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4NQO- or MNNG-resistant variants established from a human cell line, RSb, with high sensitivity to both agents
Abstract:
From a human cell line, RSb, with high sensitivity to the killing effects of 4-nitroquinoline 1-oxide (4NQO), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and 254-nm ultraviolet light, a 4NQO-resistant variant, Qr-10, and an MNNG-resistant one, Gr-10, were established using ethyl methanesulfonate as the mutagen. Cell proliferation studies and colony-formation assays revealed that Qr-10 and Gr-10 cells actively proliferated under conditions where RSb cell proliferation was greatly inhibited by 4NQO and MNNG, respectively. Total cellular DNA synthesis, as estimated by [Me-3H]thymidine uptake into acid-insoluble cell materials, was depressed in 4NQO-treated Qr-10 and MNNG-treated Gr-10 cells as it was in chemical-treated RSb cells, but recovered more markedly from such inhibition in the variants. 4NQO- and MNNG-induced DNA-repair replication synthesis was enhanced to a greater extent in Qr-10 and Gr-10 cells, respectively, than in RSb cells. The Qr-10 and Gr-10 cells showed the same respective susceptibility to the effects of MNNG and 4NQO, on cell growth and DNA synthesis and DNA-repair synthesis as did the parent cells. But, Qr-10 cells had more resistance to UV-killing and higher levels of UV-induced DNA-repair synthesis than did RSb cells, while UV-susceptibility of Gr-10 cells was the same as that of the latter.
Insights
Researchers developed resistant cell lines (Qr-10 and Gr-10) to study DNA repair mechanisms. These variants show enhanced DNA repair synthesis after exposure to specific damaging agents like 4-nitroquinoline 1-oxide (4NQO) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG).
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Human cell line RSb exhibits high sensitivity to DNA damaging agents: 4-nitroquinoline 1-oxide (4NQO), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and UV light.
- Understanding DNA repair mechanisms is crucial for cellular resistance and recovery from genotoxic stress.
Purpose of the Study:
- To establish and characterize cell lines resistant to specific DNA damaging agents.
- To investigate the DNA repair synthesis capabilities in these resistant variants.
Main Methods:
- Ethyl methanesulfonate was used as a mutagen to derive resistant variants (Qr-10 and Gr-10) from the sensitive RSb cell line.
- Cell proliferation, colony formation assays, and [Me-3H]thymidine incorporation were used to assess DNA synthesis and repair replication.
Main Results:
- Qr-10 (4NQO-resistant) and Gr-10 (MNNG-resistant) cells proliferated better than RSb cells when exposed to their respective damaging agents.
- Both variants showed more robust recovery of DNA synthesis and enhanced DNA repair replication synthesis compared to RSb cells.
- Qr-10 cells demonstrated increased resistance to UV light and higher UV-induced DNA repair synthesis, while Gr-10 cells retained similar UV sensitivity to RSb cells.
Conclusions:
- The developed resistant cell lines (Qr-10 and Gr-10) are valuable tools for studying differential DNA repair pathways.
- Enhanced DNA repair synthesis is a key mechanism conferring resistance to specific genotoxic agents.
- Cross-resistance patterns and differential repair capacities highlight the complexity of cellular responses to DNA damage.