title: Hypoxic repression of endothelial nitric-oxide synthase transcription is coupled with eviction of promoter histones.
abstract: Hypoxia elicits endothelial dysfunction, in part, through reduced expression of endothelial nitric-oxide synthase (eNOS). Here we present evidence that hypoxia causes a rapid decrease in the transcription of the eNOS/NOS3 gene, accompanied by decreased acetylation and lysine 4 (histone H3) methylation of eNOS proximal promoter histones. Surprisingly, we demonstrate that histones are rapidly evicted from the eNOS proximal promoter during hypoxia. We also demonstrate endothelium-specific H2A.Z incorporation at the eNOS promoter and find that H2A.Z is also evicted by hypoxic stimulation. After longer durations of hypoxia, histones are reincorporated at the eNOS promoter, but these histones lack substantial histone acetylation. Additionally, we identify a key role for the chromatin remodeler, BRG1, in re-establishing eNOS expression following reoxygenation of hypoxic cells. We posit that post-translational histone modifications are required to maintain constitutive eNOS transcriptional activity and that histone eviction rapidly resets histone marks and is a proximal event in the hypoxic repression of eNOS. Although nucleosome eviction has been reported in models of transcriptional activation, the observation that eviction can also accompany transcriptional repression in hypoxic mammalian cells argues that eviction may be broadly relevant to both positive and negative changes in transcription.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Jason E
authors.initials: JE
authors.lastname: Fish
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Yan
authors.forename: Charles C
authors.initials: CC
authors.lastname: Matouk
authors.forename: Rosanne
authors.initials: R
authors.lastname: St Bernard
authors.forename: J J David
authors.initials: JJ
authors.lastname: Ho
authors.forename: J J David
authors.initials: JJ
authors.lastname: Ho
authors.forename: Anna
authors.initials: A
authors.lastname: Gavryushova
authors.forename: Deepak
authors.initials: D
authors.lastname: Srivastava
authors.forename: Philip A
authors.initials: PA
authors.lastname: Marsden
mesh_terms: D000107:Acetylation; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D004265:DNA Helicases / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D052250:Nitric Oxide Synthase Type III / Q000096:biosynthesis*; D009687:Nuclear Proteins / Q000378:metabolism; D009707:Nucleosomes / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D006657:Histones; D009687:Nuclear Proteins; D009707:Nucleosomes; D014157:Transcription Factors; C077020:histone H2A.F-Z; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; C084108:SMARCA4 protein, human; D004265:DNA Helicases