The applicant's long-term objective is to elucidate the pathways that determine the pattern of neuropeptide synthesis in neural crest-derived tumors. Expression of vasoactive intestinal polypeptide (VIP) in pheochromocytoma and neuroblastoma cells is regulated by cAMP and protein kinase C-dependent pathways. The two questions that will be addressed are 1) How do second messenger systems regulate expression of the VIP gene and 2) Why is expression of the VIP gene restricted to neural crest-derived cells? During the first grant period, a 25 base pair element within the promotor region of the VIP gene was identified, which is required for stimulation of VIP synthesis of cAMP. The specific aims of the current proposal are to define the structural requirements for the cAMP-responsive element, to determine whether the element is an enhancer, a promoter, or some other kind of regulatory sequence, to characterize specific proteins that bind to the element, to determine whether the cAMP-responsive element mediates the effects of other second messenger systems, and to determine whether there are cis-acting elements within the VIP gene that permit expression only in neural crest-derived tissues. Understanding the mechanisms by which classical second messengers and other trans-acting factors regulate VIP production may help explain why some neural crest-derived tumors produce VIP.