Fossett N G, Byrne B J, Tucker A B, Arbour-Reily P, Chang S, Lee W R
Institute for Mutagenesis, Louisiana State University, Baton Rouge 70803-1725, USA.
Mutat Res. 1996 Jul 5;354(1):143-4. doi: 10.1016/0027-5107(95)00248-0.
The 2-chloroethyl methanesulfonate (2CIEMS)-induced alcohol dehydrogenase (Adh) null germline mutation frequency in treated Drosophila melanogaster second instar larval gonia was two orders of magnitude greater than the spontaneous mutation frequency. DNA sequence analysis of 83 Adh null mutations showed that 40 mutations of independent origin were at 23 sites in the Adh gene. The mutation spectrum contained only GC --> AT transitions with 35 mutations (87.5%) at the middle or 3' guanine. In addition, characteristics of glutathione (GSH)-mediated bioactivation were determined for 2CIEMS in vitro. Rates of GSH-mediated conjugation, catalyzed by purified rat liver glutathione-S-transferase (GST), and binding of [35S]GSH-mediated conjugation products to calf thymus DNA were determined for 2CIEMS, 1,2-dichloroethane (EDC) and 1,2-dibromoethane (EDB). The relative rates of GSH-mediated conjugation were the following: 5 mM EDB > 40 mM 2CIEMS > 40 mM EDC. A similar trend was observed for DNA binding of the [35S]GSH-mediated conjugation products when differences in mutagen concentration were considered: EDB > 2CIEMS > EDC. The ratios of DNA binding to GSH conjugation calculated for EDB, EDC and 2CIEMS were 6.8 x 10(-5), 9.3 x 10(-5) and 19.1 x 10(-5), respectively. A narrow range, less than a 3-fold difference, in the ratios of DNA binding to GSH conjugation indicates that the bioactivation of 2CIEMS is mediated by the same mechanism as EDB and EDC. Consequently, 2CIEMS, EDC and EDB may induce a specific mutation in premeiotic germ cells.
在经2-氯乙基甲磺酸酯（2CIEMS）处理的黑腹果蝇二龄幼虫生殖腺中，诱发的乙醇脱氢酶（Adh）无效种系突变频率比自发突变频率高两个数量级。对83个Adh无效突变进行的DNA序列分析表明，40个独立起源的突变位于Adh基因的23个位点。突变谱仅包含GC→AT转换，其中35个突变（87.5%）位于中间或3'鸟嘌呤处。此外，还在体外测定了2CIEMS的谷胱甘肽（GSH）介导的生物活化特性。测定了2CIEMS、1,2-二氯乙烷（EDC）和1,2-二溴乙烷（EDB）经纯化的大鼠肝脏谷胱甘肽-S-转移酶（GST）催化的GSH介导的结合速率，以及[35S]GSH介导的结合产物与小牛胸腺DNA的结合情况。GSH介导的结合相对速率如下：5 mM EDB＞40 mM 2CIEMS＞40 mM EDC。当考虑诱变剂浓度差异时，[35S]GSH介导的结合产物与DNA结合也观察到类似趋势：EDB＞2CIEMS＞EDC。计算得出的EDB、EDC和2CIEMS的DNA结合与GSH结合比率分别为6.8×10^(-5)、9.3×10^(-5)和19.1×10^(-5)。DNA结合与GSH结合比率的差异范围较窄，相差不到3倍，这表明2CIEMS的生物活化与EDB和EDC是由相同机制介导的。因此，2CIEMS、EDC和EDB可能在减数分裂前生殖细胞中诱发特定突变。
