Sequences required for induction of neurotensin receptor gene expression during neuronal differentiation of N1E-115 neuroblastoma cells

The promoter region of the mouse high affinity neurotensin receptor (Ntr-1) gene was characterized, and sequences required for expression in neuroblas toma cell lines that express high affinity NT-binding sites were characteri zed. Me2SO-induced neuronal differentiation of N1E-115 neuroblastoma cells increased both the expression of the endogenous Ntr-1 gene and reporter gen es driven by NTR-1 promoter sequences by 3-4-fold. Deletion analysis reveal ed that an 83-base pair promoter region containing the transcriptional star t site is required for Me2SO activation. Detailed mutational analysis of th is region revealed that a CACCC box and the central region of a large GC-ri ch palindrome are the crucial cis-regulatory elements required for Me2SO in duction. The CACCC box is bound by at least one factor that is induced upon Me2SO treatment of N1E-115 cells. The Me2SO effect was found to be both se lective and cell type-restricted. Basal expression in the neuroblastoma cel l lines required a distinct set of sequences, including an Sp1-like sequenc e, and a sequence resembling an NGFI-A-binding site; however, a more distal 5' sequence was found to repress basal activity in N1E-115 cells. These re sults provide evidence that Ntr-1 gene regulation involves both positive an d negative regulatory elements located in the 5'-flanking region and that N tr-2 gene activation involves the coordinate activation or induction of sev eral factors, including a CACCC box binding complex.