Role of DNA-PK in the process of aberration formation as studied in irradiated human glioblastoma cell lines M059K and M059J.
OBJECTIVE
The participation of various DNA double-strand break repair mechanisms in the formation of chromosome aberrations is not yet fully understood. To investigate particularly the role of non-homologous end-joining, we analysed the formation of radiation-induced aberrations in a DNA-protein kinase (PK(CS))-proficient cell line M059K and in a deficient cell line M059J.


METHODS
Plateau-phase M059K and M059J cells were irradiated with low doses of X-rays. Chromosome aberrations were determined as genomic yields of dicentric chromosomes and excess acentric fragments, scored in Giemsa-stained metaphases, and as partial yields of reciprocal translocations and total visible complex exchanges (complex aberrations) for chromosomes 4, 7 and 11 using the FISH method. M059K cells were also analysed in the presence of 50 micro m wortmannin, a DNA-PK inhibitor.


RESULTS
DNA-PK-deficient cells showed a higher yield of simple stable and unstable and of complex aberrations in comparison with DNA-PK-proficient cells. The largest differences were observed for excess acentric fragments and for complex aberrations. DNA-PK inhibition by wortmannin in M059-K cells resulted in increased aberration yield in the same qualitative and quantitative manner as in M059-J cells.


CONCLUSIONS
The results obtained with DNA-PK-deficient M059J cells and with DNA-PK-proficient M059K cells treated with wortmannin, an inhibitor of DNA-PK and ATM, suggest that the elimination of DNA-PK-dependent non-homologous end-joining can recruit a slow, error-prone repair process, which is DNA-PK independent and favours the increased formation of chromosome aberrations. The nature of this pathway and the way of its participation in aberration formation need further elucidation.
Virsik-Köpp
P
P
Abteilung für Klinische Strahlenbiologie und Klinische Strahlenphysik, Georg-August-Universität Göttingen, D-37075 Göttingen, Germany. patricia.virsik@medizin.uni-goettingen.de
Rave-Fränk
M
M
Hofman-Hüther
H
H
Schmidberger
H
H
D000730:Androstadienes / Q000494:pharmacology; D002869:Chromosome Aberrations; D004249:DNA Damage; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D005909:Glioblastoma / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D014407:Tumor Cells, Cultured; D000077191:Wortmannin
D000730:Androstadienes; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D000077191:Wortmannin