title: Epigenetic regulation of HIF-1α in renal cancer cells involves HIF-1α/2α binding to a reverse hypoxia-response element.
abstract: Inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene underlies the majority of sporadic clear cell renal cell carcinomas (CCRCCs) and is also responsible for the hereditary VHL cancer syndrome. VHL loss of function results in constitutive stabilization of hypoxia-inducible factors (HIF-1α and HIF-2α) due to insufficient proteolysis in the presence of oxygen. This activates multiple genes relevant to tumorigenesis, allowing cells to acquire further mutations and undergo malignant transformation. However, the specific role of each HIF-α subunit in CCRCC tumorigenesis is not yet well understood. The current paradigm supports that in the first stages of CCRCC formation the stabilization of HIF-1α is dominant and this limits proliferation, but later on HIF-2α increases and this induces a more aggressive cell behavior. Understanding how this transition happens is highly relevant, as it may provide novel ways to treat these cancers. Here, we show that VHL inactivation in CCRCC cells results in HIF-1α/2α-dependent downregulation of HIF-1α mRNA through direct binding of either subunit to a reverse hypoxia-response element in the HIF-1α proximal promoter. This binding activates a series of repressive histone modification marks including histone 3 lysine 27 trimethylation (H3K27me3) to make the changes stable, and if overturned reduces CCRCC cell proliferation due to excessive HIF-1α expression level. Our findings thus help understand how HIF-α subunits influence each other and also reinforce the idea that epigenetic mechanisms are a key step of CCRCC progression.
authors.affiliation: Stem Cell and Cancer Biology Group, Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, GuangzhouInstitutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, Guangdong, China.
authors.forename: J
authors.initials: J
authors.lastname: Xu
authors.forename: B
authors.initials: B
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.forename: L
authors.initials: L
authors.lastname: Sun
authors.forename: W
authors.initials: W
authors.lastname: Tian
authors.forename: D
authors.initials: D
authors.lastname: Shukla
authors.forename: R
authors.initials: R
authors.lastname: Barod
authors.forename: J
authors.initials: J
authors.lastname: Grillari
authors.forename: R
authors.initials: R
authors.lastname: Grillari-Voglauer
authors.forename: P H
authors.initials: PH
authors.lastname: Maxwell
authors.forename: M A
authors.initials: MA
authors.lastname: Esteban
mesh_terms: D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002292:Carcinoma, Renal Cell; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D017930:Genes, Reporter; D006657:Histones / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics* / Q000378:metabolism; D007680:Kidney Neoplasms; D049409:Luciferases, Firefly / Q000096:biosynthesis / Q000235:genetics; D011485:Protein Binding; D055550:Protein Stability; D034622:RNA Interference; D020218:Response Elements; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000235:genetics / Q000378:metabolism; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D006657:Histones; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D049409:Luciferases, Firefly; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human; C497446:VHL protein, human