Reduced joining of DNA double strand breaks with an abnormal mutation spectrum in rodent mutants of DNA-PKcs and Ku80.
OBJECTIVE
To characterize further the contribution of the DNA-PK-dependent dsb repair pathway in mammalian cells.


METHODS
The efficiency and fidelity of the joining of linear plasmids by DNA-PKcs-defective mouse cells (SCID) and Ku80-defective Chinese hamster ovary cells (xrs-6) was measured using either linear or circular replicating shuttle vector pZ189.


RESULTS
The authors found a 3.9-10.7-fold reduced joining of the DNA ends, as compared with wild-type cells. Mutation analysis of the joining site revealed that the joining process was not hypermutable in the mutated cells. However, the SCID and xrs-6 cells produced a different spectrum of mutations at the joining site with a significantly lower proportion of insertions or more complex mutations.


CONCLUSIONS
The remaining joining ability of the mutant cells points to an alternative DNA-PK-independent pathway of dsb repair. Comparison of these data with similar data from yeast suggest that the postulated alternative pathway of dsb repair is at least as efficient and less error-prone in rodent cells.
Tzung
T Y
TY
Department of Dermatology, Georg-August University, Göttingen, Germany.
Rünger
T M
TM
D016475:3T3 Cells / Q000378:metabolism; D000818:Animals; D034961:Antigens, Nuclear; D016466:CHO Cells / Q000378:metabolism; D006224:Cricetinae; D004247:DNA / Q000235:genetics* / Q000378:metabolism*; D004249:DNA Damage; D004265:DNA Helicases; D004260:DNA Repair; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004270:DNA, Circular / Q000235:genetics / Q000378:metabolism; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D000072200:Ku Autoantigen; D051379:Mice; D016513:Mice, SCID; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D014162:Transfection; D014169:Transformation, Bacterial
D034961:Antigens, Nuclear; D004269:DNA, Bacterial; D004270:DNA, Circular; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; C081647:high affinity DNA-binding factor, S cerevisiae; D004247:DNA; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen