Characterization of two RNA-catalyzed RNA cleavage reactions.
Characterization of two RNA-catalyzed RNA cleavage reactions.
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两种 RNA 催化的 RNA 裂解反应的表征。
DOI：
10.1101/sqb.1987.052.01.032
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Uhlenbeck,OC
中科院分区：
文献类型：
--
作者：
Sampson,JR;Sullivan,FX;Behlen,LS;DiRenzo,AB;Uhlenbeck,OC
RNA分子具有酶活性的发现导致了第一个自我复制系统仅由RNA分子发展而来的猜测（Darnell and Doolittle 1986; Gilbert 1986）。本文介绍了两个非常不同的特定RNA自裂解反应的现代例子的实验，提供了对原始核糖核酸酶的可能机制的见解。第一个例子是发生在锤头结构域的自裂反应（Hutchins et al. 1986），涉及处理某些植物类病毒和卫星病毒的RNA基因组。第二个例子是酵母tRNA Fh~ D环中pb++依赖的裂解（Dirheimer et al. 1972）。在这两种情况下，磷酸二酯键的断裂都是酯交换反应的结果，其中2'-OH攻击核苷酸间链，形成带有2‘,3’环磷酸和5'-OH的末端。我们表明，在这两种情况下，大的速率增强是RNA链折叠成促进反应的结构域的结果。我们还发现，通过将两个独立的RNA片段通过短RNA螺旋连接在一起，可以组装活跃的自切割结构域。只有当两个片段都存在于反应混合物中时，才能观察到特定的裂解。在片段之间的链交换迅速的条件下，当过量的被切割的链存在时，就会发生多轮切割。因此，未切割的链在另一条链的特定切割中起催化剂的作用。事实上，某些短RNA片段可以作为特定的核糖核酸酶，这将有助于在益生元世界中产生独特的RNA分子。
The discovery that RNA molecules can have enzymatic activities has led to the speculation that the first self-replicating systems developed with RNA molecules alone (Darnell and Doolittle 1986; Gilbert 1986). This paper presents experiments on two very different modern examples of specific RNA self-cleavage reactions that provide insight into the possible mechanism of primitive ribonucleases. The first example is the selfcleavage reaction that occurs in the hammerhead domain (Hutchins et al. 1986) involved in processing the RNA genomes of certain plant viroids and satellite viruses. The second example is the Pb++-dependent cleavage within the D loop of yeast tRNA Fh~(Dirheimer et al. 1972). In both cases, cleavage of the phosphodiester bond is the result of a transesterification reaction, where the 2'-OH attacks the internucleotide linkage to form termini with a 2', 3'-cyclic phosphate and a 5'-OH. We show that in both cases, the large rate enhancement is a consequence of the RNA chain folding into a domain that promotes the reactions. We also tind that it is possible to assemble active self-cleaving domains by combining two separate RNA fragments that are joined together by short RNA helices. Specific cleavage is only observed when both fragments are present in the reaction mixture. Under conditions where strand exchange between the fragments is rapid, many rounds of cleavage occur when an excess of the cleaved strand is present. Thus, the uncleaved strand acts as a catalyst in the specific cleavage of the other strand. The fact that certain short RNA fragments can act as specific ribonucleases would aid in the generation of unique RNA molecules in the prebiotic world.