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]

microRNAs（miRNAs），简短的非编码RNA，长度介于20-24核苷酸之间，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，参与了转录后基因表达的调控。miRNAs由RNA聚合酶II转录，形成带有帽子和多聚腺苷酸化的初级转录本（pri-miRNAs），这些转录本可能为编码或非编码型。初级转录本经Drosha核糖核酸酶III酶切割，生成约70核苷酸的发夹结构前体miRNA（pre-miRNA），随后在细胞质中的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被整合至RNA诱导的沉默复合体（RISC）中，通过与miRNA的不完美碱基配对识别靶mRNA，通常导致靶mRNA的翻译抑制或稳定性降低。RefSeq代表了预测的miRNA发夹结构。[由RefSeq提供，2009年9月]