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J Biol Chem, Vol. 273, Issue 32, 20052-20057, August 7, 1998

Cooperative Actions of HIV-1 Vpr and p53 Modulate Viral Gene Transcription

Bassel E. Sawaya, Kamel Khalili, W. Edward Mercer^§, Lyudmila Denisova, and Shohreh Amini

From the  Center for NeuroVirology and NeuroOncology, Allegheny University of the Health Sciences, Philadelphia, Pennsylvania 19102 and the ^§ Kimmel Cancer Institute, Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107

Transcription of the human immunodeficiency virus type-1 (HIV-1) genome is controlled by cooperative interaction of viral encoded proteins and host regulatory proteins. In this study, we have examined the capacity of the viral auxiliary protein, Vpr, to modulate transcriptional activity of the HIV-1 promoter sequence located within the long terminal repeat (LTR). We demonstrate that ectopic expression of Vpr in human astrocytic cells, U-87MG, enhances the basal activity of the viral promoter in transfected cells and that the GC-rich sequences, spanning nucleotides 80 to 43, are important for this activity. Since this region serves as the target for p53-induced suppression of LTR activity and interacts with the ubiquitous transcription factor, Sp1, we examined the cooperative activity of Vpr, p53, and Sp1 upon LTR transcription. Results from co-transfection studies indicated that overexpression of wild type p53, but not mutant p53, decreases the level of activation of the LTR by Vpr. Transcriptional activation of the LTR by Vpr required the presence of Sp1 since overexpression of Vpr in cells with no endogenous Sp1 failed to augment LTR activity. Results from protein-protein interaction studies indicated that Vpr is associated with both p53 and Sp1 in cells with ectopic expression of these proteins. Moreover, it was evident that p53 and Sp1 interact with each other in these cells. These functional and structural studies provided a working model on the cooperative interaction of Vpr with cellular proteins Sp1 and p53 and control of viral gene transcription at immediate early stage of infection prior to the participation of other viral regulatory proteins.

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