title: Induction of action-at-a-distance mutagenesis by 8-oxo-7,8-dihydroguanine in DNA pol λ-knockdown cells.
abstract: BACKGROUND
  In DNA, 8-oxo-7,8-dihydroguanine (G(O), 8-hydroxyguanine) is one of the most pivotal oxidatively damaged bases and induces G:C → T:A transversion mutations. DNA polymerase λ preferentially inserts dCTP opposite G(O) in vitro, and this error-free bypass function is considered to be important after A base removal from G(O):A pairs by the MUTYH DNA glycosylase. To examine the effects of reduced levels of DNA polymerase λ on the G(O)-induced mutations, the polymerase was knocked-down in human U2OS cells, and a shuttle plasmid DNA containing a G(O):C pair at position 122 in the supF gene was transfected into the cells. The plasmid DNA replicated in the cells was introduced into an Escherichia coli indicator strain, to measure the supF mutant frequency.
  
  
  RESULTS
  The knockdown of DNA polymerase λ significantly enhanced the mutant frequency of the G(O) plasmid DNA. Contrary to our expectations, the knockdown did not promote the targeted G:C → T:A transversion. Instead, substitution mutations at G:C sites other than position 122 were enhanced in the cells.
  
  
  CONCLUSIONS
  These results suggested that the knockdown of DNA polymerase λ induced action-at-a-distance mutagenesis in human cells when the G(O):C pair was present in the DNA.
authors.affiliation: Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790-8577 Japan ; Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553 Japan ; College of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama, 790-8578 Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kamiya
authors.affiliation: Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790-8577 Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurokawa
authors.affiliation: Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790-8577 Japan ; Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553 Japan.
authors.forename: Tetsuaki
authors.initials: T
authors.lastname: Makino
authors.affiliation: College of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama, 790-8578 Japan.
authors.forename: Miwako
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: College of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama, 790-8578 Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Matsuoka
keywords: 8-Hydroxyguanine; 8-Oxo-7,8-dihydroguanine; Action-at-a-distance mutagenesis; DNA polymerase λ; Knockdown