title: Effects of vacuum UV and UVC radiation on dry Escherichia coli plasmid pUC19. II. Mutational specificity at the lacZ gene.
abstract: The mutational spectra at the lacZ gene, induced either by vacuum UV at 160 nm or UVC at 254 nm in vacuum-dried preparations of Escherichia coli plasmid pUC19 DNA, have been characterized from 72 E. coli-propagated mutants by DNA sequencing. In plasmids irradiated in vacuum, vacuum UV is five times more mutagenic than UVC. In the UV-induced mutants, base substitutions largely predominate, with GC-->AT (G, guanine; C, cytosine; A, adenine; T, thymine) transitions being the most abundant type of base change for vacuum UV (61%) and UVC (47%). Most of the GC-->AT transitions appear to occur at dipyrimidine sites, which are located at the non-transcribed DNA strand. Some, but not all, hot spots for GC-->AT transitions are identical for vacuum UV and UVC. Frameshifts, resulting from a loss of the thymine residue, are specific for UVC (22%), and were not detected after treatment with vacuum UV. They occur predominantly at thymine runs of the transcribed DNA strand. Only a few deletions were detected following irradiation with vacuum UV (7.5%) and UVC (2%); however, their frequency is not enhanced compared with the spontaneous mutation spectrum. The data confirm the important role of base substitution mutations in UV-induced mutagenesis, which is not only valid for the UVC range, but extends towards the vacuum UV range.
authors.affiliation: Deutsche Forschungsanstalt für Luft- und Raumfahrt, Institut für Luft- und Raumfahrtmedizin, Abteilung Strahlenbiologie, Köln, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Wehner
authors.forename: G
authors.initials: G
authors.lastname: Horneck
mesh_terms: D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics / Q000528:radiation effects*; D007763:Lac Operon / Q000528:radiation effects*; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000528:radiation effects; D010957:Plasmids / Q000528:radiation effects*; D014466:Ultraviolet Rays; D014618:Vacuum