Thomas S M, MacPhee D G
Department of Microbiology, La Trobe University, Bundoora, Victoria, Austrialia.
Mutagenesis. 1986 May;1(3):191-4. doi: 10.1093/mutage/1.3.191.
We have studied the effects of a umuC mutation on reversion of the lacZ19124 and lacZ19136 frameshift markers of Escherichia coli. Introduction of a umuC::Tn5 mutation into a strain carrying the lacZ19136 marker resulted in enhanced reversion by 9-aminoacridine and the acridine half-mustard ICR191, whereas reversion of the lacZ19124 marker was decreased (but not abolished) in a umuC strain. The reversion frequency of the lacZ19136 marker was decreased by the presence of plasmid pKM101, and further decreased by a derivative of pKM101 in which the mucB gene was inactivated by a Tn5 insertion. The reversion frequency of the lacZ19124 marker was relatively unchanged by either plasmid. Since both 9-aminoacridine and ICR191 mutagenesis of these strains is independent of the recA+ and lexA+ gene products, these results may suggest a broader role for the UmuC protein in regulating induced mutation frequencies than has previously been suspected. The contrasting effects of the umuC and mucB mutations on reversion of the lacZ19136 marker may suggest a copy number effect, or perhaps more likely that there are inherent (functional) differences between the UmuC and MucB proteins.
我们研究了umuC突变对大肠杆菌lacZ19124和lacZ19136移码标记回复突变的影响。将umuC::Tn5突变引入携带lacZ19136标记的菌株中，导致9-氨基吖啶和吖啶半芥子气ICR191诱导的回复突变增强，而在umuC菌株中，lacZ19124标记的回复突变减少（但未消除）。质粒pKM101的存在降低了lacZ19136标记的回复突变频率，而pKM101的一个衍生物（其中mucB基因被Tn5插入失活）进一步降低了回复突变频率。两种质粒对lacZ19124标记的回复突变频率相对没有影响。由于这些菌株的9-氨基吖啶和ICR191诱变均独立于recA+和lexA+基因产物，这些结果可能表明UmuC蛋白在调节诱导突变频率方面的作用比以前认为的更为广泛。umuC和mucB突变对lacZ19136标记回复突变的相反影响可能表明存在拷贝数效应，或者更有可能的是，UmuC和MucB蛋白之间存在内在（功能）差异。
