Hypermutation in derepressed operons of<i>Escherichia coli</i>K12

Wright, Barbara E.; Longacre, Angelika; Reimers, Jacqueline M.

doi:10.1073/pnas.96.9.5089

Cited by 72 publications

(89 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Conditions for growth and determination of mutation rates have been previously described (Wright, 1996;Wright & Minnick, 1997;Wright et al, 1999). A large culture was inoculated with cells from a 7 h old nutrient agar plate and 1?5 ml aliquots were distributed into 40 2 cm diameter test tubes, which were shaken at a 45u angle at 37 uC until the supply of the limiting amino acid was exhausted and growth ceased.…”

Section: Methodsmentioning

confidence: 99%

“…Previous investigations with multiple auxotrophs of E. coli (CP78 and CP79, which are isogenic except for relA) have demonstrated a positive correlation between reversion rates in the leuB gene, ppGpp levels, and the concentration of leuB mRNA after 15 min of leucine starvation (Wright et al, 1999;Wright & Minnick, 1997). Increases in leuB and argH mRNA levels are known to be specific to the starvation conditions, i.e.…”

Section: Introductionmentioning

confidence: 95%

“…Increases in leuB and argH mRNA levels are known to be specific to the starvation conditions, i.e. leuB mRNA accumulates during leucine, but not arginine or threonine starvation, and argH mRNA accumulates during arginine, but not histidine starvation (Wright et al, 1999). These observed changes in mRNA levels in response to nutritional stress could result from a change in the rate of mRNA synthesis, degradation (stability), or both.…”

Section: Introductionmentioning

confidence: 99%

“…The amount of ppGpp produced depends upon the identity of the absent amino acid (Donini et al, 1978). Activation by ppGpp is essential to enhanced expression of the deattenuated leu operon (Wright et al, 1999), as well as a number of other amino acid operons (Morse & Morse, 1976;Perel'man & Shakulov, 1981;Smolin & Umbarger, 1975;Stephens et al, 1975;Zidwick et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Increased transcription rates correlate with increased reversion rates in leuB and argH Escherichia coli auxotrophs

et al. 2004

Self Cite

View full text Add to dashboard Cite

Escherichia coli auxotrophs of leuB and argH were examined to determine if higher rates of transcription in derepressed genes were correlated with increased reversion rates. Rates of leuB and argH mRNA synthesis were determined using half-lives and concentrations, during exponential growth and at several time points during 30 min of amino acid starvation. Changes in mRNA concentration were primarily due to increased mRNA synthesis and not to increased stability. Four strains of E. coli amino acid auxotrophs, isogenic except for relA and argR, were examined. In both the leuB and argH genes, rates of transcription and mutation were compared. In general, strains able to activate transcription with guanosine tetraphosphate (ppGpp) had higher rates of mRNA synthesis and mutation than those lacking ppGpp (relA2 mutants). argR knockout strains were constructed in relA + and relA mutant strains, and rates of both argH reversion and mRNA synthesis were significantly higher in the argR knockouts than in the regulated strains. A statistically significant linear correlation between increased rates of transcription and mutation was found for data from both genes. In general, changes in mRNA half-lives were less than threefold, whereas changes in rates of mRNA synthesis were often two orders of magnitude. The results suggest that specific starvation conditions target the biosynthetic genes for derepression and increased rates of transcription and mutation.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Increased transcription rates correlate with increased reversion rates in leuB and argH Escherichia coli auxotrophs

et al. 2004

Self Cite

View full text Add to dashboard Cite

show abstract

“…Starvation for a specific amino acid usually causes the genes for the biosynthesis of that amino acid to be derepressed, while the stringent response causes a general increase in transcription. Since active transcription tends to increase the mutation rate of the transcribed DNA [27][28][29][30][31], the stringent response provides a way that mutations can be directed to useful genes [30].…”

Section: The Stringent Responsementioning

confidence: 99%

Stress responses and genetic variation in bacteria

Foster

2005

Mutation Research/Fundamental and Molecular Mechanisms of Mutag

176

106

View full text Add to dashboard Cite

Under stressful conditions mechanisms that increase genetic variation can bestow a selective advantage. Bacteria have several stress responses that provide ways in which mutation rates can be increased. These include the SOS response, the general stress response, the heat-shock response, and the stringent response, all of which impact the regulation of error-prone polymerases. Adaptive mutation appears to be process by which cells can respond to selective pressure specifically by producing mutations. In Escherichia coli strain FC40 adaptive mutation involves the following inducible components: (i) a recombination pathway that generates mutations; (ii) a DNA polymerase that synthesizes error-containing DNA; and (iii) stress responses that regulate cellular processes. In addition, a subpopulation of cells enters into a state of hypermutation, giving rise to about 10% of the single mutants and virtually all of the mutants with multiple mutations. These bacterial responses have implications for the development of cancer and other genetic disorders in higher organisms.

show abstract

Stress‐induced Mutagenesis in Bacteria

Foster

2011

Encyclopedia of Life Sciences

View full text Add to dashboard Cite

Bacteria spend their lives experiencing repeated rounds of feast and famine. In addition, they are buffeted by a variety of environmental insults such as fluctuations in temperature, pH, osmotic pressure, as well as exposure to DNA damaging agents and antibiotics. To cope with these changing conditions, bacteria have a variety of stress‐responses that result in profound but temporary cell‐wide changes in gene expression and protein activities. Keyed into these responses are a variety of ways in which the potential for genetic change is enhanced. Research has provided a number of examples of stress‐induced mutagenesis. Such transient mutator states may be important for adaptive evolution. Key Concepts: Bacteria respond to stress by inducing temporary cell‐wide changes in gene expression and protein activities. Some of these changes can increase the cell's potential for genetic change. Adaptive evolution can be accelerated when mutation rates are high, but persistent high mutation rates are also deleterious. Thus, transient increases in mutation rates are potentially of greater evolutionary advantage than permanent increases. Stress‐induced mutagenesis appears to be widespread among bacteria. There are many mechanisms that contribute to stress‐induced mutagenesis.

show abstract

Hypermutation in derepressed operons ofEscherichia coliK12

Cited by 72 publications

References 55 publications

Increased transcription rates correlate with increased reversion rates in leuB and argH Escherichia coli auxotrophs

Increased transcription rates correlate with increased reversion rates in leuB and argH Escherichia coli auxotrophs

Stress responses and genetic variation in bacteria

Stress‐induced Mutagenesis in Bacteria

Contact Info

Product

Resources

About