Kuipers G K, Slotman B J, Poldervaart H A, Reitsma-Wijker C A, Lafleur M V
Department of Radiation Oncology, Section Radiobiology, Faculty of Medicine, Vrije Universiteit, van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands.
Mutat Res. 2000 Nov 9;461(3):189-95. doi: 10.1016/s0921-8777(00)00050-1.
One of the most predominating oxidative DNA damages, both spontaneously formed and after gamma-radiation is 7, 8-dihydro-8-oxoguanine (8oxoG). This 8oxoG is a mutagenic lesion because it can mispair with adenine instead of the correct cytosine leading to G:C to T:A transversions. In Escherichia coli (E. Coli) base excision repair (BER) is one of the most important repair systems for the repair of 8oxoG and other oxidative DNA damage. An important part of BER in E. coli is the so-called GO system which consists of three repair enzymes, MutM (Fpg), MutY and MutT which are all involved in repair of 8oxoG or 8oxoG mispairs. The aim of this study is to determine the effect of combined Fpg- and MutY-deficiency on the spontaneous and gamma-radiation-induced mutation spectrum of the lacZalpha gene. For that purpose, non-irradiated or gamma-irradiated double-stranded (ds) M13mp10 DNA, with the lacZalpha gene inserted as mutational target sequence was transfected into an E. coli strain which is deficient in both Fpg and MutY (BH1040). The resulting mutation spectra were compared with the mutation spectra of a fpg(-) E. coli strain (BH410) and a wild type E. coli strain (JM105) which were determined in an earlier study. The results of the present study indicate that combined Fpg- and MutY-deficiency induces a large increase in G:C to T:A transversions in both the spontaneous and gamma-radiation-induced mutation spectra of BH1040 (fpg(-)mutY(-)) as compared to the fpg(-) and the wild type strain. Besides the increased levels of G:C to T:A transversions, there is also an increase in G:C to C:G transversions and frameshift mutations in both the spontaneous and gamma-radiation-induced mutation spectra of BH1040 (fpg(-)mutY(-)).
7,8 - 二氢 - 8 - 氧代鸟嘌呤（8 - 氧代鸟嘌呤，8oxoG）是最主要的氧化性DNA损伤之一，既可自发形成，也可在γ辐射后形成。这种8 - 氧代鸟嘌呤是一种诱变损伤，因为它会与腺嘌呤错配，而不是与正确的胞嘧啶配对，导致G:C到T:A的颠换。在大肠杆菌（E. Coli）中，碱基切除修复（BER）是修复8 - 氧代鸟嘌呤和其他氧化性DNA损伤的最重要修复系统之一。大肠杆菌BER的一个重要部分是所谓的GO系统，它由三种修复酶组成，即MutM（Fpg）、MutY和MutT，它们都参与8 - 氧代鸟嘌呤或8 - 氧代鸟嘌呤错配的修复。本研究的目的是确定Fpg和MutY联合缺陷对lacZα基因自发和γ辐射诱导突变谱的影响。为此，将插入lacZα基因作为突变靶序列的未辐照或γ辐照双链（ds）M13mp10 DNA转染到同时缺乏Fpg和MutY的大肠杆菌菌株（BH1040）中。将所得突变谱与早期研究中确定的fpg(-)大肠杆菌菌株（BH410）和野生型大肠杆菌菌株（JM105）的突变谱进行比较。本研究结果表明，与fpg(-)和野生型菌株相比，BH1040（fpg(-)mutY(-)）的Fpg和MutY联合缺陷在自发和γ辐射诱导的突变谱中均导致G:C到T:A颠换大幅增加。除了G:C到T:A颠换水平增加外，BH1040（fpg(-)mutY(-)）的自发和γ辐射诱导突变谱中G:C到C:G颠换和移码突变也增加。
