Gaimster Hannah, Summers David
Department of Genetics, Downing Site, University of Cambridge, Cambridge CB2 3EH, United Kingdom.
Department of Genetics, Downing Site, University of Cambridge, Cambridge CB2 3EH, United Kingdom.
Plasmid. 2015 Mar;78:59-64. doi: 10.1016/j.plasmid.2014.11.002. Epub 2014 Nov 11.
Regulation by non-coding RNAs was found to be widespread among plasmids and other mobile elements of bacteria well before its ubiquity in the eukaryotic world was suspected. As an increasing number of examples was characterised, a common mechanism began to emerge. Non-coding RNAs, such as CopA and Sok from plasmid R1, or RNAI from ColE1, exerted regulation by refolding the secondary structures of their target RNAs or modifying their translation. One regulatory RNA that seemed to swim against the tide was Rcd, encoded within the multimer resolution site of ColE1. Required for high fidelity maintenance of the plasmid in recombination-proficient hosts, Rcd was found to have a protein target, elevating indole production by stimulating tryptophanase. Rcd production is up-regulated in dimer-containing cells and the consequent increase in indole is part of the response to the rapid accumulation of dimers by over-replication (known as the dimer catastrophe). It is proposed that indole simultaneously inhibits cell division and plasmid replication, stopping the catastrophe and allowing time for the resolution of dimers to monomers. The idea of a plasmid-mediated cell division checkpoint, proposed but then discarded in the 1980s, appears to be enjoying a revival.
早在人们怀疑非编码RNA在真核生物世界中普遍存在之前，就已发现其在细菌的质粒和其他移动元件中广泛存在。随着越来越多的例子被表征，一种共同机制开始显现。非编码RNA，如质粒R1中的CopA和Sok，或ColE1中的RNAI，通过重新折叠其靶RNA的二级结构或修饰其翻译来发挥调控作用。一种似乎逆流而动的调控RNA是Rcd，它编码在ColE1的多聚体分辨率位点内。Rcd是重组能力强的宿主中质粒高保真维持所必需的，它被发现有一个蛋白质靶标，通过刺激色氨酸酶来提高吲哚的产生。Rcd的产生在含有二聚体的细胞中上调，吲哚的相应增加是对过度复制导致二聚体快速积累（称为二聚体灾难）的反应的一部分。有人提出，吲哚同时抑制细胞分裂和质粒复制，阻止灾难发生，并为二聚体分解为单体留出时间。20世纪80年代提出但随后被摒弃的质粒介导的细胞分裂检查点的概念，似乎正在复兴。
