MIR221

microRNAs (miRNAs) are short (20-24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of mRNAs. miRNAs are transcribed by RNA polymerase II as part of capped and polyadenylated primary transcripts (pri-miRNAs) that can be either protein-coding or non-coding. The primary transcript is cleaved by the Drosha ribonuclease III enzyme to produce an approximately 70-nt stem-loop precursor miRNA (pre-miRNA), which is further cleaved by the cytoplasmic Dicer ribonuclease to generate the mature miRNA and antisense miRNA star (miRNA*) products. The mature miRNA is incorporated into a RNA-induced silencing complex (RISC), which recognizes target mRNAs through imperfect base pairing with the miRNA and most commonly results in translational inhibition or destabilization of the target mRNA. The RefSeq represents the predicted microRNA stem-loop. [provided by RefSeq, Sep 2009]

miRNAs（microRNAs），即微小RNA，是一类长度为20-24个核苷酸的非编码RNA，其在多细胞生物中通过影响信使RNA（mRNA）的稳定性和翻译过程，参与转录后基因表达的调控。miRNAs由RNA聚合酶II转录，作为帽状和聚腺苷酸化的初级转录物（pri-miRNAs）的一部分，这些初级转录物既可以是编码蛋白的，也可以是非编码的。初级转录物经Drosha核糖核酸酶III酶切割，生成约70个核苷酸的发夹状前体miRNA（pre-miRNA），随后该前体miRNA在细胞质中的Dicer核糖核酸酶作用下进一步切割，生成成熟的miRNA和反义miRNA星形（miRNA*）产物。成熟的miRNA被整合入RNA诱导的沉默复合体（RISC），该复合体通过与miRNA的不完全碱基配对识别靶mRNA，通常导致靶mRNA的翻译抑制或不稳定。RefSeq代表预测的miRNA发夹结构。[由RefSeq提供，2009年9月]