Prostaglandin E sub(2)-Mediated Activation of HIV-1 Long Terminal Repeat Transcription in Human T Cells Necessitates CCAAT/Enhancer Binding Protein (C/EBP) Binding Sites in Addition to Cooperative Interactions Between C/EBP beta and Cyclic Adenosine 5'-Monophosphate Response Element Binding Protein

Previous work indicates that treatment of human T cells with PGE sub(2) results in an increase of HIV-1 long terminal repeat (LTR) transcriptional activity. The noticed PGE sub(2)-mediated activation of virus gene activity required the participation of specific intracellular second messengers such as calcium and two transcription factors, i.e. NF- Kappa B and CREB. We report in this work that the nuclear transcription factor CCAAT/enhancer binding protein (C/EBP) is also important for PGE sub(2)-dependent up-regulation of HIV-1 LTR-driven gene activity. The implication of C/EBP was shown by using a trans-dominant negative inhibitor of C/EBP (i.e. liver-enriched transcriptional inhibitory protein) and several molecular constructs carrying site-directed mutations in the C/EBP binding sites located within the HIV-1 LTR. Mutated HIV-1 LTR constructs also revealed the involvement of the two most proximal C/EBP binding sites. Data from cotransfection experiments with vectors coding for dominant negative mutants and gel mobility shift assays indicated that PGE sub(2)-mediated induction of HIV-1 LTR activity results from a cooperative interaction between C/EBP beta and CREB, two members of the basic leucine zipper family of transcription factors. Altogether these findings indicate that treatment of human T cells with PGE sub(2) induces HIV-1 LTR activity through a complex interplay between C/EBP beta and CREB. Such a combinatorial regulation may represent a mechanism that permits a fine regulation of HIV-1 expression by PGE sub(2) in human T cells.