The bacterial cell cycle regulator GcrA is a σ70 cofactor that drives gene expression from a subset of methylated promoters.
The bacterial cell cycle regulator GcrA is a σ70 cofactor that drives gene expression from a subset of methylated promoters.
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DOI：
10.1101/gad.270660.115
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发表时间：
2015-11-01
影响因子：
10.5
通讯作者：
Laub MT
中科院分区：
文献类型：
--
作者：
Haakonsen DL;Yuan AH;Laub MT
Haakonsen等人发现新月柄杆菌中的基本细胞周期调节因子GcrA与RNA聚合酶形成稳定的复合物，并定位于体内几乎所有活性σ70依赖性启动子，但主要在含有某些DNA甲基化位点的启动子处激活转录。GcrA可以稳定RNA聚合酶结合，并直接刺激开放复合物的形成以激活转录。大多数生物体的细胞周期进程需要严格调控的基因表达程序。所涉及的转录因子通常通过结合启动子中的特异性DNA序列和募集RNA聚合酶来刺激基因表达。在这里，我们发现新月柄杆菌中的基本细胞周期调节因子GcrA以一种根本不同的方式激活靶基因的转录。GcrA与RNA聚合酶形成稳定的复合物，并定位于体内几乎所有的活性σ70依赖性启动子，但主要在含有某些DNA甲基化位点的启动子处激活转录。尽管大多数与σ70接触的转录因子与结构域4相互作用，但GcrA与结构域2相互作用，结构域2是在链分离过程中结合-10元件的区域。使用动力学分析和重建的体外转录测定，我们证明了GcrA可以稳定RNA聚合酶结合，并直接刺激开放复合物的形成，以激活转录。在这些研究的指导下，我们确定了一个由200个基因组成的调节子，为GcrA的基本功能提供了新的见解。总的来说，我们的工作揭示了一种新的转录调控机制，我们讨论了通过促进RNA聚合酶异构化而不是完全招募来激活转录的潜在益处。
Haakonsen et al. find that the essential cell cycle regulator GcrA in Caulobacter crescentus forms a stable complex with RNA polymerase and localizes to almost all active σ70-dependent promoters in vivo but activates transcription primarily at promoters harboring certain DNA methylation sites. GcrA could stabilize RNA polymerase binding and directly stimulate open complex formation to activate transcription. Cell cycle progression in most organisms requires tightly regulated programs of gene expression. The transcription factors involved typically stimulate gene expression by binding specific DNA sequences in promoters and recruiting RNA polymerase. Here, we found that the essential cell cycle regulator GcrA in Caulobacter crescentus activates the transcription of target genes in a fundamentally different manner. GcrA forms a stable complex with RNA polymerase and localizes to almost all active σ70-dependent promoters in vivo but activates transcription primarily at promoters harboring certain DNA methylation sites. Whereas most transcription factors that contact σ70 interact with domain 4, GcrA interfaces with domain 2, the region that binds the −10 element during strand separation. Using kinetic analyses and a reconstituted in vitro transcription assay, we demonstrated that GcrA can stabilize RNA polymerase binding and directly stimulate open complex formation to activate transcription. Guided by these studies, we identified a regulon of ∼200 genes, providing new insight into the essential functions of GcrA. Collectively, our work reveals a new mechanism for transcriptional regulation, and we discuss the potential benefits of activating transcription by promoting RNA polymerase isomerization rather than recruitment exclusively.