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Differential expression of the adenylyl cyclase-stimulatory guanosine triphosphate-binding protein Gsα in the human myometrium during pregnancy and labor involves transcriptional regulation by cyclic adenosine 3′,5′-monophosphate and binding of phosphorylated nuclear proteins to multiple GC boxes within the promoter

Lookup NU author(s): Dr Robert Phillips, Dr Jarrod Bailey, Professor Steve Robson, Professor Nick Europe-Finner

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Abstract

Gsα is the G protein subunit that stimulates adenylyl cyclase activity in the myometrium during pregnancy, raising intra-cellular levels of the smooth muscle relaxant cAMP. The promoter region of the gene encoding Gsα is GC rich and contains multiple putative binding sites for the specificity protein (Sp) transcription factor family. In electrophoretic mobility shift assays, four of these Sp sites were bound by recombinant Sp1 protein. Binding was dependent on phosphorylation of Sp1 by protein kinase A. Phosphorylated Sp1-4 proteins were observed in extracts of cultured human myometrial cells, but in electrophoretic mobility shift assays Gsα, promoter sequence binding by Sp1 was not apparent. Instead, these assays showed phosphorylation-dependent Gsα, promoter binding by lower molecular weight myometrial proteins that could not be supershifted by antibodies specific to Sp1-4 proteins. To investigate the regulation of Gsα expression, the GC-rich promoter region was used to direct transcription of a firefly luciferase reporter gene in transient transfection assays of primary human myometrial cell cultures, COS-7 and HEK 293 cells. Reporter gene expression was found to follow a biphasic response to forskolin and 8-bromo-cAMP, with an initial, concentration-dependent increase in luciferase activity, followed by a prolonged decrease. In myometrial cells, this pattern was also seen in response to treatment with human chorionic gonadotropin.


Publication metadata

Author(s): Phillips RJ, Bailey J, Robson SC, Europe-Finner GN

Publication type: Article

Publication status: Published

Journal: Journal of Clinical Endocrinology and Metabolism

Year: 2002

Volume: 87

Issue: 12

Pages: 5675-5685

ISSN (print): 0021-972X

ISSN (electronic): 1945-7197

Publisher: The Endocrine Society

URL: http://dx.doi.org/10.1210/jc.2002-020640

DOI: 10.1210/jc.2002-020640

PubMed id: 12466371


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