Bacterially produced human HIF-1α is competent for heterodimerization and specific DNA-binding

Hypoxia-inducible factor 1 alpha (HIF- 1 alpha) is the regulatory Subunit of HIF- 1. the transcriptional activator and key mediator of the cellular response to hypoxia. Regulation of HIF-1 alpha Occurs at multiple levels and involves several different post-translational modifications. In order to examine the importance of these modifications for the basic function Of 111F-1 chi we have produced in bacteria recombinant full-length human HIF-1 chi using different expression systems. We show that this unmodified form of HIF-1 chi is able to form a stable heterodimer with the second Subunit of HIF-1 (HIF-1 beta or ARNT) when both proteins are co-exprosed in Escherichia coli. Furthermore, this bacterially reconstituted heterodimer exhibits specific DNA-binding activity. These data indicate that posttranslational modification of HIF-1 chi is not essential for its interaction with ARNT and DNA, and provide an in vitro system for the characterization of the molecular properties of HIF-1 chi. (c) 2005 Elsevier Inc. All rights reserved.