MECHANISM OF EXPRESSION OF THE RAT HCNP PRECURSOR PROTEIN GENE

The hippocampal cholinergic neurostimulating peptide (HCNP), isolated from hippocampal tissue of 10- to 12-day-old rats, enhances the in vit ro synthesis of acetylcholine in medial septal tissue exp]ants. The HC NP precursor is a 21 kDa protein that binds hydrophobic ligands and Mg -ATP, and is associated with the opioid-binding protein. We employed a n HCNP-precursor cDNA as probe to clone the genomic DNA, used for mapp ing of the exon-intron structure of the gene. We also determined the n ucleotide structure of the promoter region of the rat HCNP precursor p rotein gene. By using S1 mapping and CAT as a reporter, we found multi ple promoters that were aligned in the 5' untranslated region. In addi tion, the presence of several putative enhancer binding sequences were tested by electrophoresis mobility shift assays. Northern blot analys is revealed that the gene is expressed in a variety of rat tissues and various subregions of the brain. These results suggest that HCNP-prec ursor gene expression is regulated by a general transactivation factor such as SP1, and that the specific presence of the bioactive HCNP in certain tissues results from post-translational events such as proteol ytic processing of the precursor protein, which takes place predominan tly in the hippocampus of young rats.