GENETIC STUDIES OF LAC REPRESSOR .4. MUTAGENIC SPECIFICITY IN LACI GENE OF ESCHERICHIA-COLI
GENETIC STUDIES OF LAC REPRESSOR .4. MUTAGENIC SPECIFICITY IN LACI GENE OF ESCHERICHIA-COLI
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DOI：
10.1016/0022-2836(77)90059-6
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发表时间：
1977-01-01
影响因子：
5.6
通讯作者：
MILLER, JH
中科院分区：
文献类型：
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作者：
COULONDRE, C;MILLER, JH
lacI 基因中大量琥珀色和赭色位点的特征在于生成无义密码子所需的碱基变化。这些突变用于分析大肠杆菌中一系列诱变剂的正向突变谱。检查了由N''-甲基-N''-硝基-N-亚硝基胍[NG]、甲磺酸乙酯[EMS]、4-硝基喹啉-1-氧化物[NQO]和紫外光诱导的位点，以及自发产生的位点。由 G .cntdot 诱导的位点。 C.fwdarw。 .cntdot。将 T 转变与 2-氨基嘌呤诱变产生的转变进行比较。总计超过 4000 次独立发生的琥珀色和赭色突变被制成表格，以定义各自的诱变特异性。 A .cntdot 除外。 T.fwdarw。 G.cntdot。 C 改变，所有碱基替换都会导致野生型产生无义密码子。 A .cntdot。 T.fwdarw。 G.cntdot。在还原系统中监测C转变，其中对赭石到琥珀色的转化(UAA.fwdarw.UAG)以及UAA.fwdarw.UAG进行评分。 CAA 回归。 NG 和 EMS 对 G .cntdot 具有高度特异性。 C.fwdarw。 .cntdot。 T 转变，两种情况下出现的颠换均少于 1%。 G .cntdot 水平在 1% 到 5% 之间。 C.fwdarw。 .cntdot。 T改变，NG可以刺激A.cntdot。 T.fwdarw。 G.cntdot。 C 过渡。 EMS 刺激 A .cntdot。 T.fwdarw。 G.cntdot。 C转变速率显着降低。 NQO 对 G .cntdot 也具有高度特异性。 C 碱基对，但在这些位点发现的大约 10% 的变化是颠换。自发或紫外线照射后发现的突变没有表现出 EMS、NG 或 NQO 的特异性。在这两种情况下都检测到了所有颠换。紫外线照射诱导大量串联双碱基变化。其中一些是通过蛋白质测序直接验证的。 G .cntdot 引起的琥珀色和赭色突变的发生频率。 C.fwdarw。 .cntdot。对不同诱变剂的 T 转变进行了比较，揭示了几个引人注目的热点。讨论了这些发现对于诱变机制和不同诱变剂应用的影响。
An extensive set of amber and ochre sites in the lacI gene was characterized with respect to the base change required to generate the nonsense codon. These mutations were used to analyze the forward mutational spectrum of a series of mutagens in E. coli. The sites induced by N''-methyl-N''-nitro-N-nitrosoguanidine [NG], ethyl methanesulfonate [EMS], 4-nitroquinoline-1-oxide [NQO] and UV light were examined, and those which arose spontaneously. Sites induced by the G .cntdot. C .fwdarw. A .cntdot. T transition were compared with those generated by 2-aminopurine mutagenesis. All together, more than 4000 independent occurrences of amber and ochre mutations were tabulated to define the respective mutagenic specificities. With the exception of the A .cntdot. T .fwdarw. G .cntdot. C change, all base substitutions lead to the generation of nonsense codons from wild-type. The A .cntdot. T .fwdarw. G .cntdot. C transition was monitored in a reversion system, in which the ochre to amber conversion (UAA .fwdarw. UAG) was scored, as well as the UAA .fwdarw. CAA reversion. Both NG and EMS were highly specific for the G .cntdot. C .fwdarw. A .cntdot. T transition, less than 1% transversions appearing in either case. At between 1% and 5% the level of the G .cntdot. C .fwdarw. A .cntdot. T change, NG can stimulate the A .cntdot. T .fwdarw. G .cntdot. C transition. EMS stimulates the A .cntdot. T .fwdarw. G .cntdot. C transition at a significantly lower rate. NQO is also highly specific for G .cntdot. C base-pairs, but approximately 10% of the changes found at these sites are transversions. Mutations found spontaneously or after irradiation with UV light showed none of the specificities found for EMS, NG or NQO. All transversions were detected in both cases. A significant number of tandem double base changes were induced by UV irradiation. Some of these were verified directly by protein sequencing. The frequencies of occurrence of amber and ochre mutations arising from the G .cntdot. C .fwdarw. A .cntdot. T transition were compared for different mutagens, revealing several striking hotspots. The implications of these findings with respect to the mechanism of mutagenesis and the application of different mutagens are discussed.