Spontaneous and 9-aminoacridine-induced frameshift mutagenesis: second-site frameshift mutation within the N-terminal region of the lacI gene of Escherichia coli.
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.
Gordon
A J
AJ
Department of Biology, York University, Toronto, Ontario, Canada.
Halliday
J A
JA
Horsfall
M J
MJ
Glickman
B W
BW
D000585:Aminacrine / Q000494:pharmacology*; D001483:Base Sequence; D003062:Codon / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D016368:Frameshift Mutation; D005798:Genes, Bacterial / Q000187:drug effects; D005816:Genetic Complementation Test; D005838:Genotype; D008969:Molecular Sequence Data; D016296:Mutagenesis; D014176:Protein Biosynthesis
D003062:Codon; D004269:DNA, Bacterial; D000585:Aminacrine