Transcriptional regulation of 11β-hydroxysteroid dehydrogenase type 1

• Main Author: Williams, Louise J. S.
• Published: University of Edinburgh 1997
• Subjects: 572.8
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.663832

The aim of the work described in this thesis was to elucidate the molecular mechanisms which govern transcription of steroid metabolising enzyme, primarily in liver, the site of highest expression of 11β-HSD1. Work from this laboratory, investigating activity of the rat 11β-HSD1 promoter is transfected HepG2 cells (a liver derived cell line) has shown the importance of the region between -812 and +47 in conferring C/EBPα inducibility upon a linked reporter gene, and has also demonstrated the presence of a repressor element between -812 and -599. Within this region I have shown 13 sites to which proteins from rat liver nuclear extract bind; 11 of these sites were similarly bound by bacterially expressed C/EBPα. One of these sites was a high affinity C/EBPα binding site spanning the transcription start and was investigated in some detail. The majority of complexes formed by rat liver nuclear extract on the transcription start contained C/EBPα and/or C/EBPβ. Furthermore, a minimal promoter (-88 to +8), containing this site and 2 additional weak C/EBP binding sites at -54 to -36 and -75 to -62 was transcriptionally active <I>in vitro </I>in nuclear extract from rat liver but not from HeLa cells, which lack C/EBP. 11β-HSD1 is expressed and regulated in a tissue-specific manner. The results described in this thesis suggest that this occurs through the tissue-specific transcription factors which bind to the 11β-HSD1 promoter. In liver, the central role played by C/EBP in the expression of 11β-HSD1 suggests that C/EBP may at least in part modulate glucocorticoid effects indirectly by altering the transcription of 11β-HSD1, and is consistent with the involvement of C/EBPα in regulating energy supply, and the role of C/EBPβ in the acute phase response.