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      Isolation of mammalian cell mutants that are X-ray sensitive, impaired in DNA double-strand break repair and defective for V(D)J recombination.

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          Abstract

          The Chinese hamster lung V79-4 cell line was infected with a Moloney murine leukemia retrovirus and the infected cells were subsequently screened for mutants that were sensitive to X-rays using a toothpicking/96-well replica plating technique. Four independent mutants that were sensitive to X-irradiation (sxi-1 to sxi-4) were isolated from 9000 retrovirally infected colonies. A pulse-field gel electrophoresis (PFGE) assay demonstrated that all of the sxi mutants were impaired in DNA double-strand break (DSB) repair, thus providing a molecular explanation for the observed X-ray sensitivity. Interestingly, additional PFGE experiments demonstrated that for any given X-ray dose all of the mutants incurred more DNA DSBs than the parental V79-4 cell line indicating there may be some inherent fragility to sxi chromosomes. Cross-sensitivity to other DNA-damaging agents including bleomycin, mitomycin C and methyl methanesulfonate indicated that sxi-2, sxi-3 and sxi-4 appear to be specifically hypersensitive to genotoxic agents that cause DNA DSBs, whereas sxi-1 appeared to be hypersensitive to multiple types of DNA lesions. Lastly, in preliminary experiments all of the sxi mutants demonstrated an inability to carry out V(D)J recombination, a somatic DNA rearrangement process required for the assembly of lymphoid antigen receptor genes. Thus, the sxi cell lines have interesting phenotypes which should make them valuable tools for unraveling the mechanism(s) of DNA DSB repair and recombination in mammalian cells.

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          Author and article information

          Journal
          Mutat. Res.
          Mutation research
          0027-5107
          0027-5107
          May 1995
          : 336
          : 3
          Affiliations
          [1 ] Department of Molecular Biology, Cellular Biology and Biochemistry, Brown University, Providence, RI 02912, USA.
          Article
          0921-8777(95)00002-2
          7537861
          f8e0534c-46cd-4623-98fa-6f53824c489c
          History

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