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Effect of isopropyl-beta-D-thiogalactopyranosid induction of the lac operon on the specificity of spontaneous and doxorubicin-induced mutations in Escherichia coli.

Publication ,  Journal Article
Veigl, ML; Donover, SP; Anderson, RD; Akst, L; Sedwick, CE; Sedwick, WD
Published in: Environ Mol Mutagen
1995

Previous studies of doxorubicin-induced mutations employing F' lacl/lacO as an endogenous gene target have focused on properties of large deletions with 3' endpoints residing in the lacO region of the target gene. This study considers the influence of Lac repressor binding on the distribution of these deletions. Results of the DNA sequence level analysis of spontaneous and doxorubicin-induced i-d and lacO mutations in Escherichia coli uvrB- are reported for mutants isolated under conditions where Lac repression is relieved by isopropyl-beta-D-thiogalactopyranosid (IPTG; an inducer that prevents repressor binding to lacO). The location of deletions isolated from doxorubicin-treated cultures in the presence and absence of IPTG suggests that doxorubicin preferentially focuses deletion endpoints adjacent to its binding sites in lacO and that the distribution of these deletion endpoints is not modulated by Lac repressor binding. In contrast, spontaneous deletion endpoints are preferentially clustered in the loop away from the palindromic sequences under conditions of repression. However, when the Lac repressor/lacO binding complex is dissociated by IPTG, the spontaneous 3'-deletion endpoints distribute proportionally between the putative stem and loop of the lacO palindrome. The single most striking effect of IPTG induction of the Lac operon was elimination of a "hot spot" for T:A-->C:G transitions at position +6 in lacO. This base substitution "hot spot," which accounted for 17.6% of total doxorubicin-induced mutants and 16.4% of spontaneous mutants in repressed bacterial cultures, accounted for approximately 1% of total mutations in similar experiments carried out in the presence of IPTG. A large number of mutations at the +6 position are induced only by doxorubicin in the absence of IPTG, however, suggesting that both doxorubicin-induced and spontaneous mutation at this transition "hot spot" are mediated by Lac repressor binding to lacO.

Duke Scholars

Published In

Environ Mol Mutagen

DOI

ISSN

0893-6692

Publication Date

1995

Volume

26

Issue

1

Start / End Page

16 / 25

Location

United States

Related Subject Headings

  • beta-Galactosidase
  • Toxicology
  • Species Specificity
  • Sequence Deletion
  • Repressor Proteins
  • Point Mutation
  • Mutagens
  • Molecular Sequence Data
  • Lac Repressors
  • Lac Operon
 

Citation

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MLA
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Veigl, M. L., Donover, S. P., Anderson, R. D., Akst, L., Sedwick, C. E., & Sedwick, W. D. (1995). Effect of isopropyl-beta-D-thiogalactopyranosid induction of the lac operon on the specificity of spontaneous and doxorubicin-induced mutations in Escherichia coli. Environ Mol Mutagen, 26(1), 16–25. https://doi.org/10.1002/em.2850260104
Veigl, M. L., S. P. Donover, R. D. Anderson, L. Akst, C. E. Sedwick, and W. D. Sedwick. “Effect of isopropyl-beta-D-thiogalactopyranosid induction of the lac operon on the specificity of spontaneous and doxorubicin-induced mutations in Escherichia coli.Environ Mol Mutagen 26, no. 1 (1995): 16–25. https://doi.org/10.1002/em.2850260104.
Veigl, M. L., et al. “Effect of isopropyl-beta-D-thiogalactopyranosid induction of the lac operon on the specificity of spontaneous and doxorubicin-induced mutations in Escherichia coli.Environ Mol Mutagen, vol. 26, no. 1, 1995, pp. 16–25. Pubmed, doi:10.1002/em.2850260104.

Published In

Environ Mol Mutagen

DOI

ISSN

0893-6692

Publication Date

1995

Volume

26

Issue

1

Start / End Page

16 / 25

Location

United States

Related Subject Headings

  • beta-Galactosidase
  • Toxicology
  • Species Specificity
  • Sequence Deletion
  • Repressor Proteins
  • Point Mutation
  • Mutagens
  • Molecular Sequence Data
  • Lac Repressors
  • Lac Operon