Nucleic Acids Research, 2002, Vol. 30, No. 22 4845-4854
© 2002 Oxford University Press
A novel mechanism of repression of the vascular endothelial growth factor promoter, by single strand DNA binding cold shock domain (Y-box) proteins in normoxic fibroblasts
Division of Human Immunology, The Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science, Frome Road, Adelaide, SA 5000, Australia
*To whom correspondence should be addressed. Tel: +61 08 82223432; Fax: +61 08 82324092; Email: leeanne.coles{at}imvs.sa.gov.au
Overexpression of vascular endothelial growth factor (VEGF) is implicated in a number of diseases. It is therefore critical that mechanisms exist to strictly regulate VEGF expression. A hypoxia-responsive (HR) region of the VEGF promoter which binds the HIF-1 transcription factor is a target for many signals that up-regulate VEGF transcription. Repressors targeting the HIF-1 transcription factor have been identified but no repressors directly binding the HR promoter region had been reported. We now report a novel mechanism of repression of the VEGF HR region involving DNA binding. We find that single strand DNA-specific cold shock domain (CSD or Y-box) proteins repress the HR region via a binding site downstream of the HIF-1 site. The repressor site is functional in unstimulated, normoxic fibroblasts and represents a novel means to prevent expression of VEGF in the absence of appropriate stimuli. We characterized complexes forming on the VEGF repressor site and identified a previously unreported nuclear CSD protein complex containing dbpA. Nuclear dbpA appears to bind as a dimer and we determined a means by which nuclear CSD proteins may enter double strand DNA to bind to their single strand sites to bring about repression of the VEGF HR region.