Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
Mutat Res. 2022 Jul-Dec;825:111794. doi: 10.1016/j.mrfmmm.2022.111794. Epub 2022 Aug 18.
8-Oxo-7,8-dihydroguanine (8-hydroxyguanine, G°) is a major oxidized base that is considered to play pivotal roles in the pathogenesis of various diseases, including cancer. G° induces G:C → T:A transversions at the damage site and untargeted (action-at-a-distance) mutations of G bases at 5'-GpA sequences. In this study, we examined the distribution of the action-at-a-distance mutations and the effects of the replication origin position relative to G° on the untargeted mutagenesis. The G° base was introduced into two shuttle plasmids, each with the SV40 replication origin at a different position with respect to the supF gene. The oxidized base was located at an upstream or downstream site (outside of the gene), or the center of the region encoding the pre-tRNA sequence of the gene, in the sense strand. These shuttle plasmids were introduced into human U2OS cells. The action-at-a-distance mutations were more frequently induced when the G° base was located downstream of the supF gene than upstream of the gene. In addition, more action-at-a-distance mutations were observed when the SV40 origin was present on the 5'-side of the G° base. These results indicated that the action-at-a-distance mutations are predominantly induced on the 5'-side of the lesion and occurred more frequently when the damaged base was located on the lagging strand template.
8-氧代-7,8-二氢鸟嘌呤（8-羟基鸟嘌呤，G°）是一种主要的氧化碱基，被认为在各种疾病的发病机制中发挥关键作用，包括癌症。G°在损伤部位诱导 G:C→T:A 颠换，并在 5'-GpA 序列中的 G 碱基发生非靶向（远距离作用）突变。在这项研究中，我们检查了非靶向突变的分布以及复制起点位置相对于 G°对非靶向诱变的影响。G°碱基被引入两个穿梭质粒中，每个质粒的 SV40 复制起点相对于 supF 基因的位置不同。氧化碱基位于有义链上的基因上游或下游（基因之外）或编码基因前 tRNA 序列的区域的中心。这些穿梭质粒被引入人 U2OS 细胞。当 G°碱基位于 supF 基因下游而不是上游时，非靶向突变的诱导更为频繁。此外，当 SV40 起点位于 G°碱基的 5'侧时，观察到更多的非靶向突变。这些结果表明，非靶向突变主要在损伤部位的 5'侧诱导，并且当受损碱基位于滞后链模板上时，发生的频率更高。
