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.
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.
Lim
Jung Hwa
JH
Gene Therapy Research Unit, Korea Research Institute of Bioscience and Biotechnology, Yusong, Daejeon 305-806, Republic of Korea.
Jung
Cho-Rok
CR
Lee
Chan-Hee
CH
Im
Dong-Soo
DS
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*
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