Structural and functional analysis of the promoter region of the nerve growth factor gene

Molecular clones containing the NGF gene promoter regions and exons I were isolated from mouse and rat genomic libraries with synthetic oligonucleotide hybridization probes that corresponded to the 5' end of mouse submandibular gland NGF mRNA. The nucleotide sequences of the 5' flanking regions and exons I were determined and compared. There was 95% similarity in exons I and the adjacent promoter regions between mouse and rat sequences. Further upstream, the similarity decreased to 76%. Both mouse and rat promoter regions were only 33% similar to the presumptive human NGF gene promoter region. Upstream from the capsite of submandibular gland NGF mRNA as determined by an S1-nuclease protection assay, two promoter-like TATA-boxes were found at positions -28 and -49, resp., and two CAAT-like boxes at -379 and -546, resp. Both promoter regions contained a cluster of conserved CpG dinucleotide sequences in a GC-rich island whereas less conserved upstream regions contained only one CpG sequence. The promoter regions were fused to the human growth hormone gene reporter function. Transient expression in L929 cells yielded appropriate fusion mRNAs and secretion of hGH, demonstrating that the cloned promoters are functional.