Relationship between 3' end formation and SL2-specific trans-splicing in polycistronic Caenorhabditis elegans pre-mRNA processing.
Relationship between 3' end formation and SL2-specific trans-splicing in polycistronic Caenorhabditis elegans pre-mRNA processing.
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发表时间：
1997-03
期刊：
影响因子：
4.5
通讯作者：
S. Kuersten;K. Lea;M. MacMorris;J. Spieth;T. Blumenthal
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作者：
S. Kuersten;K. Lea;M. MacMorris;J. Spieth;T. Blumenthal
线虫秀丽隐杆线虫中大约 25% 的基因位于操纵子（多顺反子转录单位）中，其中基因仅相距 100-400 bp。通过上游 mRNA 3' 端的切割和聚腺苷酸化以及下游 mRNA 5' 端的 SL2 反式剪接的组合，操纵子前体 mRNA 被加工成单顺反子 mRNA。为了确定 3' 末端形成和 SL2 反式剪接是否以机械方式耦合，我们测试了由秀丽隐杆线虫热休克启动子驱动的 gpd-2/gpd-3 操纵子构建体，并测量了 3' 末端形成和/或反式剪接的抑制对多顺反子 RNA 体内加工的影响。结果表明，下游 mRNA 反式剪接的 SL2 特异性需要操纵子中上游 mRNA 的正确 3' 端形成。相反，下游 mRNA 的转拼对于上游 mRNA 的正确 3' 端形成来说不是必需的。此外，缩短gpd-2（上游基因）的5'帽和AAUAAA之间的距离会降低3'末端形成的效率，并且伴随着下游基因gpd-3的反式剪接位点处的SL2被SL1取代。这些结果表明，线虫中的 SL2 反式剪接在多顺反子前 mRNA 加工过程中与 3' 末端形成机械耦合。
About 25% of the genes in the nematode Caenorhabditis elegans are in operons, polycistronic transcription units in which the genes are only 100-400 bp apart. The operon pre-mRNAs are processed into monocistronic mRNAs by a combination of cleavage and polyadenylation at the 3' end of the upstream mRNA and SL2 trans-splicing at the 5' end of the downstream mRNA. To determine whether 3' end formation and SL2 trans-splicing are coupled mechanistically, we tested a gpd-2/gpd-3 operon construct driven by a C. elegans heat shock promoter, and measured the effects of inhibition of 3' end formation and/or trans-splicing on the processing of the polycistronic RNA in vivo. The results indicate that proper 3' end formation of the upstream mRNA in an operon is required for SL2-specificity of downstream mRNA trans-splicing. In contrast, trans-splicing of the downstream mRNA is not necessary for correct 3' end formation of the upstream mRNA. In addition, shortening the distance between the 5' cap and the AAUAAA of gpd-2 (the upstream gene) decreases the efficiency of 3' end formation and is accompanied by a replacement of SL2 with SL1 at the trans-splice site of gpd-3, the downstream gene. These results indicate that SL2 trans-splicing, in C. elegans, is coupled mechanistically to 3' end formation in the processing of polycistronic pre-mRNAs.