The 3′ Flanking Region of the Human Tyrosine Hydroxylase Gene Directs Reporter Gene Expression in Peripheral Neuroendocrine Tissues

Abstract

Cell type-specific expression of the catecholamine synthetic enzyme, tyrosine hydroxylase (TH), appears to be mediated in part by cis-acting elements located at the 3′ end of the human gene. Further delineation of this region indicated sequences corresponding to a CACGTG motif significantly stimulated transcription of a heterologous promoter in various cell types. Mutation of this site led to a complete loss of activity. DNase footprinting, gel retardation, and UV cross-linking experiments indicated that a 74-kDa cellular factor(s) bound specifically to the CACGTG motif in the pheochromocytoma cell line PC12. The size of this protein and its pattern of expression are compatible with those of the CACGTG binding protein TFE3. Transgenic animals were created using a 261-bp human TH 3′ fragment encompassing the CACGTG motif in front of a thymidine kinase promoter/chloramphenicol acetyltransferase reporter gene. In three lines of mice this fragment was sufficient to direct a pattern of mRNA expression in peripheral neuroendocrine tissues that mimicked TH mRNA distribution. However, these sequences were not sufficient for CNS-specific patterns of expression. Thus, multiple cell type-specific enhancers may regulate TH gene expression in the CNS and periphery.