Mitochondrial targeting of human DNA glycosylases for repair of oxidative DNA damage.
Oxidative damage to mitochondrial DNA has been implicated in human degenerative diseases and aging. Although removal of oxidative lesions from mitochondrial DNA occurs, the responsible DNA repair enzymes are poorly understood. By expressing the epitope-tagged proteins in COS-7 cells, we examined subcellular localizations of gene products of human DNA glycosylases: hOGG1, hMYH and hNTH1. A gene encoding for hOGG1 which excises 7,8-dihydro-8-oxoguanine (8-oxoG) from DNA generates four isoforms by alternative splicing (types 1a, 1b, 1c and 2). Three tagged isoforms (types 1b, 1c and 2) were localized in the mitochondria. Type 1a protein, which exclusively contains a putative nuclear localization signal, was sorted to the nucleus and lesser amount to the mitochondria. hMYH, a human homolog gene product of Escherichia coli mutY was mainly transported into the mitochondria. hNTH1 protein excising several pyrimidine lesions was transported into both the nucleus and mitochondria. In contrast to the three DNA glycosylases, translocation of the human major AP endonuclease (hAPE) into the mitochondria was hardly observed in COS-7 cells. These results suggest that the previously observed removal of oxidative base lesions in mitochondrial DNA is initiated by the above DNA glycosylases.
Takao
M
M
Department of Molecular Genetics, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-77, Japan.
Aburatani
H
H
Kobayashi
K
K
Yasui
A
A
D000818:Animals; D016466:CHO Cells; D019556:COS Cells; D019757:Carbon-Oxygen Lyases / Q000032:analysis; D002467:Cell Nucleus; D006224:Cricetinae; D004249:DNA Damage; D045647:DNA Glycosylases; D004260:DNA Repair / Q000502:physiology*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D029968:Escherichia coli Proteins; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000201:enzymology*; D009699:N-Glycosyl Hydrolases / Q000032:analysis* / Q000235:genetics; D019913:Nuclear Localization Signals; D011993:Recombinant Fusion Proteins / Q000032:analysis; D014162:Transfection
D029968:Escherichia coli Proteins; D019913:Nuclear Localization Signals; D011993:Recombinant Fusion Proteins; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase; D019757:Carbon-Oxygen Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase