The ability to form full-length intron RNA circles is a general property of nuclear group I introns
The ability to form full-length intron RNA circles is a general property of nuclear group I introns
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DOI：
10.1261/rna.5290903
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发表时间：
2003-12-01
期刊：
影响因子：
4.5
通讯作者：
Johansen, S
中科院分区：
文献类型：
--
作者：
Nielsen, H;Fiskaa, T;Johansen, S
除了剪接之外，I组内含子RNA还能够通过另一种两步加工途径形成全长内含子环状RNA。环化途径通过在3'剪接位点处的水解裂解开始，然后是酯交换反应，其中内含子末端鸟苷攻击以类似于剪接的第一步的结构存在的5'剪接位点。反应的产物是全长环状内含子和未连接的外显子。由于这个原因，环化反应是以牺牲宿主为代价而有利于内含子的。环化途径具有不同于剪接的不同结构要求，并且似乎在体内被特异性抑制。形成全长环的能力在所有类型的核I组内含子中发现，包括来自四膜虫核糖体DNA的那些。全长圆圈的生物学功能尚不清楚，但圆圈包含内含子的整个遗传信息的事实表明内含子移动性中的作用。
In addition to splicing, group I intron RNA is capable of an alternative two-step processing pathway that results in the formation of full-length intron circular RNA. The circularization pathway is initiated by hydrolytic cleavage at the 3' splice site and followed by a transesterification reaction in which the intron terminal guanosine attacks the 5' splice site presented in a structure analogous to that of the first step of splicing. The products of the reactions are full-length circular intron and unligated exons. For this reason, the circularization reaction is to the benefit of the intron at the expense of the host. The circularization pathway has distinct structural requirements that differ from those of splicing and appears to be specifically suppressed in vivo. The ability to form full-length circles is found in all types of nuclear group I introns, including those from the Tetrahymena ribosomal DNA. The biological function of the full-length circles is not known, but the fact that the circles contain the entire genetic information of the intron suggests a role in intron mobility.