DNA single-strand break repair is impaired in aprataxin-related ataxia.
OBJECTIVE
Early-onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH)/ataxia with oculomotor apraxia type 1 (AOA1) is an autosomal recessive form of cerebellar ataxia. The causative protein for EAOH/AOA1, aprataxin (APTX), interacts with X-ray repair cross-complementing 1 (XRCC1), a scaffold DNA repair protein for single-strand breaks (SSBs). The goal of this study was to prove the functional involvement of APTX in SSB repair (SSBR).


METHODS
We visualized the SSBR process with a recently developed laser irradiation system that allows real-time observation of SSBR proteins and with a local ultraviolet-irradiation system using a XPA-UVDE cell line that repairs DNA lesions exclusively via SSBR. APTX was knocked down using small interference RNA in the cells. Oxidative stress-induced DNA damage and cell death were assessed in EAOH fibroblasts and cerebellum.


RESULTS
Our systems showed the XRCC1-dependent recruitment of APTX to SSBs. SSBR was impaired in APTX-knocked-down cells. Oxidative stress in EAOH fibroblasts readily induced SSBs and cell death, which were blocked by antioxidants. Accumulated oxidative DNA damage was confirmed in EAOH cerebellum.


CONCLUSIONS
This study provides the first direct evidence for the functional involvement of APTX in SSBR and in vivo DNA damage in EAOH/AOA1, and suggests a benefit of antioxidant treatment.
Hirano
Makito
M
Department of Neurology, Radioisotope Research Center, Nara Medical University, Nara, Japan. hirano_makito@yahoo.co.jp
Yamamoto
Aya
A
Mori
Toshio
T
Lan
Li
L
Iwamoto
Taka-aki
TA
Aoki
Masashi
M
Shimada
Keiji
K
Furiya
Yoshiko
Y
Kariya
Shingo
S
Asai
Hirohide
H
Yasui
Akira
A
Nishiwaki
Tomohisa
T
Imoto
Kyoko
K
Kobayashi
Nobuhiko
N
Kiriyama
Takao
T
Nagata
Tetsuya
T
Konishi
Noboru
N
Itoyama
Yasuto
Y
Ueno
Satoshi
S
D000328:Adult; D000818:Animals; D000911:Antibodies, Monoclonal; D016923:Cell Death; D002478:Cells, Cultured; D002524:Cerebellar Ataxia / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D002531:Cerebellum / Q000378:metabolism; D053904:DNA Breaks, Single-Stranded; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D004347:Drug Interactions; D004355:Drug Stability; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005808:Genes, Recessive; D006801:Humans; D007834:Lasers; D008297:Male; D009154:Mutation; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D018384:Oxidative Stress; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D014466:Ultraviolet Rays; D000076105:X-ray Repair Cross Complementing Protein 1
C438188:APTX protein, human; D000911:Antibodies, Monoclonal; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D018809:Proliferating Cell Nuclear Antigen; D034741:RNA, Small Interfering; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; D046988:Proteasome Endopeptidase Complex