title: Activation of the carbohydrate response element binding protein (ChREBP) in response to anoxia in the turtle Trachemys scripta elegans.
abstract: BACKGROUND
  ChREBP (carbohydrate response element binding protein) is a glucose-responsive transcription factor that is known to be an important regulator of glycolytic and lipogenic genes in response to glucose. We hypothesized that activation of ChREBP could be relevant to anoxia survival by the anoxia-tolerant turtle, Trachemys scripta elegans.
  
  
  METHODS
  Expression of ChREBP in response to 5 and 20h of anoxia was examined using RT-PCR and Western immunoblotting. In addition, subcellular localization and DNA-binding activity of ChREBP protein were assessed and transcript levels of liver pyruvate kinase (LPK), a downstream gene under ChREBP control were quantified using RT-PCR.
  
  
  RESULTS
  ChREBP was anoxia-responsive in kidney and liver, with transcript levels increasing by 1.2-1.8 fold in response to anoxia and protein levels increasing by 1.8-1.9 fold. Enhanced nuclear presence under anoxia was also observed in both tissues by 2.2-2.8 fold. A 4.2 fold increase in DNA binding activity of ChREBP was also observed in liver in response to 5h of anoxia. In addition, transcript levels of LPK increased by 2.1 fold in response to 5h of anoxia in the liver.
  
  
  CONCLUSIONS
  The results suggest that activation of ChREBP in response to anoxia might be a crucial factor for anoxia survival in turtle liver by contributing to elevated glycolytic flux in the initial phases of oxygen limitation.
  
  
  CONCLUSIONS
  This study provides the first demonstration of activation of ChREBP in response to anoxia in a natural model of anoxia tolerance, further improving our understanding of the molecular nature of anoxia tolerance.
authors.affiliation: Institute of Biochemistry, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada. Electronic address: krivoruchko@gmail.com.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Krivoruchko
authors.affiliation: Institute of Biochemistry, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada.
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Storey
mesh_terms: D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D000860:Hypoxia / Q000378:metabolism* / Q000473:pathology; D008099:Liver / Q000378:metabolism*; D011770:Pyruvate Kinase / Q000096:biosynthesis*; D013997:Time Factors; D014426:Turtles
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D011770:Pyruvate Kinase
keywords: Anoxia; ChREBP; Metabolic depression; Pyruvate kinase; Red-eared slider