title: Influence of neighbouring base sequences on the mutagenesis induced by 7,8-dihydro-8-oxoguanine in yeast.
abstract: We have analysed the influence of neighbouring base sequences on the mutagenesis induced by 7,8-dihydro-8-oxoguanine (8-oxoG or G(o)), a typical oxidative lesion of DNA, using the yeast oligonucleotide transformation technique. Two oligonucleotides, oligo-CCG(o) and oligo-CGG(o), each possessing a single 8-oxoG residue and represented by the sequences 5'-CCG(o)-3' and 5'-CGG(o)-3', respectively, were introduced into a chromosome of Saccharomyces cerevisiae and their mutagenic potentials were compared. In a wild-type strain, 8-oxoG showed very weak mutagenic potential in both cases. However, the lesion in 5'-CCG(o)-3' can cause efficient G-to-T transversion in a strain lacking the rad30 gene which encodes yeast DNA polymerase eta (Ypoleta). To explore the properties associated with this translesion synthesis (TLS), the same two oligonucleotides possessing an 8-oxoG were used as templates for a standing-start primer extension assay, and the nucleotide incorporation opposite 8-oxoG was investigated. We found that dATP incorporation opposite 8-oxoG with Ypoleta was low for both sequences. In particular, very low dATP incorporation was observed for the 5'-CCG(o)-3' sequence. These results account for the efficient inhibition of mutagenesis by Ypoleta. TLS plays an important role in one DNA sequence in terms of avoiding mutagenesis induced by 8-oxoG in yeast. In contrast, human yeast DNA polymerase eta showed higher dATP incorporation rates even with the 5'-CCG(o)-3' sequence.
authors.affiliation: Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700-8530, Japan.
authors.forename: Chin-Wei
authors.initials: CW
authors.lastname: Yung
authors.forename: Yoji
authors.initials: Y
authors.lastname: Okugawa
authors.forename: Chie
authors.initials: C
authors.lastname: Otsuka
authors.forename: Keinosuke
authors.initials: K
authors.lastname: Okamoto
authors.forename: Sakae
authors.initials: S
authors.lastname: Arimoto
authors.forename: David
authors.initials: D
authors.lastname: Loakes
authors.forename: Kazuo
authors.initials: K
authors.lastname: Negishi
authors.forename: Tomoe
authors.initials: T
authors.lastname: Negishi