Cullin 4B Is Recruited to Tristetraprolin-Containing Messenger Ribonucleoproteins and Regulates TNF-α mRNA Polysome Loading
Cullin 4B Is Recruited to Tristetraprolin-Containing Messenger Ribonucleoproteins and Regulates TNF-α mRNA Polysome Loading
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DOI：
10.4049/jimmunol.1102837
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发表时间：
2012-02-15
影响因子：
4.4
通讯作者：
Brooks, Seth A.
中科院分区：
文献类型：
--
作者：
Pfeiffer, Jason R.;Brooks, Seth A.
TNF-α是炎症的中心介质，对于宿主对感染和损伤的反应至关重要。TNF-α生物合成受转录和转录后机制控制，允许快速、瞬时产生。Tristetraprolin（TTP）是一种富含AU的元件结合蛋白，可调节TNF-α mRNA的稳定性。使用屏幕，以确定TTP相互作用的蛋白质，我们确定了Cullin 4 B（Cul 4 B），泛素E3连接酶的Cullin环指连接酶家族的支架组件。Cul 4 B的短发夹RNA敲低导致LPS刺激的小鼠巨噬细胞RAW 264.7细胞中TNF-α蛋白和mRNA的显著减少以及TTP蛋白的减少。在LPS刺激的细胞中，TNF-α信使t（1/2）从69分钟降低至33分钟。利用野生型和突变型TTP-AA（S52 A，S178 A）的TNF-3'非翻译区荧光素酶测定表明，TTP功能在Cul 4 B短发夹RNA细胞中增强。重要的是，Cul 4 B敲低降低了响应于LPS刺激的TNF-α mRNA多核糖体加载的倍数诱导。Cul 4 B存在于多聚核糖体上，并与TTP共定位于外泌体和加工体，这是mRNA降解的位点。我们得出结论，Cul 4 B许可证的TTP含TNF-α信使核糖核蛋白装载到多核糖体上，Cul 4 B表达的减少分流到降解途径的信使核糖核蛋白。免疫学杂志，2012，188：1828-1839。
TNF-alpha is a central mediator of inflammation and critical for host response to infection and injury. TNF-alpha biosynthesis is controlled by transcriptional and posttranscriptional mechanisms allowing for rapid, transient production. Tristetraprolin (TTP) is an AU-rich element binding protein that regulates the stability of the TNF-alpha mRNA. Using a screen to identify TTP-interacting proteins, we identified Cullin 4B (Cul4B), a scaffolding component of the Cullin ring finger ligase family of ubiquitin E3 ligases. Short hairpin RNA knockdown of Cul4B results in a significant reduction in TNF-alpha protein and mRNA in LPS-stimulated mouse macrophage RAW264.7 cells as well as a reduction in TTP protein. TNF-alpha message t(1/2) was reduced from 69 to 33 min in LPS-stimulated cells. TNF-3' untranslated region luciferase assays utilizing wild-type and mutant TTP-AA (S52A, S178A) indicate that TTP function is enhanced in Cul4B short hairpin RNA cells. Importantly, the fold induction of TNF-alpha mRNA polysome loading in response to LPS stimulation is reduced by Cul4B knockdown. Cul4B is present on the polysomes and colocalizes with TTP to exosomes and processing bodies, which are sites of mRNA decay. We conclude that Cul4B licenses the TTP-containing TNF-alpha messenger ribonucleoprotein for loading onto polysomes, and reduction of Cul4B expression shunts the messenger ribonucleoproteins into the degradative pathway. The Journal of Immunology, 2012, 188: 1828-1839.