Characterization of the Effects of an rpoC Mutation That Confers Resistance to the Fst Peptide Toxin-Antitoxin System Toxin
Characterization of the Effects of an rpoC Mutation That Confers Resistance to the Fst Peptide Toxin-Antitoxin System Toxin
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DOI：
10.1128/jb.01597-12
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发表时间：
2013-01-01
影响因子：
3.2
通讯作者：
Weaver, Keith E.
中科院分区：
文献类型：
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作者：
Brinkman, Cassandra L.;Bumgarner, Roger;Weaver, Keith E.
粪肠球菌（Enterococcus faecalis）菌株OG1X中Fst毒素的过度表达导致染色体分离、细胞分裂和最终膜完整性的缺陷。OG1X的M7突变体衍生物可以抵抗大多数这些影响，但在没有Fst的情况下表现出轻微的生长缺陷。全基因组测序揭示了M7与其OG1X亲本之间的两个差异。首先，OG1X包含一个移码突变，使etaR反应调节基因失活，而M7是etaR的野生型逆转基因。其次，M7突变体在编码RNA聚合酶β亚基的rpoC基因中含有一个错义突变。诱变实验表明，rpoC突变是抗性表型的主要原因。微阵列分析显示，当Fst过表达时，OG1X中会诱导许多转运蛋白。M7对Fst的反应没有诱导这些转运蛋白，进一步的实验表明这对突变细胞有直接的保护作用。因此，细胞暴露于Fst似乎具有级联效应，首先引起膜应激，然后通过某些转运蛋白的过度表达增强这些效应。
Overexpression of the Fst toxin in Enterococcus faecalis strain OG1X leads to defects in chromosome segregation, cell division and, eventually, membrane integrity. The M7 mutant derivative of OG1X is resistant to most of these effects but shows a slight growth defect in the absence of Fst. Full-genome sequencing revealed two differences between M7 and its OG1X parent. First, OG1X contains a frameshift mutation that inactivates the etaR response regulator gene, while M7 is a wild-type revertant for etaR. Second, the M7 mutant contains a missense mutation in the rpoC gene, which encodes the beta' subunit of RNA polymerase. Mutagenesis experiments revealed that the rpoC mutation was primarily responsible for the resistance phenotype. Microarray analysis revealed that a number of transporters were induced in OG1X when Fst was overexpressed. These transporters were not induced in M7 in response to Fst, and further experiments indicated that this had a direct protective effect on the mutant cells. Therefore, exposure of cells to Fst appears to have a cascading effect, first causing membrane stress and then potentiation of these effects by overexpression of certain transporters.