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94 PGE2-Mediated Activation of HIV-1 LTR Transcription in Human T Cells Necessitates C/EBP Binding Sites in Addition to Cooperative Interactions between C/EBP? and CREB
Salim Bounou*, Nancy Dumais, Martin Olivier, and Michel J. Tremblay
Infectious Diseases Res. Ctr., CHUQ, Pavillon CHUL, and Faculty of Med., Laval Univ., Québec, Canada
Background: Previous work indicates that treatment of human T cells with prostaglandin E2 (PGE2) results in an increase of human immunodeficiency virus type-1 (HIV-1) long terminal repeat (LTR) transcriptional activity. The noticed PGE2-mediated activation of virus gene activity required the participation of specific intracellular second messengers such as calcium and 2 transcription factors, i.e., NF-kappaB and cAMP-response element-binding protein (CREB). We report here that the nuclear transcription factor CCAAT/enhancer-binding protein (C/EBP) is also required for PGE2-dependent up-regulation of HIV-1 LTR-driven gene activity.
Methods: The human Jurkat T lymphoid cell line was transiently cotransfected with an HIV-1 LTR-driven luciferase construct bearing a mutation in NF-kappaB binding sites and a trans-dominant negative inhibitor of C/EBP (i.e., LIP). In addition, in some experiments several molecular constructs carrying site-directed mutations in the C/EBP binding sites located within the HIV-1 LTR were used. The possible synergism between C/EBP and CREB was explored by gel mobility shift assay.
Results: Our results indicate that the nuclear transcription factor CCAAT/enhancer-binding protein (C/EBP) is also important for PGE2-dependent up-regulation of HIV-1 LTR-driven gene activity. Mutated HIV-1 LTR constructs also revealed the involvement of the 2 most proximal C/EBP binding sites. Data from cotransfection experiments with vectors coding for dominant negative mutants and gel mobility shift assays indicated that PGE2-mediated induction of HIV-1 LTR activity results from a cooperative interaction between C/EBP? and CREB, 2 members of the ?-ZIP family of transcription factors.
Conclusions: Altogether these findings indicate that treatment of human T cells with PGE2 induces HIV-1 LTR activity through a complex interplay between C/EBP? and CREB. Such a combinatorial regulation may represent a mechanism that permits a fine regulation of HIV-1 expression by PGE2 in human T cells. A better understanding of factors controlling virus production is crucial to achieve a control of this disease by chemotherapeutic and vaccine strategies.
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