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Molecular and Cellular Biology, September 2005, p. 7473-7483, Vol. 25, No. 17
0270-7306/05/$08.00+0 doi:10.1128/MCB.25.17.7473-7483.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
B-Repressing Factor Inhibits Elongation of Human Immunodeficiency Virus Type 1 Transcription by DRB Sensitivity-Inducing Factor
Institute of Pharmacology, Medical School Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany,1 Institute of Clinical and Molecular Virology, University of Erlangen-Nürnberg, Schlossgarten 4, D-91054 Erlangen, Germany2
Received 24 February 2005/ Returned for modification 7 April 2005/ Accepted 7 June 2005
Human immunodeficiency virus type 1 (HIV-1) is able to establish a latent infection during which the integrated provirus remains transcriptionally silent. In response to specific stimuli, the HIV-1 long terminal repeat (LTR) is highly activated, enhancing both transcriptional initiation and elongation. Here, we have identified a specific binding sequence of the nuclear NF-
B-repressing factor (NRF) within the HIV-1 LTR. The aim of this work was to define the role of NRF in regulating the LTR. Our data show that the endogenous NRF is required for transcriptional activation of the HIV-1 LTR in stimulated cells. In unstimulated cells, however, NRF inhibits HIV-1 LTR activity at the level of transcription elongation. Binding of NRF to the LTR in unstimulated cells prevents recruitment of elongation factor DRB sensitivity-inducing factor and formation of processive elongation complexes by hyperphosphorylated RNA polymerase II. Our data suggest that NRF interrupts the regulatory coupling of LTR binding factors and transcription elongation events. This inhibitory mechanism might contribute to transcriptional quiescence of integrated HIV-1 provirus.
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