title: Role of ETS transcription factors in the hypoxia-inducible factor-2 target gene selection.
abstract: Tumor hypoxia often directly correlates with aggressive phenotype, metastasis progression, and resistance to chemotherapy. Two transcription factors [hypoxia-inducible factor-1alpha (HIF-1alpha) and HIF-2alpha] are dramatically induced in hypoxic areas and regulate the expression of genes necessary for tumor adaptation to the conditions of low oxygen; however, the relative contribution of these factors is controversial. We used RNA interference-mediated inactivation of HIF-1alpha or HIF-2alpha followed by microarray analysis to identify genes specifically regulated by either HIF-1 or HIF-2 in hypoxia. We found that, in the MCF7 cell line, the vast majority of hypoxia-responsive genes (>80%) were dependent on the presence of HIF-1alpha. However, a small group of genes were preferentially regulated by HIF-2alpha. Promoter analysis for this group of genes revealed that all of them have putative binding sites for ETS family transcription factors, and 10 of 11 HIF-2alpha-dependent genes had at least one potential hypoxia-responsive element (HRE) in proximity to an ETS transcription factor binding site. Knockdown of ELK-1, the most often represented member of ETS family, significantly reduced hypoxic induction of the HIF-2alpha-dependent genes. Physical and functional interaction between ELK-1 and HIF-2alpha were supported by coimmunoprecipitation of these two proteins, luciferase reporter assay using CITED2 promoter, and binding of ELK-1 protein to the promoters of CITED2 and WISP2 genes in proximity to a HRE. These data suggest that the choice of the target genes by HIF-1 or HIF-2 depends on availability and cooperation of HIFs with other factors recognizing their cognate elements in the promoters.
authors.affiliation: Laboratory of Biosystems and Cancer, National Cancer Institute, NIH, Bethesda, Maryland, USA. apreliko@mail.nih.gov
authors.forename: Olga
authors.initials: O
authors.lastname: Aprelikova
authors.forename: Matthew
authors.initials: M
authors.lastname: Wood
authors.forename: Sean
authors.initials: S
authors.lastname: Tackett
authors.forename: Gadisetti V R
authors.initials: GV
authors.lastname: Chandramouli
authors.forename: J Carl
authors.initials: JC
authors.lastname: Barrett
mesh_terms: D051792:Basic Helix-Loop-Helix Proteins; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D015687:Cell Hypoxia / Q000235:genetics; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D050783:Proto-Oncogene Proteins c-ets / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics*; D015533:Transcriptional Activation; D050807:ets-Domain Protein Elk-1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D050783:Proto-Oncogene Proteins c-ets; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human