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Biological Chemistry

Editor-in-Chief: Brüne, Bernhard

Editorial Board Member: Buchner, Johannes / Ludwig, Stephan / Sies, Helmut / Turk, Boris / Wittinghofer, Alfred

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Modulation of glucokinase expression by hypoxia-inducible factor 1 and upstream stimulatory factor 2 in primary rat hepatocytes

U. Roth / K. Jungermann / T. Kietzmann

Citation Information: Biological Chemistry. Volume 385, Issue 3-4, Pages 239–247, ISSN (Print) 1431-6730, DOI: 10.1515/BC.2004.018, June 2005

Publication History

Published Online:
2005-06-01

Abstract

Glucokinase (GK) is the key enzyme of glucose utilization in liver and is localized in the less aerobic perivenous area. Until now, the O2-responsive elements in the liverspecific GK promoter are unknown, and therefore the aim of this study was to identify the O2-responsive element in this promoter. We found that the GK promoter sequence -87/-80 matched the binding site for hypoxia inducible factor 1 (HIF-1) and upstream stimulatory factor (USF). In primary rat hepatocytes we could show that venous pO2 enhanced HIF-1α and USF-2a levels, both of which activated GK expression. Furthermore, transfection experiments revealed that the GK sequence -87/-80 mediated the HIF-1α or USF-2-dependent activation of the GK promoter. The binding of HIF-1 and USF to the GKHRE was corroborated by electrophoretic mobility shift assay (EMSA). However, the maximal response to HIF-1α or USF was only achieved when constructs with the -87/ -80 sequence in context with a 39-36 bp native GK promoter sequence containing a hepatocyte nuclear factor 4 (HNF-4) binding site were used. HIF-1α and HNF-4 additively activated the GK promoter, while USF-2 and HNF-4 together did not show this additive activation. Thus, HIF-1 and USF may play differential roles in the modulation of GK expression in response to O2.

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