The CcrM DNA methyltransferase of Agrobacterium tumefaciens is essential, and its activity is cell cycle regulated
The CcrM DNA methyltransferase of Agrobacterium tumefaciens is essential, and its activity is cell cycle regulated
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DOI：
10.1128/jb.183.10.3065-3075.2001
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发表时间：
2001-05-01
影响因子：
3.2
通讯作者：
Shapiro, L
中科院分区：
文献类型：
--
作者：
Kahng, LS;Shapiro, L
DNA甲基化现在被认为是多种细菌细胞过程的调节器。CCRM是一种DNA腺嘌呤甲基转移酶，发现于蛋白质细菌的α细分中，就像DAM酶一样，主要在大肠杆菌和其他伽马蛋白质细菌中发现，它似乎不是DNA限制修饰系统的一部分。根癌农杆菌的CCRM同源物被发现是生存所必需的，CCRM的过表达与细胞形态和DNA倍体的显著异常有关，转录起点的图谱揭示了全球反应调节因子CtrA在-35位的保守结合基序；该基序是由纯化的新月弯杆菌CtrA蛋白在其磷酸化状态下足迹。我们已经成功地分离了同步的农杆菌细胞群体，并分析了它们在细胞周期中的进展。我们证明了DNA复制和细胞分裂可以有序地进行，鞭毛蛋白的表达是周期性的，这与我们观察到的细胞周期中运动性的变化是一致的。利用这些同步的群体，我们发现染色体的CCRM甲基化被限制在细胞周期的晚期S阶段。因此，在α细分中，存在一种保守的细胞周期依赖性和控制CCRM表达的调控机制。
DNA methylation is now recognized as a regulator of multiple bacterial cellular processes. CcrM is a DNA adenine methyltransferase found in the alpha subdivision of the proteobacteria, Like the Dam enzyme, which is found primarily in Escherichia coli and other gamma proteobacteria, it does not appear to be part of a DNA restriction-modification system. The CcrM homolog of Agrobacterium tumefaciens was found to be essential for viability, Overexpression of CcrM is associated with significant abnormalities of cell morphology and DNA ploidy, Mapping of the transcriptional start site revealed a conserved binding motif for the global response regulator CtrA, at the -35 position; this motif was footprinted by purified Caulobacter crescentus CtrA protein in its phosphorylated state. We have succeeded in isolating synchronized populations of Agrobacterium cells and analyzing their progression through the cell cycle. We demonstrate that DNA replication and cell division can be followed in an orderly manner and that flagellin expression is cyclic, consistent with our observation that motility varies during the cell cycle. Using these synchronized populations, we show that CcrM methylation of the chromosome is restricted to the late S phase of the cell cycle. Thus, within the alpha subdivision, there is a conserved cell cycle dependence and regulatory mechanism controlling ccrM expression.