title: Interaction of a tissue-specific factor with an essential rat growth hormone gene promoter element.
abstract: Rat growth hormone (rGH) gene expression is normally restricted to the anterior pituitary. As a model of this tissue specificity, we compared the transient expression of an rGH-chloramphenicol acetyltransferase (CAT) hybrid gene in rGH-producing rat pituitary tumor (GC) cells and in non-rGH-producing rat fibroblast (rat-2) cells. Deletion analysis of the rGH portion of this hybrid gene demonstrated that DNA sequences within 140 base pairs 5' to the rGH gene were sufficient for correct cell type-specific expression. Deletion of an additional 35 base pairs of the rGH 5'-flanking DNA resulted in a loss of expression of the transfected hybrid gene and correlated with the interaction of a putative trans-acting factor with this region of the rGH promoter. This factor was detectable by DNase I footprinting in a crude nuclear extract from GC cells but not from rat-2 cells. Site-directed mutagenesis of the footprint region caused complete loss of expression of a hybrid gene containing 530 base pairs 5' to the rGH gene. Thus, the interaction of this factor, which we term GC2, is likely to be essential for the tissue-specific expression of the rGH gene.
mesh_terms: D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D002872:Chromosome Deletion; D004247:DNA / Q000235:genetics; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000235:genetics*; D009928:Organ Specificity; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011401:Promoter Regions, Genetic; D051381:Rats; D014157:Transcription Factors / Q000235:genetics*; D014162:Transfection
chemical_list: D014157:Transcription Factors; D013006:Growth Hormone; D004247:DNA