Spectra of Base Substitution Mutations Induced in Escherichia coli by Tritiated Water and the Decay of Incorporated Tritiated Thymidine

1984 ◽  
Vol 97 (1) ◽  
pp. 200 ◽  
Author(s):  
Tuneo Ise ◽  
Takesi Kato ◽  
Barry W. Glickman
Keyword(s):  
Escherichia Coli ◽  
Tritiated Thymidine ◽  
Tritiated Water ◽  
Base Substitution ◽  
Substitution Mutations

DNA Alkylation Repair Limits Spontaneous Base Substitution Mutations in Escherichia coli :

1994 ◽  
Vol 176 (16) ◽  
pp. 5193.1-5193
Author(s):  
William J. Mackay ◽  
Song Han ◽  
Leona D. Samson
Keyword(s):  
Escherichia Coli ◽  
Dna Alkylation ◽  
Base Substitution ◽  
Substitution Mutations

scholarly journals Transcription-Dependent Increase in Multiple Classes of Base Substitution Mutations in Escherichia coli

2002 ◽  
Vol 184 (24) ◽  
pp. 6866-6872 ◽  
Author(s):  
Joanna Klapacz ◽  
Ashok S. Bhagwat
Keyword(s):  
Escherichia Coli ◽  
Genetic System ◽  
Base Substitution ◽  
E Coli ◽  
Base Substitutions ◽  
Selection For ◽  
Substitution Mutations ◽  
High Level ◽  
C To T Mutations ◽  
Genetic Assay

ABSTRACT We showed previously that transcription in Escherichia coli promotes C · G-to-T · A transitions due to increased deamination of cytosines to uracils in the nontranscribed but not the transcribed strand (A. Beletskii and A. S. Bhagwat, Proc. Natl. Acad. Sci. USA 93:13919-13924, 1996). To study mutations other than that of C to T, we developed a new genetic assay that selects only base substitution mutations and additionally excludes C · G to T · A transitions. This novel genetic reversion system is based on mutations in a termination codon and involves positive selection for resistance to bleomycin or kanamycin. Using this genetic system, we show here that transcription from a strong promoter increases the level of non-C-to-T as well as C-to-T mutations. We find that high-level transcription increases the level of non-C-to-T mutations in DNA repair-proficient cells in three different sequence contexts in two genes and that the rate of mutation is higher by a factor of 2 to 4 under these conditions. These increases are not caused by a growth advantage for the revertants and are restricted to genes that are induced for transcription. In particular, high levels of transcription do not create a general mutator phenotype in E. coli. Sequence analysis of the revertants revealed that the frequency of several different base substitutions increased upon transcription of the bleomycin resistance gene and that G · C-to-T · A transversions dominated the spectrum in cells transcribing the gene. These results suggest that high levels of transcription promote many different spontaneous base substitutions in E. coli.

scholarly journals Role of the dinB Gene Product in Spontaneous Mutation in Escherichia coli with an Impaired Replicative Polymerase

2000 ◽  
Vol 182 (23) ◽  
pp. 6742-6750 ◽  
Author(s):  
B. S. Strauss ◽  
R. Roberts ◽  
L. Francis ◽  
P. Pouryazdanparast
Keyword(s):  
Escherichia Coli ◽  
Mismatch Repair ◽  
Spontaneous Mutation ◽  
Luria Bertani ◽  
Base Substitution ◽  
Temperature Sensitive ◽  
Selection Scheme ◽  
Mutator Effect ◽  
Substitution Mutations

ABSTRACT We isolated several new mutator mutations of the Escherichia coli replicative polymerase dnaE subunit alpha and used them and a previously reported dnaE mutation to study spontaneous frameshift and base substitution mutations. Two of thesednaE strains produce many more mutants when grown on rich (Luria-Bertani) than on minimal medium. A differential effect of the medium was not observed when these dnaE mutations were combined with a mismatch repair mutation. The selection scheme for thednaE mutations required that they be able to complement a temperature-sensitive strain. However, the ability to complement is not related to the mutator effect for at least one of the mutants. Comparison of the mutation rates for frameshift and base substitution mutations in mutS and dnaE mutS strains suggests that the mismatch repair proteins respond differently to the two types of change. Deletion of dinB from both chromosome and plasmid resulted in a four- to fivefold decrease in the rate of frameshift and base substitution mutations in a dnaE mutSdouble mutant background. This reduction indicates that most mistakes in replication occur as a result of the action of the auxiliary rather than the replicative polymerase in this dnaE mutant. Deletion of dinB from strains carrying a wild-typednaE had a measurable effect, suggesting that a fraction of spontaneous mutations occur as a result of dinB polymerase action even in cells with a normal replicative polymerase.

scholarly journals Mutational Consequences of Ciprofloxacin in Escherichia coli

2016 ◽  
Vol 60 (10) ◽  
pp. 6165-6172 ◽  
Author(s):  
Lisa Yun Song ◽  
Marisa Goff ◽  
Christina Davidian ◽  
Zhiyuan Mao ◽  
Marisa London ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Thymidylate Synthase ◽  
Gene Knockout ◽  
Mutagenic Activity ◽  
Point Mutations ◽  
Base Substitution ◽  
Induced Mutations ◽  
Content Type ◽  
Sublethal Doses ◽  
Substitution Mutations

ABSTRACTWe examined the mutagenic specificity of the widely used antibiotic ciprofloxacin (CPR), which displays weak to moderate mutagenic activity in several bacteria and generates short in-frame deletions inrpoBinStaphylococcus aureus. To determine the spectrum of mutations in a system where any gene knockout would result in a recovered mutant, including frameshifts and both short and long deletions, we examined CPR-induced mutations in the thymidylate synthase-encodingthyAgene. Here, any mutation resulting in loss of thymidylate synthase activity generates trimethoprim (Trm) resistance. We found that deletions and insertions in all three reading frames predominated in the spectrum. They tend to be short deletions and cluster in two regions, one being a GC-rich region with potential extensive secondary structures. We also exploited the well-characterizedrpoB-Rifrsystem inEscherichia colito determine that cells grown in the presence of sublethal doses of CPR not only induced short in-frame deletions inrpoB, but also generated base substitution mutations resulting from induction of the SOS system. Some of the specific point mutations prominent in the spectrum of a strain that overproduces thedinB-encoded Pol IV were also present after growth in CPR. However, these mutations disappeared in CPR-treateddinBmutants, whereas the deletions remained. Moreover, CPR-induced deletions also occurred in a strain lacking all three SOS-induced polymerases. We discuss the implications of these findings for the consequences of overuse of CPR and other antibiotics.

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