Temperature-dependence of lethal and mutagenic actions of HNO2 on phage T4

Ishiwa, Hiromi; Yan, Yonhon; Kondo, Sohei

doi:10.1016/0926-6550(64)90181-1

Cited by 3 publications

(2 citation statements)

References 6 publications

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“…§ In doing so, it was found (curves and calculations not shown) that Amps AmpR activation energies were 2.2 eV (SG902) and 2.0 eV (DG17), while those for the Rifs --RifR reaction amounted to 2.4 eV (SG902) and 0.8 eV (DG17) (1 eV = 1.6 X 10-'9 J). Similar values of activation energy have been reported for spontaneous or induced mutations in bacteriophage T4 (9,22), and for spontaneous mutations in E. coli strains with polA or recA defects (9). The differences in activation energies may imply that different mechanisms or pathways of mutation are involved in the two classes of mutation reactions and in the two strains that we observed.…”

supporting

confidence: 63%

Mutator action by Escherichia coli strains carrying dnaE mutations

Sevastopoulos

Glaser

1977

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

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Several newly isolated temperature-sensitive dnaE mutants of Escherichia coli exhibit powerful mutagenic action at permissive temperatures. Mutation rates for the two most active mutants were assayed at four different temperatures and compared to wild-type behavior. Temperature-resistant revertants of the original temperature-sensitive dnaE mutants exhibited lower, nearly normal, mutation rates, but no antimutator strains were found.The appearance of new mutants in a population is an essential part of the evolution of a species. It is now believed that most, if not all, spontaneous mutations arise as errors in DNA replication, recombination, or repair. Mutation rates are genetically controlled and genes that lead to an appreciable alteration in the rate of mutation of other genes have been recognized and studied in several organisms (1-6). These mutation-controlling genes, which can carry mutations themselves, are known as mutator or antimutator genes, depending on whether their effect results in an increase or decrease of spontaneous mutation rates. In bacteriophage T4, for example, some mutant alleles of gene 43 (the structural gene for the phage DNA polymerase) act as mutators (3, 7); other mutations in the same gene 43 act as antimutators (7). These studies suggest that the wild-type rate in T4 is not the theoretically possible minimum, again suggesting that mutation rates can be adjusted by selection. How the polymerase is involved in control of mutation rates is not fully understood, but recent results with T4 suggest that spontaneous mutation rates reflect relative rates of polymerization and proofreading during DNA synthesis (8); mutations altering the normal ratio of 5'-to-3' polymerase activity to 3'-to-5' exonuclease "editing" activity might act as mutators when the ratio is increased, and as antimutators when the ratio is decreased.In Escherichia coli, at least two classes of mutants with altered DNA polymerase, polA (9) and dnaE (10), have been shown to increase the spontaneous mutation rate to a small extent, i.e., they exhibit mild mutator activity. There are at least six other known mutator genes in E. coli, all causing dramatic increases in mutation rates; one of these, mutT, may be involved in DNA replication because DNA synthesis is required for mutT action (6, 11). Little is known about the enzymatic functions of the E. coli mutator genes (6).Because no antimutator activity has ever been observed in E. coil, we decided to screen our collection of newly isolated temperature-sensitive strains (12), defective in DNA replication (dnats mutants), for mutator/antimutator effects at permissive temperatures. The mutagenic character of these dnat, strains was studied by measuring mutation frequencies at 340 for three independent mutational events: reversion to leucine independence (Leu -Leu+) and acquisition of resistance to L-valine and 6-azauracil (Vals -, VaIR, Azas -AzaR). These events were selected for experimental convenience and also to facilitate comparisons with previously reported mu...

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supporting

confidence: 63%

Mutator action by Escherichia coli strains carrying dnaE mutations

Sevastopoulos

Glaser

1977

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

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“…However, these reagents also block or remove amino groups on nucleic acid bases, leading to disruption of hydrogenbonded base pairs and disorganization of helical secondary structure. Dilute solutions of nitrous acid, in fact, are commonly used (9,11, and references cited therein) to produce controlled alterations of DNA molecules. Thus, experiments with these reagents will not decide the relative importance of protein binding and nucleic acid secondary structure in determining the staining of nucleoproteins.…”

Section: Mechanism Of Differential Staining Of Nucleic Adds In Tissuementioning

confidence: 99%

Studies on Nucleic Acid Metachromasy

Feder

Wolf

1965

The Journal of Cell Biology

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Acrolcin-fixed, polyester wax-cmbcddcd tissue sections showed excellent preservation of light microscopic architecture and, when stained with toluidinc blue, intense color contrast between DNA, which stained orthochromatically, and RNA, which stained metachromatically. This method has practical value for differentiating DNA from RNA in the same section. The color c~)ntrast was impaired by substituting formaldehyde for acrolcin or paraffin for polyester wax, and was ncgligible in tissues fixed in formaldehyde or Carnoy's fluid and cmbeddcd in paraffin. Quality of structural preservation paralleled degrcc of color contrast. Mctachromatic staining can be analysed, by the quantitative parameters of Bradley and colleagues, to provide inferences regarding the conformation of biopolymers in tissue sections. Comparison of the nucleic acid color contrasts in toluidine bluc-stained sections with titrations of fixative-treated nuclcic acids against toluidine blue in solution indicated a grcater difference in conformation betwecn DNA-and RNA-protein in acroleinpolyester sections than between acrolein-trcated frce DNA and RNA in solution. This is supported by recent cvidencc that the conformation of ribosomal RNA is quite different in whole ribosomes from that assumed by the same RNA free in solution. The acrolcinpolyester method may enhance color contrast by providing superior preservation of ordered nucleoprotein conformations.

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Effects of nitrous acid treatment on the survival and mutagenesis of Escherichia coli cells lacking base excision repair(hypoxanthine-DNA glycosylase-ALK A protein) and/or nucleotide excision repair

1997

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Deoxyinosine occurs in DNA by spontaneous deamination of adenine or by incorporation of dITP during replication. Hypoxanthine residues (HX) are mutagenic and give rise to A-T-->G-C transition. They are substrates for the Escherichia coli product of the alkA gene, the 3-methyl-adenine-DNA glycosylase II (ALK A protein). In mammalian cells and in yeast, HX is excised by the counterpart of ALK A protein, the ANPG or the MAG proteins respectively. We have investigated in vivo the contribution of the alkA gene to counteract the lethal and/or mutagenic effects of HX residues induced by nitrous acid treatment. Using an E.coli strain allowing the detection of A-T-->G-C transition, we show that the alkA mutant has a slightly increased spontaneous rate of mutation and about the same sensitivity when treated with HNO2 as compared with the wild-type strain. Using the E.coli alkA mutant carrying a multicopy plasmid expressing the ALK A protein or the ANPG protein, we barely observe any effect of HNO2 treatment on sensitivity and mutation rate of the bacteria. In contrast, the same experiment performed with a uvrA- strain, deficient in nucleotide excision repair (NER), shows that this mutant is extremely sensitive to HNO2 treatment. Furthermore, the sensitivity and the spontaneous mutation rate observed in the double mutant alkA- uvrA- are almost identical to those of the uvrA- mutant. Hence, NER has the major role in vivo for the repair of lethal and mutagenic lesions induced by HNO2.

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Temperature-dependence of lethal and mutagenic actions of HNO2 on phage T4

Cited by 3 publications

References 6 publications

Mutator action by Escherichia coli strains carrying dnaE mutations

Mutator action by Escherichia coli strains carrying dnaE mutations

Studies on Nucleic Acid Metachromasy

Effects of nitrous acid treatment on the survival and mutagenesis of Escherichia coli cells lacking base excision repair(hypoxanthine-DNA glycosylase-ALK A protein) and/or nucleotide excision repair

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