Project description:MicroRNA biogenesis is known to be modulated by a variety of RNA binding proteins (RBPs), but in most cases, individual RBPs appear to influence the processing of a small number of selective targets. We herein report binding of the NONO/PSF heterodimer to hundreds of expressed pri-miRNAs in HeLa cells to globally enhance pri-miRNA processing by the Drosha/DGCR8 Microprocessor. As NONO/PSF are key components of paraspeckles organized by the lncRNA NEAT1, we find that NEAT1 also has profound effects on global pri-miRNA processing. Mechanistic dissection reveals that NEAT1 broadly interacts with NONO/PSF as well as many other RBPs, and that multiple RNA segments in NEAT1, including a “pseudo pri-miRNA” near its 3’ end, help attract the Microprocessor. These findings suggest a bird nest model for a large lncRNA to orchestrate efficient processing of an entire class of small RNAs in the nucleus.we used small RNA-seq to identify miRNA level in response to secific knockdowns relative to siGFP treatment control
Project description:MicroRNAs (miRNAs) are small RNAs that regulate gene expression. miRNAs are produced from primary miRNAs (pri-miRNAs), the cleavage of which is catalyzed by the Microprocessor complex. Microprocessor therefore plays a key role in determining the efficiency and precision of miRNA production, and thus the function of the final miRNA product. In this study, we utilized high-throughput sequencing-integrated enzymology with purified Microprocessor proteins and randomized pri-miRNA sequences to investigate the catalytic mechanism of Microprocessor. We identified multiple mismatches and wobble base pairs in the upper stem of pri-miRNAs, which determine the efficiency and accuracy of pri-miRNA processing. The existence of these RNA elements helps to explain the alternative cleavage mechanism of Microprocessor, which occurs for some human pri-miRNAs. We also showed that these RNA elements are targets of RNA-editing or single nucleotide polymorphisms (SNPs) for regulating miRNA biogenesis. These findings considerably improve our understanding of pri-miRNA processing mechanisms, and provide a foundation for interpreting differential miRNA expression by several mechanisms, such as RNA modifications and SNPs.
Project description:Microprocessor is responsible for conversion of pri-miRNA transcripts into pre-miRNA hairpins in miRNA biogenesis. The in vivo properties of this process remain enigmatic. Here, we present the first study of in vivo transcriptome-wide pri-miRNA processing using next-generation sequencing of chromatin-associated pri-miRNAs. We identify a distinctive Microprocessor signature in the transcriptome profile, from which efficiency of the endogenous processing event can be accurately quantified. This analysis reveals differential susceptibility to Microprocessor cleavage as a key regulatory step in miRNA biogenesis. Processing is highly variable among pri-miRNAs and a better predictor of miRNA abundance than primary transcription itself. Processing is also largely stable across three cell lines, suggesting a major contribution of sequence determinants. Based on differential processing efficiencies we define functionality for short sequence features adjacent to the pre-miRNA hairpin. In conclusion, we identify Microprocessor as the main hub for diversified miRNA output and suggest a role for uncoupling miRNA biogenesis from host gene expression.
Project description:MicroRNA (miRNA) play a major role in the post-transcriptional regulation of gene expression. In mammals most miRNA derive from the introns of protein coding genes where they exist as hairpin structures in the primary gene transcript, synthesized by RNA polymerase II (Pol II). These are cleaved co-transcriptionally by the Microprocessor complex, comprising DGCR8 and the RNase III endonuclease Drosha, to release the precursor (pre-)miRNA hairpin, so generating both miRNA and spliced messenger RNA1-4. However, a substantial minority of miRNA originate from Pol II-synthesized long non coding (lnc) RNA where transcript processing is largely uncharacterized5. Here, we show that most lnc-pri-miRNA do not use the canonical cleavage and polyadenylation (CPA) transcription termination pathway6, but instead use Microprocessor cleavage both to release pre-miRNA and terminate transcription. We present a detailed characterization of one such lnc-pri-miRNA that generates the highly expressed liver-specific miR-1227. Genome-wide analysis then reveals that Microprocessor-mediated transcription termination is commonly used by lnc-pri-miRNA but not by protein coding miRNA genes. This identifies a fundamental difference between lncRNA and pre-mRNA processing. Remarkably, inactivation of the Microprocessor can lead to extensive transcriptional readthrough of lnc-pri-miRNA, resulting in inhibition of downstream genes by transcriptional interference. Consequently we define a novel RNase III-mediated, polyadenylation-independent mechanism of Pol II transcription termination in mammalian cells. Chromatin associated RNA-seq from sicntrl,siDrosha,siDGCR8 treated Hela cells. Same for sicntrl and siDGCR8 from Huh7 cells. Nuclear polyA + and polyA- RNA-seq from sicntrl and siDGCR8 in HeLa cells. Chromatin associated RNA-seq from siDicer treated Hela cells.
Project description:The cellular abundance of mature microRNAs (miRNAs) is dictated by the efficiency of nuclear processing of primary miRNA transcripts (pri-miRNAs) into pre-miRNA intermediates. The Microprocessor complex of Drosha and DGCR8 carries this out, but it has been unclear what controls Microprocessor's differential processing of various pri-miRNAs. Here, we show that Drosophila DGCR8 (Pasha) directly associates with the C terminal domain of the RNA polymerase II elongation complex when it is phosphorylated by the Cdk9 kinase (pTEFb). When association is blocked by loss of Cdk9 activity, a global change in pri-miRNA processing is detected. Processing of pri-miRNAs with a UGU sequence motif in their apical junction domain increases, while processing of pri-miRNAs lacking this motif decreases. Therefore, phosphorylation of RNA polymerase II recruits Microprocessor for co-transcriptional processing of non-UGU pri-miRNAs that would otherwise be poorly processed. In contrast, UGU-positive pri-miRNAs are robustly processed by Microprocessor independent of RNA polymerase association.
Project description:The microRNA (miRNA) biogenesis is responsible for the production of miRNAs that play critical roles in gene expression and numerous human diseases. The adequate biogenesis of miRNAs is largely determined by the efficiency and fidelity of primary microRNA (pri-miRNA) processing by Microprocessor. Here, we investigated the roles of a secondary RNA element, an RNA bulge, in pri-miRNA processing. We discovered that the 3p-strand bulges in positions 7-9 from the Microprocessor cleavage sites (midB_7-9) contributes to determining the cleavage sites of Microprocessor, the 5p- and 3p-strand bugles in positions 10-12 (midB_10-12) blocked the unproductive cleavage, and the 3p-strand bulges in positions 6-7 (seedB) inhibited the productive cleavage of Microprocessor. The 5p-strand midB_10-12 was found enriched and conserved in many pri-miRNAs of humans and other organisms. In addition, by analyzing the published Microprocessor-RNA structure and doing mutagenesis, we identified several amino acid residues of Microprocessor that explains a structure basis for the processing inhibition caused by seedB. The revealed functions of bulges in our study improves our understanding of the pri-miRNA processing by Microprocessor and implies their roles in regulating miRNA expression.
Project description:MicroRNA (miRNA) play a major role in the post-transcriptional regulation of gene expression. In mammals most miRNA derive from the introns of protein coding genes where they exist as hairpin structures in the primary gene transcript, synthesized by RNA polymerase II (Pol II). These are cleaved co-transcriptionally by the Microprocessor complex, comprising DGCR8 and the RNase III endonuclease Drosha, to release the precursor (pre-)miRNA hairpin, so generating both miRNA and spliced messenger RNA1-4. However, a substantial minority of miRNA originate from Pol II-synthesized long non coding (lnc) RNA where transcript processing is largely uncharacterized5. Here, we show that most lnc-pri-miRNA do not use the canonical cleavage and polyadenylation (CPA) transcription termination pathway6, but instead use Microprocessor cleavage both to release pre-miRNA and terminate transcription. We present a detailed characterization of one such lnc-pri-miRNA that generates the highly expressed liver-specific miR-1227. Genome-wide analysis then reveals that Microprocessor-mediated transcription termination is commonly used by lnc-pri-miRNA but not by protein coding miRNA genes. This identifies a fundamental difference between lncRNA and pre-mRNA processing. Remarkably, inactivation of the Microprocessor can lead to extensive transcriptional readthrough of lnc-pri-miRNA, resulting in inhibition of downstream genes by transcriptional interference. Consequently we define a novel RNase III-mediated, polyadenylation-independent mechanism of Pol II transcription termination in mammalian cells.
Project description:Microprocessor, which consists of a ribonuclease III DROSHA and its cofactor DGCR8, initiates microRNA (miRNA) maturation by cleaving primary miRNA transcripts (pri-miRNAs). We recently demonstrated that the DGCR8 dimer recognizes the apical elements of pri-miRNAs, including the UGU motif, to accurately locate and orient Microprocessor on pri-miRNAs. However, the mechanism underlying the selective RNA binding remains unknown. In this study, we find that hemin, a ferric ion-containing porphyrin, enhances the specific interaction between the apical UGU motif and the DGCR8 dimer, allowing Microprocessor to achieve high efficiency and fidelity of pri-miRNA processing in vitro. Furthermore, by generating a DGCR8 mutant cell line and carrying out rescue experiments, we discover that hemin preferentially stimulates the expression of miRNAs possessing the UGU motif, thereby conferring differential regulation of miRNA maturation. Our findings reveal the molecular action mechanism of hemin in pri-miRNA processing and establish a novel function of hemin in inducing specific RNA-protein interaction.
Project description:Microprocessor initiates processing of microRNAs (miRNAs) from hairpin regions of primary transcripts (pri-miRNAs). Pri-miRNAs often contain multiple miRNA hairpins, and this clustered arrangement can assist processing of otherwise defective hairpins. We find that miR-451, which derives from a hairpin with a suboptimal terminal loop and a suboptimal stem length, accumulates to 40-fold higher levels when clustered with a helper hairpin. This phenomenon tolerates changes in hairpin order, linker lengths, and the identities of the helper hairpin, the recipient hairpin, the linker-sequence, and the RNA polymerase that transcribes the hairpins. It can act reciprocally and need not occur co-transcriptionally. It requires Microprocessor recognition of the helper hairpin and linkage of the two hairpins, yet predominantly manifests after helper-hairpin processing. It also requires Enhancer of Rudimentary Homology (ERH), which copurifies with Microprocessor and can dimerize and interact with other proteins that can dimerize, suggesting a model in which Microprocessor recruits another Microprocessor.
Project description:microRNAs (miRNAs) accomplish a remarkable variety of biological functions. Their expression is tightly controlled, and the final production of a miRNA is dependent on the cooperation of multiple mechanisms and their net effect. Here we show that miR-124-1 is transcriptionally activated during erythroid differentiation by GATA-1, however its post-transcriptional processing is attenuated. We found that QKI5 binds to a distal QKI response element (QRE) embedded in the primary transcript of miR-124-1 (pri-124-1) and modulates Microprocessor function by direct association with DGCR8. Strikingly, Microprocessor recruitment to pri-124-1 is disrupted upon RNAi-mediated depletion of QKI5, consistent with the decrease in mature miR-124. Moreover, addition of QKI5 increases the conversion efficiency of pri-124-1 in cell-free extracts. For erythropoiesis, the decreased QKI5 leads to attenuated Microprocessor-mediated processing of pri-124-1, which confers the exquisite miRNA abundance necessary for development. This regulation also gives rise to a unique miRNA signature required for normal erythropoiesis. Thus, this QKI5-regulated miRNA processing may represent a common paradigm for erythroid development, and specifically, it may serve as a post-transcriptional fault security to prevent misexpression of certain miRNAs, that is essential for the establishment of particular gene expression patterns during development. Two samples are analyzed: K562 cells transduced with GFP lentivirus; and K562 cells transduced with QKI5-overexpressing lentivirus.