Nuclear protein‐induced bending and flexing of the hypoxic response element of the rat vascular endothelial growth factor promoter

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Abstract
Bending and flexing of DNA may con- tribute to transcriptional regulation. Because hypoxia and other physiological signals induce formation of an abasic site at a key base within the hypoxic response element (HRE) of the vascular endothelial growth factor (VEGF) gene (FASEB J. 19, 387-394, 2005) and because abasic sites can introduce flexibility in model DNA sequences, in the present study we used a fluo- rescence resonance energy transfer-based reporter sys- tem to assess topological changes in a wild-type (WT) sequence of the HRE of the rat VEGF gene and in a sequence harboring a single abasic site mimicking the effect of hypoxia. Binding of the hypoxia-inducible transcriptional complex present in hypoxic pulmonary artery endothelial cell nuclear extract to the WT se- quence failed to alter sequence topology whereas nu- clear protein binding to the modified HRE engendered considerable sequence flexibility. Topological effects of nuclear proteins on the modified VEGF HRE were dependent on the transcription factor hypoxia-induc- ible factor-1 and on formation of a single-strand break at the abasic site mediated by the coactivator, Ref-1/ Ape1. These observations suggest that oxidative base modifications in the VEGF HRE evoked by physiologi- cal signals could be a precursor to single-strand break formation that has an impact on gene expression by modulating sequence flexibility.—Breit, J. F., Ault-Ziel, K., Al-Mehdi, A.-B., Gillespie, M. N. Nuclear protein- induced bending and flexing of the hypoxic response element of the rat vascular endothelial growth factor promoter. FASEB J. 22, 19-29 (2008)
Funding Information
  • National Institutes of Health (RO1 HL058234, RO1 HL073244, R21 HL084521, PO1 HL066299)

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