Lack of responsiveness of a nuclear factor-kappaB-regulated promoter to transactivation by human immunodeficiency virus 1 Tat in HeLa cells.
Transcriptional activation by Tat protein is in large part dependent on interactions with the TAR RNA element located in the 5'-untranslated region of all human immunodeficiency virus type 1 (HIV-1) transcripts. In addition, Tat has been shown to induce nuclear translocation of nuclear factor-kappaB (NF-kappaB), potentially contributing to gene induction. The NF-kappaB responsive reporter construct, (PRDII)(4)-CAT, was used to explore transcription resulting from NF-kappaB activated by Tat. Tat did not activate (PRDII)(4)-CAT, whereas (PRDII)(4)-CAT was highly responsive to either transfected Rel A or to tumor necrosis factor-alpha (TNF-alpha). Despite its inability to directly induce, Tat enhanced the responsiveness of (PRDII)(4)-CAT to either transfected Rel A or to TNF-alpha by approximately 2.5-fold. High levels of CAT activity were seen with HIV-LTR-derived reporters that contained kappaB and TAR elements in response to transfected Tat in the absence of either transfected Rel A or exogenous TNF-alpha, and overexpression of IkappaBalpha with Tat inhibited CAT activity by 60% to 80%, suggesting that some activation of NF-kappaB by Tat was occurring. HIV-LTR reporter activities were enhanced three fold to sixfold compared with Tat alone when additional NF-kappaB was provided by transfection or by activation with TNF-alpha. These data indicate that Tat is unable to activate some NF-kappaB-responsive promoters but is able to synergize with NF-kappaB in the activation of both HIV-derived and non-HIV-derived promoters.
Kelly
G D
GD
Department of Medicine, Emory University, Atlanta, Georgia 30322, USA.
Morris
C B
CB
Offermann
M K
MK
D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics* / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D051996:Transcription Factor RelA; D015533:Transcriptional Activation; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D016328:NF-kappa B; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D054322:tat Gene Products, Human Immunodeficiency Virus