miRNA前体结构中不对称凸起的位置影响miRNA生成的分子机制

miRNA是动植物中普遍存在的具有基因表达调控作用的小分子RNA。植物miRNA的生成主要依赖DCL1，且长度主要为21 nt。当miRNA/miRNA*的miRNA链上有一个不对称凸起时miRNA的长度由21 nt变成22 nt，这种改变能触发靶基因产生phasiRNA，说明miRNA前体中的不对称凸起能通过影响miRNA的长度进而影响其作用机制。但人们对不对称凸起位置对miRNA生成的影响了解较少。项目前期发现不对称凸起的位置对植物体内miRNA的长度和丰度均很重要，暗示其位置会影响miRNA的生物合成过程。本项目拟系统探究不对称凸起的位置对miRNA生成的影响，并通过DCL1切割miRNA前体和HEN1甲基化miRNA/miRNA*这两个方面，揭示不对称凸起的位置影响miRNA生成的作用机理。本项目对我们深入了解miRNA的生成、优化miRNA的表达和基因沉默效率有着重要指导意义。

miRNAs are small non-coding RNAs that can regulate the expression of endogenous genes and exist ubiquitously in plants and animal. In plants, biosynthesis of miRNAs is largely dependent on DCL1, which mainly produces miRNA of 21 nt. However, presence of an asymmetric bulge in the mature miRNA strand of miRNA/miRNA* duplex will change the length of mature miRNA from 21 nt to 22 nt, and this subtle change confers the miRNA unique capacity to trigger phasiRNA synthesis from target transcripts, indicating that asymmetric bulges in miRNA precursor could affect the function of miRNA by affecting the length of miRNA. However, positional effect of asymmetric bulges on miRNA biogenesis is poorly understood. Our previous studies show that asymmetric bulges in different positions in miRNA precursor differentially affect miRNA length and abundance, indicating that asymmetric bulge positions in miRNA precursor can affect miRNA biogenesis. The purpose of this project is to comprehensively investigate the positional effects of asymmetric bulges on miRNA biogenesis, and to reveal the mechanism through DCL1-mediated processing of miRNA precursor and HEN1-mediated miRNA/miRNA* methylation. The expected results from this project will advance current understanding about miRNA biogenesis and obtain new knowledge for optimization of miRNA-mediated gene silencing efficiency.