Involvement of Ets, rel and Sp1-like proteins in lipopolysaccharide-mediated activation of the HIV-1 LTR in macrophages.

The HIV-1 promoter was used as a model to identify transcription factors involved in LPS-dependent transcription in RAW 264 murine macrophages. Expression plasmids for Ets-2 and PU.1 trans-activated the HIV-1 LTR and recombinant PU.1 and an Ets-2 DNA binding domain/GST fusion protein bound to the 5' kappa B site of the HIV-1 enhancer. Ets-2 mRNA was LPS-inducible in RAW 264 cells and LPS stimulated phosphorylation of threonine 72 residue within the Ets-2 pointed domain. Induction of Ets-2 and other LPS-responsive transcription factors was also observed upon addition of plasmid DNA, which complicates interpretation of transient transfections. The proximal promoter region, containing two Sp1 sites, was also LPS-responsive. We propose that the kappa B elements and the tandem Sp1 sites act as LPS response elements and that kappa B-mediated LPS action involves Ets and rel factors.