Spontaneous and 9-aminoacridine-induced frameshift mutagenesis: second-site frameshift mutation within the N-terminal region of the lacI gene of Escherichia coli

• Published in: Molecular & general genetics Vol. 227; no. 1; p. 160
• Main Authors: Gordon, A J, Halliday, J A, Horsfall, M J, Glickman, B W
• Format: Journal Article
• Language: English
• Published: Germany 01.05.1991
• Subjects: Aminacrine - pharmacology; Base Sequence; Codon - genetics; DNA, Bacterial - genetics; Escherichia coli - drug effects; Escherichia coli - genetics; Frameshift Mutation; Genes, Bacterial - drug effects; Genetic Complementation Test; Genotype; Molecular Sequence Data; Mutagenesis; Protein Biosynthesis
• ISSN: 0026-8925
• DOI: 10.1007/BF00260722

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.