中文摘要：

microRNA是一大类长度约22 nt的非编码RNA,可与靶基因的3＇UTR区部分或完全配对结合,进而通过降低靶mRNA的稳定性或抑制翻译而下调目的基因的表达.microRNA不仅参与细胞的增殖、分化、死亡等正常生理过程,而且还与包括癌症在内的诸多病理过程密切相关.microRNA通常位于编码基因的内含子区,主要由RNA聚合酶Ⅱ催化而转录为初始microRNA,接着经过一系列的核内、胞浆内酶切步骤而组装成有功能的RNA诱导的沉默复合体.本文将在简要介绍microRNA生物合成和调控功能的基础上,重点综述microRNA被调控的研究进展,主要包括表观遗传学水平、转录水平、转录后水平和降解的调控.近年来的研究,逐步丰富甚至推翻了以往对microRNA的认识,体现了microRNA生物学的复杂性.可以预见,随着研究的深入,microRNA将在疾病的早期防治中发挥越来越重要的作用.

英文摘要：

microRNAs are a category of small （ - 22 nt ） non-coding RNAs that are completely or partially base-paired with 3＇ UTR of target gene transcripts and downregulate their expression by degradation or repressing translation. microRNAs play a key role in physiological processes of cell proliferation, differentiation and death, and are also involved in cancer-related pathological conditions. microRNAs are typically located within introns of coding genes and transcribed by RNA polymerase II. Following enzymatic processing at both the nucleus and cytoplasm, mature microRNAs are assembled into RNA-induced silencing complex for functions. In this review, we summarized the present understanding of microRN A biogenesis and the regulatory functions of miRN As with the focus on the mechanisms of miRNAs expression at the control of epigenetic, transcriptional, post-transcriptional and degradation levels. Recent studies have presented various views about the microRN As system of biological complexity.