Mitochondrial localization of APE/Ref-1 in thyroid cells.
Mutations of mitochondrial DNA (mtDNA) are associated with different human diseases, including cancer and aging. Reactive oxygen species produced during oxidative phosphorylation are a major source of mtDNA damage. It is not clear, however, whether DNA repair mechanisms, able to abolish effects due to oxidative damage, are present in mitochondria. APE/Ref-1 is a nuclear protein possessing both redox activity (by which activates, "in vitro", the DNA-binding functions of several transcription factors) and DNA repair activity over apurinic/apyrimidinic sites. Immunohistochemical evidences indicate that in follicular thyroid cells, APE/Ref-1 is located in both nucleus and cytoplasm. Electronmicroscopy immunocytochemistry performed in the rat thyroid FRTL-5 cell line, indicates that part of the cytoplasmatic APE/Ref-1 is located in mitochondria. The presence of APE/Ref-1 inside mitochondria is further demonstrated by western blot analysis after cell fractionation. In the Kimol cell line (which is derived from FRTL-5, transformed by the Ki-ras oncogene) the amount of mitochondrial APE/Ref-1 is reduced by three to fourfold with respect to the normal FRTL-5 cells. These results suggest that: (i) a machinery capable of repairing DNA damaged by oxidative stress is present in mitochondria and (ii) mtDNA repair mechanisms may be impaired during cell transformation.
Tell
G
G
Dipartimento di Biochimica Biofisica e Chimica delle Macromolecole, Università degli Studi di Trieste, Trieste, Italy. tell@bbcm.univ.trieste.it
Crivellato
E
E
Pines
A
A
Paron
I
I
Pucillo
C
C
Manzini
G
G
Bandiera
A
A
Kelley
M R
MR
Di Loreto
C
C
Damante
G
G
D000818:Animals; D019757:Carbon-Oxygen Lyases / Q000032:analysis / Q000378:metabolism*; D002460:Cell Line; D004260:DNA Repair; D004272:DNA, Mitochondrial / Q000378:metabolism; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D018384:Oxidative Stress; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D018631:ras Proteins / Q000378:metabolism
D004272:DNA, Mitochondrial; D017382:Reactive Oxygen Species; D018631:ras Proteins; D019757:Carbon-Oxygen Lyases; C470319:Apex1 protein, rat; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase