J. Kollet et al., Deletional analysis of the murine IL-12 p35 promoter comparing IFN-gamma and lipopolysaccharide stimulation, J IMMUNOL, 167(10), 2001, pp. 5653-5663
IL-12, pivotal to the development of Th1 cells and formed by association of
p35 and p40 subunits, is made by macrophages and the macrophage cell line
RAW264.7. In this study, the promoter for p35 was cloned and analyzed. The
murine IL-12 p35 gene has promoters upstream from each of the first two exo
ns. The exon 1 and exon 2 promoters, cloned into a reporter vector, were re
sponsive to LPS or IFN-gamma /CD40 ligation in transfected RAW264.7 cells.
The exon 2 promoter containing bp -809 to +1 has significant homology to th
e human p35 promoter. Thus, deletion analysis was performed to determine th
e regions required for responsiveness to LPS, CD40, and/or IFN-gamma. Base
pairs -809 to -740 influenced responsiveness to LPS. In contrast, bp -740 t
o -444 and bp -122 to -100 were required for responses to IFN-gamma, IFN-ga
mma /LPS, or IFN-gamma /CD40 ligation. Removal of bp -444 to -392 increased
the response of the exon 2 promoter to each stimulant. IFN regulatory fact
or (IRF)-1 is involved in the activity of this promoter at bp -108 to -103
because levels of nuclear IRF-1 correlated with exon 2 promoter activity in
response to IFN-gamma and IRF-1 overexpression stimulated and enhanced exo
n 2 promoter activity. Also, site or deletion mutation of the IRF-1 element
at bp -108 to -103 reduced the responsiveness of the promoter and IRF-1 bo
und to an oligonucleotide containing bp -108 to -103. The data suggest that
the response of the p35 promoter to IFN-gamma requires a distinct IRF-1 po
sitive regulatory element at bp -108 to -103.