Characterization of the Promoter for the Human Long Pentraxin PTX3

The “long pentraxins” are an emerging family of genes that have conserved in their carboxy-terminal halves a pentraxin domain homologous to the prototypical acute phase protein pentraxins (C-reactive protein and serum amyloid P component) and acquired novel amino-terminal domains. In this report, a genomic fragment of 1371 nucleotides from the human “long pentraxin” gene PTX3 is characterized as a promoter on tumor necrosis factor-α (TNFα) and interleukin (IL)-1β exposure in transfected 8387 human fibroblasts by chloramphenicol acetyltransferase and RNase protection assays. In the same cells, the PTX3 promoter does not respond to IL-6 stimulation. Furthermore, IL-1β and TNFα responsiveness is not seen in the Hep 3B hepatoma cell line. The minimal promoter contains one NF-κB element which is shown to be necessary for induction and able to bind p50 homodimers and p65 heterodimers but not c-Rel. Mutants in this site lose the ability to bind NF-κB proteins and to respond to TNFα and IL-1β in functional assays. Sp1- and AP-1 binding sites lying in proximity to the NF-κB site do not seem to play a major role for cytokine responsiveness. Finally, cotransfection experiments with expression vectors validate that the natural promoter contains a functional NF-κB site.