micrornas（micrornas）是短的（20-24nt）非编码RNAs，通过影响mRNas的稳定性和翻译，参与多细胞生物中基因表达的转录后调控。小RNA被RNA聚合酶II转录，作为可编码蛋白质或不编码的有帽和多聚腺苷酸化的初级转录物（pri-mirnas）的一部分。初级转录物被Drosha核糖核酸酶III酶切割，产生一个大约70 nt的干环前体小RNA（前小RNA），然后被细胞质骰子核糖核酸酶进一步切割，产生成熟的小RNA和反义的小RNA星（小RNA*）产物。成熟的小RNA被整合到一个RNA诱导的沉默复合物（RISC）中，该复合物通过与小RNA的不完全碱基配对识别目标mRNAs，最常见的结果是对目标mRNa的翻译抑制或失稳。refseq代表预测的microRNA干环。
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.