Von Hippel-Lindau tumor suppressor protein represses platelet-derived growth factor B-chain gene expression via the Sp1 binding element in the proximal PDGF-B promoter.

Abstract

VHL is the causative gene for von Hippel-Lindau disease and sporadic clear cell renal cancer. It has been shown that pVHL can suppress the expression of certain genes that are overexpressed in renal carcinomas. One such gene is that encoding the potent mitogen and chemoattractant, platelet-derived growth factor B-chain (PDGF-B). The regulatory mechanisms underlying pVHL suppression of PDGF-B expression, however, are completely unknown. This understanding would shed vital light on the control of growth factor gene expression by this tumor suppressor. Here we report that pVHL can repress both endogenous steady-state PDGF-B mRNA expression and PDGF-B promoter-dependent transcription in WKY12-22 cells. Transient transfection analysis utilizing PDGF-B promoter-chloramphenicol acetyl transferase (CAT) reporter constructs revealed that pVHL inhibition of PDGF-B expression is mediated via the Sp1-binding element in the proximal region of the PDGF-B promoter. Recent studies have demonstrated a physical interaction between pVHL and Sp1, which activates the PDGF-B promoter. We show that Sp1 can rescue PDGF-B promoter activity and endogenous PDGF-B mRNA expression from pVHL repression. These findings thus demonstrate a pivotal role for Sp1 in pVHL inhibition of PDGF-B transcription.