Transcriptional activation of the tat-defective human immunodeficiency virus type-1 provirus: effect of interferon.
The effect of human interferon-alpha 2 (HuIFN-alpha 2) on the activation of HIV-1 provirus was studied in cell lines containing either an integrated tat-defective HIV-1 provirus (HIV-1 (-tat)) (HNHIVdt4 cells) or the HIV-1 (-tat) provirus and a plasmid in which the expression of HuIFN-alpha 2 was under the control of HIV LTR (HNHIV alpha 1 cells). In both cell lines, the expression of HIV-1 RNA was below the limit of detection, but transcription of the HIV-1 (-tat) provirus could be induced either by transfection with Tat-expressing plasmid or by treatment with TPA and cycloheximide (CHX). By contrast, stimulation with TPA alone induced HIV-1 transcription only in HNHIVdt4 cells, but not in HNHIV alpha 1 cells that produced low levels of IFN-alpha constitutively. Similarly in a transient expression assay, TPA upregulated transcription of the transfected HIV-1 CAT plasmid only in HNHIVdt4 cells, but not in HNHIV alpha 1 cells. UV-crosslinking analysis of NF-kappa B-specific proteins induced in TPA-treated cells showed the presence of 45 and 55 kDa NF-kappa B-binding protein in TPA-induced HNHIVdt4 cells while, in HNHIV alpha 1 cells, we detected only 55-, 110-, and 200-kDa proteins, but no 45-kDa protein. The transcriptional effects of IFN could not, however, be seen in the presence of Tat protein, suggesting that the virus developed a mechanism to overcome the IFN-mediated restrictions.
Popik
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Oncology Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
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D015870:Gene Expression; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000502:physiology*; D015756:Genes, tat; D015497:HIV-1 / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D007370:Interferon Type I / Q000235:genetics / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism; D011533:Proviruses / Q000235:genetics; D011994:Recombinant Proteins; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014779:Virus Replication / Q000187:drug effects*; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D007370:Interferon Type I; D016328:NF-kappa B; D011994:Recombinant Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D013755:Tetradecanoylphorbol Acetate