An early event in adipogenesis, the nuclear selection of the CCAAT enhancer-binding protein β (C/EBPβ) mRNA by HuR and its translocation to the cytosol
An early event in adipogenesis, the nuclear selection of the CCAAT enhancer-binding protein β (C/EBPβ) mRNA by HuR and its translocation to the cytosol
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DOI：
10.1074/jbc.m502011200
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发表时间：
2005-07-01
影响因子：
4.8
通讯作者：
Pekala, PH
中科院分区：
文献类型：
--
作者：
Gantt, K;Cherry, J;Pekala, PH
HuR是在3 '-非翻译区含有腺苷酸-尿苷酸富集元件的核mRNA的配体。一旦与mRNA结合，HuR被衔接蛋白识别，然后促进复合物的核输出。在胞质溶胶中，HuR被认为起控制其配体信息的稳定性和翻译的作用。在3 T3-L1细胞中，HuR是组成性表达的，并且主要定位于前脂肪细胞的细胞核。然而，在30分钟内暴露于分化刺激的细胞质中的HuR含量增加，与HuR调节翻译相关mRNA的可用性一致。使用体外RNA凝胶位移，我们已经证明了CCAAT增强子结合蛋白β（C/EBP β）信息是HuR的配体。在分化过程开始的2小时内，含有C/EBP β mRNA的HuR复合物可以从胞质隔室中分离出来。重要的是，该过程似乎是高度选择性的，因为细胞周期蛋白D1，其中包含一个假定的HuR结合位点，并在相同的时间框架上表达的C/EBP β，没有发现在免疫沉淀信使核糖核蛋白复合物。该事件与脂肪形成刺激的接近性以及C/EBP β对分化过程的重要性使我们假设HuR在脂肪形成开始的调节中的作用。为了支持这一假设，小干扰RNA抑制HuR蛋白含量导致C/EBP β蛋白表达的抑制和分化过程的减弱。
HuR is a ligand for nuclear mRNAs containing adenylate-uridylate-rich elements in the 3'-untranslated region. Once bound to the mRNA, HuR is recognized by adapter proteins that then facilitate nuclear export of the complex. In the cytosol, HuR is thought to function to control stability and translation of its ligand message. In the 3T3-L1 cells HuR is constitutively expressed and localized predominantly to the nucleus in the preadipocytes. However, within 30 min of exposure to the differentiation stimulus the HuR content in the cytosol increases, consistent with HuR regulating the availability of relevant mRNAs for translation. Using in vitro RNA gel shifts, we have demonstrated that the CCAAT enhancer-binding protein beta (C/EBP beta) message is a ligand for HuR. Within 2 h of initiation of the differentiation process, HuR complexes containing C/EBP beta mRNA could be isolated from the cytosolic compartment. Importantly, the process appears to be highly selective, as cyclin D1, which contains a putative HuR binding site and is expressed on the same time frame as C/EBP beta, was not found in the immunoprecipitated messenger ribonucleoprotein complexes. The proximity of this event to adipogenic stimuli and the importance of C/EBP beta to the differentiation process have led us to hypothesize a role for HuR in the regulation of the onset of adipogenesis. In support of this hypothesis, small interfering RNA suppression of HuR protein content resulted in an inhibition of C/EBP beta protein expression and an attenuation of the differentiation process.