A conserved major groove antideterminant for Saccharomyces cerevisiae RNase III recognition.
A conserved major groove antideterminant for Saccharomyces cerevisiae RNase III recognition.
复制标题
用于酿酒酵母 RNase III 识别的保守主沟抗决定簇。
DOI：
10.1021/bi047483u
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
Chanfreau,Guillaume
中科院分区：
文献类型：
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作者：
Sam,Mui;Henras,AnthonyK;Chanfreau,Guillaume
Rnt 1 p是唯一已知的酵母核糖核酸酶III双链RNA内切酶，在核糖体RNA前体、核和核仁小RNA的加工以及未剪接前体mRNA的监视中起重要作用。Rnt 1 p切割的特异性依赖于RNA四环结构的存在，其在靶dsRNA的顶部具有共有序列AGNN。79真菌RNase III底物的序列进行了检查，以确定额外的保守序列元件或反决定簇，可能有助于Rnt 1 p识别的双链RNA。令人惊讶的是，发现除了一个检查的序列之外，在与保守的末端四环（闭合碱基对）相邻的碱基对处的U-A序列不存在。封闭碱基对的化学修饰变体的分析表明，在嘌呤大沟3'至四环的最后一个核苷酸中存在环外基团抑制Rnt 1 p切割，而不强烈抑制Rnt 1 p结合。我们建议，这些基团干扰识别的RNA底物的催化结构域的Rnt 1 p。这些结果确定四环下游的大沟中的嘌呤环外基团是S. ParaeRNase III活性中的主要反决定簇，并提出了它们在RNA加工位点中的明显反选择的基本原理。
Rnt1p, the only knownSaccharomyces cerevisiaeRNase III double-stranded RNA endonuclease, plays important roles in the processing of precursors of ribosomal RNAs and small nuclear and nucleolar RNAs and in the surveillance of unspliced pre-mRNAs. Specificity of cleavage by Rnt1p relies on the presence of RNA tetraloop structures with the consensus sequence AGNN at the top of the target dsRNA. The sequences of 79 fungal RNase III substrates were inspected to identify additional conserved sequence elements or antideterminants that may contribute to Rnt1p recognition of the double-stranded RNA. Surprisingly, U-A sequences at the base pair adjacent to the conserved terminal tetraloop (closing base pair) were found to be absent from all but one inspected sequence. Analysis of chemically modified variants of the closing base pair showed that the presence of exocyclic groups in the major groove of purines 3‘ to the last nucleotide of the tetraloop inhibits Rnt1p cleavage without strongly inhibiting Rnt1p binding. We propose that these groups interfere with the recognition of the RNA substrate by the catalytic domain of Rnt1p. These results identify exocyclic groups of purines in the major groove downstream of the tetraloop as a major antideterminant inS. cerevisiaeRNase III activity, and suggest a rationale for their apparent counter selection in RNA processing sites.