Egr-1 and serum response factor are involved in growth factors- and serum-mediated induction of E2-EPF UCP expression that regulates the VHL-HIF pathway

J Cell Biochem. 2008 Nov 1;105(4):1117-27. doi: 10.1002/jcb.21914.

Abstract

E2-EPF ubiquitin carrier protein (UCP) has been shown to be highly expressed in common human cancers and target von Hippel-Lindau (VHL) for proteosomal degradation in cells, thereby stabilizing hypoxia-inducible factor (HIF)-1alpha. Here, we investigated cellular factors that regulate the expression of UCP gene. Promoter deletion assay identified binding sites for early growth response-1 (Egr-1) and serum response factor (SRF) in the UCP promoter. Hepatocyte or epidermal growth factor (EGF), or phorbol 12-myristate 13-acetate induced UCP expression following early induction of Egr-1 expression in HeLa cells. Serum increased mRNA and protein levels of SRF and UCP in the cell. By electrophoretic mobility shift and chromatin immunoprecipitation assays, sequence-specific DNA-binding of Egr-1 and SRF to the UCP promoter was detected in nuclear extracts from HeLa cells treated with EGF and serum, respectively. Overexpression of Egr-1 or SRF increased UCP expression. RNA interference-mediated depletion of endogenous Egr-1 or SRF impaired EGF- or serum-mediated induction of UCP expression, which was required for cancer cell proliferation. Systemic delivery of EGF into mice also increased UCP expression following early induction of Egr-1 expression in mouse liver. The induced UCP expression by the growth factors or serum increased HIF-1alpha protein level under non-hypoxic conditions, suggesting that the Egr-1/SRF-UCP-VHL pathway is in part responsible for the increased HIF-1alpha protein level in vitro and in vivo. Thus, growth factors and serum induce expression of Egr-1 and SRF, respectively, which in turn induces UCP expression that positively regulates cancer cell growth.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Proliferation
  • Early Growth Response Protein 1 / physiology*
  • HeLa Cells
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • Intercellular Signaling Peptides and Proteins / pharmacology
  • Neoplasms / pathology
  • Protein Stability
  • Serum
  • Serum Response Factor / physiology*
  • Transcriptional Activation / drug effects*
  • Ubiquitin-Conjugating Enzymes / genetics*
  • Von Hippel-Lindau Tumor Suppressor Protein / metabolism*

Substances

  • EGR1 protein, human
  • Early Growth Response Protein 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Intercellular Signaling Peptides and Proteins
  • Serum Response Factor
  • Ube2S protein, human
  • Ubiquitin-Conjugating Enzymes
  • Von Hippel-Lindau Tumor Suppressor Protein