Paschoud Serge, Dogar Afzal M, Kuntz Catherine, Grisoni-Neupert Barbara, Richman Larry, Kühn Lukas C
Swiss Institute for Experimental Cancer Research, Genetics Unit, Chemin des Boveresses 155, CH-1066 Epalinges, Switzerland.
Mol Cell Biol. 2006 Nov;26(22):8228-41. doi: 10.1128/MCB.01155-06. Epub 2006 Sep 5.
Interleukin-6 mRNA is unstable and degraded with a half-life of 30 min. Instability determinants can entirely be attributed to the 3' untranslated region. By grafting segments of this region to stable green fluorescent protein mRNA and subsequent scanning mutagenesis, we have identified two conserved elements, which together account for most of the instability. The first corresponds to a short noncanonical AU-rich element. The other, 80 nucleotides further 5', comprises a sequence predicted to form a stem-loop structure. Neither element alone was sufficient to confer full instability, suggesting that they might cooperate. Overexpression of myc-tagged AUF1 p37 and p42 isoforms as well as suppression of endogenous AUF1 by RNA interference stabilized interleukin-6 mRNA. Both effects required the AU-rich instability element. Similarly, the proteasome inhibitor MG132 stabilized interleukin-6 mRNA probably through an increase of AUF1 levels. The mRNA coimmunoprecipitated specifically with myc-tagged AUF1 p37 and p42 in cell extracts but only when the AU-rich instability element was present. These results indicate that AUF1 binds to the AU-rich element in vivo and promotes IL-6 mRNA degradation.
白细胞介素-6信使核糖核酸（mRNA）不稳定，半衰期为30分钟，会发生降解。不稳定的决定因素完全可归因于3'非翻译区。通过将该区域的片段嫁接到稳定的绿色荧光蛋白mRNA上，并随后进行扫描诱变，我们鉴定出了两个保守元件，它们共同导致了大部分的不稳定性。第一个元件对应一个短的非典型富含AU元件。另一个元件在5'端再往上游80个核苷酸处，包含一个预测会形成茎环结构的序列。单独任何一个元件都不足以赋予完全的不稳定性，这表明它们可能协同发挥作用。用myc标签的AUF1 p37和p42亚型进行过表达，以及通过RNA干扰抑制内源性AUF1，均可使白细胞介素-6 mRNA稳定。这两种效应都需要富含AU的不稳定元件。同样，蛋白酶体抑制剂MG132可能通过提高AUF1水平来稳定白细胞介素-6 mRNA。在细胞提取物中，mRNA能与用myc标签的AUF1 p37和p42特异性共免疫沉淀，但前提是存在富含AU的不稳定元件。这些结果表明，AUF1在体内与富含AU的元件结合，并促进白细胞介素-6 mRNA的降解。
