NCBI Summary:
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]
General function
RNA processing
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Cellular localization
Nuclear
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Ovarian function
Oocyte maturation
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MicroRNA-574 suppresses oocyte maturation via targeting hyaluronan synthase 2 in porcine cumulus cells. Pan B et al. (2017) MicroRNAs (miRNAs) have been established as important regulators of gene expression in the mammalian ovary. A previous screen of small RNA in the porcine ovary identified the down regulation of miR-574 during oocyte maturation, although its role during this process was not established. Here, we found that miR-574 directly targets the transcript for hyaluron synthase 2 protein (HAS2), a key enzyme in the production of extracellular matrix by the surrounding cumulus cells. Inhibiting this miRNA during in vitro maturation (IVM) increased HAS2 levels along with several markers of oocyte quality. Furthermore, inhibiting miR-574 increased oocyte meiotic progression. We then stably over expressed miR-574 using a lentiviral vector to transduce cumulus cells during IVM. This gain-of-function approach resulted in a 50% decrease in HAS2 expression and nearly 20% reduction in oocyte progression through meiosis. To confirm the specific targeting of HAS2 by miR-574 we constructed several luciferase vectors harbouring the HAS2 3' untranslated region. Co-transfection of the reporter and miR-574 attenuated luciferase activity. After mutating the putative miR-574 binding site, however, this effect was abolished and luciferase activity remained high. Our results show that the direct targeting of HAS2 by miR-574 negatively impacts oocyte quality during IVM and that inhibiting miR-574 derepresses HAS2 expression and subsequently improves oocyte maturation. Taken together, we help to elucidate a mechanism of post-transcriptional regulation by miRNA in the mammalian ovary.//////////////////
Expression regulated by
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Ovarian localization
Oocyte, Cumulus
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Small RNA Profile of the Cumulus Oocyte Complex and Early Embryos in the Pig. Yang CX et al. Small RNA represent several unique non-coding RNA classes that have important function in the development of germ cells and early embryonic development. Deep sequencing was performed on small RNA from cumulus cells, oocytes at GV and MII stages, as well as in vitro fertilized derived embryos at 60 h post fertilization (4- to 8-cell) and on Day 6 blastocysts. Additionally, a heterologous miRNA microarray method was also used to identify miRNA expressed in the oocyte during in vitro maturation. Similar to the expression analysis of other species, these data demonstrate dynamic expression regulation of multiple classes of non-coding RNA during oocyte maturation and development to the blastocyst stage. Mapping small RNA to the pig genome indicates dynamic distribution of small RNA organization across the genome. Additionally, a cluster of miRNA and piRNA was discovered on chromosome 6. Many of the small RNA mapped to annotated repetitive elements in the pig genome, of which the SINE/tRNA-Glu and LINE/L1 elements represented a large proportion. Two piRNA (piR84651 and piR16993) and 7 miRNA (MIR574, MIR24, LET7E, MIR23B, MIR30D, MIR320, and MIR30C) were further characterized using quantitative RT-PCR. Secretory carrier membrane protein 4 (SCAMP4) was predicted to be subject to posttranscriptional gene regulation mediated by small RNA, by annotating small RNA reads mapped to exonic regions in the pig genome. Consistent with the prediction results, SCAMP4 was further confirmed to be differentially expressed at both transcriptional and translational levels. These data establish a small RNA expression profile of the pig cumulus-oocyte complex and early embryos, and demonstrate their potential capacity to be utilized to make predictions of functional posttranscriptional regulatory events.