A new X-ray sensitive CHO cell mutant of ionizing radiation group 7,XR-C2, that is defective in DSB repair but has only a mild defect in V(D)J recombination.
- Abstract:
- The DNA-dependent protein kinase (DNA-PK) complex plays a key role in DNA double-strand break (DSB) repair and V(D)J recombination. Using a genetic approach we have isolated cell mutants sensitive to ionizing radiation (IR) in the hope of elucidating the mechanism and components required for these pathways. We describe here, an X-ray-sensitive and DSB repair defective Chinese hamster ovary (CHO) cell line, XR-C2, which was assigned to the X-Ray Cross Complementation (XRCC) group 7. This group of mutants is defective in the XRCC7/SCID/Prkdc gene, which encodes the catalytic subunit of DNA-PK (DNA-PKcs). Despite the fact that XR-C2 cells expressed normal levels of DNA-PKcs protein, no DNA-PK catalytic activity could be observed in XR-C2, confirming the genetic analyses that these cells harbor a dysfunctional gene for DNA-PKcs. In contrast to other IR group 7 mutants, which contain undetectable or low levels of DNA-PKcs protein and which show a severe defect in V(D)J recombination, XR-C2 cells manifested only a mild defect in both coding and signal junction formation. The unique phenotype of the XR-C2 mutant suggests that a normal level of kinase activity is critical for radiation resistance but not for V(D)J recombination, whereas the overall structure of the DNA-PKcs protein appears to be of great importance for this process.
- Authors:
- A Errami, WJ Overkamp, DM He, AA Friedl, DA Gell, F Eckardt-Schupp, SP Jackson, EA Hendrickson, PH Lohman, MZ Zdzienicka
- Journal:
- Mutat Res
- Citation info:
- 461(1):59-69
- Publication date:
- 15th Sep 2000
- Full text
- DOI