Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan.
Genetics. 2011 Jan;187(1):123-30. doi: 10.1534/genetics.110.121798. Epub 2010 Oct 26.
RNase LS was originally identified as a potential antagonist of bacteriophage T4 infection. When T4 dmd is defective, RNase LS activity rapidly increases after T4 infection and cleaves T4 mRNAs to antagonize T4 reproduction. Here we show that rnlA, a structural gene of RNase LS, encodes a novel toxin, and that rnlB (formally yfjO), located immediately downstream of rnlA, encodes an antitoxin against RnlA. Ectopic expression of RnlA caused inhibition of cell growth and rapid degradation of mRNAs in ΔrnlAB cells. On the other hand, RnlB neutralized these RnlA effects. Furthermore, overexpression of RnlB in wild-type cells could completely suppress the growth defect of a T4 dmd mutant, that is, excess RnlB inhibited RNase LS activity. Pull-down analysis showed a specific interaction between RnlA and RnlB. Compared to RnlA, RnlB was extremely unstable, being degraded by ClpXP and Lon proteases, and this instability may increase RNase LS activity after T4 infection. All of these results suggested that rnlA-rnlB define a new toxin-antitoxin (TA) system.
RNase LS 最初被鉴定为噬菌体 T4 感染的潜在拮抗剂。当 T4 dmd 缺失时，T4 感染后 RNase LS 活性迅速增加，并切割 T4 mRNA 以拮抗 T4 繁殖。在这里，我们表明，RNase LS 的结构基因 rnlA 编码一种新型毒素，而位于 rnlA 下游的 rnlB（正式命名为 yfjO）编码一种针对 RnlA 的解毒剂。RnlA 的异位表达导致 ΔrnlAB 细胞的细胞生长抑制和 mRNA 的快速降解。另一方面，RnlB 中和了这些 RnlA 效应。此外，在野生型细胞中过表达 RnlB 可以完全抑制 T4 dmd 突变体的生长缺陷，即过量的 RnlB 抑制了 RNase LS 活性。下拉分析显示 RnlA 和 RnlB 之间存在特异性相互作用。与 RnlA 相比，RnlB 极不稳定，被 ClpXP 和 Lon 蛋白酶降解，这种不稳定性可能会增加 T4 感染后的 RNase LS 活性。所有这些结果表明，rnlA-rnlB 定义了一个新的毒素-抗毒素（TA）系统。
