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The AP-1 binding sites located in the pol gene intragenic regulatory region of HIV-1 are important for virus infectivity

We have previously identified three AP-1 binding sites in the pol gene of human immunodeficiency virus type 1 (HIV-1) and shown that short oligonucleotides containing these sites functioned as phorbol ester-inducible enhancers (Van Lint et al., 1991, J. Virol., 65:7066-7072). These sites are located in a region, called fragment 5103, exhibiting a phorbol ester-inducible enhancing activity on the viral thymidine kinase promoter in HeLa cells. In this study, we have further characterized each of the AP-1 binding sites and have shown that transcription factors c-Fos, JunB and JunD interacted in vitro with these motifs. For each site, we have identified mutations abolishing AP-1 factor binding without altering the underlying amino acid sequence of the HIV-1 reverse transcriptase. By transient transfection assays, we have demonstrated that the intragenic AP-1 binding sites were entirely responsible for the PMA-dependent transcriptional activity of fragment 5103. Moreover, this PMA-stimulated activity of fragment 5103 was inhibited by a dominant-negative A-Fos mutant provided the AP-1 sites were not mutated. Finally, we have investigated the biological significance of the intragenic AP-1 binding sites in HIV-1 replication and have shown that these sites are important for viral infectivity.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Vandenhoudt, N., de Walque, S., Van Driessche, B. et al. The AP-1 binding sites located in the pol gene intragenic regulatory region of HIV-1 are important for virus infectivity. Retrovirology 6 (Suppl 2), P89 (2009).

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