Regulation of mitochondrial genome replication by hypoxia: The role of DNA oxidation in D-loop region.
Mitochondria of mammalian cells contain multiple copies of mitochondrial (mt) DNA. Although mtDNA copy number can fluctuate dramatically depending on physiological and pathophysiologic conditions, the mechanisms regulating mitochondrial genome replication remain obscure. Hypoxia, like many other physiologic stimuli that promote growth, cell proliferation and mitochondrial biogenesis, uses reactive oxygen species as signaling molecules. Emerging evidence suggests that hypoxia-induced transcription of nuclear genes requires controlled DNA damage and repair in specific sequences in the promoter regions. Whether similar mechanisms are operative in mitochondria is unknown. Here we test the hypothesis that controlled oxidative DNA damage and repair in the D-loop region of the mitochondrial genome are required for mitochondrial DNA replication and transcription in hypoxia. We found that hypoxia had little impact on expression of mitochondrial proteins in pulmonary artery endothelial cells, but elevated mtDNA content. The increase in mtDNA copy number was accompanied by oxidative modifications in the D-loop region of the mitochondrial genome. To investigate the role of this sequence-specific oxidation of mitochondrial genome in mtDNA replication, we overexpressed mitochondria-targeted 8-oxoguanine glycosylase Ogg1 in rat pulmonary artery endothelial cells, enhancing the mtDNA repair capacity of transfected cells. Overexpression of Ogg1 resulted in suppression of hypoxia-induced mtDNA oxidation in the D-loop region and attenuation of hypoxia-induced mtDNA replication. Ogg1 overexpression also reduced binding of mitochondrial transcription factor A (TFAM) to both regulatory and coding regions of the mitochondrial genome without altering total abundance of TFAM in either control or hypoxic cells. These observations suggest that oxidative DNA modifications in the D-loop region during hypoxia are important for increased TFAM binding and ensuing replication of the mitochondrial genome.
Department of Pharmacology and Center for Lung Biology, University of South Alabama College of Medicine, Mobile, AL 36688, USA. Electronic address: vpastukh@southalabama.edu.
Viktor M
VM
Pastukh
Department of Pharmacology and Center for Lung Biology, University of South Alabama College of Medicine, Mobile, AL 36688, USA. Electronic address: gorodnya@southalabama.edu.
Olena M
OM
Gorodnya
Department of Pharmacology and Center for Lung Biology, University of South Alabama College of Medicine, Mobile, AL 36688, USA. Electronic address: mgillesp@southalabama.edu.
Mark N
MN
Gillespie
Department of Pharmacology and Center for Lung Biology, University of South Alabama College of Medicine, Mobile, AL 36688, USA. Electronic address: mruchko@southalabama.edu.
Mykhaylo V
MV
Ruchko
D000818:Animals; D015687:Cell Hypoxia / Q000235:genetics*; D049109:Cell Proliferation / Q000235:genetics; D004249:DNA Damage / Q000235:genetics; D045647:DNA Glycosylases / Q000235:genetics*; D004261:DNA Replication / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D004268:DNA-Binding Proteins; D042783:Endothelial Cells / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D054629:Genome, Mitochondrial / Q000235:genetics; D006801:Humans; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D001678:Organelle Biogenesis; D018384:Oxidative Stress / Q000235:genetics*; D011651:Pulmonary Artery / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D017382:Reactive Oxygen Species; C489030:Tfam protein, rat; D014157:Transcription Factors; D045647:DNA Glycosylases; C483741:OGG1 protein, rat
D-loop; Hypoxia; Mitochondrial DNA replication; Ogg1 overexpression; Oxidative DNA modifications; Reactive oxygen species; TFAM binding