Response of ataxia telangiectasia cells to restriction endonuclease induced DNA double-strand breaks: I. Cytogenetic characterization.
Ataxia telangiectasia (AT) and normal human lymphoblastoid cell lines have been treated with either X-rays or the restriction endonucleases PvuII and BamHI using streptolysin-O poration, and the frequencies of micronuclei or chromosomal aberrations measured. We report that AT cells (AT-PA) are hypersensitive to the restriction endonucleases PvuII and BamHI, inducing DNA double-strand breaks (dsb) with either blunt or cohesive termini, respectively. Our data indicates that AT-PA cells have a dsb processing defect that leads to a higher rate of conversion of dsb into chromosomal aberrations than in normal cells. AT-PA cells showed up to a 5-fold enhanced sensitivity to PvuII over the normal (N-SW) line, a result of an increase in frequencies of chromatid aberrations. Chromosome-type aberrations appeared not to be increased in AT-PA cells over those induced in the normal N-SW line. Particularly striking was the appearance in AT-PA of high frequencies of chromatid aberrations at the 24 h sampling time. BamHI also caused enhanced aberration frequencies in AT-PA cells although the cohesive-ended dsb caused by BamHI still appeared to be less effective in causing chromosomal aberrations than the blunt-ended dsb caused by PvuII in both AT-PA and N-SW, as we have previously reported for Chinese hamster cells. The enhanced effectiveness of cohesive-ended dsb in AT-PA cells over normal cells may be a result of altered processing of dsb by AT-PA cells or may be caused by conversion of some cohesive-ended dsb into blunt-ended dsb by exonuclease digestion before ligation can take place.
Liu
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School of Biological and Medical Sciences, University of St Andrews, Fife, UK.
Bryant
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PE
D001260:Ataxia Telangiectasia / Q000473:pathology*; D001426:Bacterial Proteins; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D004247:DNA / Q000187:drug effects* / Q000528:radiation effects; D004249:DNA Damage; D015245:Deoxyribonuclease BamHI / Q000494:pharmacology*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000494:pharmacology*; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D015162:Micronucleus Tests; D013301:Streptolysins / Q000494:pharmacology
D001426:Bacterial Proteins; D013301:Streptolysins; C025964:streptolysin O; D004247:DNA; D015245:Deoxyribonuclease BamHI; C025630:CAGCTG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific