HIV-1 Tat inhibits IL-2 gene transcription through qualitative and quantitative alterations of the cooperative Rel/AP1 complex bound to the CD28RE/AP1 composite element of the IL-2 promoter.
Dysregulation of cytokine secretion plays an important role in AIDS pathogenesis. Here, we demonstrate that expression of HIV-1 Tat protein in Jurkat cells induces a severe impairment of IL-2 but not TNF gene transcription. Interestingly, this inhibition correlates with the effect of the viral protein on the transactivation of the CD28RE/AP1 composite element (-164/-154), but not with that observed on the NFAT/AP1 site of the IL-2 gene promoter, neither with the effect on NF-kappa B- nor AP1-independent binding sites. Endogenous expression of Tat induced a decrease in the amount of the specific protein complex bound to the CD28RE/AP1 probe after PMA plus calcium ionophore stimulation. This effect was accompanied by qualitative alterations of the AP1 complex. Thus, in wild-type Jurkat cells, c-jun was absent from the complex, whereas in Tat-expressing cells, c-jun was increasingly recruited overtime. By contrast, similar amounts of c-rel and a small amount of NFAT1 were detected both in wild type and in Jurkat Tat(+) cells. Furthermore, Tat not only induced the participation of c-jun in the cooperative complex but also a decrease in its transactivation activity alone or in combination with c-rel. Thus, the interaction of Tat with the components of this rel/AP1 cooperative complex seems to induce quantitative and qualitative alterations of this complex as activation progresses, resulting in a decrease of IL-2 gene transcription. Altogether our results suggest the existence of tuned mechanisms that allow the viral protein to specifically affect cooperative interactions between transcription factors.
Centro de Biología Molecular Severo Ochoa Consejo Superior de Investigaciones Cientificas-Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain.
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González
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Punzón
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González
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Fresno
D000818:Animals; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D018106:CD28 Antigens / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology; D015536:Down-Regulation / Q000276:immunology; D015696:Gene Products, tat / Q000096:biosynthesis / Q000502:physiology*; D015497:HIV-1 / Q000276:immunology; D006801:Humans; D007376:Interleukin-2 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D019169:Jurkat Cells / Q000276:immunology / Q000378:metabolism; D007700:Kinetics; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic / Q000276:immunology*; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D020569:Proto-Oncogene Proteins c-rel / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D020218:Response Elements / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology; D014158:Transcription, Genetic / Q000276:immunology*; D015533:Transcriptional Activation / Q000276:immunology; D054322:tat Gene Products, Human Immunodeficiency Virus
D018106:CD28 Antigens; D004268:DNA-Binding Proteins; D015696:Gene Products, tat; D007376:Interleukin-2; D016328:NF-kappa B; D050778:NFATC Transcription Factors; C494006:NFATC2 protein, human; D009687:Nuclear Proteins; D016755:Proto-Oncogene Proteins c-jun; D020569:Proto-Oncogene Proteins c-rel; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D054322:tat Gene Products, Human Immunodeficiency Virus