Tissue Specific and Hormonal Regulation of Gene Expression.

摘要

The hypothalamic neuropeptide hormone, Corticotropin Releasing Hormone (CRH), is also expressed in the placentas of humans and higher primates and may play an important role in the regulation of labor. In choriocarcinoma cell lines, which are models for placental trophoblasts, activation of cAMP dependent pathways increases human (h)CRH reporter gene expression. In addition to the cAMP response element (CRE) located at -220 bp in the human CRH promoter, a cAMP responsive region has been identified between -200 and -99 bp and a candidate 58 kDa transcription factor was identified in nuclear extracts of human, but not rodent, choriocarcinoma cell lines. This region, which does not contain a canonical CRE, transfers protein kinase A responsiveness to a heterologous promoter. Electromobility shift assays and methylation and uracil interference studies localized factor binding to a 20 base pair region from -128 to -109 bp of the hCRH promoter. Base contacts identified in interference studies were confirmed as critical for binding, as a mutation of these bases abolished factor binding. Furthermore, a CRH promoter containing this mutation exhibited a diminished response to 8-Br-cAMP. These data identify this 58 kDa protein as the human-specific CRH activator previously identified as a candidate factor contributing to the species-specific expression of CRH in human placenta.