MAC3A and MAC3B, Two Core Subunits of the MOS4-Associated Complex, Positively Influence miRNA Biogenesis
MAC3A and MAC3B, Two Core Subunits of the MOS4-Associated Complex, Positively Influence miRNA Biogenesis
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DOI：
10.1105/tpc.17.00953
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发表时间：
2018-02-01
期刊：
影响因子：
11.6
通讯作者：
Yu, Bin
中科院分区：
文献类型：
--
作者：
Li, Shengjun;Liu, Kan;Yu, Bin
MAC3A和MAC3B是真核生物中保守的含有u -box的蛋白。它们是mos4相关复合体（MAC）的亚基，在拟南芥的植物免疫和发育中起重要作用。然而，它们的功能机制仍然难以捉摸。在这里，我们发现拟南芥MAC3A和MAC3B在microRNA （miRNA）生物发生中起冗余作用。MAC3B - MAC3B双突变体中缺少MAC3A和MAC3B减少了miRNA的积累，导致miRNA靶点转录水平升高。mac3a mac3b也会降低初级miRNA转录物（pri-miRNA）的水平。然而，MAC3A和MAC3B不影响miRNAs编码基因（MIR基因）的启动子活性，提示它们可能不影响MIR转录。这一结果，再加上MAC3A在体内与primiRNAs结合的事实，表明MAC3A和MAC3B可以稳定primiRNAs。此外，我们发现MAC3A和MAC3B与DCL1复合物相互作用，催化miRNA成熟，促进DCL1活性，并且是定位DCL1复合物组分HYL1所必需的。除了MAC3A和MAC3B，另外两个MAC亚基CDC5和PRL1也在miRNA生物发生中发挥作用。基于这些结果，我们提出MAC作为一个复合物通过调节pri-miRNA的转录、加工和稳定性来控制miRNA水平。
MAC3A and MAC3B are conserved U-box-containing proteins in eukaryotes. They are subunits of the MOS4-associated complex (MAC) that plays essential roles in plant immunity and development in Arabidopsis thaliana. However, their functional mechanisms remain elusive. Here, we show that Arabidopsis MAC3A and MAC3B act redundantly in microRNA (miRNA) biogenesis. Lack of both MAC3A and MAC3B in the mac3b mac3b double mutant reduces the accumulation of miRNAs, causing elevated transcript levels of miRNA targets. mac3a mac3b also decreases the levels of primary miRNA transcripts (pri-miRNAs). However, MAC3A and MAC3B do not affect the promoter activity of genes encoding miRNAs (MIR genes), suggesting that they may not affect MIR transcription. This result, together with the fact that MAC3A associates with primiRNAs in vivo, indicates that MAC3A and MAC3B may stabilize pri-miRNAs. Furthermore, we find that MAC3A and MAC3B interact with the DCL1 complex that catalyzes miRNA maturation, promote DCL1 activity, and are required for the localization of HYL1, a component of the DCL1 complex. Besides MAC3A and MAC3B, two other MAC subunits, CDC5 and PRL1, also function in miRNA biogenesis. Based on these results, we propose that MAC functions as a complex to control miRNA levels through modulating pri-miRNA transcription, processing, and stability.