HIV-1 Tat overcomes inefficient transcriptional elongation in vitro

Laspia, M. F., Wendel, P., Mathews, M. B. (August 1993) HIV-1 Tat overcomes inefficient transcriptional elongation in vitro. J Mol Biol, 232 (3). pp. 732-46. ISSN 0022-2836 (Print)

DOI: 10.1006/jmbi.1993.1427


Tat, the transactivator protein encoded by HIV-1, acts in vivo to increase transcriptional initiation and stabilize elongation. We examined the effects of purified, bacterially-expressed Tat on HIV-1 transcription in a cell-free system. Tat specifically stimulated HIV-directed transcription 12-fold in HeLa cell nuclear extracts and this effect was principally due to increased transcriptional elongation. The degree of transactivation was greatest at later times during the transcription reaction when basal levels of transcription were reduced. At early times, the proportion of basal transcriptional complexes that elongate efficiently was high. Ongoing transcription increased the number of complexes requiring Tat for efficient elongation, possibly due to the activation of a repressor(s). To examine this hypothesis, the effects of the detergent Sarkosyl on HIV transcription were studied. Sarkosyl stimulated HIV-1 transcription to a level similar to that occurring in the presence of Tat alone by improving elongation. Transcription was elevated by Sarkosyl at concentrations inhibitory to reinitiation indicating that inefficient elongation is due to transcriptional pausing. Transcriptional stimulation by Sarkosyl was a general phenomenon as it was also observed with heterologous eukaryotic promoters. Tat was capable of stimulating elongation from a heterologous promoter when Tat binding was provided by a downstream TAR element. We propose that Tat acts as a general transcription factor whose binding at the promoter overcomes inefficient transcriptional elongation.

Item Type: Paper
Uncontrolled Keywords: Cell-Free System Gene Products, tat/genetics/ physiology HIV-1/ physiology Hela Cells Humans Models, Genetic Promoter Regions (Genetics)/drug effects/physiology RNA, Viral/genetics Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. Sarcosine/analogs & derivatives/pharmacology Trans-Activation (Genetics)/genetics/ physiology Transcription, Genetic/drug effects/genetics/ physiology
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > transcription
diseases & disorders > viral diseases > HIV
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > DNA expression > promoter
CSHL Authors:
Communities: CSHL labs
Depositing User: Matt Covey
Date: 5 August 1993
Date Deposited: 15 Apr 2016 19:09
Last Modified: 15 Apr 2016 19:09
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