title: 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.
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.
authors.affiliation: Gene Therapy Research Unit, Korea Research Institute of Bioscience and Biotechnology, Yusong, Daejeon 305-806, Republic of Korea.
authors.forename: Jung Hwa
authors.initials: JH
authors.lastname: Lim
authors.forename: Cho-Rok
authors.initials: CR
authors.lastname: Jung
authors.forename: Chan-Hee
authors.initials: CH
authors.lastname: Lee
authors.forename: Dong-Soo
authors.initials: DS
authors.lastname: Im
mesh_terms: D049109:Cell Proliferation; D051766:Early Growth Response Protein 1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D009369:Neoplasms / Q000473:pathology; D055550:Protein Stability; D044967:Serum; D026362:Serum Response Factor / Q000502:physiology*; D015533:Transcriptional Activation / Q000187:drug effects*; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics*; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000378:metabolism*
chemical_list: C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D036341:Intercellular Signaling Peptides and Proteins; D026362:Serum Response Factor; C544962:Ube2S protein, human; D044763:Ubiquitin-Conjugating Enzymes; D051794:Von Hippel-Lindau Tumor Suppressor Protein