Analysis of mutation spectra in UVB-exposed mouse skin epidermis and dermis:: Frequent occurrence of C→T transition at methylated CpG-associated dipyrimidine sites
Analysis of mutation spectra in UVB-exposed mouse skin epidermis and dermis:: Frequent occurrence of C→T transition at methylated CpG-associated dipyrimidine sites
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DOI：
10.1002/em.10153
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发表时间：
2003-01-01
影响因子：
2.8
通讯作者：
Ono, T
中科院分区：
文献类型：
--
作者：
Ikehata, H;Masuda, T;Ono, T
我们最近报道了UVB对转基因Muta(TM)小鼠皮肤表皮和真皮的诱变动力学[Ikehata and Ono，Mutat Res 508：41-47,2002]。在本研究中，我们从紫外线照射和对照小鼠的真皮和表皮中分离出208个突变株，测定了LacZ转基因的完整DNA序列。结果真皮和表皮的突变模式是相似的，尽管只在UVB诱导的表皮突变中检测到了两个CC->；TT串联替换，这是紫外线损伤的标志性突变之一。UVB诱导的突变和对照突变的光谱均以C-->；T跃迁为主(83%和62%)；然而，照射小鼠的C-->；T跃迁几乎完全发生在双嘧啶位点，而对照小鼠的C-->；T跃迁主要发生在CpG位点。因此，检测到的辐照皮肤组织的突变光谱与背景光谱和紫外线特异的光谱不同，证实了转基因系统在体内UVB诱变研究中的实用性。对辐射小鼠突变的胞嘧啶相邻碱基的分析表明，UVB诱发突变的首选双嘧啶位点为5‘-TC-3’>；5‘-CC-3’>；5‘-CT-3’。在来自受辐射小鼠的突变体中，C-->；T转变经常在与CpG相关的双嘧啶位点恢复。我们发现，在Muta(TM)小鼠的LacZ转基因中，CpG位点在表皮和真皮中都高度甲基化。因此，CpG甲基化可能导致UVB诱导哺乳动物基因组中的重复突变或热点突变。(C)2003年Wiley-Liss，Inc.
We recently reported the kinetics of mutation induction by UVB in the skin epidermis and dermis of transgenic Muta(TM) mice [Ikehata and Ono, Mutat Res 508:41-47, 2002]. In the present study we determined the complete DNA sequence of the lacZ transgene in 208 mutants isolated from the dermis and epidermis of UVB-irradiated and control mice. The resulting mutation patterns for the dermis and epidermis were similar, although two CC-->TT tandem substitutions, one of the signature mutations for UV insult, were detected only among the UVB-induced epidermal mutants. The spectra of the UVB-induced and control mutations were both dominated by C-->T transitions (83% and 62%); however, the C-->T transitions from irradiated mice occurred almost exclusively in dipyrimidine sites, while those from control mice preferred CpG sites. Thus, the mutation spectrum detected for the irradiated skin tissues was different from the background spectrum and UV-specific, confirming the utility of the transgenic system for UVB-induced mutation studies in vivo. An analysis of the bases adjacent to the mutated cytosines from irradiated mice revealed that the dipyrimidine sites preferred for UVB-induced mutation were 5'-TC-3' > 5'-CC-3' > 5'-CT-3'. Among mutants from irradiated mice, C-->T transitions were recovered frequently at dipyrimidine sites associated with CpG. We showed that CpG sites in the lacZ transgene of Muta(TM) mice were heavily methylated in both the epidermis and dermis. Thus, CpG methylation could contribute to the UVB-induced recurrent or hotspot mutations in the mammalian genome. (C) 2003 Wiley-Liss, Inc.