Humphreys David T, Westman Belinda J, Martin David I K, Preiss Thomas
Molecular Genetics Program, Victor Chang Cardiac Research Institute (VCCRI), 384 Victoria Street, Darlinghurst (Sydney) NSW 2010, Australia.
Proc Natl Acad Sci U S A. 2005 Nov 22;102(47):16961-6. doi: 10.1073/pnas.0506482102. Epub 2005 Nov 15.
MicroRNAs (miRNAs) repress translation of target mRNAs by interaction with partially mismatched sequences in their 3' UTR. The mechanism by which they act on translation has remained largely obscure. We examined the translation of mRNAs containing four partially mismatched miRNA-binding sites in the 3' UTR in HeLa cells cotransfected with a cognate miRNA. The mRNAs were prepared by in vitro transcription and were engineered to employ different modes of translation initiation. We find that the 5' cap structure and the 3' poly(A) tail are each necessary but not sufficient for full miRNA-mediated repression of mRNA translation. Replacing the cap structure with an internal ribosome entry site from either the cricket paralysis virus or the encephalomyocarditis virus impairs miRNA-mediated repression. Collectively, these results demonstrate that miRNAs interfere with the initiation step of translation and implicate the cap-binding protein eukaryotic initiation factor 4E as a molecular target.
微小RNA（miRNA）通过与靶mRNA的3'非翻译区（UTR）中部分错配的序列相互作用来抑制其翻译。它们作用于翻译的机制在很大程度上仍不清楚。我们检测了在与同源miRNA共转染的HeLa细胞中，3'UTR含有四个部分错配miRNA结合位点的mRNA的翻译情况。这些mRNA通过体外转录制备，并设计采用不同的翻译起始模式。我们发现，5'帽结构和3'聚腺苷酸尾对于miRNA介导的mRNA翻译的完全抑制都是必要的，但不是充分的。用来自蟋蟀麻痹病毒或脑心肌炎病毒的内部核糖体进入位点取代帽结构会损害miRNA介导的抑制作用。总的来说，这些结果表明miRNA干扰翻译的起始步骤，并表明帽结合蛋白真核起始因子4E是一个分子靶点。
