Spontaneous and 9-aminoacridine-induced frameshift mutagenesis: second-site frameshift mutation within the N-terminal region of thelacI gene ofEscherichia coli
✍ Scribed by Gordon, Alasdair J. E. ;Halliday, Jennifer A. ;Horsfall, Michael J. ;Glickman, Barry W.
- Publisher
- Springer
- Year
- 1991
- Tongue
- English
- Weight
- 515 KB
- Volume
- 227
- Category
- Article
- ISSN
- 0026-8925
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✦ Synopsis
A novel forward mutational system, based on the acquisition of an Iq-d dominant phenotype from an initial Iq- recessive state, was used to identify second-site frameshift mutation [+/- 1(+/- 3n) events] within the N-terminal region of the lacI gene of Escherichia coli. The DNA sequences are described of forty-six spontaneous and twenty 9-aminoacridine(9-AA)-induced second site mutations. Although -1 frameshift events dominate both spectra, the nature and site specificity of these events clearly distinguish two mutational distributions. The spontaneous distribution contains two -(A:T) frameshift hotspots; one within a monotonic A5 run (9 occurrences), the other at a 5'-CACAACAAC-3' sequence (12 occurrences). In contrast 17 of the 20 mutations recovered after 9-AA treatment involve the loss of a G:C pair, 14 of which occur at a single site (5'-CGGGC-3'). The striking specificity of the observed mutational hotspots is of interest since this open genetic target contains similar sequences which were infrequently recovered.