Neuroendocrine cell type-specific and inducible expression of the chromogranin B gene: Crucial role of the proximal promoter

Chromogranin B, a soluble acidic secretory protein, is widely distributed i n neuroendocrine and neuronal cells, although not in other cell types. To i dentify the elements governing such widespread, yet selective, expression o f the gene, we characterized the isolated mouse chromogranin B promoter. 5' -Promoter deletions localized neuroendocrine cell type-specific expression to the proximal chromogranin B promoter (from -216 to -91 bp); this region contains an E box (at [-206 bp]CACCTG[-201 bp]), four G/C-rich regions (at [-196 bp]CCCCGC[-191 bp], [-134 bp]CCGCCCGC[-127 bp], [-125 bp]GGCGCCGCC[-1 17 bp], and [-115 bp]CGGGGC[-110 bp]), and a cAMP response element (CRE; at [-102 bp]TGACGTCA[-95 bp]). A 60-bp core promoter region, defined by an in ternal deletion from -134 to -74 bp upstream of the cap site and spanning t he CRE and three G/C-rich regions, directed tissue-specific expression of t he gene. The CRE motif directed cell type-specific expression of the chromo granin B gene in neurons, whereas three of the G/C-rich regions played a cr ucial role in neuroendocrine cells. Both the endogenous chromogranin B gene and the transfected chromogranin B promoter were induced by preganglionic secretory stimuli (pituitary adenylyl cyclase-activating polypeptide, vasoa ctive intestinal peptide, or a nicotinic cholinergic agonist), establishing stimulus-transcription coupling for this promoter. The adenylyl cyclase ac tivator forskolin, nerve growth factor, and retinoic acid also activated th e chromogranin B gene. Secretagogue-inducible expression of chromogranin B also mapped onto the proximal promoter; inducible expression was entirely l ost upon internal deletion of the 60-bp core (from -134 to -74 bp). We conc lude that CRE and G/C-rich domains are crucial determinants of both cell ty pe-specific and secretagogue-inducible expression of the chromogranin B gen e.