title: X-ray-induced mutations in Escherichia coli K-12 strains with altered DNA polymerase I activities.
abstract: Spectra of ionizing radiation mutagenesis were determined by sequencing X-ray-induced endogenous tonB gene mutations in Escherichia coli polA strains. We used two polA alleles, the polA1 mutation, defective for Klenow domain, and the polA107 mutation, defective for flap domain. We demonstrated that irradiation of 75 and 50 Gy X-rays could induce 3.8- and 2.6-fold more of tonB mutation in polA1 and polA107 strains, respectively, than spontaneous level. The radiation induced spectrum of 51 tonB mutations in polA1 and 51 in polA107 indicated that minus frameshift, A:T-->T:A transversion and G:C-->T:A transversion were the types of mutations increased. Previously, we have reported essentially the same X-ray-induced tonB mutation spectra in the wild-type strain. These results indicate that (1) X-rays can induce minus frameshift, A:T-->T:A transversion and G:C-->T:A transversion in E. coli and (2) presence or absence of polymerase I (PolI) of E. coli does not have any effects on the process of X-ray mutagenesis.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, 980-8577 Sendai, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nagata
authors.forename: Masakado
authors.initials: M
authors.lastname: Kawata
authors.forename: Jun-ichiro
authors.initials: J
authors.lastname: Komura
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ono
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D004256:DNA Polymerase I / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000528:radiation effects; D029968:Escherichia coli Proteins; D008565:Membrane Proteins / Q000235:genetics; D009154:Mutation / Q000528:radiation effects*; D014965:X-Rays
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C057616:tonB protein, Bacteria; C489181:tonB protein, E coli; D004256:DNA Polymerase I