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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A possible role of DNA methylation as a factor in HIV latency was studied by methylating a HIV1-LTR-CAT plasmid in vitro and measuring its expression after transfection on Vero cells. Methylation with a eukaryotic DNA methylase resulted in a 70% inhibition of chloramphenicol acetyltransferase expression, in the absence as well as in the presence of the HIV1 trans-activator protein TAT in the cell. A similar degree of transcription inhibition was obtained by methylation of the only Hpa II site at position-143 in the HIV1-LTR with the bacterial Hpa II methylase. In contrast to the effect by eukaryotic methylation, the inhibition by Hpa II methylation could be partially reversed by cotransfection of the TAT gene. The reason may lie in an about 40% demethylation at the Hpa II site which was concomitantly observed.
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PMID:Transcription of HIV1 is inhibited by DNA methylation. 232 94

We report here the discovery of HMBP, a protein in nuclei of human T-helper lymphocytes and other human cell types, which binds with enhanced affinity to a promoter element in the HIV-1 long terminal repeat when that element is methylated at CpGs, the target site of the human DNA methyltransferase. This promoter element contains three (degenerate) binding sites for Sp1, a general activator of transcription. Gel shift assays and footprinting experiments indicate that HMBP binding overlaps two of these methylated Sp1 sites. Although HMBP binds these methylated Sp1 sites, it does not bind consensus Sp1 sites. Competition studies, differences in binding site specificities, binding conditions, and, in some cases, chromatographic separation further distinguish HMBP from Sp1 and from each of four previously identified methylated-DNA binding proteins. HMBP binds hemimethylated DNA in a strand dependent manner. These binding characteristics suggest that HMBP may recognize newly replicated DNA and thereby play a role in differentiation. If HMBP is able to compete with Sp1 for binding at methylated, non-consensus Sp1 sites in vivo and repress transcription, it may play a role in AIDS latency.
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PMID:A nuclear protein with enhanced binding to methylated Sp1 sites in the AIDS virus promoter. 828 30

The immune response to pathogens is regulated by a delicate balance of cytokines. The dysregulation of cytokine gene expression, including interleukin-12, tumor necrosis factor alpha, and gamma interferon (IFN-gamma), following human retrovirus infection is well documented. One process by which such gene expression may be modulated is altered DNA methylation. In subsets of T-helper cells, the expression of IFN-gamma, a cytokine important to the immune response to viral infection, is regulated in part by DNA methylation such that mRNA expression inversely correlates with the methylation status of the promoter. Of the many possible genes whose methylation status could be affected by viral infection, we examined the IFN-gamma gene as a candidate. We show here that acute infection of cells with human immunodeficiency virus type 1 (HIV-1) results in (i) increased DNA methyltransferase expression and activity, (ii) an overall increase in methylation of DNA in infected cells, and (iii) the de novo methylation of a CpG dinucleotide in the IFN-gamma gene promoter, resulting in the subsequent downregulation of expression of this cytokine. The introduction of an antisense methyltransferase construct into lymphoid cells resulted in markedly decreased methyltransferase expression, hypomethylation throughout the IFN-gamma gene, and increased IFN-gamma production, demonstrating a direct link between methyltransferase and IFN-gamma gene expression. The ability of increased DNA methyltransferase activity to downregulate the expression of genes like the IFN-gamma gene may be one of the mechanisms for dysfunction of T cells in HIV-1-infected individuals.
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PMID:Infection with human immunodeficiency virus type 1 upregulates DNA methyltransferase, resulting in de novo methylation of the gamma interferon (IFN-gamma) promoter and subsequent downregulation of IFN-gamma production. 971 Jun 1

The human T-lymphoid cell line H9 resistant to 3'-azido-2',3'-dideoxythymidine (AZT) has a very low level of thymidine kinase (TK) expression which accounts for the failure of AZT to inhibit HIV-1 replication. In the present study DNA methylation and histone deacetylation as possible mechanisms of decreased TK gene expression in the resistant cells were investigated. The resistant cells expressed high levels of DNA methyltransferases (DNMTs) 3a and 3b. The DNA methylation inhibitor, 5-aza-cytidine (5-aza-C), increased TK gene expression and antiviral activity of AZT in the resistant cells, while histone deacetylase inhibitor trichostatin A (TSA) had no effect. The results suggest that hypermethylation of the TK gene but not histone deacetylation in AZT-resistant H9 cells accounts for decreased TK gene expression and failure of AZT to inhibit HIV-1 replication probably due to overexpression of DNMT 3a and 3b.
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PMID:The mechanism of 3'-azido-2',3'-dideoxythymidine resistance to human lymphoid cells. 1273 16

In 1995, we discovered new antiherpetic antibiotics, called fattiviracins. The producing organism was classified as a strain belonging to Streptomyces microflavus. The strain produced at least 13 fattiviracin derivatives (FV-1 to FV-13). Fattiviracins were obtained as a white amorphous powder, and their molecular weights are in the range of 1400 to 1500. They are readily soluble in water, methanol, pyridine, and DMSO, but insoluble in other organic solvents. Fattiviracins have macrocyclic diesters formed by the binding of two trihydroxy fatty acids and two D-glucose residues in the molecule, and they can be divided into five families according to the length of the fatty acid moiety. Fattiviracins have potent activity against enveloped DNA viruses such as the herpes family, HSV-1, and VZV and enveloped RNA viruses such as influenza A and B viruses, and three strains of HIV-1, with EC(50) values on the order of a few micrograms per milliliter. The biosynthetic pathway of fattiviracins is also becoming clearer. Using bacitracin-resistant strains, enhanced and astringent production of fattiviracin was achieved. Fattiviracin FV-13, which has the longest fatty acid chains in the molecule, was dramatically enhanced by a C(55)-isoprenyl phosphate metabolism. In addition, we have screened various inhibitors of enzymes such as alkaline protease, glucosyltransferase, glucuronidase, phospholipase, deoxyribonuclease, DNA methyltransferase, and DNA topoisomerase. All the inhibitors we discovered are briefly summarized in this paper.
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PMID:[Metabolites produced by actinomycetes--antiviral antibiotics and enzyme inhibitors]. 1529 17

Lens epithelium-derived growth factor (LEDGF)/p75 functions as a bimodal tether during lentiviral DNA integration: its C-terminal integrase-binding domain interacts with the viral preintegration complex, whereas the N-terminal PWWP domain can bind to cellular chromatin. The molecular basis for the integrase-LEDGF/p75 interaction is understood, while the mechanism of chromatin binding is unknown. The PWWP domain is homologous to other protein interaction modules that together comprise the Tudor clan. Based on primary amino acid sequence and three-dimensional structural similarities, 24 residues of the LEDGF/p75 PWWP domain were mutagenized to garner essential details of its function during human immunodeficiency virus type 1 (HIV-1) infection. Mutating either Trp-21 or Ala-51, which line the inner wall of a hydrophobic cavity that is common to Tudor clan members, disrupts chromatin binding and virus infectivity. Consistent with a role for chromatin-associated LEDGF/p75 in stimulating integrase activity during infection, recombinant W21A protein is preferentially defective for enhancing integration into chromatinized target DNA in vitro. The A51P mutation corresponds to the S270P change in DNA methyltransferase 3B that causes human immunodeficiency, centromeric instability, and facial anomaly syndrome, revealing a critical role for this amino acid position in the chromatin binding functions of varied PWWP domains. Our results furthermore highlight the requirement for a conserved Glu in the hydrophobic core that mediates interactions between other Tudor clan members and their substrates. This initial systematic mutagenesis of a PWWP domain identifies amino acid residues critical for chromatin binding function and the consequences of their changes on HIV-1 integration and infection.
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PMID:Identification and characterization of PWWP domain residues critical for LEDGF/p75 chromatin binding and human immunodeficiency virus type 1 infectivity. 1879 76

Current anti-HIV-1 strategies reduce replication through targeting of viral proteins and RNA; meanwhile, targeting at the level of the integrated provirus has been less explored. We show here that mobilization-competent vectors containing small noncoding RNAs targeted to transcriptionally active regions of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) can take advantage of integrated virus and modulate HIV-1 replication. Transcriptional silencing of HIV-1 correlates with an increase in silent-state epigenetic marks including histone and DNA methylation, a loss of nuclear factor-kappaB (NF-kappaB) recruitment, and requires Argonaute 1 (Ago-1), histone deacetylase 1 (HDAC-1), and DNA methyltransferase 3a (DNMT3a) localization to the LTR. Long-term suppression of the virus was observed for 1 month with no evidence of viral resistance. These data show that RNA-directed transcriptional silencing of HIV-1 can be delivered by a mobilization-competent vector, suggesting that this system could be used to target long-term selective pressures on conserved promoter elements to evolve less pathogenic variants of HIV-1.
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PMID:Mobilization-competent Lentiviral Vector-mediated Sustained Transcriptional Modulation of HIV-1 Expression. 1906 94

We previously reported prolonged HIV-1 transcriptional gene silencing by an RNA duplex targeting a sequence located within the NF-kappaB binding motif of the HIV-1 promoter in a susceptible HeLa cell line. Here we report extremely prolonged suppression of productive HIV-1 infection in a T-cell line (Molt-4) by a retrovirally delivered short-hairpin RNA (shRNA) targeting the same region (shkappaB). Following retroviral delivery of an shRNA we established shRNA-expressing CD4(+) T-cell lines. HIV-1 gene expression was profoundly suppressed for 1 year. Results of nuclear run-on assays and HIV-1 LTR-luciferase reporter assays revealed that shkappaB acted by inhibition of HIV-1 transcription. The effect was reversed by a histone deacetylase inhibitor, trichostatin-A (TSA), but not by a DNA methyltransferase inhibitor, 5-azacytidine (5-AzaC). Furthermore, chromatin immunoprecipitation assays (ChIP) demonstrated rapid, sustained induction of heterochromatin structures within the HIV-1 promoter region, with enrichment of histone 3 lysine 27 tri-methylation (H3K27me3) and H3K9 methylation. H3K27me3 enrichment was the most pronounced. This prolonged suppression could not be recapitulated by either retrovirally delivered anti-sense or sense strands alone or in combination. Our data strongly suggest that shkappaB induces high level, sustained transcriptional gene silencing of HIV-1 and offers the possibility of new therapeutic strategies.
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PMID:Retroviral delivery of promoter-targeted shRNA induces long-term silencing of HIV-1 transcription. 1923 10

The Human I-mfa domain-Containing protein, HIC, is a 246 amino acid protein that functions as a transcriptional regulator. Although the precise function of HIC remains to be clarified, the association of the HIC gene locus with myeloid neoplasms, its interactions with lymphotropic viruses such as EBV, HIV-1 and HTLV-1 and its expression in immune tissues suggest that HIC might have a modulatory role in immune cells. To further characterise the HIC functional relationship with the immune system, we sought to analyse the HIC gene expression profile in immune cells and to determine if immunomodulatory cytokines, such as interleukin (IL)-2, could regulate the expression of HIC mRNA. Relative quantitative real-time RT-PCR revealed that HIC mRNA is highly expressed in PBMCs and in various hematopoietic cell lines. The immunomodulatory cytokine IL-2 up-regulated HIC gene expression in PBMCs, CEM, MT-2 and U937 but markedly reduced HIC gene expression in Raji. Addition of cycloheximide indicated that the IL-2 effects were independent of de novo protein synthesis and that the HIC gene is a direct target of IL-2. Two cell lines (Jurkat and BJAB) displayed a distinct loss in HIC gene expression. However, when these cell lines were subjected to a combination of DNA methyltransferase and histone-deacetylase inhibitors, (5-aza-2-deoxycytidine and trichostatin A, respectively), HIC expression was de-repressed, indicating possible epigenetic control of HIC expression. Overall, our study describes that the immune expression of HIC is cell-specific, dynamic, and identifies the HIC gene as an IL-2 responsive gene. Furthermore, our de-repression studies support the hypothesis that HIC might represent a candidate tumor suppressor gene. Overall, this report provides new insights for a putative role of HIC in the modulation of immune and inflammatory responses and/or hematological malignancies.
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PMID:Expression profile and differential regulation of the Human I-mfa domain-Containing protein (HIC) gene in immune cells. 1942 67

HIV-infected subjects on highly active antiretroviral therapy (HAART) are susceptible to comorbid microbial infections in the oral cavity. We observed that primary oral epithelial cells (POECs) isolated from HIV+ subjects on HAART grow more slowly and are less innate immune responsive to microbial challenge when compared with POECs from normal subjects. These aberrant cells also demonstrate epigenetic differences that include reduction in histone deacetylase 1 (HDAC-1) levels and reduced total DNA methyltransferase (DNMT) activity specific to enzymes DNMT1 and DNMT3A. The DNMT activity correlates well with global DNA methylation, indicating that aberrant DNMT activity in HIV+ (on HAART) POECs leads to an aberrantly methylated epithelial cell phenotype. Overall, our results lead us to hypothesize that, in patients with chronic HIV infection on HAART, epigenetic changes in key genes result in increased vulnerability to microbial infection in the oral cavity.
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PMID:Comparison of epigenetic profiles of human oral epithelial cells from HIV-positive (on HAART) and HIV-negative subjects. 2380 46


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