Induction and repair of chromosome aberrations in scid cells measured by premature chromosome condensation.
Severe combined immunodeficient (scid) murine cells, which are defective in both repair of DNA double-strand breaks and V(D)J recombination, are deficient in DNA-dependent protein kinase (DNA-PK), a protein which forms an activated complex with the DNA end-binding Ku proteins (p80 and p70) upon association with damaged DNA. Xrs 5 cells are deficient in the Ku p80 protein and also fail to form an active DNA-PK repair complex. Since both scid and xrs cells are defective in the same protein complex, we compared the kinetics of chromosome repair in scid cells to results published previously for xrs 5 cells. C.B-17 cells, scid cells and scid cells complemented with a single human chromosome 8 were irradiated with 6 Gy and allowed to repair from 0-24 h before fusion to HeLa cells for chromosome condensation. Breaks and dicentrics were visualized by fluorescence in situ hybridization. All cells had the same initial amount of chromosome damage, but scid cells had a slower rate of rejoining, more unrejoined breaks and more dicentrics than C.B-17 and scid cells with human chromosome 8. The scid cells appear to respond differently than xrs 5 cells, despite both cells lacking an essential component of the same DNA repair complex.
Department of Radiation Oncology, Stanford University School of Medicine, California 94305-5468, USA.
J W
JW
Evans
X F
XF
Liu
C U
CU
Kirchgessner
J M
JM
Brown
D000465:Algorithms; D000818:Animals; D034961:Antigens, Nuclear; D002459:Cell Fusion; D002460:Cell Line; D002869:Chromosome Aberrations; D002875:Chromosomes / Q000502:physiology / Q000528:radiation effects*; D002898:Chromosomes, Human, Pair 8; D004249:DNA Damage; D004265:DNA Helicases; D004254:DNA Nucleotidyltransferases / Q000172:deficiency / Q000235:genetics; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007700:Kinetics; D000072200:Ku Autoantigen; D051379:Mice; D016513:Mice, SCID; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics; D011836:Radiation Tolerance; D016511:Severe Combined Immunodeficiency / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism; D045567:VDJ Recombinases
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D004254:DNA Nucleotidyltransferases; D045567:VDJ Recombinases; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen