NusA-dependent transcription termination prevents misregulation of global gene expression.
NusA-dependent transcription termination prevents misregulation of global gene expression.
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DOI：
10.1038/nmicrobiol.2015.7
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发表时间：
2016-01-11
影响因子：
28.3
通讯作者：
Babitzke P
中科院分区：
文献类型：
--
作者：
Mondal S;Yakhnin AV;Sebastian A;Albert I;Babitzke P
内源性转录终止子由RNA发夹和富含U的束组成，这些信号可以在不涉及其他因子的情况下触发终止。虽然已知NusA在体外刺激内在终止，但NusA的体内靶点和整体影响尚不清楚，因为它对生存力至关重要。利用全基因组3′端定位的工程枯草芽孢杆菌NusA耗竭菌株，我们表明，弱次优终止子是NusA的主要底物。此外，还鉴定了一种完全依赖NusA进行有效终止的弱非典型终止子亚类。NusA依赖性终止子倾向于具有弱发夹和/或远端U束中断，支持NusA直接参与终止机制的模型。NusA的耗尽直接和间接地通过通读次优终止子改变了全局基因表达。NusA依赖性终止子的通读导致参与基本细胞功能的基因的失调，特别是DNA复制和代谢。我们进一步表明，nusA是自动调节的转录衰减机制，不依赖于antiterminator结构。相反，NusA刺激的5′ UTR终止决定了转录到操纵子中的程度，从而确保对细胞NusA水平的严格控制。
Intrinsic transcription terminators consist of an RNA hairpin followed by a U-rich tract, and these signals can trigger termination without the involvement of additional factors. Although NusA is known to stimulate intrinsic termination in vitro, the in vivo targets and global impact of NusA are not known because it is essential for viability. Using genome-wide 3′ end-mapping on an engineered Bacillus subtilis NusA depletion strain, we show that weak suboptimal terminators are the principle NusA substrates. Moreover, a subclass of weak non-canonical terminators was identified that completely depend on NusA for effective termination. NusA-dependent terminators tend to have weak hairpins and/or distal U-tract interruptions, supporting a model in which NusA is directly involved in the termination mechanism. Depletion of NusA altered global gene expression directly and indirectly via readthrough of suboptimal terminators. Readthrough of NusA-dependent terminators caused misregulation of genes involved in essential cellular functions, especially DNA replication and metabolism. We further show that nusA is autoregulated by a transcription attenuation mechanism that does not rely on antiterminator structures. Instead, NusA-stimulated termination in its 5′ UTR dictates the extent of transcription into the operon, thereby ensuring tight control of cellular NusA levels.