Viral Protein U ◽

Immunodeficiency Virus ◽

Membrane Bound ◽

Hiv 1

Download Full-text

Viral Protein U (Vpu)-Mediated Enhancement of Human Immunodeficiency Virus Type 1 Particle Release Depends on the Rate of Cellular Proliferation

Journal of Virology ◽

10.1128/jvi.75.14.6714-6718.2001 ◽

2001 ◽

Vol 75 (14) ◽

pp. 6714-6718 ◽

Cited By ~ 19

Author(s):

Aparna Deora ◽

Lee Ratner

Keyword(s):

Human Immunodeficiency Virus ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Viral Protein ◽

Cellular Proliferation ◽

Expression System ◽

Particle Release ◽

Viral Protein U ◽

Immunodeficiency Virus

ABSTRACT Viral protein U (Vpu) is a 17-kDa phosphoprotein that enhances the release of viral particles from human immunodeficiency virus type 1-infected cells. This study shows that the effect of Vpu on efficient particle release depends on the rate of cell proliferation. Cells arrested by contact inhibition, chemical arresting agents, or terminal differentiation (i.e., macrophages) all exhibited a striking dependence on Vpu for efficient particle release, as shown by examination of particle production from transfections with full-length clones, infections, and the vaccinia virus expression system. In contrast, actively proliferating cells did not exhibit enhanced particle release with Vpu expression. This study demonstrates the necessity of Vpu for efficient viral particle release from quiescent cells.

Download Full-text

Human immunodeficiency virus-1 BF intersubtype recombinant viral protein U second alpha helix plays an important role in viral release and BST-2 degradation

Journal of General Virology ◽

10.1099/vir.0.047746-0 ◽

2013 ◽

Vol 94 (4) ◽

pp. 758-766 ◽

Cited By ~ 1

Author(s):

Cristian De Candia ◽

Constanza Espada ◽

Gabriel Duette ◽

Horacio Salomón ◽

Mauricio Carobene

Keyword(s):

Viral Protein ◽

Transmembrane Domain ◽

Alpha Helix ◽

Protein Variant ◽

Viral Release ◽

Subtype B ◽

Viral Protein U ◽

Intersubtype Recombination ◽

Α Helix ◽

The Impact

We previously reported a naturally occurring BF intersubtype recombinant viral protein U (Vpu) variant with an augmented capacity to enhance viral replication. Structural analysis of this variant revealed that its transmembrane domain and α-helix I in the cytoplasmic domain (CTD) corresponded to subtype B, whereas the α-helix II in the CTD corresponded to subtype F1. In this study, we aimed to evaluate the role of the Vpu cytoplasmic α-helix II domain in viral release enhancement and in the down-modulation of BST-2 and CD4 from the cell surface. In addition, as serine residues in Vpu amino acid positions 61 or 64 have been shown to regulate Vpu intracellular half-life, which in turn could influence the magnitude of viral release, we also studied the impact of these residues on the VpuBF functions, since S61 and S64 are infrequently found among BF recombinant Vpu variants. Our results showed that the exchange of Vpu α-helix II between subtypes (B→F) directly correlated with the enhancement of viral release and, to a lesser extent, with changes in the capacity of the resulting chimera to down-modulate BST-2 and CD4. No differences in viral release and BST-2 down-modulation were observed between VpuBF and VpuBF-E61S. On the other hand, VpuBF-A64S showed a slightly reduced capacity to enhance viral production, but was modestly more efficient than VpuBF in down-modulating BST-2. In summary, our observations clearly indicate that α-helix II is actively involved in Vpu viral-release-promoting activity and that intersubtype recombination between subtypes B and F1 created a protein variant with a higher potential to boost the spread of the recombinant strain that harbours it.

Download Full-text

Various plus unique: Viral protein U as a plurifunctional protein for HIV-1 replication

Experimental Biology and Medicine ◽

10.1177/1535370217697384 ◽

2017 ◽

Vol 242 (8) ◽

pp. 850-858 ◽

Cited By ~ 4

Author(s):

Andrew Soper ◽

Guillermo Juarez-Fernandez ◽

Hirofumi Aso ◽

Miyu Moriwaki ◽

Eri Yamada ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Viral Replication ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Viral Protein ◽

Viral Protein U ◽

Immunodeficiency Virus ◽

Immunodeficiency Syndrome ◽

Hiv 1

Human immunodeficiency virus type 1 (HIV-1), the causative agent of acquired immunodeficiency syndrome, encodes four accessory genes, one of which is viral protein U (Vpu). Recently, the study of Vpu has been of great interest. For instance, various cellular proteins are degraded (e.g. CD4) and down-modulated (e.g. tetherin) by Vpu. Vpu also antagonizes the function of tetherin and inhibits NF-κB. Moreover, Vpu is a viroporin forming ion channels and may represent a promising target for anti-HIV-1 drugs. In this review, we summarize the domains/residues that are responsible for Vpu’s functions, describe the current understanding of the role of Vpu in HIV-1-infected cells, and review the effect of Vpu on HIV-1 in replication and pathogenesis. Future investigations that simultaneously assess a combination of Vpu functions are required to clearly delineate the most important functions for viral replication. Impact statement Viral protein U (Vpu) is a unique protein encoded by human immunodeficiency virus type 1 (HIV-1) and related lentiviruses, playing multiple roles in viral replication and pathogenesis. In this review, we briefly summarize the most up-to-date knowledge of HIV-1 Vpu.

Download Full-text