Lebruska L L, Maher L J
Department of Biochemistry and Molecular Biology, Mayo Foundation, Rochester, Minnesota 55905, USA.
Biochemistry. 1999 Mar 9;38(10):3168-74. doi: 10.1021/bi982515x.
Despite their chemical similarity, DNA and RNA sequences typically adopt very different structures within cells and are recognized by different proteins. However, a few interesting examples of proteins with dual specificity for DNA and RNA have previously been noted. These observations raise the possibility that RNA surrogates might be identified for many transcription factors that normally bind DNA. As an initial test of this novel concept, we used in vitro selection to isolate a small RNA aptamer that binds with nanomolar affinity to human transcription factor NF-kappa B, a key regulator of inflammation, HIV-1 gene expression, and apoptosis. Selected RNAs contain a 31-nucleotide core domain that was shown by mutation and deletion analyses to be necessary and sufficient for NF-kappa B binding. Neither DNA nor 2'-O-methyl RNA analogues of the aptamer bound NF-kappa B. The results of competition experiments demonstrate that binding of the RNA aptamer blocks the ability of NF-kappa B to bind duplex DNA. Expression of this aptamer structure within heterologous nuclear RNA transcripts may provide a new strategy to inhibit NF-kappa B function in vivo. Aptamers that inhibit transcription factors might be useful in a variety of applications.
尽管DNA和RNA在化学性质上相似，但它们在细胞内通常具有非常不同的结构，并且能被不同的蛋白质识别。然而，此前已经注意到一些对DNA和RNA具有双重特异性的有趣蛋白质实例。这些观察结果提出了一种可能性，即对于许多通常结合DNA的转录因子，可能会找到RNA替代物。作为对这一新概念的初步测试，我们利用体外筛选分离出一种小RNA适体，它以纳摩尔亲和力与人转录因子NF-κB结合，NF-κB是炎症、HIV-1基因表达和细胞凋亡的关键调节因子。筛选出的RNA含有一个31个核苷酸的核心结构域，通过突变和缺失分析表明该结构域对于NF-κB结合是必需且足够的。适体的DNA和2'-O-甲基RNA类似物均不与NF-κB结合。竞争实验结果表明，RNA适体的结合会阻断NF-κB结合双链DNA的能力。在异源核RNA转录本中表达这种适体结构可能为在体内抑制NF-κB功能提供一种新策略。抑制转录因子的适体可能在多种应用中有用。
