title: HIF-1alpha induces cell cycle arrest by functionally counteracting Myc.
abstract: Hypoxia induces angiogenesis and glycolysis for cell growth and survival, and also leads to growth arrest and apoptosis. HIF-1alpha, a basic helix-loop-helix PAS transcription factor, acts as a master regulator of oxygen homeostasis by upregulating various genes under low oxygen tension. Although genetic studies have indicated the requirement of HIF-1alpha for hypoxia-induced growth arrest and activation of p21(cip1), a key cyclin-dependent kinase inhibitor controlling cell cycle checkpoint, the mechanism underlying p21(cip1) activation has been elusive. Here we demonstrate that HIF-1alpha, even in the absence of hypoxic signal, induces cell cycle arrest by functionally counteracting Myc, thereby derepressing p21(cip1). The HIF-1alpha antagonism is mediated by displacing Myc binding from p21(cip1) promoter. Neither HIF-1alpha transcriptional activity nor its DNA binding is essential for cell cycle arrest, indicating a divergent role for HIF-1alpha. In keeping with its antagonism of Myc, HIF-1alpha also downregulates Myc-activated genes such as hTERT and BRCA1. Hence, we propose that Myc is an integral part of a novel HIF-1alpha pathway, which regulates a distinct group of Myc target genes in response to hypoxia.
authors.affiliation: Laboratory of Human Carcinogenesis, NCI, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Minori
authors.initials: M
authors.lastname: Koshiji
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kageyama
authors.forename: Erin A
authors.initials: EA
authors.lastname: Pete
authors.forename: Izumi
authors.initials: I
authors.lastname: Horikawa
authors.forename: J Carl
authors.initials: JC
authors.lastname: Barrett
authors.forename: L Eric
authors.initials: LE
authors.lastname: Huang
mesh_terms: D000256:Adenoviridae; D000818:Animals; D019313:BRCA1 Protein / Q000378:metabolism; D001667:Binding, Competitive / Q000235:genetics; D015153:Blotting, Western; D019556:COS Cells; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002522:Chlorocebus aethiops; D047369:Chromatin Immunoprecipitation; D050759:Cyclin-Dependent Kinase Inhibitor p21; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D047468:Immunoprecipitation; D018613:Microscopy, Confocal; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000037:antagonists & inhibitors*; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D019098:Telomerase / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
chemical_list: D019313:BRCA1 Protein; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D017931:DNA Primers; D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C489427:MYC protein, human; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; D014157:Transcription Factors; D019098:Telomerase