Immediate mediators of the inflammatory response are poised for gene activation through RNA polymerase II stalling
Immediate mediators of the inflammatory response are poised for gene activation through RNA polymerase II stalling
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DOI：
10.1073/pnas.0910177106
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发表时间：
2009-10-27
影响因子：
11.1
通讯作者：
Rogatsky, Inez
中科院分区：
文献类型：
--
作者：
Adelman, Karen;Kennedy, Megan A.;Rogatsky, Inez
细胞因子基因表达的动力学和幅度受到严格调控，以对病原体产生平衡的反应，这是转录和mRNA稳定性综合变化的结果。然而，单一的微生物刺激如何在数分钟内诱导某些基因（肿瘤坏死因子α）达到转录峰值，而其他基因（干扰素诱导蛋白10）则需要数小时，这仍不清楚。在此，我们剖析了巨噬细胞中几种脂多糖（LPS）诱导基因的激活情况，巨噬细胞是哺乳动物中介导炎症反应的一种重要细胞类型。我们发现这些基因之间的一个关键差异在于它们受调控的转录周期阶段。具体而言，对于肿瘤坏死因子α，RNA聚合酶II在静息巨噬细胞中启动转录，但在启动子附近停滞，直到LPS触发负延伸因子（NELF）复合物的快速且短暂释放以及有效延伸。相比之下，在诱导前在干扰素诱导蛋白10启动子附近检测不到NELF或聚合酶，并且LPS依赖的聚合酶募集是转录的限速步骤。我们进一步证明这种策略被其他免疫介质所共有，并且与负责基因激活的诱导物和信号通路无关。最后，作为进化保守的一个显著例子，肿瘤坏死因子α基因的果蝇同源物eiger显示出所有依赖NELF的聚合酶停滞的特征。我们提出聚合酶停滞确保了从果蝇到哺乳动物的炎症基因表达程序的协调、及时激活。
The kinetics and magnitude of cytokine gene expression are tightly regulated to elicit a balanced response to pathogens and result from integrated changes in transcription and mRNA stability. Yet, how a single microbial stimulus induces peak transcription of some genes (TNF alpha) within minutes whereas others (IP-10) require hours remains unclear. Here, we dissect activation of several lipopolysaccharide (LPS)-inducible genes in macrophages, an essential cell type mediating inflammatory response in mammals. We show that a key difference between the genes is the step of the transcription cycle at which they are regulated. Specifically, at TNF alpha, RNA Polymerase II initiates transcription in resting macrophages, but stalls near the promoter until LPS triggers rapid and transient release of the negative elongation factor (NELF) complex and productive elongation. In contrast, no NELF or polymerase is detectible near the IP-10 promoter before induction, and LPS-dependent polymerase recruitment is rate limiting for transcription. We further demonstrate that this strategy is shared by other immune mediators and is independent of the inducer and signaling pathway responsible for gene activation. Finally, as a striking example of evolutionary conservation, the Drosophila homolog of the TNF alpha gene, eiger, displayed all of the hallmarks of NELF-dependent polymerase stalling. We propose that polymerase stalling ensures the coordinated, timely activation the inflammatory gene expression program from Drosophila to mammals.