A gene encoding an RNase D exonuclease-like protein is required for post-transcriptional silencing in Arabidopsis
A gene encoding an RNase D exonuclease-like protein is required for post-transcriptional silencing in Arabidopsis
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DOI：
10.1046/j.1365-313x.2003.01810.x
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发表时间：
2003-08-01
期刊：
影响因子：
7.2
通讯作者：
Levin, JZ
中科院分区：
文献类型：
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作者：
Glazov, E;Phillips, K;Levin, JZ
转录后基因沉默（PTGS）和与之密切相关的RNA干扰（RNAi）现象是由靶mRNA的初始核酸内切切割引起的，然后推测靶mRNA被核糖核酸外切酶完全水解。迄今为止，没有已知PTGS所需的植物基因编码核糖核酸外切酶。拟南芥Werner综合征样核酸外切酶（WEX）基因编码与人Werner综合征蛋白（WRN）最相似的RNA酶D结构域，但缺乏RecQ解旋酶结构域。它也与秀丽隐杆线虫mut-7相关，其对于RNAi、PTGS和转座子活性是必需的。我们分离出一个功能缺失突变体wex-1，它表现出WEX mRNA表达的显著降低和早花。虽然wex-1并没有影响一个强大的标记转录基因沉默（TGS）的表达，PTGS的绿色荧光蛋白（GFP）报告基因被阻止在wex-1和恢复的异位表达WEX，表明WEX是所需的PTGS，但不是TGS。因此，RNase D蛋白家族的成员是植物和动物中PTGS所必需的。有趣的是，WEX已被证明与拟南芥RecQ解旋酶相互作用，这表明这些蛋白质可能包含WRN的功能等价物。
Post-transcriptional gene silencing (PTGS) and the closely related phenomenon RNA interference (RNAi) result from the initial endonucleolytic cleavage of target mRNAs, which are then presumed to be completely hydrolyzed by exoribonucleases. To date, no plant genes required for PTGS are known to encode exoribonucleases. The Arabidopsis Werner Syndrome-like exonuclease (WEX) gene encodes an RNase D domain most similar to that in human Werner Syndrome protein (WRN), but lacks the RecQ helicase domain. It is also related to Caenorhabditis elegans mut-7, which is essential for RNAi, PTGS, and transposon activity. We isolated a loss-of-function mutant, wex-1, that showed greatly reduced expression of WEX mRNA and early flowering. Although wex-1 did not affect expression of a robust marker for transcriptional gene silencing (TGS), PTGS of a green-fluorescent-protein (GFP) reporter gene was blocked in wex-1 and restored by ectopic expression of WEX, indicating that WEX is required for PTGS but not TGS. Thus, members of the RNase D protein family are required for PTGS in both plants and animals. Interestingly, WEX has been shown to interact with an Arabidopsis RecQ helicase, suggesting that these proteins might comprise a functional equivalent of WRN.