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Mol. Cell. Biol., Sep 1997, 5629-5639, Vol 17, No. 9
D Mukhopadhyay, B Knebelmann, HT Cohen, S Ananth and VP Sukhatme
The von Hippel-Lindau tumor suppressor gene (VHL) has a critical role in
the pathogenesis of clear-cell renal cell carcinoma (RCC), as VHL mutations
have been found in both von Hippel-Lindau disease-associated and sporadic
RCCs. Recent studies suggest that vascular endothelial growth factor (VEGF)
mRNA is upregulated in RCC- and von Hippel-Lindau disease-associated
tumors. We have therefore assessed the effect of the VHL gene product on
VEGF expression. VEGF promoter-luciferase constructs were transiently
cotransfected with a wild-type VHL (wt-VHL) vector in several cell lines,
including 293 embryonic kidney and RCC cell lines. wt-VHL protein inhibited
VEGF promoter activity in a dose- dependent manner up to 5- to 10-fold.
Deletion analysis defined a 144- bp region of the VEGF promoter necessary
for VHL repression. This VHL- responsive element is GC rich and
specifically binds the transcription factor Sp1 in crude nuclear extracts.
In Drosophila cells, cotransfected VHL represses Sp1-mediated activation
but not basal activity of the VEGF promoter. We next demonstrated in
coimmunoprecipitates that VHL and Sp1 were part of the same complex and, by
using a glutathione-S-transferase-VHL fusion protein and purified Sp1, that
VHL and Sp1 directly interact. Furthermore, endogenous VEGF mRNA levels
were suppressed in permanent RCC cell lines expressing wt-VHL, and nuclear
run-on studies indicated that VHL regulation of VEGF occurs at least partly
at the transcriptional level. These observations support a new mechanism
for VHL-mediated transcriptional repression via a direct inhibitory action
on Sp1 and suggest that loss of Sp1 inhibition may be important in the
pathogenesis of von Hippel-Lindau disease and RCC.
Copyright © 1997, American Society for Microbiology
The von Hippel-Lindau tumor suppressor gene product interacts with Sp1 to repress vascular endothelial growth factor promoter activity
Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
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