Bacterial toxin YafQ is an endoribonuclease that associates with the ribosome and blocks translation elongation through sequence-specific and frame-dependent mRNA cleavage
Bacterial toxin YafQ is an endoribonuclease that associates with the ribosome and blocks translation elongation through sequence-specific and frame-dependent mRNA cleavage
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DOI：
10.1111/j.1365-2958.2008.06572.x
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发表时间：
2009-03-01
影响因子：
3.6
通讯作者：
Woychik, Nancy A.
中科院分区：
文献类型：
--
作者：
Prysak, Meredith H.;Mozdzierz, Christopher J.;Woychik, Nancy A.
自由生活的细菌染色体上的毒素-抗毒素（TA）系统似乎通过诱导可逆的生长停滞状态来促进细胞在压力间隔期间的存活。然而，在长时间的压力下，TA毒素的作用导致细胞死亡。它们与一些重要的临床现象有关——抗生素治疗期间细菌的持久性、生物膜的形成和细菌的发病机制——并且是病原体的有吸引力的新的抗生素靶点。我们确定了DinJ-YafQ TA系统中YafQ毒素的作用方式。表达YafQ可抑制翻译，但不抑制转录或复制。纯化的YafQ在体外表现出强大的核糖核酸酶活性，这种活性被添加DinJ特异性阻断。然而，YafQ在体内与核糖体相关，并通过在AAA赖氨酸密码子上切割G或a，促进了5'端附近mRNA的快速降解。YafQ（H87Q）突变体失去了毒性和切割活性，但保留了核糖体的关联。最后，LexA结合到dinJ-yafQ回文并在DNA损伤后触发模块转录。YafQ功能不同于其他TA毒素：它通过50S亚基与核糖体结合，介导序列特异性和框架依赖性的（5‘）AAA - G/A（3’）序列的mRNA裂解，导致可能由mRNA降解体促进的快速衰变。
Toxin-antitoxin (TA) systems on the chromosomes of free-living bacteria appear to facilitate cell survival during intervals of stress by inducing a state of reversible growth arrest. However, upon prolonged stress, TA toxin action leads to cell death. They have been implicated in several clinically important phenomena - bacterial persistence during antibiotic treatment, biofilm formation and bacterial pathogenesis - and serve as attractive new antibiotic targets for pathogens. We determined the mode of action of the YafQ toxin of the DinJ-YafQ TA system. YafQ expression resulted in inhibition of translation, but not transcription or replication. Purified YafQ exhibited robust ribonuclease activity in vitro that was specifically blocked by the addition of DinJ. However, YafQ associated with ribosomes in vivo and facilitated rapid mRNA degradation near the 5' end via cleavage at AAA lysine codons followed by a G or A. YafQ(H87Q) mutants lost toxicity and cleavage activity but retained ribosome association. Finally, LexA bound to the dinJ-yafQ palindrome and triggered module transcription after DNA damage. YafQ function is distinct from other TA toxins: it associates with the ribosome through the 50S subunit and mediates sequence-specific and frame-dependent mRNA cleavage at (5')AAA - G/A(3') sequences leading to rapid decay possibly facilitated by the mRNA degradosome.