A pathway for the biogenesis of trans-acting siRNAs in Arabidopsis
A pathway for the biogenesis of trans-acting siRNAs in Arabidopsis
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DOI：
10.1101/gad.1352605
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发表时间：
2005-09-15
影响因子：
10.5
通讯作者：
Poethig, RS
中科院分区：
文献类型：
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作者：
Yoshikawa, M;Peragine, A;Poethig, RS
拟南芥基因TAS 2和TAS 1a产生结构相似的非编码转录本，通过RNA沉默途径转化为短（21-核苷酸[nt]）和长（24-nt）siRNA。这些短siRNA中的一些指导蛋白质编码转录物的切割，并且因此作为反式作用siRNA（ta-siRNA）起作用。使用遗传分析，我们确定了从这些基因座产生ta-siRNA和其他短siRNA的途径。该过程由miR 173指导的初级poly（A）转录物的切割启动。然后通过SGS 3、RDR 6和DCL 4的顺序活性将3'片段转化为短siRNA：SGS 3稳定片段，RDR 6产生互补链，DCL 4将所得双链分子切割成短siRNA，从末端的miR 173切割位点开始，并从该点以21-nt增量进行。5'切割片段也通过该途径加工，但效率较低。产生长siRNA的DCL 3依赖性途径不需要miRNA指导的切割，并且在这些基因座的沉默中起次要作用。我们的研究结果定义了拟南芥转录后基因沉默途径的核心组成部分，并揭示了一些功能，直接转录到这个途径。
The Arabidopsis genes, TAS2 and TAS1a, produce structurally similar noncoding transcripts that are transformed into short (21-nucleotide [nt]) and long (24-nt) siRNAs by RNA silencing pathways. Some of these short siRNAs direct the cleavage of protein-coding transcripts, and thus function as trans-acting siRNAs (ta-siRNAs). Using genetic analysis, we defined the pathway by which ta-siRNAs and other short siRNAs are generated from these loci. This process is initiated by the miR173-directed cleavage of a primary poly(A) transcript. The 3' fragment is then transformed into short siRNAs by the sequential activity of SGS3, RDR6, and DCL4: SGS3 stabilizes the fragment, RDR6 produces a complementary strand, and DCL4 cleaves the resulting double-stranded molecule into short siRNAs, starting at the end with the miR173 cleavage site and proceeding in 21-nt increments from this point. The 5' cleavage fragment is also processed by this pathway, but less efficiently. The DCL3-dependent pathway that generates long siRNAs does not require miRNA-directed cleavage and plays a minor role in the silencing of these loci. Our results define the core components of a post-transcriptional gene silencing pathway in Arabidopsis and reveal some of the features that direct transcripts to this pathway.