Site-specific mutagenesis induced by single O6-alkylguanines (O6-n-propyl, O6-n-butyl, O6-n-octyl) in vivo.
The mutagenic activity of a series of longer chain O6-n-alkylguanine residues (O6-n-propyl, O6-n-butyl, O6-n-octyl) has been analyzed using a plasmid molecule (pUC 9) in which single O6-alkylguanines were positioned in the unique Pstl recognition site by shot gun ligation (Nucleic Acids Res. 13, 3305-3316 (1985)) of overlapping synthetic oligonucleotides. After transfection of these vectors into E. coli cells having normal DNA repair systems, progeny plasmids were produced, of which 2.6%, 2.8% and 4.3% were mutated in their Pstl site when containing O6-n-propylguanine, O6-n-butylguanine, O6-n-octylguanine, respectively. DNA sequence analysis of mutant plasmid genomes revealed that O6-n-propylguanine and O6-n-butylguanine induced exclusively G-->A transitions located specifically at the preselected site. O6-n-octylguanine induced apart from G-->A transitions (70%) also targeted G-->T transversions (30%). These results indicate that the mutation frequency of longer chain O6-alkylguanines can be substantial in cells with normal repair systems and that the mutation pattern depends on the nature of the alkyl group.
Baumgart
P M
PM
Department of Molecular Toxicology, German Cancer Research Center, Heidelberg.
Kliem
H C
HC
Gottfried-Anacker
J
J
Wiessler
M
M
Schmeiser
H H
HH
D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D004260:DNA Repair; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000235:genetics*; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed
D004269:DNA, Bacterial; D006147:Guanine