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The Exoribonuclease Nibbler Controls 3' End Processing of MicroRNAs in Drosophila

ABSTRACT: MicroRNAs (miRNAs) are endogenous noncoding small RNAs with important roles in many biological pathways; their generation and activity are under precise regulation. Emerging evidence suggests that miRNA pathways are precisely modulated with controls at the level of transcription, processing, and stability, with miRNA deregulation linked with diseases and neurodegenerative disorders. In the Drosophila miRNA biogenesis pathway, long primary miRNA transcripts undergo sequential cleavage to release the embedded miRNAs. Mature miRNAs are then loaded into Argonaute1 (Ago1) within the RNA-induced silencing complex (RISC). Intriguingly, we found that Drosophila miR-34 displays multiple isoforms that differ at the 3M-bM-^@M-2 end, suggesting a novel biogenesis mechanism involving 3M-bM-^@M-2 end processing. To define the cellular factors responsible, we performed an RNA interference (RNAi) screen and identified a putative 3M-bM-^@M-2M-bM-^FM-^R5M-bM-^@M-2 exoribonuclease CG9247/nibbler essential for the generation of the smaller isoforms of miR-34. Nibbler (Nbr) interacts with Ago1 and processes miR-34 within RISC. Deep sequencing analysis revealed a larger set of multi-isoform miRNAs that are controlled by nibbler. These findings suggest that Nbr-mediated 3M-bM-^@M-2 end processing represents a critical step in miRNA maturation that impacts miRNA diversity. Total RNA was isolated using mirVana (Ambion) and size-fractionated by PAGE into 18-30nt. These were independently processed and sequenced using the Illumina GAII platform. In total, four libraries were analyzed.

ORGANISM(S): Drosophila melanogaster

SUBMITTER: Jui-Hung Hung

PROVIDER: E-GEOD-31689 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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The Exoribonuclease Nibbler Controls 3' End Processing of MicroRNAs in Drosophila

Project description:MicroRNAs (miRNAs) are endogenous noncoding small RNAs with important roles in many biological pathways; their generation and activity are under precise regulation. Emerging evidence suggests that miRNA pathways are precisely modulated with controls at the level of transcription, processing, and stability, with miRNA deregulation linked with diseases and neurodegenerative disorders. In the Drosophila miRNA biogenesis pathway, long primary miRNA transcripts undergo sequential cleavage to release the embedded miRNAs. Mature miRNAs are then loaded into Argonaute1 (Ago1) within the RNA-induced silencing complex (RISC). Intriguingly, we found that Drosophila miR-34 displays multiple isoforms that differ at the 3′ end, suggesting a novel biogenesis mechanism involving 3′ end processing. To define the cellular factors responsible, we performed an RNA interference (RNAi) screen and identified a putative 3′→5′ exoribonuclease CG9247/nibbler essential for the generation of the smaller isoforms of miR-34. Nibbler (Nbr) interacts with Ago1 and processes miR-34 within RISC. Deep sequencing analysis revealed a larger set of multi-isoform miRNAs that are controlled by nibbler. These findings suggest that Nbr-mediated 3′ end processing represents a critical step in miRNA maturation that impacts miRNA diversity.

2011-11-17 | GSE31689 | GEO

Genes affected upon dsRNA knockdown treatment for nbr/CG9247 in Drosophila DL1 cells

Project description:nbr/CG9247 gene function regulates the length of the 3'end of miRNAs. Such 3'end heterogeneity of miRNAs may impact miRNA target gene silencing. To address this, we performed microarray analysis for genes altered upon nbr knockdown in Drosophila DL1 cells. This approach revealed a subset of genes upregulated upon nbr knockdown. Five independent replicates of DL1 cells treated with control (dsRNA to renilla) or nbr (dsRNA RNA to nbr/CG9247) were collected 5 days after dsRNA bathing. Total RNA from from each replicate was extracted using TRIzol reagent (Invitrogen). A portion of total RNA for each replicate was used to confirm the effect of nbr knockdown on one of the nbr-dependent miRNAs, miR-34, by small RNA northern.

2011-11-01 | E-GEOD-32683 | biostudies-arrayexpress

Farnesylated Heat Shock Protein 40 is a component of membrane-bound RISC in Arabidopsis

Project description:ARGONAUTE1 (AGO1) binds directly to small regulatory RNA and is a key effector protein of post-transcriptional gene silencing mediated by microRNA (miRNA) and small interfering RNA (siRNA). The formation of an RNA induced silencing complex (RISC) of AGO1 and small RNA requires the function of the Heat Shock Protein 70/90 chaperone system. Some functions of AGO1 occur in association with endomembranes, in particular the rough endoplasmic reticulum (rER), but proteins interacting with AGO1 in membrane fractions remain unidentified. In this study, we show that the farnesylated Heat Shock Protein 40 homologs, J2 and J3, associate with AGO1 in membrane fractions in a manner that involves protein farnesylation. We also show that three changes in AGO1 function are detectable in mutants in protein farnesylation and J2/J3. First, perturbations of the HSP40/70/90 pathway by mutation of j3, hsp90 and farnesyl transferase affect the amounts of AGO1 associated with membranes. Second, miRNA association with membrane-bound AGO1, and with membrane-bound polysomes is increased in farnesyl transferase and farnesylationdeficient J2/J3 mutants. Third, silencing by non-cell autonomously acting short interfering RNAs (siRNAs) is impaired. These observations highlight the involvement of farnesylated J2/J3 in small RNA-mediated gene regulation, and suggest that the importance of chaperone-AGO1 interaction is not limited to the RISC assembly process.

2018-09-10 | PXD010197 | Pride

Genes affected upon dsRNA knockdown treatment for nbr/CG9247 in Drosophila DL1 cells

2011-11-01 | GSE32683 | GEO

MCMV infection of cultured mouse cells induces expression of miR-7a.

Project description:One goal of viral infection is to reprogram the host cell to optimize viral replication. As part of this process, viral miRNAs may compete for components of the miRNA/siRNA pathway as well as regulate cellular targets. Mouse Cytomegalovirus has been described to generate large numbers of viral miRNAs during lytic infection and was therefore used to analyze the impact of viral miRNAs on the host cell small RNA system as well as to check for sorting of viral small RNAs into specific Ago-proteins. Deep sequencing analysis of MCMV infected cells revealed that viral miRNAs represent only app. 13% of all detected miRNAs. All previously described MCMV miRNAs with the exception of miR-m88-1* were confirmed and for the MCMV miR-m01-1 hairpin an additional miRNA, designated miR-m01-1-3p, was found. Its presence was confirmed by qPCR and Northern Blot. Deep sequencing after RISC IP with antibodies specific for either Ago1 or Ago2 showed that all MCMV miRNAs are loaded into both RISC complexes. The ratio of MCMV to mouse miRNAs was not increased after immunoprecipitation of Ago-proteins. Viral miRNAs therefore do not overwhelm the host miRNA processing system nor are they preferentially incorporated into RISC. We found that 3 mouse miRNAs showed an altered expression due to MCMV infection. Down-regulation of miR-27a, as previously described, could be confirmed. In addition, miR-26a was down-regulated and an up-regulation of miR-7a dependent on viral protein expression could be observed. Examination of small RNA expression in uninfected vs. infected cells, immunoprecipitation + sequencing of Ago1 and Ago2 loaded small RNAs in infected cells

2012-06-30 | E-GEOD-36919 | biostudies-arrayexpress

RNAi knock-down of CAF1-CCR4-NOT1 deadenylase complex or AGO1 in D. melanogaster S2 cells

Project description:miRNAs silence gene expression by repressing translation and/or by promoting mRNA decay. AGO1 is a key protein required for miRNA-mediated gene silencing. In animal cells, mRNA degradation of partially complementary miRNA targets occurs via deadenylation by the CAF1-CCR4-NOT1 deadenylase complex, followed by decapping and subsequent exonucleolytic digestion. To determine how generally miRNAs trigger deadenylation, we compared mRNA expression profiles in D. melanogaster cells depleted of AGO1, CAF1 or NOT1. We show that approximately 45% of AGO1-targets are regulated by both CAF1 and NOT1, indicating deadenylation is a widespread effect of miRNA regulation.<br><br>We employed RNA interference using long double-stranded RNAs to deplete cultured S2 cells of AGO1 (CG6671, 2 independent samples), CAF1 (CG5684, 2 independent samples), or NOT1 (CG1884, 3 independent samples). Further, we used Affymetrix oligonucleotide microarrays to analyze expression profiles in these samples. We included the following controls: mock RNAi treatment and GFP dsRNA treatment (3 and 2 independent samples, respectively).<br>

2008-12-03 | E-MEXP-1713 | biostudies-arrayexpress

Differentiated Truncation and Uridylation Patterns of miRNAs in Arabidopsis and Rice hen1 Mutants Suggest miRNAs May Re-program RISC

Project description:miRNA levels depend on both biogenesis and turnover. The methyltransferase HEN1 stabilizes plant miRNAs, animal piRNAs, and siRNAs in both kingdoms via 3' terminal methylation. Loss of HEN1 in plants results in non-templated oligo-uridylation and accelerated degradation of miRNAs. In hen1 mutants from Arabidopsis and rice, we found that the patterns of miRNA truncation and uridylation differ substantially among miRNA families, but such patterns for the same miRNA are conserved between species. miR166 and miR163 are truncated predominantly to ~17 and ~16 nt, and subsequently recover via uridylation to approximately their original sizes, 21 and 24 nt, suggesting that in these cases miRNA truncation triggers uridylation. miR171 is untruncated but uridylated to 22 nt in hen1 mutants, gaining the ability to trigger production of phased, secondary siRNAs. Truncated and tailed variants were bound by ARGONAUTE1 (AGO1) in hen1, implying that these events occur while miRNAs are still bound by AGO1. Unexpectedly, a portion of miR158 in wildtype remains unmethylated and thus subject to uridylation and destabilization, suggesting that plants naturally utilize miRNA methylation to modulate miRNA accumulation. Our results suggest that the AGO1-containing RISC complex may undergo programming to reflect each bound miRNA, determining a defined, distinct decay destiny.

2013-07-22 | GSE35562 | GEO

Effect of Nbr on the length of piRNAs and endo-siRNAs in Drosophila

Project description:nbr/CG9247 gene regulates the length of a subset of miRNAs. It is not clear whether Nbr affects the length of other classes of small RNAs, such as piRNAs and endo-siRNAs. To address this, we compared small RNA population in wild-type, Df(2L)BSC312/+, nbr null (nbrf02257/Df(2L)BSC312), (nbr null; pCaSper-nbr (WT)), and (nbr null; pCaSper-nbr (D435A,E437A)). This approach revealed that, in addition to miRNAs, piRNAs and endo-siRNAs were also affected in their length in nbr null and nbr null; pCaSper-nbr (D435A,E437A).

2015-02-02 | GSE50055 | GEO

Slicing-Independent RISC Activation Requires the Argonaute PAZ Domain

Project description:Small RNAs regulate the genetic networks through a ribonucleoprotein complex called the RNA induced silencing complexes (RISC), which in mammals contains at its center one of four Argonaute proteins (Ago1-4). A key regulatory event in the RNAi and miRNA pathways is Ago loading, where double stranded small RNA duplexes are incorporated into RISC (pre-RISC) and then become single stranded (mature-RISC), a process that is not well understood. The Agos contain an evolutionary conserved PAZ (Piwi/Argonaute/Zwille) domain whose primary function is to bind the 3’-end of small RNAs. We created multiple Paz domain disrupted Ago mutant proteins and studied their biochemical properties and biological functionality in cells. We found that the Paz domain is dispensable for Ago loading of slicing-competent RISC. In contrast, in the absence of slicer activity or slicer substrate duplex RNAs, Paz-disrupted Agos bound duplex siRNAs but were unable to unwind/eject the passenger strand and form functional RISC complexes. We have discovered that the highly conserved Paz domain plays an important role in RISC activation, providing new mechanistic insights into how miRNAs regulate genes, as well as new insights for future design of miRNA and RNAi-based therapeutics.

2012-07-12 | GSE39146 | GEO

Slicing-Independent RISC Activation Requires the Argonaute PAZ Domain

2012-07-12 | E-GEOD-39146 | biostudies-arrayexpress

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