中文摘要：

MicroRNA（miRNA）是一类长约21～25nt的内源性单链小分子RNA（small RNA），可调节与其序列互补mRNA的表达，普遍存在于高等生物界，在不同物种间具有高度的保守性，表达具有细胞特异性或组织特异性。通过与mRNAs特异性的碱基配对，引导靶序列进入降解或（和）翻译抑制，以此参与个体发育、细胞分化、细胞增殖、物种进化以及疾病发生过程中的基因表达调控。该文简述了近年对miRNA的形成、功能、作用机制等研究的新进展，并对其在基因沉默中的作用作了重点概述。

英文摘要：

MicroRNA （miRNA） are endogenous single-stranded small RNAs existing in plants and animdals that regulate gene expression by binding with complementary sequences and repressing translation of target cell transcripts. The construction of miRNA has high conservation among different species. Increasing evidences indicate that miRNA has distinct expression profiles and negatively regulate their targets in one of two ways depending on the degree of complementarity between the miRNA and their targets. They play a crucial role in regulating development, cell differentiation, proliferation, species evolution and diseases pathogenesis. In this review ,we have discussed the pathogenesis, function, action mechanisms of miRNA, and summarized the miRNA＇s dinstinct roles in gene silencing in recent years.