Yamamoto Mizuki, Yamamoto Ryohei, Takenaka Shigeo, Matsuyama Satoshi, Kubo Kihei
Department of Advanced Pathobiology, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-58 Rinku Ourai-Kita, Izumisano, Osaka 598-8531, Japan.
Department of Advanced Pathobiology, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-58 Rinku Ourai-Kita, Izumisano, Osaka 598-8531, Japan
J Radiat Res. 2015 Jul;56(4):607-14. doi: 10.1093/jrr/rrv010. Epub 2015 Mar 31.
In mammalian cells, murine N-methylpurine DNA glycosylase (MPG) removes bases damaged spontaneously or by chemical agents through the process called base excision repair (BER). In this study, we investigated the influence of POL β deficiency on MPG-initiated BER efficiency and the expression levels of BER-related proteins in log-phase and growth-arrested (G(0)) mouse embryonic fibroblasts (MEFs). G(0) wild-type (WT) or POL β-deficient (Pol β-KO) cells showed greater resistance to methyl methanesulfonate than did log-phase cells, and repair of methylated bases was less efficient in the G(0) cells. Apex1 mRNA expression was significantly lower in Pol β-KO or G(0) WT MEFs than in log-phase WT MEFs. Moreover, although Mpg mRNA levels did not differ significantly among cell types, MPG protein levels were significantly higher in log-phase WT cells than in log-phase Pol β-KO cells or either type of G(0) cells. Additionally, proliferating cell nuclear antigen protein levels were also reduced in log-phase Pol β-KO cells or either type of G(0) cells. These results indicated that MPG-initiated BER functions mainly in proliferating cells, but less so in G(0) cells, and that POL β may be involved in regulation of the amount of intracellular repair proteins.
在哺乳动物细胞中，小鼠N-甲基嘌呤DNA糖基化酶（MPG）通过碱基切除修复（BER）过程去除自发受损或受化学试剂损伤的碱基。在本研究中，我们调查了POLβ缺陷对对数期和生长停滞（G(0)）小鼠胚胎成纤维细胞（MEF）中MPG启动的BER效率以及BER相关蛋白表达水平的影响。与对数期细胞相比，G(0)野生型（WT）或POLβ缺陷型（Polβ-KO）细胞对甲磺酸甲酯表现出更强的抗性，并且G(0)细胞中甲基化碱基的修复效率较低。在Polβ-KO或G(0) WT MEF中，Apex1 mRNA表达明显低于对数期WT MEF。此外，尽管不同细胞类型之间Mpg mRNA水平没有显著差异，但对数期WT细胞中的MPG蛋白水平明显高于对数期Polβ-KO细胞或任何一种G(0)细胞。另外，对数期Polβ-KO细胞或任何一种G(0)细胞中的增殖细胞核抗原蛋白水平也降低。这些结果表明，MPG启动的BER主要在增殖细胞中起作用，而在G(0)细胞中作用较小，并且POLβ可能参与细胞内修复蛋白量的调节。
