Isolation and characterization of the rat corticotropin-releasing hormone (CRH)-binding protein gene: transcriptional regulation by cyclic adenosine monophosphate and CRH.
The CRH-binding protein (CRH-BP) antagonizes the ACTH-releasing activity of the neuropeptide CRH in vitro. However, the function of CRH-BP in vivo and the molecular mechanisms that regulate CRH-BP expression are not well understood. In this study, the rat CRH-BP gene was characterized, and CRH-BP promoter sequences were identified. The rat CRH-BP gene spans almost 12 kilobases and contains 7 exons. Ribonuclease protection experiments indicate that transcription of the CRH-BP gene initiates at multiple sites in rat cerebral cortex. Transfection experiments with CRH-BP-reporter constructs, containing 88-3500 bp 5' flanking and 66 bp 5' untranslated DNA from the rat CRH-BP gene, demonstrate basal promoter activity in multiple cell lines. CRH-BP-reporter constructs also demonstrate positive regulation of promoter activity by cAMP in a variety of cell lines and by CRH in cells expressing the CRH receptor. The DNA sequences between -341 and -88 bp, including the cAMP response element-like sequence at -127 bp, are required for maximal cAMP and CRH regulation of CRH-BP promoter activity. These studies suggest that CRH-BP transcription in vivo may be positively regulated by cAMP and CRH.
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