scholarly journals The Human Immunodeficiency Virus Type 1 Tat Protein Up-Regulates the Promoter Activity of the Beta-Chemokine Monocyte Chemoattractant Protein 1 in the Human Astrocytoma Cell Line U-87 MG: Role of SP-1, AP-1, and NF-κB Consensus Sites

2000 ◽  
Vol 74 (4) ◽  
pp. 1632-1640 ◽  
Author(s):  
Siew Pheng Lim ◽  
Alfredo Garzino-Demo
Keyword(s):  
Human Immunodeficiency Virus ◽  
Promoter Activity ◽  
Tat Protein ◽  
Monocyte Chemoattractant Protein 1 ◽  
Monocyte Chemoattractant ◽  
Monocyte Chemoattractant Protein ◽  
Astrocytoma Cell ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT It has been shown that the human immunodeficiency virus type 1 (HIV-1) Tat protein can specifically enhance expression and release of monocyte chemoattractant protein 1 (MCP-1) from human astrocytes. In this study, we show evidence that Tat-induced MCP-1 expression is mediated at the transcriptional level. Transient transfection of an expression construct encoding the full-length Tat into the human glioblastoma-astrocytoma cell line U-87 MG enhances reporter gene activity from cotransfected deletion constructs of the MCP-1 promoter. HIV-1 Tat exerts its effect through a minimal construct containing 213 nucleotides upstream of the translational start site. Site-directed mutagenesis studies indicate that an SP1 site (located between nucleotides −123 and −115) is critical for both constitutive and Tat-enhanced expression of the human MCP-1 promoter, as mutation of this SP1 site significantly diminished reporter gene expression in both instances. Gel retardation experiments further demonstrate that Tat strongly enhances the binding of SP1 protein to its DNA element on the MCP-1 promoter. Moreover, we also observe an increase in the binding activities of transcriptional factors AP1 and NF-κB to the MCP-1 promoter following Tat treatment. Mutagenesis studies show that an upstream AP1 site and an adjacent NF-κB site (located at −128 to −122 and −150 to −137, respectively) play a role in Tat-mediated transactivation. In contrast, a further upstream AP1 site (−156 to −150) does not appear to be crucial for promoter activity. We postulate that a Tat-mediated increase in SP1 binding activities augments the binding of AP1 and NF-κB, leading to synergistic activation of the MCP-1 promoter.

scholarly journals Upregulation of c-Fos in Activated T Lymphoid and Monocytic Cells by Human Immunodeficiency Virus-1 Tat Protein

Blood ◽  
1997 ◽  
Vol 89 (5) ◽  
pp. 1654-1664 ◽  
Author(s):  
Davide Gibellini ◽  
Antonella Caputo ◽  
Silvano Capitani ◽  
Michele La Placa ◽  
Giorgio Zauli
Keyword(s):  
Human Immunodeficiency Virus ◽  
Cell Lines ◽  
Promoter Activity ◽  
Jurkat Cells ◽  
U937 Cells ◽  
Tat Protein ◽  
Fos Protein ◽  
Significant Difference ◽  
Immunodeficiency Virus ◽  
Hiv 1

Abstract The regulatory Tat protein of the human immunodeficiency virus type-1 (HIV-1) is essential for viral replication and also shows pleiotropic activities on various cell functions. To get further insights into the molecular mechanisms underlying the biological activity of Tat, we investigated the effect of endogenous and exogenous Tat protein on c-fos gene expression in T lymphoblastoid (Jurkat) and monocytic (U937) cell lines, as well as in primary peripheral blood mononuclear cells (PBMC). Transient cotransfection of tat cDNA in sense orientation (tat/S), together with a plasmid containing the c-fos promoter (FC3, from −711 to +42) in front of the bacterial chloramphenicol acetyltransferase (CAT) gene significantly enhanced CAT activity in Jurkat cells activated by the addition of 15% fetal calf serum (FCS) or 5 μg/mL phytohemagglutinin plus 10−7 mol/L phorbol myristate acetate (PMA) and U937 cells activated by 15% FCS or 10−7 mol/L PMA. This effect was specifically due to Tat, since Jurkat and U937 cells cotransfected either with tat cDNA in antisense orientation (tat/AS), tat carrying a mutation in the aminoacid cys22 - gly22 (tat 22/S) or with the backbone vector alone (pRPneo-SL3) did not show any significant difference in c-fos promoter activity as compared to cells transfected with FC3 plasmid alone. By using deletion mutants of the c-fos promoter, we found that the minimal DNA sequence required for Tat activity was located between nucleotides −404/−220 and that the serum responsive element (SRE, −317/−288), present within this region, was still responsive to Tat. A single point mutation in the SRE completely abrogated the responsiveness to tat/S. Exogenous recombinant Tat protein was also able to upregulate c-fos promoter activity in serum-activated Jurkat and U937 cells, as well as endogenous c-fos mRNA expression and c-Fos protein synthesis in both serum-activated cell lines and primary PBMC. c-Fos protein was shown essential for an optimal transactivation of the HIV-1 long terminal repeat (LTR) by Tat: incubation of Jurkat cells with antisense, but not sense, c-fos oligonucleotides significantly reduced either the Tat-enhanced expression of an LTR-CAT reporter construct or the levels of gag p24 in the culture supernatants of Jurkat cells and PBMC acutely infected with HIV-1. Our data suggest that the c-fos upregulation mediated by Tat might play a significant role in the control of viral gene transactivation.

scholarly journals Tat Protein of Human Immunodeficiency Virus Type 1 Subtype C Strains Is a Defective Chemokine

2004 ◽  
Vol 78 (5) ◽  
pp. 2586-2590 ◽  
Author(s):  
Udaykumar Ranga ◽  
Raj Shankarappa ◽  
Nagadenahalli B. Siddappa ◽  
Lakshmi Ramakrishna ◽  
Ramalingam Nagendran ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
The United States ◽  
Tat Protein ◽  
Subtype C ◽  
Monocyte Migration ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1)-associated dementia (HAD) is correlated with increased monocyte migration to the brain, and the incidence of HAD among otherwise asymptomatic subjects appears to be lower in India than in the United States and Europe (1 to 2% versus 15 to 30%). Because of the genetic differences between HIV-1 strains circulating in these regions, we sought to identify viral determinants associated with this difference. We targeted Tat protein for these studies in view of its association with monocyte chemotactic function. Analyses of Tat sequences representing nine subtypes revealed that at least six amino acid residues are differentially conserved in subtype C Tat (C-Tat). Of these, cysteine (at position 31) was highly (>99%) conserved in non-subtype C viruses and more than 90% of subtype C viruses encoded a serine. We hypothesized a compromised chemotactic function of C-Tat due to the disruption of CC motif and tested it with the wild type C-Tat (CS) and its two isogenic variants (CC and SC) derived by site-directed mutagenesis. We found that the CS natural variant was defective for monocyte chemotactic activity without a loss in the transactivation property. While the CC mutant is functionally competent for both the functions, in contrast, the SC mutant was defective in both. Therefore, the loss of the C-Tat chemotactic property may underlie the reduced incidence of HAD; although not presenting conclusive evidence, this study provides the first evidence for a potential epidemiologic phenomenon associated with biological differences in the subtype C viruses.

scholarly journals The Human Immunodeficiency Virus Type 1 Tat Protein Enhances Cryptosporidium parvum-Induced Apoptosis in Cholangiocytes via a Fas Ligand-Dependent Mechanism

2006 ◽  
Vol 75 (2) ◽  
pp. 684-696 ◽  
Author(s):  
Steven P. O'Hara ◽  
Aaron J. Small ◽  
Jeremy B. Nelson ◽  
Andrew D. Badley ◽  
Xian-Ming Chen ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Cryptosporidium Parvum ◽  
Fas Ligand ◽  
Tat Protein ◽  
Immunodeficiency Virus ◽  
Induced Apoptosis ◽  
Hiv 1 ◽  
Dependent Mechanism

ABSTRACT While Cryptosporidium parvum infection of the intestine has been reported in both immunocompetent and immunocompromised individuals, biliary infection is seen primarily in adult AIDS patients and is associated with development of AIDS cholangiopathy. However, the mechanisms of pathogen-induced AIDS cholangiopathy remain unclear. Since we previously demonstrated that the Fas/Fas ligand (FasL) system is involved in paracrine-mediated C. parvum cytopathicity in cholangiocytes, we also tested the potential synergistic effects of human immunodeficiency virus type 1 (HIV-1) transactivator of transcription (Tat)-mediated FasL regulation on C. parvum-induced apoptosis in cholangiocytes by semiquantitative reverse transcription-PCR, immunoblotting, immunofluorescence analysis, and immunogold electron microscopy. H69 cells do not express CXCR4 and CCR5, which are receptors required for direct HIV-1 viral infection. However, recombinant biologically active HIV-1-associated Tat protein increased FasL expression in the cytoplasm of cholangiocytes without a significant increase in apoptosis. We found that C. parvum-induced apoptosis was associated with translocation of intracellular FasL to the cell membrane surface and release of full-length FasL from infected H69 cells. Tat significantly (P < 0.05) increased C. parvum-induced apoptosis in bystander cells in a dose-dependent manner. Moreover, Tat enhanced both C. parvum-induced FasL membrane translocation and release of full-length FasL. In addition, the FasL neutralizing antibody NOK-1 and the caspase-8 inhibitor Z-IETD-fmk both blocked C. parvum-induced apoptosis in cholangiocytes. The data demonstrated that HIV-1 Tat enhances C. parvum-induced cholangiocyte apoptosis via a paracrine-mediated, FasL-dependent mechanism. Our results suggest that concurrent active HIV replication, with associated production of Tat protein, and C. parvum infection synergistically increase cholangiocyte apoptosis and thus jointly contribute to AIDS-related cholangiopathies.

scholarly journals A functional genetic approach suggests a novel interaction between the human immunodeficiency virus type 1 (HIV-1) Tat protein and HIV-1 TAR RNA in vivo

2003 ◽  
Vol 84 (3) ◽  
pp. 603-606 ◽  
Author(s):  
Lars H. Lund ◽  
Britta Wahren ◽  
Mariano A. Garcia-Blanco
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Tat Protein ◽  
Cyclin T1 ◽  
Immunodeficiency Virus ◽  
Tar Rna ◽  
Hiv 1

Human immunodeficiency virus type 1 (HIV-1) Tat and human Cyclin T1 form a complex and together recognize the viral TAR RNA element with specificity. Using HIV-1/equine infectious anaemia virus TAR chimeras, we show that in addition to the well-characterized interaction with the bulge, Tat recognizes the distal stem and the loop of TAR. These data support previously proposed, but unproven, molecular models.

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