Hypoxia-inducible factor-1-dependent overexpression of myeloid cell factor-1 protects hypoxic cells against tert-butyl hydroperoxide-induced apoptosis.
Increased levels of Mcl-1 (myeloid cell factor-1) have been reported in several cancers, suggesting an important role played by Mcl-1 in cancer cell survival. Mcl-1 is an anti-apoptotic protein shown to delay or block apoptosis. In this work, using semiquantitative immunofluorescence, real-time PCR, and RNase protection assay, an increase in Mcl-1 expression was detected in hepatoma HepG2 cells incubated under hypoxia or in the presence of cobalt chloride. Through analysis of the Mcl-1 promoter sequence, a putative HIF-1 (hypoxiainducible factor-1) binding site was identified. A Mcl-1 promoter fragment containing this hypoxia-responsive element was able to bind HIF-1 in vitro. It also induced hypoxia-dependent transcription of a luciferase reporter gene, which was suppressed by anti-HIF-1alpha short interfering RNA. Finally, overexpression of Mcl-1 protected HepG2 cells against apoptosis induced by tert-butyl hydroperoxide as shown by inhibition of caspase-3 activation and DNA fragmentation. All these data suggest a potential anti-apoptotic role of HIF-1 that could protect cells against apoptosis under hypoxia by overexpression of the Mcl-1 protein.
Piret
Jean-Pascal
JP
Laboratory of Biochemistry and Cellular Biology, University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium.
Minet
Emmanuel
E
Cosse
Jean-Philippe
JP
Ninane
Noelle
N
Debacq
Christophe
C
Raes
Martine
M
Michiels
Carine
C
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008113:Liver Neoplasms; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics*; D009687:Nuclear Proteins / Q000502:physiology*; D016133:Polymerase Chain Reaction; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D014157:Transcription Factors / Q000502:physiology*; D020122:tert-Butylhydroperoxide / Q000494:pharmacology*
D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D014157:Transcription Factors; D020122:tert-Butylhydroperoxide