Analysis of trifluorothymidine-resistant (TFTr) mutants of L5178Y/TK+/− mouse lymphoma cells

Moore, Martha M.; Clive, D.; Hozier, John; Howard, Barry E.; Batson, Amie; Turner, Nancy A.; Sawyer, Jeffrey R.

doi:10.1016/0027-5107(85)90194-0

Cited by 145 publications

(53 citation statements)

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confidence: 54%

“…It was observed that 90% of X-rayinduced tk-mutants were slowly growing, suggesting that a gene needed for rapid cell growth is located near tk (53). Consistent with this idea, slow-growth mutants were found to be associated with cytogenetically visible alterations (24,25,54,55). More recently, Applegate et al (5) reported that slowgrowth mutants exhibited loss of heterozygosity (LOH) at tk, and resulted from both deletion and recombinational events.…”

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confidence: 89%

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Different capacities for recombination in closely related human lymphoblastoid cell lines with different mutational responses to X-irradiation.

Xia¹,

Amundson²,

Nickoloff³

et al. 1994

Mol. Cell. Biol.

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WIL2-NS and TK6 are two distinct human lymphoblast cell lines derived from a single male donor. WIL2-NS cells are significantly more resistant to the cytotoxic effects of X-irradiation but considerably more sensitive to induced mutation. In an effort to determine the mechanistic basis for these differences, we analyzed the physical structures of thymidine kinase (tk)-deficient mutants isolated after X-ray treatment of tk heterozygotes derived from TK6 and the more mutable WIL2-NS. Southern analysis showed that while 84% of TK6-derived mutants had arisen by loss of heterozygosity (LOH), all 106 mutants from WIL2-NS derivatives arose with LOH at tk and all but one showed LOH at other linked loci on chromosome 17. We adapted a fluorescence in situ hybridization technique to distinguish between LOH due to deletion, which results in retention of only one tk allele, and LOH due to a mechanism involving the homologous chromosome (e.g., recombination), which results in the retention of two alleles. Among the LOH mutants derived that were analyzed in this way, 9 of 26 from WIL2-NS and 11 of 17 from TK6 cell lines arose by deletion. The remaining mutants retained two copies of the tk gene and thus arose by a mechanism involving the homologous allele. Since many of these mutants arising by a homologous mechanism retained partial heterozygosity of chromosome 17, they must have arisen by recombination or gene conversion, and not chromosome loss and reduplication. Finally, the recombinational capacities of WIL2-NS and TK6 were compared in transfection assays with plasmid recombination substrates. Intermolecular recombination frequencies were greater in WIL2-NS than in TK6. These data are consistent with a model suggesting that a recombinational repair system is functioning at a higher level in WIL2-NS than in TK6; the greater mutability of the tk locus in WIL2-NS results from more frequent inter-and intramolecular recombination events.Mutations that activate oncogenes or inactivate tumor suppressors are intimately involved in carcinogenic pathways. Therefore, it is important to study factors that affect mutation rates in human cells, because this will improve our understanding of cancer risk from environmental exposures and spontaneous processes. A number of studies suggest that the frequencies at which mutations are observed at various gene targets vary tremendously, depending on their location in the genome (reviewed in reference 56). Single gene mutations that inactivate a genetic locus are theoretically equally likely to occur at hemizygous loci (+/0: one active allele, no homologous allele) or heterozygous loci (+/-: one active and one inactive allele). Very large deletions may have a higher probability of being lethal if they span hemizygous regions of the genome and include an essential locus, while loss of one copy of such loci from chromosomal regions that exist in duplicate may not be lethal. Homologous recombination or gene conversion, processes that can convert a heterozygous locus to a homozygous state (-/-, with...

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confidence: 54%

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confidence: 89%

Different capacities for recombination in closely related human lymphoblastoid cell lines with different mutational responses to X-irradiation.

Xia¹,

Amundson²,

Nickoloff³

et al. 1994

Mol. Cell. Biol.

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“…Similarly, in the TK mutation test, cells deˆcient in thymidine kinase due to the mutation of TK ＋/-to TK -/-are resistant to the cytotoxic eŠects of the pyrimidine analogue tri‰uorothymidine (TFT). Thus mutant cells are selected in the presence of TFT (23). However, the HPRT gene mutation assay and TK gene mutation assay detect diŠerent spectra of genetic events: the former detects only intragenic mutations such as point mutations and small deletions (24), while the latter is capable of detecting a wide range of mutational events, including point mutations, large scale chromosomal changes, recombination, aneuploidy and others (25).…”

Section: Mammalian Gene Mutation Assays At the Hprt And Tk Locimentioning

confidence: 99%

Genotoxicity of Acrylamide and Glycidamide: A Review of the Studies by HPRT Gene and TK Gene Mutation Assays

Cao

2012

Genes and Environment

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Acrylamide (AA), a proven rodent carcinogen, is found in a variety of commonly consumed human foods, which has raised public health concerns. AA is largely oxidized to the chemically reactive epoxide, glycidamide (GA), by cytochrome P450 2E1. The genotoxic eŠects of AA and GA have been extensively evaluated. However, the results in mammalian gene mutation tests were inconsistent, especially the genotoxic eŠects at the HPRT gene and TK gene. In this article, the relevant mutations induced by AA and GA on both gene loci in various test systems involving in vivo and in vitro tests are reviewed. It is conˆrmed that AA acts directly as a clastogen and produces weakly mutagenic eŠects at the HPRT gene probably by metabolic conversion of AA to GA. On the other hand, GA is a strong mutagen with high reactivity to DNA, inducing predominantly point mutations. The molecular mutation spectra of AA and GA at the HPRT and TK genes are also compared and summarized here, for better clarifying the mechanisms of mutation induced by these two compounds. These data would help to understand the mutagenicity of AA and its contribution to human cancers.

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“…Les mutants à la croissance normale et à la croissance faible sont reconnus sous forme de grande colonie ou de petite colonie de mutants dans l'essai MLA, et en tant que colonie de mutants apparaissant précocement ou tardivement dans l'essai sur TK6. La nature moléculaire et cytogénétique des deux sortes de colonies de mutants dans l'essai MLA (petites et grandes) a été étudiée en détail (8) (10) (11) (12) (13). La nature moléculaire et cytogénétique des mutants TK6 apparaissant précocement et tardivement a aussi été largement étudiée (14) (15) (16) (18).…”

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Essai n° 490 : Essai In Vitro de Mutation Génique Sur Cellules de Mammifères Utilisant le Gène de la Thymidine Kinase

2016

Lignes Directrices De l'OCDE Pour Les Essais De Produits Chimiques, Section 4

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Analysis of trifluorothymidine-resistant (TFTr) mutants of L5178Y/TK+/− mouse lymphoma cells

Cited by 145 publications

References 30 publications

Different capacities for recombination in closely related human lymphoblastoid cell lines with different mutational responses to X-irradiation.

Different capacities for recombination in closely related human lymphoblastoid cell lines with different mutational responses to X-irradiation.

Genotoxicity of Acrylamide and Glycidamide: A Review of the Studies by HPRT Gene and TK Gene Mutation Assays

Essai n° 490 : Essai In Vitro de Mutation Génique Sur Cellules de Mammifères Utilisant le Gène de la Thymidine Kinase

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