In vitro activation of the HIV-1 enhancer in extracts from cells treated with a phorbol ester tumor promoter.
The transition from persistent to lytic infection by the human immunodeficiency virus, HIV, is marked by a burst of viral replication and gene expression that occurs when infected cells are stimulated by physiological inducers or tumor promoters like 12-O-tetradecanoyl phorbol acetate (TPA). We report here that the HIV enhancer is activated specifically by TPA in several non-lymphoid cell types, and that this transcriptional regulation can be reproduced in a cell-free system. In vitro transcription experiments revealed a 6-fold activation of the HIV promoter in nuclear extracts prepared from TPA-induced HeLa tk- cells, whereas a control (human alpha-globin) promoter was transcribed with equal efficiency in either induced or uninduced cell extracts. A corresponding increase in the activity of a cellular DNA-binding protein that interacts with the HIV enhancer was detected in TPA-treated cells with DNase I footprint experiments. This increase occurred in the absence of de novo protein synthesis, suggesting a post-transcriptional activation mechanism. Analysis of HIV deletion mutants suggests that the enhancer is the target for the TPA effect both in vitro and in vivo. The cell-free system described here should facilitate studies on the mechanism of phorbol ester induction of gene-specific transcription factors.
Molecular Biology and Virology Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037.
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Dinter
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Chiu
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Imagawa
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Karin
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Jones
D002460:Cell Line; D004742:Enhancer Elements, Genetic / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects*; D005814:Genes, Viral / Q000187:drug effects*; D006678:HIV / Q000187:drug effects / Q000235:genetics*; D006367:HeLa Cells / Q000187:drug effects; D006801:Humans; D012367:RNA, Viral / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects
D012367:RNA, Viral; D013755:Tetradecanoylphorbol Acetate