Isolation and characterization of a novel promoter for the XXXX growth hormone receptor gene.

@entity291 @entity7036
The use of alternative promoters represents an important mechanism for the regulation of growth hormone receptor ( @entity7036 ) gene expression. Two promoters have been isolated previously for the @entity7036 gene: the P1 promoter that drives liver-specific expression, and the P2 promoter that drives ubiquitous expression. In the present study, we isolated a third @entity7036 promoter termed P3. The P3 promoter was GC-rich and TATA-less. The P3 promoter was able to drive the expression of a luciferase reporter gene in cell lines Hep G2, PLC/PRF/5, and BHK-21. In vivo, the P3 promoter initiated transcription from two major sites in exon 1C of the @entity7036 gene in many tissues. In the adult @entity291 liver, the P3-transcribed @entity7036 mRNA represented only 10% of the total @entity7036 mRNA pool. In non-hepatic tissues such as kidney, skeletal muscle, mammary gland, and uterus, P3-transcribed @entity7036 mRNA represented 30-40% of the total @entity7036 mRNA pool. Within the @entity291 @entity7036 gene, the P3 promoter was located immediately downstream from the P2 promoter. In transfected cells, the P2 promoter served as an enhancer for the P3 promoter. Existence and co-regulation of two ubiquitous promoters may be a mechanism for achieving a high level of expression of the @entity7036 gene in multiple tissues.
