ABSTRACT
Self-assembled nucleic acid nanostructures have been widely explored for gene therapy applications due to their unique advantages. Their roles are not limited to offer intracellular delivery platforms but additionally provide a biological function to induce targeted gene regulation. Here, we report a self-assembled artificial primary-miRNA (pri-miRNA) for achieving simultaneous multimodal gene regulation. Artificial pri-miRNAs are designed to play a role as substrate RNAs to recruit and interact with Drosha/DGCR8 (Microprocessor). Incorporation of functional RNA motifs and site-specific chemical modification of the primary miRNA are utilized for the biogenesis of two individual gene-regulating oligonucleotides. Once they are cleaved by the endogenous Drosha/DGCR8 complex, basal strands and pre-miRNA can be generated inside of cells. In this study, we integrated basal strands with either SMN2 ASO or anti-miR21 to induce multimodal gene regulation. Microprocessing and subsequent gene regulation were first evaluated by measuring the activity of reporter pre-miRNA. Chemical modification on the primary miRNA was optimized through a series of in vitro Drosha cleavage tests and targeted gene silencing in cells. Primary miRNA with the basal ASO or anti-miR strands showed a successful in vitro activity and resulted in simultaneous multimodal gene regulation in cells. Artificial primary miRNA may offer synergistic therapeutic effects for treating various diseases, including spinal muscular atrophy and cancer.
Subject(s)
MicroRNAs , Antagomirs , MicroRNAs/metabolism , Oligonucleotides , Oligonucleotides, Antisense/genetics , RNA, Small Interfering/genetics , RNA-Binding Proteins/metabolismABSTRACT
RNA-protein interaction is central to post-transcriptional gene regulation. Identification of RNA-binding proteins relies mainly on UV-induced crosslinking (UVX) followed by the enrichment of RNA-protein conjugates and LC-MS/MS analysis. However, UVX has limited applicability in tissues of multicellular organisms due to its low penetration depth. Here, we introduce formaldehyde crosslinking (FAX) as an alternative chemical crosslinking for RNA interactome capture (RIC). Mild FAX captures RNA-protein interaction with high specificity and efficiency in cell culture. Unlike UVX-RIC, FAX-RIC robustly detects proteins that bind to structured RNAs or uracil-poor RNAs (e.g. AGO1, STAU1, UPF1, NCBP2, EIF4E, YTHDF proteins and PABP), broadening the coverage. Applied to Xenopus laevis oocytes and embryos, FAX-RIC provided comprehensive and unbiased RNA interactome, revealing dynamic remodeling of RNA-protein complexes. Notably, translation machinery changes during oocyte-to-embryo transition, for instance, from canonical eIF4E to noncanonical eIF4E3. Furthermore, using Mus musculus liver, we demonstrate that FAX-RIC is applicable to mammalian tissue samples. Taken together, we report that FAX can extend the RNA interactome profiling into multicellular organisms.
Subject(s)
Proteomics/methods , Ribonucleoproteins/analysis , Animals , Cross-Linking Reagents , Embryo, Nonmammalian/metabolism , Formaldehyde , HeLa Cells , Humans , Liver/metabolism , Male , Mice , Oocytes/metabolism , Peptides , Ribonucleoproteins/metabolism , Ultraviolet Rays , Xenopus laevisABSTRACT
The microprocessor complex cleaves the primary transcript of microRNA (pri-miRNA) to initiate miRNA maturation. Microprocessor is known to consist of RNase III DROSHA and dsRNA-binding DGCR8. Here, we identify Enhancer of Rudimentary Homolog (ERH) as a new component of Microprocessor. Through a crystal structure and biochemical experiments, we reveal that ERH uses its hydrophobic groove to bind to a conserved region in the N-terminus of DGCR8, in a 2:2 stoichiometry. Knock-down of ERH or deletion of the DGCR8 N-terminus results in a reduced processing of suboptimal pri-miRNAs in polycistronic miRNA clusters. ERH increases the processing of suboptimal pri-miR-451 in a manner dependent on its neighboring pri-miR-144. Thus, the ERH dimer may mediate 'cluster assistance' in which Microprocessor is loaded onto a poor substrate with help from a high-affinity substrate in the same cluster. Our study reveals a role of ERH in the miRNA biogenesis pathway.
Subject(s)
Cell Cycle Proteins/metabolism , RNA Processing, Post-Transcriptional , RNA-Binding Proteins/metabolism , Transcription Factors/metabolism , HCT116 Cells , HEK293 Cells , Humans , K562 Cells , MicroRNAs/metabolism , Protein Binding , Protein ConformationABSTRACT
RNA-binding sites (RBSs) can be identified by liquid chromatography and tandem mass spectrometry analyses of the protein-RNA conjugates created by crosslinking, but RBS mapping remains highly challenging due to the complexity of the formed RNA adducts. Here, we introduce RBS-ID, a method that uses hydrofluoride to fully cleave RNA into mono-nucleosides, thereby minimizing the search space to drastically enhance coverage and to reach single amino acid resolution. Moreover, the simple mono-nucleoside adducts offer a confident and quantitative measure of direct RNA-protein interaction. Using RBS-ID, we profiled ~2,000 human RBSs and probed Streptococcus pyogenes Cas9 to discover residues important for genome editing.
Subject(s)
Molecular Biology/methods , RNA/chemistry , RNA/metabolism , Amino Acids/metabolism , Binding Sites , CRISPR-Associated Protein 9/metabolism , Chromatography, Liquid , Cross-Linking Reagents/chemistry , HeLa Cells , Humans , Hydrofluoric Acid/chemistry , Proteome/genetics , Proteome/metabolism , Ribonucleoproteins/metabolism , Tandem Mass SpectrometryABSTRACT
Microprocessor, composed of DROSHA and its cofactor DGCR8, initiates microRNA (miRNA) biogenesis by processing the primary transcripts of miRNA (pri-miRNAs). Here we investigate the mechanism by which Microprocessor selects the cleavage site with single-nucleotide precision, which is crucial for the specificity and functionality of miRNAs. By testing â¼40,000 pri-miRNA variants, we find that for some pri-miRNAs the cleavage site is dictated mainly by the mGHG motif embedded in the lower stem region of pri-miRNA. Structural modeling and deep-sequencing-based complementation experiments show that the double-stranded RNA-binding domain (dsRBD) of DROSHA recognizes mGHG to place the catalytic center in the appropriate position. The mGHG motif as well as the mGHG-recognizing residues in DROSHA dsRBD are conserved across eumetazoans, suggesting that this mechanism emerged in an early ancestor of the animal lineage. Our findings provide a basis for the understanding of miRNA biogenesis and rational design of accurate small-RNA-based gene silencing.
Subject(s)
MicroRNAs/metabolism , Nucleotide Motifs , RNA Processing, Post-Transcriptional , Ribonuclease III/metabolism , HCT116 Cells , HEK293 Cells , High-Throughput Nucleotide Sequencing , Humans , MicroRNAs/chemistry , MicroRNAs/genetics , Models, Molecular , Nucleic Acid Conformation , Protein Interaction Domains and Motifs , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , Ribonuclease III/genetics , Structure-Activity Relationship , Substrate SpecificityABSTRACT
MicroRNA maturation is initiated by RNase III DROSHA that cleaves the stem loop of primary microRNA. DROSHA functions together with its cofactor DGCR8 in a heterotrimeric complex known as Microprocessor. Here, we report the X-ray structure of DROSHA in complex with the C-terminal helix of DGCR8. We find that DROSHA contains two DGCR8-binding sites, one on each RNase III domain (RIIID), which mediate the assembly of Microprocessor. The overall structure of DROSHA is surprisingly similar to that of Dicer despite no sequence homology apart from the C-terminal part, suggesting that DROSHA may have evolved from a Dicer homolog. DROSHA exhibits unique features, including non-canonical zinc-finger motifs, a long insertion in the first RIIID, and the kinked link between Connector helix and RIIID, which explains the 11-bp-measuring "ruler" activity of DROSHA. Our study implicates the evolutionary origin of DROSHA and elucidates the molecular basis of Microprocessor assembly and primary microRNA processing.
Subject(s)
MicroRNAs/metabolism , RNA Processing, Post-Transcriptional , Ribonuclease III/chemistry , Amino Acid Sequence , Crystallography, X-Ray , DEAD-box RNA Helicases/chemistry , DEAD-box RNA Helicases/metabolism , Evolution, Molecular , Humans , MicroRNAs/chemistry , Models, Chemical , Models, Molecular , Molecular Sequence Data , Nucleic Acid Conformation , Protein Folding , Protein Structure, Tertiary , RNA-Binding Proteins/metabolism , Ribonuclease III/genetics , Ribonuclease III/metabolism , Sequence Alignment , Structural Homology, ProteinABSTRACT
MicroRNA (miRNA) maturation is initiated by Microprocessor composed of RNase III DROSHA and its cofactor DGCR8, whose fidelity is critical for generation of functional miRNAs. To understand how Microprocessor recognizes pri-miRNAs, we here reconstitute human Microprocessor with purified recombinant proteins. We find that Microprocessor is an â¼364 kDa heterotrimeric complex of one DROSHA and two DGCR8 molecules. Together with a 23-amino acid peptide from DGCR8, DROSHA constitutes a minimal functional core. DROSHA serves as a "ruler" by measuring 11 bp from the basal ssRNA-dsRNA junction. DGCR8 interacts with the stem and apical elements through its dsRNA-binding domains and RNA-binding heme domain, respectively, allowing efficient and accurate processing. DROSHA and DGCR8, respectively, recognize the basal UG and apical UGU motifs, which ensure proper orientation of the complex. These findings clarify controversies over the action mechanism of DROSHA and allow us to build a general model for pri-miRNA processing.
Subject(s)
MicroRNAs/metabolism , RNA Processing, Post-Transcriptional , RNA-Binding Proteins/chemistry , Ribonuclease III/chemistry , Base Sequence , Dimerization , Humans , MicroRNAs/genetics , Molecular Sequence Data , Nucleotide Motifs , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Ribonuclease III/genetics , Ribonuclease III/metabolismABSTRACT
Genetic screening based on loss-of-function phenotypes is a powerful discovery tool in biology. Although the recent development of clustered regularly interspaced short palindromic repeats (CRISPR)-based screening approaches in mammalian cell culture has enormous potential, RNA interference (RNAi)-based screening remains the method of choice in several biological contexts. We previously demonstrated that ultracomplex pooled short-hairpin RNA (shRNA) libraries can largely overcome the problem of RNAi off-target effects in genome-wide screens. Here, we systematically optimize several aspects of our shRNA library, including the promoter and microRNA context for shRNA expression, selection of guide strands, and features relevant for postscreen sample preparation for deep sequencing. We present next-generation high-complexity libraries targeting human and mouse protein-coding genes, which we grouped into 12 sublibraries based on biological function. A pilot screen suggests that our next-generation RNAi library performs comparably to current CRISPR interference (CRISPRi)-based approaches and can yield complementary results with high sensitivity and high specificity.
Subject(s)
Genome , RNA Interference , Animals , Artificial Intelligence , Humans , Mice , RNA, Small Interfering/geneticsABSTRACT
Uridylation occurs pervasively on mRNAs, yet its mechanism and significance remain unknown. By applying TAIL-seq, we identify TUT4 and TUT7 (TUT4/7), also known as ZCCHC11 and ZCCHC6, respectively, as mRNA uridylation enzymes. Uridylation readily occurs on deadenylated mRNAs in cells. Consistently, purified TUT4/7 selectively recognize and uridylate RNAs with short A-tails (less than â¼ 25 nt) in vitro. PABPC1 antagonizes uridylation of polyadenylated mRNAs, contributing to the specificity for short A-tails. In cells depleted of TUT4/7, the vast majority of mRNAs lose the oligo-U-tails, and their half-lives are extended. Suppression of mRNA decay factors leads to the accumulation of oligo-uridylated mRNAs. In line with this, microRNA induces uridylation of its targets, and TUT4/7 are required for enhanced decay of microRNA targets. Our study explains the mechanism underlying selective uridylation of deadenylated mRNAs and demonstrates a fundamental role of oligo-U-tail as a molecular mark for global mRNA decay.
Subject(s)
DNA-Binding Proteins/metabolism , RNA Nucleotidyltransferases/metabolism , RNA Stability , HeLa Cells , Humans , MicroRNAs/metabolism , Poly A/metabolism , Poly(A)-Binding Proteins/metabolism , RNA, Messenger/metabolism , Uridine Monophosphate/metabolismABSTRACT
RNA-binding proteins (RBPs) have essential roles in RNA-mediated gene regulation, and yet annotation of RBPs is limited mainly to those with known RNA-binding domains. To systematically identify the RBPs of embryonic stem cells (ESCs), we here employ interactome capture, which combines UV cross-linking of RBP to RNA in living cells, oligo(dT) capture and MS. From mouse ESCs (mESCs), we have defined 555 proteins constituting the mESC mRNA interactome, including 283 proteins not previously annotated as RBPs. Of these, 68 new RBP candidates are highly expressed in ESCs compared to differentiated cells, implicating a role in stem-cell physiology. Two well-known E3 ubiquitin ligases, Trim25 (also called Efp) and Trim71 (also called Lin41), are validated as RBPs, revealing a potential link between RNA biology and protein-modification pathways. Our study confirms and expands the atlas of RBPs, providing a useful resource for the study of the RNA-RBP network in stem cells.
Subject(s)
DNA-Binding Proteins/metabolism , Embryonic Stem Cells/metabolism , RNA-Binding Proteins/metabolism , Transcription Factors/metabolism , Animals , Cells, Cultured , DNA-Binding Proteins/genetics , Embryonic Stem Cells/cytology , Gene Regulatory Networks , Humans , Induced Pluripotent Stem Cells/cytology , Induced Pluripotent Stem Cells/metabolism , Mice , Proto-Oncogene Proteins c-myc/genetics , Proto-Oncogene Proteins c-myc/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , RNA-Binding Proteins/genetics , Species Specificity , Transcription Factors/genetics , UbiquitinationABSTRACT
RNase III Drosha initiates microRNA (miRNA) maturation by cleaving a primary miRNA transcript and releasing a pre-miRNA with a 2 nt 3' overhang. Dicer recognizes the 2 nt 3' overhang structure to selectively process pre-miRNAs. Here, we find that, unlike prototypic pre-miRNAs (group I), group II pre-miRNAs acquire a shorter (1 nt) 3' overhang from Drosha processing and therefore require a 3'-end mono-uridylation for Dicer processing. The majority of let-7 and miR-105 belong to group II. We identify TUT7/ZCCHC6, TUT4/ZCCHC11, and TUT2/PAPD4/GLD2 as the terminal uridylyl transferases responsible for pre-miRNA mono-uridylation. The TUTs act specifically on dsRNAs with a 1 nt 3' overhang, thereby creating a 2 nt 3' overhang. Depletion of TUTs reduces let-7 levels and disrupts let-7 function. Although the let-7 suppressor, Lin28, induces inhibitory oligo-uridylation in embryonic stem cells, mono-uridylation occurs in somatic cells lacking Lin28 to promote let-7 biogenesis. Our study reveals functional duality of uridylation and introduces TUT7/4/2 as components of the miRNA biogenesis pathway.
Subject(s)
DNA-Binding Proteins/metabolism , MicroRNAs/metabolism , Polynucleotide Adenylyltransferase/metabolism , RNA Nucleotidyltransferases/metabolism , RNA Processing, Post-Transcriptional , Uridine Monophosphate/metabolism , Base Sequence , HeLa Cells , Humans , Molecular Sequence Data , RNA-Binding Proteins/metabolism , mRNA Cleavage and Polyadenylation FactorsABSTRACT
LIN28 plays a critical role in developmental transition, glucose metabolism, and tumorigenesis. At the molecular level, LIN28 is known to repress maturation of let-7 microRNAs and enhance translation of certain mRNAs. In this study, we obtain a genome-wide view of the molecular function of LIN28A in mouse embryonic stem cells by carrying out RNA crosslinking-immunoprecipitation-sequencing (CLIP-seq) and ribosome footprinting. We find that, in addition to let-7 precursors, LIN28A binds to a large number of spliced mRNAs. LIN28A recognizes AAGNNG, AAGNG, and less frequently UGUG, which are located in the terminal loop of a small hairpin. LIN28A is localized to the periendoplasmic reticulum (ER) area and inhibits translation of mRNAs that are destined for the ER, reducing the synthesis of transmembrane proteins, ER or Golgi lumen proteins, and secretory proteins. Our study suggests a selective regulatory mechanism for ER-associated translation and reveals an unexpected role of LIN28A as a global suppressor of genes in the secretory pathway.
Subject(s)
Protein Biosynthesis , RNA, Messenger/metabolism , RNA-Binding Proteins/metabolism , Animals , Embryonic Stem Cells/metabolism , High-Throughput Nucleotide Sequencing , Immunoprecipitation/methods , Mice , MicroRNAs/metabolism , Ribosomes/metabolism , Secretory Pathway , Sequence Analysis, RNAABSTRACT
The Drosha-DGCR8 complex, also known as Microprocessor, is essential for microRNA (miRNA) maturation. Drosha functions as the catalytic subunit, while DGCR8 (also known as Pasha) recognizes the RNA substrate. Although the action mechanism of this complex has been intensively studied, it remains unclear how Drosha and DGCR8 are regulated and if these proteins have any additional role(s) apart from miRNA processing. Here, we report that Drosha and DGCR8 regulate each other posttranscriptionally. The Drosha-DGCR8 complex cleaves the hairpin structures embedded in the DGCR8 mRNA and thereby destabilizes the mRNA. We further find that DGCR8 stabilizes the Drosha protein via protein-protein interaction. This crossregulation between Drosha and DGCR8 may contribute to the homeostatic control of miRNA biogenesis. Furthermore, microarray analyses suggest that a number of mRNAs may be downregulated in a Microprocessor-dependent, miRNA-independent manner. Our study reveals a previously unsuspected function of Microprocessor in mRNA stability control.