Neurotensin (NT),2 a tridecapeptide predominantly localized to specialized enteroendocrine N cells with greatest abundance in the jejenum and ileum of the gastrointestinal (GI) tract, is released by intraluminal fats (1-3). It serves several functions in the GI tract including stimulation of pancreatic and biliary secretion (4 -6), inhibition of gastric and small bowel motility (7,8), and facilitation of fatty acid translocation from the intestinal lumen (9 -12). Furthermore, NT stimulates the growth of various GI tissues including the pancreas (13), colon (14), and small bowel (15-18), as well as certain colonic, pancreatic, prostatic, and lung cancers that possess NT receptors (1). The primary sequences of both the rat and human genes encoding NT and the structurally related hexapeptide, neuromedin N, have been elucidated (19,20). In the GI tract, the NT/neuromedin N (NT/N) gene is developmentally regulated in the human and rat intestines in a temporospatial manner (21-23). The promoter proximal 5Ј-flanking region of the rat NT/N gene has previously been shown to integrate multiple environmental stimuli in neuroendocrine PC12 cells and to be sufficient for cell-specific expression in enteroendocrine BON cells (24,25). These results indicated that an array of distinct cis-regulatory motifs localized in the proximal 120 bp of the 5Ј-flanking sequence are required for both inducible and high level, constitutive NT/N expression, depending on the cell type. A proximal promoter cAMP-responsive element (CRE)/AP-1 site and a purine-rich imperfect direct repeat sequence were particularly important for expression in BON cells.The regulation of gene expression in eukaryotic cells involves the specific interaction of DNA-binding proteins with cis-acting DNA sequences located in the 5Ј-flanking region upstream from the transcriptional start site. The trans-acting factors that interact with these DNA elements either activate or repress gene transcription, and depending on the cell type, these factors, such as AP-1 and CRE-binding protein (CREB)/ ATF (activating transcription factor), may be ubiquitous. The nuclear factor AP-1 superfamily consists of the jun (c-Jun, JunB, and JunD) and fos (c-Fos, Fra-1, and Fra-2) gene subfamilies that bind the AP-1 site (TGAGTCA) as either homoor heterodimers (26, 27). Another large family of transcription factors, comprising at least 10 related proteins that bind the CRE site (TGACGTCA), includes CREB (CRE binding), ATF, and CREM (CRE modulator) (28). Moreover, members of the steroid hormone receptor superfamily also regulate transcription of a large variety of genes and play a crucial role in developmental processes (29,30). In addition to the classi-