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A screening method for isolating DNA repair-deficient mutants of CHO cells
Abstract:
A simple procedure for isolating mutagen-sensitive clones of CHO cells was developed and applied in mutant hunts in which colonies were screened for hypersensitivity to killing by ultraviolet radiation (UV, ethyl methanesulfonate (EMS), or mitomycin C (MMC). Each of two UV-sensitive clones studied in detail had a D37 dose of 1.0 J/m2 compared to 7.0 J/m2 for the wild-type cells, and each was shown to have no detectable repair replication following exposure to UV doses of up to 26 J/m2. Although these mutants resemble xeroderma pigmentosum human mutants with respect to their repair defect and cross-sensitivity to the carcinogen 4-nitroquinoline-1-oxide, one of two clones (UV-20) is characterized by extreme hypersensitivity to MMC (80-fold as compared to the wild type). Clones having hypersensitivity to alkylating agents, but not UV, were obtained using MMC and EMS. In the latter case the two clones had significantly increased sensitivity to the killing action of 60Co gamma-rays.
Insights
Researchers developed a method to find mutagen-sensitive Chinese hamster ovary (CHO) cell clones. These mutants show increased sensitivity to DNA-damaging agents like UV radiation and ethyl methanesulfonate (EMS).
Area of Science:
- Cell Biology
- Molecular Genetics
- Radiation Biology
Background:
- Identifying cells with defects in DNA repair mechanisms is crucial for understanding mutagenesis and developing cancer therapies.
- Chinese hamster ovary (CHO) cells are a widely used model system for genetic toxicology studies.
Purpose of the Study:
- To develop a straightforward procedure for isolating mutagen-sensitive clones of CHO cells.
- To screen these clones for hypersensitivity to killing by ultraviolet radiation (UV), ethyl methanesulfonate (EMS), and mitomycin C (MMC).
Main Methods:
- A novel mutant hunt procedure was employed to isolate mutagen-sensitive CHO cell clones.
- Colonies were screened for hypersensitivity to killing by UV radiation, EMS, and MMC.
- Detailed characterization of UV-sensitive clones included D37 dose determination and assessment of repair replication.
Main Results:
- Two UV-sensitive clones exhibited significantly reduced D37 doses (1.0 J/m2) compared to wild-type cells (7.0 J/m2) and lacked detectable repair replication after UV exposure.
- These UV-sensitive mutants showed cross-sensitivity to 4-nitroquinoline-1-oxide, similar to human xeroderma pigmentosum mutants.
- One clone (UV-20) displayed extreme hypersensitivity (80-fold) to MMC; other clones showed hypersensitivity to alkylating agents (EMS, MMC) but not UV, and increased sensitivity to gamma-rays.
Conclusions:
- The developed procedure effectively isolates mutagen-sensitive CHO cell clones with distinct DNA repair defects.
- The characterized mutants provide valuable tools for studying DNA repair pathways and the cellular response to genotoxic agents.
- The findings highlight the heterogeneity of DNA repair defects and their implications for sensitivity to various DNA-damaging agents.