Transcriptional Regulation of the CYP2C12 Gene in Female Rats.

Abstract

The purpose of this study was to clarify the mechanism (s) responsible for the growth hormone (GH)-induced expression of the CYP2C12 gene. To identify a functional GH-responsive element (GHRE) in vivo, we performed the direct injection of promoter-luciferase chimeric genes into female rat livers. The results showed that the luciferase activity was decreased to approximately 20% by the deletion of the sequence between nucleotides -4213 and -4161. Within this region, two copies of a possible GHRE were present. The sequence of the GHRE was overlapped with that of an interferon-y-activated sequence (GAS), known to be recognized by the signal transducer and activator of transcription (STAT) proteins. In fact, a super shift assay showed that STAT5 was capable of binding to the core sequence of the GHRE. Furthermore, a luciferase assay with reporter plasmids, which lacks HNF4 or HNF6-binding sites, revealed that the GH-stimulated expression of the CYP2C12 gene was regulated cooperatively by STAT5, HNF-4, HNF-6 and the factor(s) which binds to the elements, 2C12-I (-4095 to -4074) and 2C12-II (-4072 to -4045). The cooperative regulation by STAT5 and the liver-enriched transcription factors account for the GH-dependent and the liver-specific expression of the CYP2C12 gene in female rats.