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L M Kemp

Publications and source records attributed to L M Kemp.

21 records · Page 2Linked to original sources
PubMed1983

X-ray-sensitive mutants of Chinese hamster ovary cell line. Isolation and cross-sensitivity to other DNA-damaging agents.

A standard technique of microbial genetics, which involves the transfer of cells from single colonies by means of sterile toothpicks, has been adapted to somatic cell genetics. Its use has been demonstrated in the isolation of X-ray-sensitive mutants of CHO cells. 9000 colonies have been tested and 6 appreciably X-ray-sensitive mutants were isolated. (D10 values 5-10-fold of wild-type D10 value.) A further 6 mutants were obtained which showed a slight level of sensitivity (D10 values less than 2-fold of wild-type D10 value). The 6 more sensitive mutants were also sensitive to bleomycin, a chemotherapeutic agent inducing X-ray-like damage. Cross-sensitivity to UV-irradiation and treatment with the alkylating agents, MMS, EMS and MNNG, was investigated for these mutants. Some sensitivity to these other agents was observed, but in all cases it was less severe than the level of sensitivity to X-irradiation. Each mutant showed a different overall response to the spectrum of agents examined and these appear to represent new mutant phenotypes derived from cultured mammalian cell lines. One mutant strain, xrs-7, was cross-sensitive to all the DNA-damaging agents, but was proficient in the repair of single-strand breaks.

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PubMedDate not supplied

X-ray sensitive mutants of Chinese hamster ovary cells defective in double-strand break rejoining.

Six CHO mutants have previously been described as being sensitive to ionizing radiation and bleomycin treatment, with little or no cross sensitivity to UV-radiation (Jeggo and Kemp, 1983). Their ability to rejoin single- and double-strand breaks has been examined here. Using two techniques, gradient sedimentation and alkaline elution, no difference could be observed between wild-type and mutant strains in the initial number of single-strand breaks induced, the rate of rejoining, or the final level of single-strand breaks rejoined. Thus, a major inability to rejoin single-strand breaks is not the basis for sensitivity in these mutants. In contrast, all 6 mutants showed a decreased ability to rejoin the double-strand breaks induced by gamma-irradiation as measured by neutral elution. Rejoining of half of the breaks occurred in 37 min in wild-type cells and reached a maximum level of 72% after 2 h. All the mutants showed a decreased rate of rejoining, and the final level was 17% of that observed in the wild-type in the most defective mutant, and ranged from 35 to 69% in the other 5 mutants. These are the first mammalian cell mutants to be described with a defect in double-strand break rejoining.

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