Induction and repair of cyclobutane pyrimidine dimers in the Escherichia coli tRNA gene tyrT: Fis protein affects dimer induction in the control region and suppresses preferential repair in the coding region of the transcribed strand, except in a short region near the transcription start site
Induction and repair of cyclobutane pyrimidine dimers in the Escherichia coli tRNA gene tyrT: Fis protein affects dimer induction in the control region and suppresses preferential repair in the coding region of the transcribed strand, except in a short region near the transcription start site
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DOI：
10.1006/jmbi.1997.1154
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发表时间：
1997-08-08
影响因子：
5.6
通讯作者：
Waters, R
中科院分区：
文献类型：
--
作者：
Li, SS;Waters, R
我们分析了紫外线诱导的嘧啶二聚体在大肠杆菌tRNA基因tyrT中的诱导和修复。在野生型(WT)对数或稳定期，三个FIS结合位点和控制区的核心启动子-35序列出现了不同的诱导模式：这在FIS(-)细胞中是不存在的。在静止的WT细胞中，缓慢的、相似的修复速度发生在整个非转录链(NTS)中。在WT测井阶段，NTS控制区发生了更快的修复。FIS(-)细胞的NTS修复类似，除了控制区在不同时相之间的差异较小。异质性修复发生在转录链(TS)上。对照区修复快于NTS。TS编码区的修复在生长阶段之间发生变化，或者如果修复发生在不同的介质中。当照射后的对数相WT细胞在富含液中时，有两个明显的TS结构域：一个是转录起始点31个核苷酸范围内的快速修复结构域，另一个是由TS的其余部分组成的修复较慢的结构域。在小区域内存在一个陡峭的梯度，开始时修复非常快，到结束时修复逐渐减弱。小结构域中的快速转录偶联修复(TCR)在TS大结构域中缺失，修复类似于NTS和mfd(-)细胞中的整个TS。在同样处理的稳定期WT细胞中，TCR出现在较大的区域。FIS的缺失在较小程度上恢复了TCR，而上游激活序列中FIS结合部位的5个核苷酸的替换恢复了TCR。TCR的恢复也是通过将受照射的WT细胞孵育在不含所需氨基酸的最低盐的培养液中来实现的。我们的结果表明，FIS通过刺激转录间接抑制TS大结构域中的优先修复。(C)1997年学术出版社有限公司。
We analysed induction and repair of UV induced pyrimidine dimers in the Escherichia coli tRNA gene tyrT. In wild-type (WT) log or stationary phase different patterns of induction occurred in the three Fis binding sites and the core promoter -35 sequence of the control region: this was absent in fis(-) cells. In stationary WT cells, slow, similar rates of repair occurred throughout the non-transcribed strand (NTS). Faster repair occurred in the NTS control region in WT log phase. NTS repair in fis(-) cells was similar, except the control region differed less between phases. Heterogeneous repair occurred along the transcribed strand (TS). Ln the control region repair was faster than in the NTS. Repair in the TS coding region changed between growth phases or if repair took place in different media. When irradiated log phase WT cells were in rich medium, two TS domains were evident: a fast-repaired domain within 31 nucleotides from the transcription start site; and a more slowly repaired domain composed of the rest of the TS. A sharp gradient existed in the small domain with very fast repair at the beginning and diminished repair towards the end. Fast transcription coupled repair (TCR) in the small domain was absent in the TS large domain, where repair was similar to the NTS and to the entire TS in mfd(-) cells. Ln similarly treat-ed stationary phase WT cells, TCR occurred in the large domain. Depletion of Fis reinstates TCR to a lesser extent, whilst a substitution of five nucleotides at the Fis binding sites in the upstream activating sequence reinstates TCR. Reinstatement of TCR was also achieved by incubating irradiated WT cells in minimal salt medium without the required amino acid. Our results suggest that Fis indirectly suppresses preferential repair in the TS large domain by stimulating transcription. (C) 1997 Academic Press Limited.