Thymineless Mutagenesis in Bacteria

Kunz, Bernard A.

doi:10.1007/978-1-4613-2449-2_12

Cited by 2 publications

(3 citation statements)

References 68 publications

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“…The primary DNA lesions caused by UV-C light, MMS, and FdUrd are most likely repaired by several different enzymatic pathways in chloroplasts of C. reinhardtii (13,37,43,57). However, these genotoxic agents also induce secondary lesions, such as double-strand breaks, interstrand cross-links, and/or damage in single-stranded regions, that require recombination for their repair (7,18,25,37,43,44,58). In fact, recombinational repair in E. coli seems to overcome, at least partially, the damage induced by many different genotoxic compounds (7,18,58).…”

Section: Resultsmentioning

confidence: 99%

“…Since the ⌬N42recA transformants are defective in chloroplast DNA repair and recombination, the marked reduction in hybridizable plastid DNA induced by MMS and FdUrd might reflect increased degradation of damaged genomes, as observed in recA mutants of E. coli exposed to DNA-damaging agents (37,56,63). However, the ⌬N42RecA protein may also affect the replication of chloroplast DNA under genotoxic stress.…”

Section: Discussionmentioning

confidence: 99%

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Inhibition of Chloroplast DNA Recombination and Repair by Dominant Negative Mutants of Escherichia coli RecA

Cerutti

Johnson

Boynton

et al. 1995

Molecular and Cellular Biology

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The occurrence of homologous DNA recombination in chloroplasts is well documented, but little is known about the molecular mechanisms involved or their biological significance. The endosymbiotic origin of plastids and the recent finding of an Arabidopsis nuclear gene, encoding a chloroplast-localized protein homologous to Escherichia coli RecA, suggest that the plastid recombination system is related to its eubacterial counterpart. Therefore, we examined whether dominant negative mutants of the E. coli RecA protein can interfere with the activity of their putative homolog in the chloroplast of the unicellular green alga Chlamydomonas reinhardtii. Transformants expressing these mutant RecA proteins showed reduced survival rates when exposed to DNA-damaging agents, deficient repair of chloroplast DNA, and diminished plastid DNA recombination. These results strongly support the existence of a RecA-mediated recombination system in chloroplasts. We also found that the wild-type E. coli RecA protein enhances the frequency of plastid DNA recombination over 15-fold, although it has no effect on DNA repair or cell survival. Thus, chloroplast DNA recombination appears to be limited by the availability of enzymes involved in strand exchange rather than by the level of initiating DNA substrates. Our observations suggest that a primary biological role of the recombination system in plastids is in the repair of their DNA, most likely needed to cope with damage due to photooxidation and other environmental stresses. This hypothesis could explain the evolutionary conservation of DNA recombination in chloroplasts despite the predominantly uniparental inheritance of their genomes.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Inhibition of Chloroplast DNA Recombination and Repair by Dominant Negative Mutants of Escherichia coli RecA

Cerutti

Johnson

Boynton

et al. 1995

Molecular and Cellular Biology

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“…Mutagenesis as a result of nucleotide pool perturbations has been examined in a number of eukaryotic (1)(2)(3)(4)(5) and prokaryotic (6,7) systems. In cultured mammalian cells, alteration of the intracellular precursor pools can result in mutations (8,9) and in gross chromosomal abnormalities, such as large deletions (10), breaks (11), and sister chromatid exchanges (12).…”

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confidence: 99%

Thymidine-induced mutations in mammalian cells: sequence specificity and implications for mutagenesis in vivo.

Kresnak

Davidson

1992

Proc. Natl. Acad. Sci. U.S.A.

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Imbalances in the intracellular nucleotide precursor pools in mammalian cells can result in the induction of mutations during the DNA replication process. By using a shuttle vector system developed in our laboratory, we have analyzed the sequence specificity of mutations induced in mouse A9 cells by exposure of the cells to a high concentration of thymidine. The target for mutagenesis in these studies was the bacterial gpt gene stably integrated into the chromosomal DNA of the mouse cells. Previous studies in this laboratory had generated a large panel of xanthine guanine phosphoribosyltransferase (EC 2.4.2.22)-negative mutant lines that possess single-base mutations within the gpt coding sequence. This study utilized four xanthine guanine phosphoribosyltransferase-negative mutant lines to assess the frequency ofmutation induced by thymidine at guanine residues in four sequence contexts: the 5' and 3' guanine residues of a GG doublet, the middle guanine residue of a GGG triplet, and the 3' guanine residue of a GGGG quartet. The results of this study demonstrate that treatment of cultured cells with a high concentration of thymidine can result in G-C -A-T transition mutations that occur preferentially at the 3' ganine residue of a run of two or more adjacent guanines. Guanine residues flanked on their 3' side by other guanine residues are severalfold less mutable by thymidine than are guanine residues flanked on their 3' side by a different base. This study demonstrates a sequence-specific mode for thymidine-induced mutations and suggests implications for mutagenesis in vivo.The fidelity of DNA replication in mammalian cells strongly depends upon a balanced supply of deoxyribonucleotide triphosphates available as precursors for DNA synthesis. Mutagenesis as a result of nucleotide pool perturbations has been examined in a number of eukaryotic (1-5) and prokaryotic (6, 7) systems. In cultured mammalian cells, alteration of the intracellular precursor pools can result in mutations (8,9) and in gross chromosomal abnormalities, such as large deletions (10), breaks (11), and sister chromatid exchanges (12). Thymidylate deprivation induces mutation in bacteriophage T4 (13), mitotic recombination in yeast (14), and the RecAdependent error-prone response in Escherichia coli (15). Precursor pool imbalances also disrupt the accuracy of DNA synthesis in cell-free DNA replication systems (16, 17).In cultured mammalian cells, perturbation of the intracellular nucleotide precursor pools can be accomplished by exposing the cells to high concentrations of exogenous deoxyribonucleosides or their analogs. One commonly used agent is the thymidine analog 5-bromodeoxyuridine (BrdUrd). Apparently, high levels of exogenous BrdUrd disrupt intracellular deoxycytidine metabolism (through inhibition of the enzyme ribonucleotide reductase) such that the dCTP pools available for DNA synthesis are reduced (18)(19)(20), resulting in misincorporation of BrdUrd opposite guanine residues. Experiments involving mutagenesis of a bacterial gp...

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Thymineless Mutagenesis in Bacteria

Cited by 2 publications

References 68 publications

Inhibition of Chloroplast DNA Recombination and Repair by Dominant Negative Mutants of Escherichia coli RecA

Inhibition of Chloroplast DNA Recombination and Repair by Dominant Negative Mutants of Escherichia coli RecA

Thymidine-induced mutations in mammalian cells: sequence specificity and implications for mutagenesis in vivo.

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