REVERSE SELF-SPLICING OF GROUP-II INTRON RNAS INVITRO
REVERSE SELF-SPLICING OF GROUP-II INTRON RNAS INVITRO
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DOI：
10.1038/343383a0
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发表时间：
1990-01-25
期刊：
影响因子：
64.8
通讯作者：
SCHWEYEN, RJ
中科院分区：
文献类型：
--
作者：
AUGUSTIN, S;MULLER, MW;SCHWEYEN, RJ
第二组内含子，这是一个保守的二级结构1的基础上分类在一起，发现在低等真核生物和植物的细胞器基因。与核前信使RNA中的内含子一样，它们通过两步剪接反应被切除，以产生分支环状RNA，即所谓的lariats 2。II组内含子的一个显著特征是它们在体外的自我剪接活性3 -6。在不存在核苷酸辅因子的情况下，内含子RNA催化两个连续的酯交换反应，这导致从前体mRNA自催化切除IXIIVS并伴随外显子连接。凭借其特异性结合5'外显子7的能力，内含子也可以催化外源RNA底物上的此类反应8。这种序列特异性连接可以使II组内含子通过反向剪接整合到未修饰的RNA中，其过程类似于自剪接四膜虫I组内含子9。在这里，我们报告说，第二组IXIVVS确实可以重新整合到RNA组成的连接外显子在体外。这是通过自剪接过程发生的，该过程完全逆转了正向反应的两个酯交换步骤：它涉及IRNA的2 '-5'磷酸二酯键转变为重建的5'剪接点的3'-5 '键。
GROUP II introns, which are classed together on the basis of a conserved secondary structure1, are found in organellar genes of lower eukaryotes and plants. Like introns in nuclear pre-messenger RNA, they are excised by a two-step splicing reaction to generate branched circular RNAs, the so-called lariats2. A remarkable feature of group II introns is their self-splicing activityin vitro3–6. In the absence of a nucleotide cofactor, the intron RNAs catalyse two successive transesterification reactions which lead to autocatalytic excision of the lariat IVS from pre-mRNA and concomitantly to exon ligation. By virtue of its ability to specifically bind the 5' exon7, the intron can also catalyse such reactions on exogenous RNA substrates8. This sequence-specific attachment could enable group II introns to integrate into unreá-lated RNAs by reverse splicing, in a process similar to that described for the self-splicingTetrahymenagroup I intron9. Here we report that group II lariat IVS can indeed reintegrate itself into an RNA composed of the ligated exonsin vitro. This occurs by a process of self-splicing that completely reverses both transesterification steps of the forward reaction: it involves a transition of the 2'–5' phosphodiester bond of the lariat RNA into the 3'–5' bond of the reconstituted 5' splice junction.