The nuclear factor NF-IL6 activates human placental lactogen gene expression.

Transient transfection studies using deletion mutants of the hPL promoter indicate that the DNA elements for NF-IL6 responsiveness are located between -2.3 to -1.1 kb. Subsequent transfection studies using a hPL promoter fragment containing the region between -1376 to -1088 bp ligated to a heterologous SV40 CAT vector (NF-IL6/hPL-CAT) demonstrated that the NF-IL6/hPL-CAT construct is responsive to NF-IL6. Mobility shift assays using nuclear extracts from BeWo choriocarcinoma cells overexpressing NF-IL6 demonstrated specific binding of the extracts to a labeled oligonucleotide probe to this region of the hPL promoter. These studies therefore strongly suggest that the effect of IL-6 on hPL gene expression is mediated, at least in part, by the binding of NF-IL6 to a region of the hPL promoter that contains three NF-IL6 responsive elements.