水稻microRNA的效应复合体和靶标
2009年11月10日，北京生命科学研究所戚益军实验室在The Plant Cell杂志在线发表题为“水稻microRNA的效应复合体和靶标”的研究论文。该论文报道了水稻中microRNA (miRNA)效应复合体的生化特性，并在基因组水平系统分析了受miRNA调控的靶标基因。
miRNAs是一类在真核生物中广泛存在的，可以调控靶标基因表达的非编码RNAs。miRNAs通过与Argonaute蛋白结合后形成基因沉默效应复合体，切割靶标mRNA或抑制其翻译。水稻(Orzya_sativa)编码四个Argonaute1同源基因(AGO1a,AGO1b, AGO1c, andAGO1d)。戚益军实验室利用RNAi方法同时敲除了水稻的四个AGO1基因，发现转基因植株具有复杂的发育表型，并且许多miRNAs的靶标基因表达量上升。作者纯化了其中三个AGO1复合体，AGO1a，AGO1b，和AGO1c。研究发现这三个AGO1蛋白都具有切割mRNA的活性，并且它们都对U起始的小分子RNA具有偏好性。作者进一步克隆了与AGO1结合的小分子RNAs并进行高通量测序，发现AGO1s主要结合已知的miRNAs，而且大部分miRNAs均匀地分配到每一个AGO1中，表明这些AGO1s具有功能上的冗余性。同时，该研究还发现了一部分miRNAs只进入其中某一个或某两个AGO1蛋白，说明这些AGO1s在功能上也具有一定的特异性。本研究还对水稻MiRNAs的标靶基因进行了全基因组水平的分析和验证，发现这些目标靶基因编码包括参与重要发育的转录因子和参与其它各种生理过程的蛋白，揭示了miRNAs在水稻生长发育过程中发挥着非常重要而广泛的作用。
北京生命科学研究所博士研究生武亮，技术员张青青和周环宇为该文章的共同第一作者，论文的其他作者还有倪方锐和邬雪影。戚益军博士为本文的通讯作者。此项研究为科技部863计划和北京市科委资助课题，在北京生命科学研究所完成。（生物谷Bioon.com）
相关研究：The Plant Journal：人工miRNA介导基因沉默
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Plant Cell November 10, 2009; 10.1105/tpc.109.070938
Rice MicroRNA Effector Complexes and Targets
Liang Wu 1, Qingqing Zhang 2, Huanyu Zhou 2, Fangrui Ni 2, XueyingWu 2, and Yijun Qi 2*
1 National Institute of Biological Sciences, Beijing 102206, China;College of Life Sciences, Beijing Normal University, Beijing100875, China
2 National Institute of Biological Sciences, Beijing 102206,China
MicroRNAs (miRNAs) are small silencing RNAs with regulatory rolesin gene expression. miRNAs interact with Argonaute (AGO) proteinsto form effector complexes that cleave target mRNAs or represstranslation. Rice (Oryza sativa) encodes four AGO1 homologs (AGO1a,AGO1b, AGO1c, and AGO1d). We used RNA interference (RNAi) to knockdown the four AGO1s. The RNAi lines displayed pleiotropicdevelopmental phenotypes and had increased accumulation of miRNAtargets. AGO1a, AGO1b, and AGO1c complexes were purified andfurther characterized. The three AGO1s all have a strong preferencefor binding small RNAs (sRNAs) with 5' U and have Slicer activity.We cataloged the sRNAs in each AGO1 complex by deep sequencing andfound that all three AGO1s predominantly bound known miRNAs. Mostof the miRNAs were evenly distributed in the three AGO1 complexes,suggesting a redundant role for the AGO1s. Intriguingly, a subsetof miRNAs were specifically incorporated into or excluded from oneof the AGO1s, suggesting functional specialization among the AGO1s.Furthermore, we identified rice miRNA targets at a global level.The validated targets include transcription factors that controlmajor stages of development and also genes involved in a variety ofphysiological processes, indicating a broad regulatory role formiRNAs in rice.