A CHO-cell strain having hypersensitivity to mutagens, a defect in DNA strand-break repair, and an extraordinary baseline frequency of sister-chromatid exchange

L. H. Thompson, K. W. Brookman, L. E. Dillehay, A. V. Carrano, J. A. Mazrimas, C. L. Mooney, J. L. Minkler

Research output: Contribution to journalArticle

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Abstract

A mutant of CHO cells (strain EM9) previously isolated on the basis of hypersensitivity to killing by ethyl methanesulfonate (EMS) is approx. 10-fold more sensitive than the parental line, AA8, to killing by both EMS and MMS. It is also hypersensitive to killing by other alkylating agents (ethyl nitrosourea and N-methyl-N′-nitro-N′-nitrosoguanidine), X-rays, and ultraviolet radiation. The production and repair of DNA single-strand breaks (SSB) were studied using the technique of alkaline elution of DNA from filters. After exposure to 4 Gy of X-rays at 0°C and subsequent incubation at 25°C, SSb were repaired within 12 min in AA8, but little repair occurred in EM9. Similarly, with doses of EMS or MMS that produced comparable numbers of SSB in AA8 and EM9 at the end of a 10-min exposure, repair of SSB occurred more rapidly in AA8 than in EM9, suggesting that individual SSB are longer lived in EM9. EM9 was found to be hypersensitive also to the induction of mutations and sister-chromatid exchanges (SCE) by EMS; per unit dose the mutant had twice as many mutations to thioguanine resistance, 3 times as many mutations to azaadenine resistance, and a 7-fold enhancement in SCE, compared to AA8. Moreover, the baseline frequency of SCE in the mutant was extraordinarily high, i.e., 8.6 ± 0.6 vs. 107 ± 5 SCE/cell for AA8 and EM9, respectively, with 10 μM BrdUrd in the medium. The high frequency in EM9 did not vary significantly with BrdUrd concentration over the range examined from 2.5 to 20 μM, and the percentage of 5-bromouracil substitution in the DNA was the same in EM9 and AA8 under these conditions. These data, however, do not rule out the possibility that the high SCE frequency in EM9 is a consequence of an altered sensitivity to incorporated BrdUrd. Thus, EM9 may carry a pleiotropic mutation affecting some function in DNA replication and/or DNA repair and ausing the variety of phenotypic properties described in this study.

Original languageEnglish (US)
Pages (from-to)427-440
Number of pages14
JournalMutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
Volume95
Issue number2-3
DOIs
StatePublished - 1982
Externally publishedYes

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Sister Chromatid Exchange
DNA Breaks
CHO Cells
Ethyl Methanesulfonate
Mutagens
Hypersensitivity
Mutation
Bromouracil
X-Rays
Thioguanine
Single-Stranded DNA Breaks
Methylnitronitrosoguanidine
Alkylating Agents
DNA
DNA Replication
DNA Repair
Radiation

ASJC Scopus subject areas

  • Molecular Biology
  • Health, Toxicology and Mutagenesis
  • Medicine(all)

Cite this

A CHO-cell strain having hypersensitivity to mutagens, a defect in DNA strand-break repair, and an extraordinary baseline frequency of sister-chromatid exchange. / Thompson, L. H.; Brookman, K. W.; Dillehay, L. E.; Carrano, A. V.; Mazrimas, J. A.; Mooney, C. L.; Minkler, J. L.

In: Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis, Vol. 95, No. 2-3, 1982, p. 427-440.

Research output: Contribution to journalArticle

Thompson, L. H. ; Brookman, K. W. ; Dillehay, L. E. ; Carrano, A. V. ; Mazrimas, J. A. ; Mooney, C. L. ; Minkler, J. L. / A CHO-cell strain having hypersensitivity to mutagens, a defect in DNA strand-break repair, and an extraordinary baseline frequency of sister-chromatid exchange. In: Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis. 1982 ; Vol. 95, No. 2-3. pp. 427-440.
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abstract = "A mutant of CHO cells (strain EM9) previously isolated on the basis of hypersensitivity to killing by ethyl methanesulfonate (EMS) is approx. 10-fold more sensitive than the parental line, AA8, to killing by both EMS and MMS. It is also hypersensitive to killing by other alkylating agents (ethyl nitrosourea and N-methyl-N′-nitro-N′-nitrosoguanidine), X-rays, and ultraviolet radiation. The production and repair of DNA single-strand breaks (SSB) were studied using the technique of alkaline elution of DNA from filters. After exposure to 4 Gy of X-rays at 0°C and subsequent incubation at 25°C, SSb were repaired within 12 min in AA8, but little repair occurred in EM9. Similarly, with doses of EMS or MMS that produced comparable numbers of SSB in AA8 and EM9 at the end of a 10-min exposure, repair of SSB occurred more rapidly in AA8 than in EM9, suggesting that individual SSB are longer lived in EM9. EM9 was found to be hypersensitive also to the induction of mutations and sister-chromatid exchanges (SCE) by EMS; per unit dose the mutant had twice as many mutations to thioguanine resistance, 3 times as many mutations to azaadenine resistance, and a 7-fold enhancement in SCE, compared to AA8. Moreover, the baseline frequency of SCE in the mutant was extraordinarily high, i.e., 8.6 ± 0.6 vs. 107 ± 5 SCE/cell for AA8 and EM9, respectively, with 10 μM BrdUrd in the medium. The high frequency in EM9 did not vary significantly with BrdUrd concentration over the range examined from 2.5 to 20 μM, and the percentage of 5-bromouracil substitution in the DNA was the same in EM9 and AA8 under these conditions. These data, however, do not rule out the possibility that the high SCE frequency in EM9 is a consequence of an altered sensitivity to incorporated BrdUrd. Thus, EM9 may carry a pleiotropic mutation affecting some function in DNA replication and/or DNA repair and ausing the variety of phenotypic properties described in this study.",
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T1 - A CHO-cell strain having hypersensitivity to mutagens, a defect in DNA strand-break repair, and an extraordinary baseline frequency of sister-chromatid exchange

AU - Thompson, L. H.

AU - Brookman, K. W.

AU - Dillehay, L. E.

AU - Carrano, A. V.

AU - Mazrimas, J. A.

AU - Mooney, C. L.

AU - Minkler, J. L.

PY - 1982

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N2 - A mutant of CHO cells (strain EM9) previously isolated on the basis of hypersensitivity to killing by ethyl methanesulfonate (EMS) is approx. 10-fold more sensitive than the parental line, AA8, to killing by both EMS and MMS. It is also hypersensitive to killing by other alkylating agents (ethyl nitrosourea and N-methyl-N′-nitro-N′-nitrosoguanidine), X-rays, and ultraviolet radiation. The production and repair of DNA single-strand breaks (SSB) were studied using the technique of alkaline elution of DNA from filters. After exposure to 4 Gy of X-rays at 0°C and subsequent incubation at 25°C, SSb were repaired within 12 min in AA8, but little repair occurred in EM9. Similarly, with doses of EMS or MMS that produced comparable numbers of SSB in AA8 and EM9 at the end of a 10-min exposure, repair of SSB occurred more rapidly in AA8 than in EM9, suggesting that individual SSB are longer lived in EM9. EM9 was found to be hypersensitive also to the induction of mutations and sister-chromatid exchanges (SCE) by EMS; per unit dose the mutant had twice as many mutations to thioguanine resistance, 3 times as many mutations to azaadenine resistance, and a 7-fold enhancement in SCE, compared to AA8. Moreover, the baseline frequency of SCE in the mutant was extraordinarily high, i.e., 8.6 ± 0.6 vs. 107 ± 5 SCE/cell for AA8 and EM9, respectively, with 10 μM BrdUrd in the medium. The high frequency in EM9 did not vary significantly with BrdUrd concentration over the range examined from 2.5 to 20 μM, and the percentage of 5-bromouracil substitution in the DNA was the same in EM9 and AA8 under these conditions. These data, however, do not rule out the possibility that the high SCE frequency in EM9 is a consequence of an altered sensitivity to incorporated BrdUrd. Thus, EM9 may carry a pleiotropic mutation affecting some function in DNA replication and/or DNA repair and ausing the variety of phenotypic properties described in this study.

AB - A mutant of CHO cells (strain EM9) previously isolated on the basis of hypersensitivity to killing by ethyl methanesulfonate (EMS) is approx. 10-fold more sensitive than the parental line, AA8, to killing by both EMS and MMS. It is also hypersensitive to killing by other alkylating agents (ethyl nitrosourea and N-methyl-N′-nitro-N′-nitrosoguanidine), X-rays, and ultraviolet radiation. The production and repair of DNA single-strand breaks (SSB) were studied using the technique of alkaline elution of DNA from filters. After exposure to 4 Gy of X-rays at 0°C and subsequent incubation at 25°C, SSb were repaired within 12 min in AA8, but little repair occurred in EM9. Similarly, with doses of EMS or MMS that produced comparable numbers of SSB in AA8 and EM9 at the end of a 10-min exposure, repair of SSB occurred more rapidly in AA8 than in EM9, suggesting that individual SSB are longer lived in EM9. EM9 was found to be hypersensitive also to the induction of mutations and sister-chromatid exchanges (SCE) by EMS; per unit dose the mutant had twice as many mutations to thioguanine resistance, 3 times as many mutations to azaadenine resistance, and a 7-fold enhancement in SCE, compared to AA8. Moreover, the baseline frequency of SCE in the mutant was extraordinarily high, i.e., 8.6 ± 0.6 vs. 107 ± 5 SCE/cell for AA8 and EM9, respectively, with 10 μM BrdUrd in the medium. The high frequency in EM9 did not vary significantly with BrdUrd concentration over the range examined from 2.5 to 20 μM, and the percentage of 5-bromouracil substitution in the DNA was the same in EM9 and AA8 under these conditions. These data, however, do not rule out the possibility that the high SCE frequency in EM9 is a consequence of an altered sensitivity to incorporated BrdUrd. Thus, EM9 may carry a pleiotropic mutation affecting some function in DNA replication and/or DNA repair and ausing the variety of phenotypic properties described in this study.

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