Sequence Elements Required for Function of the MHC Class II AβGene Promoter in Murine Macrophages

We have studied the DNA sequence elements of the murine MHC class II Aβgene involved in transcriptional regulation in macrophages. For this study, the Aβpromoter was fused to the human growth hormone gene and transfected into bone marrow-derived macrophages. These macrophages were stimulated by interferon-γ (IFN-γ), after which cellular RNA was assayed for the amount of human growth hormone transcripts. A −146 to +14 fragment of the Aβpromoter was found to be sufficient to confer positive regulation by IFN-γ. Induction was suppressed by bacterial lipopolysaccharide, tumor necrosis factor (TNF-α), or maleylated bovine serum albumin. Substitution mutations were made within each of the conserved sequence elements of the promoter as well as within the spacer regions between these elements. All four conserved sequences found in class II promoters, the H, X1, X2, and Y elements, were found to be essential for promoter activation in macrophages.