NUCLEAR FACTOR-1 REGULATES THE DISTAL SILENCER OF THE HUMAN PIT1 GHF1GENE/

Here we report the characterization of 12 kb genomic DNA upstream of t he human PIT1/GHF1 promoter. Different regions involved in the modulat ion of human PIT1/GHF1 gene expression were defined by transient trans fection studies. Two regions, one proximal and (-7.1/-2.3) one distal (-11.8/-10.9), presented an enhancer activity in pituitary cells when placed upstream of the SV40 promoter. The 0.9 kb distal region was ana lysed further and found to decrease the basal transcriptional activity of the human PIT1/GHF1 minimal promoter, indicating that this region behaves as a silencer for its own promoter. Three Pit-1/GHF-1-binding sites and two ubiquitous nuclear factor 1 (NF-1)-binding sites were id entified by DNase I footprinting in the distal regulatory region. Dele tion analysis indicated that NF-1 or NF-1-related protein(s) participa te in the down-regulation of human PIT1/GHF1 gene expression by intera cting with an NF-1-binding site within the distal regulatory region.