Regulation of Microprocessor assembly and localization via Pasha’s WW domain in C. elegans
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ABSTRACT: Primary microRNA (pri-miRNA) transcripts are processed by a protein complex called the Microprocessor comprised of the ribonuclease Drosha and its RNA binding partner DGCR8/Pasha. We sequenced small RNAs from animals containing a mutation in the WW domain of C. elegans pash-1. We found that these mutants have a modest but widespread reduction in miRNA levels when grown at 20˚C, which is further enhanced when grown at 25˚C. The results demonstrate a requirement for the WW domain in processing miRNAs in C. elegans.
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 Microprocessor, composed of Drosha and Pasha/DGCR8, is necessary for the biogenesis of canonical microRNAs (miRNAs), and required for animal embryogenesis. However, the cause for this requirement is largely unknown. The Microprocessor may be required to produce one or few essential miRNAs, or alternatively, many individually non-essential miRNAs. Additionally, Drosha and Pasha/DGCR8 may be required for processing non-miRNA substrates. To distinguish between these possibilities, we developed a system in C. elegans to stringently deplete embryos from the Microprocessor and miRNAs. We show that the early embryonic arrest upon loss of the Microprocessor is rescued by the addition of two individual miRNAs from the miR-35 and miR-51 families, resulting in morphologically normal larvae. Thus, just two canonical miRNAs are sufficient for morphogenesis and organogenesis in C. elegans, and indicate that miRNA processing explains the essential requirement for the Microprocessor during embryogenesis.
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:The Microprocessor plays an essential role in canonical miRNA biogenesis by facilitating cleavage of stem-loop structures in primary transcripts to yield pre-miRNAs. Although miRNA biogenesis has been extensively studied through biochemical and molecular genetic approaches, it has yet to be addressed to what extent the current miRNA biogenesis models hold true in intact cells. To address the issues of in vivo recognition and cleavage by the Microprocessor, we investigate RNAs that are associated with DGCR8 and Drosha by using immunoprecipitation coupled with next-generation sequencing. Here, we present global protein-RNA interactions with unprecedented sensitivity and specificity. Our data indicate that precursors of canonical miRNAs and miRNA-like hairpins are the major substrates of the Microprocessor. As a result of specific enrichment of nascent cleavage products, we are able to pinpoint the Microprocessor-mediated cleavage sites per se at single-nucleotide resolution. Unexpectedly, a 2-nt 3M-bM-^@M-^Y overhang invariably exists at the ends of cleaved bases instead of nascent pre-miRNAs. Besides canonical miRNA precursors, we find that two novel miRNA-like structures embedded in mRNAs are cleaved to yield pre-miRNA-like hairpins, uncoupled from miRNA maturation. Our data provide a framework for in vivo Microprocessor-mediated cleavage and a foundation for experimental and computational studies on miRNA biogenesis in living cells. CLIP-seq for DGCR8 and Drosha, RIP-seq for DGCR8, sequencing of AGO2-assocated miRNA
Project description:The human Microprocessor complex cleaves primary microRNA (miRNA) transcripts (pri-miRNAs) to initiate miRNA synthesis. Microprocessor consists of DROSHA (an RNase III enzyme), and DGCR8. DROSHA has two conserved RNase III domains, which make double cuts on each of pri-miRNA strands. In this study, we show that Microprocessor has an unexpected single-cut activity, which creates a single cut on just one of the pri-miRNA strands using one of the two RNase III domains of DROSHA. This cleavage does not lead to the production of miRNA but instead it downregulates miRNA expression. We also demonstrate that certain RNA elements facilitate the single-cut activity of Microprocessor, and by manipulating these elements, we can regulate the ratio of single-cut to double-cut activities, thus controlling miRNA production both in vitro and in vivo.
Project description:The Drosha-DGCR8 complex (Microprocessor) is required for microRNA (miRNA) biogenesis. DGCR8 contains two double-stranded RNA binding motifs that recognize the RNA substrate, whereas Drosha functions as the endonuclease. We have used high-throughput sequencing of RNAs isolated by crosslinking immunoprecipitation (HITS-CLIP) to identify endogenous RNA targets of DGCR8 in mammalian cells. Unexpectedly, miRNAs were not the most abundant targets. DGCR8-bound RNAs comprised several hundred mRNAs as well as snoRNAs and long non-coding RNAs. We found that DGCR8 together with Drosha controls the abundance of several mRNAs, as well as long non-coding RNAs, such as MALAT-1. By contrast, the DGCR8-mediated cleavage of snoRNAs is independent of Drosha, suggesting the involvement of DGCR8 in cellular complexes with other endonucleases. Interestingly, binding of DGCR8 to cassette exons, acts as a novel mechanism to regulate the relative abundance of alternatively spliced isoforms. Collectively, these data provide new insights in the complex role of DGCR8 in controlling the fate of several classes of RNAs. Comparison of RNAs associated to both endogenous (D8) and overexpressed (T7) DGCR8 in HEK293T cells
Project description:The Microprocessor complex, consisting of DROSHA and DGCR8, is essential for miRNA maturation and plays a critical role in gene regulation. Mutations in this complex's components are frequently associated with Wilms tumor (WiT), a common pediatric kidney cancer. Understanding the functional impacts of these mutations is key to elucidating WiT pathogenesis. To this end, we developed an innovative Microsensor system to dynamically evaluate Microprocessor function in human cellular environments. Using this tool, we introduced and analyzed the DGCR8-E518K mutation, previously identified in WiT patients. This mutation was shown to significantly disrupt cellular homeostasis, affecting proliferation, apoptosis, and migration. On a molecular level, we demonstrated that the E518K mutation impairs the Microprocessor's efficiency in processing a specific subset of pri-miRNAs that lack the canonical 16-20 nucleotide mismatch feature, leading to abnormal miRNA expression profiles. Additionally, cells expressing the E518K mutant exhibited increased susceptibility to ferroptosis, as indicated by heightened sensitivity to the pro-ferroptotic agent RSL3. Our findings provide new insights into the Microprocessor's role in WiT, with the Microsensor system offering a robust platform for exploring the molecular mechanisms of Microprocessor-associated mutations. This study lays the groundwork for future in vivo research and the potential development of therapeutic strategies targeting the Microprocessor pathway in WiT.
Project description:The Microprocessor complex, consisting of DROSHA and DGCR8, is essential for miRNA maturation and plays a critical role in gene regulation. Mutations in this complex's components are frequently associated with Wilms tumor (WiT), a common pediatric kidney cancer. Understanding the functional impacts of these mutations is key to elucidating WiT pathogenesis. To this end, we developed an innovative Microsensor system to dynamically evaluate Microprocessor function in human cellular environments. Using this tool, we introduced and analyzed the DGCR8-E518K mutation, previously identified in WiT patients. This mutation was shown to significantly disrupt cellular homeostasis, affecting proliferation, apoptosis, and migration. On a molecular level, we demonstrated that the E518K mutation impairs the Microprocessor's efficiency in processing a specific subset of pri-miRNAs that lack the canonical 16-20 nucleotide mismatch feature, leading to abnormal miRNA expression profiles. Additionally, cells expressing the E518K mutant exhibited increased susceptibility to ferroptosis, as indicated by heightened sensitivity to the pro-ferroptotic agent RSL3. Our findings provide new insights into the Microprocessor's role in WiT, with the Microsensor system offering a robust platform for exploring the molecular mechanisms of Microprocessor-associated mutations. This study lays the groundwork for future in vivo research and the potential development of therapeutic strategies targeting the Microprocessor pathway in WiT.
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.