scholarly journals Opposing Effects of a Tyrosine-Based Sorting Motif and a PDZ-Binding Motif Regulate Human T-Lymphotropic Virus Type 1 Envelope Trafficking

2010 ◽  
Vol 84 (14) ◽  
pp. 6995-7004 ◽  
Author(s):  
Anna Ilinskaya ◽  
Gisela Heidecker ◽  
David Derse
Keyword(s):  
Virus Type ◽  
Protein Complexes ◽  
Adaptor Protein ◽  
Degradation Pathway ◽  
Target Cells ◽  
Binding Motif ◽  
Wild Type ◽  
T Lymphotropic Virus ◽  
In Cells

ABSTRACT Human T-lymphotropic virus type 1 (HTLV-1) envelope (Env) glycoprotein mediates binding of the virus to its receptor on the surface of target cells and subsequent fusion of virus and cell membranes. To better understand the mechanisms that control HTLV-1 Env trafficking and activity, we have examined two protein-protein interaction motifs in the cytoplasmic domain of Env. One is the sequence YSLI, which matches the consensus YXXΦ motifs that are known to interact with various adaptor protein complexes; the other is the sequence ESSL at the C terminus of Env, which matches the consensus PDZ-binding motif. We show here that mutations that destroy the YXXΦ motif increased Env expression on the cell surface and increased cell-cell fusion activity. In contrast, mutation of the PDZ-binding motif greatly diminished Env expression in cells, which could be restored to wild-type levels either by mutating the YXXΦ motif or by silencing AP2 and AP3, suggesting that interactions with PDZ proteins oppose an Env degradation pathway mediated by AP2 and AP3. Silencing of the PDZ protein hDlg1 did not affect Env expression, suggesting that hDlg1 is not a binding partner for Env. Substitution of the YSLI sequence in HTLV-1 Env with YXXΦ elements from other cell or virus membrane-spanning proteins resulted in alterations in Env accumulation in cells, incorporation into virions, and virion infectivity. Env variants containing YXXΦ motifs that are predicted to have high-affinity interaction with AP2 accumulated to lower steady-state levels. Interestingly, mutations that destroy the YXXΦ motif resulted in viruses that were not infectious by cell-free or cell-associated routes of infection. Unlike YXXΦ, the function of the PDZ-binding motif manifests itself only in the producer cells; AP2 silencing restored the incorporation of PDZ-deficient Env into virus-like particles (VLPs) and the infectivity of these VLPs to wild-type levels.

scholarly journals A Conserved Calcineurin-binding Motif in Human T Lymphotropic Virus Type 1 p12IFunctions to Modulate Nuclear Factor of Activated T Cell Activation

2003 ◽  
Vol 278 (18) ◽  
pp. 15550-15557 ◽  
Author(s):  
Seung-jae Kim ◽  
Wei Ding ◽  
Björn Albrecht ◽  
Patrick L. Green ◽  
Michael D. Lairmore
Keyword(s):  
T Cell ◽  
Virus Type ◽  
T Cell Activation ◽  
Cell Activation ◽  
Binding Motif ◽  
Nuclear Factor ◽  
T Lymphotropic Virus ◽  
Activated T Cell

scholarly journals Human T-Lymphotropic Virus Type 1 Tax Protein Complexes with P-TEFb and Competes for Brd4 and 7SK snRNP/HEXIM1 Binding

2010 ◽  
Vol 84 (24) ◽  
pp. 12801-12809 ◽  
Author(s):  
Won-Kyung Cho ◽  
Moon Kyoo Jang ◽  
Keven Huang ◽  
Cynthia A. Pise-Masison ◽  
John N. Brady
Keyword(s):  
Molecular Weight ◽  
Rna Polymerase Ii ◽  
Virus Type ◽  
T Lymphotropic Virus ◽  
Cyclin T1 ◽  
Tax Protein ◽  
In Cells

ABSTRACT Positive transcription elongation factor b (P-TEFb) plays an important role in stimulating RNA polymerase II elongation for viral and cellular gene expression. P-TEFb is found in cells in either an active, low-molecular-weight (LMW) form or an inactive, high-molecular-weight (HMW) form. We report here that human T-lymphotropic virus type 1 (HTLV-1) Tax interacts with the cyclin T1 subunit of P-TEFb, forming a distinct Tax/P-TEFb LMW complex. We demonstrate that Tax can play a role in regulating the amount of HMW complex present in the cell by decreasing the binding of 7SK snRNP/HEXIM1 to P-TEFb. This is seen both in vitro using purified Tax protein and in vivo in cells transduced with Tax expression constructs. Further, we find that a peptide of cyclin T1 spanning the Tax binding domain inhibits the ability of Tax to disrupt HMW P-TEFb complexes. These results suggest that the direct interaction of Tax with cyclin T1 can dissociate P-TEFb from the P-TEFb/7SK snRNP/HEXIM1 complex for activation of the viral long terminal repeat (LTR). We also show that Tax competes with Brd4 for P-TEFb binding. Chromatin immunoprecipitation (ChIP) assays demonstrated that Brd4 and P-TEFb are associated with the basal HTLV-1 LTR, while Tax and P-TEFb are associated with the activated template. Furthermore, the knockdown of Brd4 by small interfering RNA (siRNA) activates the HTLV-1 LTR promoter, which results in an increase in viral expression and production. Our studies have identified Tax as a regulator of P-TEFb that is capable of affecting the balance between its association with the large inactive complex and the small active complex.

scholarly journals XBP-1, a Novel Human T-Lymphotropic Virus Type 1 (HTLV-1) Tax Binding Protein, Activates HTLV-1 Basal and Tax-Activated Transcription

2008 ◽  
Vol 82 (9) ◽  
pp. 4343-4353 ◽  
Author(s):  
Sebastian C. Y. Ku ◽  
Jialing Lee ◽  
Joanne Lau ◽  
Meera Gurumurthy ◽  
Raymond Ng ◽  
...  
Keyword(s):  
Virus Type ◽  
Binding Protein ◽  
Host Cells ◽  
Mrna Levels ◽  
Transcription Activator ◽  
Basic Leucine Zipper ◽  
T Lymphotropic Virus ◽  
In Cells

ABSTRACT X-box binding protein 1 (XBP-1), a basic leucine zipper transcription factor, plays a key role in the cellular unfolded protein response (UPR). There are two XBP-1 isoforms in cells, spliced XBP-1S and unspliced XBP-1U. XBP-1U has been shown to bind to the 21-bp Tax-responsive element of the human T-lymphotropic virus type 1 (HTLV-1) long terminal repeat (LTR) in vitro and transactivate HTLV-1 transcription. Here we identify XBP-1S as a transcription activator of HTLV-1. Compared to XBP-1U, XBP-1S demonstrates stronger activating effects on both basal and Tax-activated HTLV-1 transcription in cells. Our results show that both XBP-1S and XBP-1U interact with Tax and bind to the HTLV-1 LTR in vivo. In addition, elevated mRNA levels of the gene for XBP-1 and several UPR genes were detected in the HTLV-1-infected C10/MJ and MT2 T-cell lines, suggesting that HTLV-1 infection may trigger the UPR in host cells. We also identify Tax as a positive regulator of the expression of the gene for XBP-1. Activation of the UPR by tunicamycin showed no effect on the HTLV-1 LTR, suggesting that HTLV-1 transcription is specifically regulated by XBP-1. Collectively, our study demonstrates a novel host-virus interaction between a cellular factor XBP-1 and transcriptional regulation of HTLV-1.

scholarly journals Nef Does Not Affect the Efficiency of Human Immunodeficiency Virus Type 1 Fusion with Target Cells

2003 ◽  
Vol 77 (19) ◽  
pp. 10645-10650 ◽  
Author(s):  
Minoru Tobiume ◽  
Janet E. Lineberger ◽  
Christopher A. Lundquist ◽  
Michael D. Miller ◽  
Christopher Aiken
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Intracellular Transport ◽  
Target Cells ◽  
Wild Type ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Soluble Cd4

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) accessory protein Nef stimulates viral infectivity by an unknown mechanism. Recent studies have suggested that Nef may act by regulating the efficiency of virus entry into cells. Here we provide evidence to the contrary. Using a quantitative assay of HIV-1 virus-cell fusion, we observed equivalent rates and extents of fusion of wild-type and Nef-defective HIV-1 particles with MT-4 cells and CD4-expressing HeLa cells. In studies using soluble CD4 (sCD4) to inhibit infection, wild-type and Nef-defective HIV-1 escaped the sCD4 block with similar kinetics. We conclude that Nef acts at a postentry step in infection, probably by facilitating intracellular transport of the HIV-1 ribonucleoprotein complex.

scholarly journals The Protein Tyrosine Kinase p56lck Is Required for Triggering NF-κB Activation upon Interaction of Human Immunodeficiency Virus Type 1 Envelope Glycoprotein gp120 with Cell Surface CD4

1998 ◽  
Vol 72 (7) ◽  
pp. 6207-6214 ◽  
Author(s):  
Laurence Briant ◽  
Véronique Robert-Hebmann ◽  
Claire Acquaviva ◽  
Annegret Pelchen-Matthews ◽  
Mark Marsh ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Nuclear Translocation ◽  
Mutant Form ◽  
Wild Type ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
In Cells

ABSTRACT We have previously shown that NF-κB nuclear translocation can be observed upon human immunodeficiency virus type 1 (HIV-1) binding to cells expressing the wild-type CD4 molecule, but not in cells expressing a truncated form of CD4 that lacks the cytoplasmic domain (M. Benkirane, K.-T. Jeang, and C. Devaux, EMBO J. 13:5559–5569, 1994). This result indicated that the signaling cascade which controls HIV-1-induced NF-κB activation requires the integrity of the CD4 cytoplasmic tail and suggested the involvement of a second protein that binds to this portion of the molecule. Here we investigate the putative role of p56 lck as a possible cellular intermediate in this signal transduction pathway. Using human cervical carcinoma HeLa cells stably expressing CD4, p56 lck , or both molecules, we provide direct evidence that expression of CD4 and p56 lck is required for HIV-1-induced NF-κB translocation. Moreover, the fact that HIV-1 stimulation did not induce nuclear translocation of NF-κB in cells expressing a mutant form of CD4 at position 420 (C420A) and the wild-type p56 lck indicates the requirement for a functional CD4-p56 lck complex.

scholarly journals Human T-Lymphotropic Virus Type 1 Mitochondrion-Localizing Protein p13II Is Required for Viral Infectivity In Vivo

2006 ◽  
Vol 80 (7) ◽  
pp. 3469-3476 ◽  
Author(s):  
Hajime Hiraragi ◽  
Seung-Jae Kim ◽  
Andrew J. Phipps ◽  
Micol Silic-Benussi ◽  
Vincenzo Ciminale ◽  
...  
Keyword(s):  
Virus Infection ◽  
Cell Line ◽  
Virus Type ◽  
Mononuclear Cells ◽  
Ex Vivo ◽  
Start Codon ◽  
Wild Type ◽  
T Lymphotropic Virus

ABSTRACT Human T-lymphotropic virus type 1 (HTLV-1), the etiological agent of adult T-cell leukemia, encodes unique regulatory and accessory proteins in the pX region of the provirus, including the open reading frame II product p13II. p13II localizes to mitochondria, binds farnesyl pyrophosphate synthetase, an enzyme involved in posttranslational farnesylation of Ras, and alters Ras-dependent cell signaling and control of apoptosis. The role of p13II in virus infection in vivo remains undetermined. Herein, we analyzed the functional significance of p13II in HTLV-1 infection. We compared the infectivity of a human B-cell line that harbors an infectious molecular clone of HTLV-1 with a selective mutation that prevents the translation of p13II (729.ACH.p13) to the infectivity of a wild-type HTLV-1-expressing cell line (729.ACH). 729.ACH and 729.ACH.p13 producer lines had comparable infectivities for cultured rabbit peripheral blood mononuclear cells (PBMC), and the fidelity of the start codon mutation in ACH.p13 was maintained after PBMC passage. In contrast, zero of six rabbits inoculated with 729.ACH.p13 cells failed to establish viral infection, whereas six of six rabbits inoculated with wild-type HTLV-1-expressing cells (729.ACH) were infected as measured by antibody responses, proviral load, and HTLV-1 p19 matrix antigen production from ex vivo-cultured PBMC. Our data are the first to indicate that the HTLV-1 mitochondrion-localizing protein p13II has an essential biological role during the early phase of virus infection in vivo.

scholarly journals Differential Expression of Nur77 Family Members in Human T-Lymphotropic Virus Type 1-Infected Cells: Transactivation of theTR3/nur77 Gene by Tax Protein

1998 ◽  
Vol 72 (8) ◽  
pp. 6902-6906 ◽  
Author(s):  
Xiaolin Chen ◽  
Vladimir Zachar ◽  
Chawnshang Chang ◽  
Peter Ebbesen ◽  
Xiangdong Liu
Keyword(s):  
Differential Expression ◽  
Virus Type ◽  
Luciferase Reporter ◽  
Binding Motif ◽  
Luciferase Reporter Gene ◽  
Functional Protein ◽  
T Lymphotropic Virus ◽  
Tax Protein ◽  
Infected Cells

ABSTRACT We analyzed the differential expression and regulation of three members of the Nur77 transcription factor family by the human T-lymphotropic virus type 1 (HTLV-1) Tax protein. We have demonstrated that in both HTLV-1-infected cells and Tax-expressing JPX-9 cells,TR3/nur77 is highly expressed, whereas neitherNOR-1 nor NOT expression is detectable. Transient transfection analysis further confirmed the Tax transactivation of the TR3/nur77 promoter but not theNOR-1 promoter in different cell types. Furthermore, expression of a luciferase reporter gene driven by the NGFI-B (rat homolog of TR3/Nur77) response element (NBRE) provided evidence that Tax-mediated transactivation resulted in the induction of a functional protein. Cotransfection assays with the TR3/nur77 promoter sequence or the NBRE binding motif together with a series of Tax mutants have shown that Tax-induced TR3/nur77 expression is mediated by CREB/ATF-related transcription factors.

scholarly journals Mutations in the env gene of human immunodeficiency virus type 1 NDK isolates and the use of African green monkey CXCR4 as a co-receptor in COS-7 cells

1999 ◽  
Vol 80 (8) ◽  
pp. 1975-1982 ◽  
Author(s):  
Julie Dumonceaux ◽  
Chantal Chanel ◽  
Susana Valente ◽  
Laurence Quivet ◽  
Pascale Briand ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
African Green Monkey ◽  
Target Cells ◽  
Wild Type ◽  
First Case ◽  
Immunodeficiency Virus ◽  
Green Monkey

A previous report from this laboratory described the isolation of the first CD4-independent human immunodeficiency virus type 1 isolate, m7NDK. This independence of CD4 is due to seven mutations located in the C2, V3 and C3 regions of the gp120 protein. The present report describes the entry features of the m5NDK virus, which contains five of the seven m7NDK mutations, located in the V3 loop and C3 region. The entry of this virus is strictly CD4-dependent but it can fuse with African green monkey (agm) COS-7 cells bearing human CD4 (h-CD4). This fusion is directly due to the five mutations in the env gene. It has also been shown that entry of m7NDK is CD4-independent in COS-7 cells. Since the wild-type NDK and m7NDK viruses use the human CXCR4 protein as co-receptor, agm-CXCR4 was cloned and used in transfection and fusion inhibition experiments to show that this receptor can be used by the m5 and m7NDK viruses. The wild-type NDK virus, which does not enter COS-7 cells, can use agm-CXCR4, but only when the receptor is transfected into target cells. Although co-receptor nature and expression levels are still major determinants of virus entry, this is the first case where a few mutations in the env gene can overcome this restriction.

scholarly journals Emerin Is Hyperphosphorylated and Redistributed in Herpes Simplex Virus Type 1-Infected Cells in a Manner Dependent on both UL34 and US3

2007 ◽  
Vol 81 (19) ◽  
pp. 10792-10803 ◽  
Author(s):  
Natalie Leach ◽  
Susan L. Bjerke ◽  
Desire K. Christensen ◽  
Jacques M. Bouchard ◽  
Fan Mou ◽  
...  
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Virus Type ◽  
Herpes Simplex Virus Type ◽  
Nuclear Lamina ◽  
Wild Type ◽  
Simplex Virus ◽  
In Cells ◽  
Hsv 1

ABSTRACT Cells infected with wild-type herpes simplex virus type 1 (HSV-1) show disruption of the organization of the nuclear lamina that underlies the nuclear envelope. This disruption is reflected in changes in the localization and phosphorylation of lamin proteins. Here, we show that HSV-1 infection causes relocalization of the LEM domain protein emerin. In cells infected with wild-type virus, emerin becomes more mobile in the nuclear membrane, and in cells infected with viruses that fail to express UL34 protein (pUL34) and US3 protein (pUS3), emerin no longer colocalizes with lamins, suggesting that infection causes a loss of connection between emerin and the lamina. Infection causes hyperphosphorylation of emerin in a manner dependent upon both pUL34 and pUS3. Some emerin hyperphosphorylation can be inhibited by the protein kinase Cδ (PKCδ) inhibitor rottlerin. Emerin and pUL34 interact physically, as shown by pull-down and coimmunoprecipitation assays. Emerin expression is not, however, necessary for infection, since virus growth is not impaired in cells derived from emerin-null transgenic mice. The results suggest a model in which pUS3 and PKCδ that has been recruited by pUL34 hyperphosphorylate emerin, leading to disruption of its connections with lamin proteins and contributing to the disruption of the nuclear lamina. Changes in emerin localization, nuclear shape, and lamin organization characteristic of cells infected with wild-type HSV-1 also occur in cells infected with recombinant virus that does not make viral capsids, suggesting that these changes occur independently of capsid envelopment.

scholarly journals Analysis of Human Cell Heterokaryons Demonstrates that Target Cell Restriction of Cyclosporine-Resistant Human Immunodeficiency Virus Type 1 Mutants Is Genetically Dominant

2007 ◽  
Vol 81 (21) ◽  
pp. 11946-11956 ◽  
Author(s):  
Chisu Song ◽  
Christopher Aiken
Keyword(s):  
Human Immunodeficiency Virus ◽  
Cell Lines ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Cell Protein ◽  
Target Cells ◽  
Wild Type ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The host cell protein cyclophilin A (CypA) binds to CA of human immunodeficiency virus type 1 (HIV-1) and promotes HIV-1 infection of target cells. Disruption of the CypA-CA interaction, either by mutation of the CA residue at G89 or P90 or with the immunosuppressive drug cyclosporine (CsA), reduces HIV-1 infection. Two CA mutants, A92E and G94D, previously were identified by selection for growth of wild-type HIV-1 in cultures of CD4+ HeLa cell cultures containing CsA. Interestingly, infection of some cell lines by these mutants is enhanced in the presence of CsA, while in other cell lines these mutants are minimally affected by the drug. Little is known about this cell-dependent phenotype of the A92E and G94D mutants, except that it is not dependent on expression of the host factor TRIM5α. Here, we show that infection by the A92E and G94D mutants is restricted at an early postentry stage of the HIV-1 life cycle. Analysis of heterokaryons between CsA-dependent HeLa-P4 cells and CsA-independent 293T cells indicated that the CsA-dependent infection by A92E and G94D mutants is due to a dominant cellular restriction. We also show that addition of CsA to target cells inhibits infection by wild-type HIV-1 prior to reverse transcription. Collectively, these results support the existence of a cell-specific human cellular factor capable of restricting HIV-1 at an early postentry step by a CypA-dependent mechanism.

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