Small RNA loading licenses Argonaute for assembly into a transcriptional silencing complex
Ontology highlight
ABSTRACT:
ORGANISM(S): Schizosaccharomyces pombe
SUBMITTER: Daniel Holoch
PROVIDER: E-GEOD-65223 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:The assembly of fission yeast pericentromeric heterochromatin and generation of small interfering RNAs (siRNAs) from noncoding centromeric transcripts are mutually dependent processes. How this interdependent positive feedback loop is first triggered is a fundamental unanswered question. Here we show that two distinct Argonaute (Ago1)-dependent pathways mediate small RNA generation. RNA-dependent RNA polymerase complex (RDRC) and Dicer act on specific noncoding RNAs to generate siRNAs by a mechanism that requires the slicer activity of Ago1 but is independent of pre-existing heterochromatin. In the absence of RDRC or Dicer, a distinct class of small RNAs, called primal small RNAs (priRNAs), associate with Ago1. priRNAs are degradation products of abundant transcripts, which bind to Ago1 and target antisense transcripts that result from bidirectional transcription of DNA repeats. Our results suggest that a transcriptome surveillance mechanism based on the random association of RNA degradation products with Argonaute triggers siRNA amplification and heterochromatin assembly within DNA repeats. small RNA profiling in wild type S. pombe cells and in 12 mutant cells
2010-02-23 | E-GEOD-19734 | biostudies-arrayexpress
Project description:RNA interference is involved in silencing of transposable and repetitive elements. How these elements are initially recognized by RNAi is a fundamental and unanswered question. We previously identified a class of Dicer-independent small RNAs, called primal small RNAs (priRNAs), in fission yeast. The mechanism by which Dicer-independent small RNAs are generated is not clear for any species. Here we reconstitute priRNA biogenesis in vitro and demonstrate that priRNAs can nucleate RNAi in vivo. We identify 3'-5' exonuclease Trimmer and show that Argonaute, loaded with longer RNA precursors, recruits Trimmer to generate the new 3' end. Next, we show that antisense priRNAs accumulate in rrp6M-NM-^T cells and nucleate RNAi at subset of protein coding genes in a Trimmer- and priRNA-dependent manner. Thus, Rrp6-mediated degradation of antisense transcripts and priRNA precursors protects the genome from spurious RNAi. Our results suggest that Argonaute association with random RNA degradation products triggers RNAi in a process of transcriptome surveillance. small RNA profiling in wild type S. pombe cells and in mutant cells
2014-04-21 | E-GEOD-38636 | biostudies-arrayexpress
Project description:We analyzed the small RNAs bound to the fission yeast RITS and ARC complexes, and to Ago1 in wild-type and ARC mutant cells, to gain insight into the molecular role of ARC. We found that ARC contains longer heterochromatic siRNAs than RITS, and that ARC subunit Arb1 is required for loading small RNAs onto Ago1.
2015-03-01 | GSE65223 | GEO
Project description:RNA interference (RNAi) is a gene silencing mechanism conserved from fungi to mammals. Small interfering RNAs are products and mediators of the RNAi pathway and act as specificity factors in recruiting effector complexes. The Schizosaccharomyces pombe genome encodes one of each of the core RNAi proteins, Dicer, Argonaute and RNA-dependent RNA polymerase (dcr1, ago1, rdp1). Even though the function of RNAi in heterochromatin assembly in S. pombe is established, its role in controlling gene expression is elusive. Here, we report the identification of small RNAs mapped anti-sense to protein coding genes in fission yeast. We demonstrate that these genes are up-regulated at the protein level in RNAi mutants, while their mRNA levels are not significantly changed. We show that the repression by RNAi is not a result of heterochromatin formation. Thus, we conclude that RNAi is involved in post-transcriptional gene silencing in S. pombe. Small RNA library from wild type S. pombe.
2014-01-23 | E-GEOD-54194 | biostudies-arrayexpress
Project description:Background: Eukaryotic cells express a complex layer of noncoding RNAs. An intriguing family of regulatory RNAs includes transcripts from the opposite strand of protein coding genes, so called natural antisense transcripts (NATs). Here, we test the hypothesis that antisense transcription triggers RNA interference and gives rise to endogenous short RNAs (endo-siRNAs). Methods/Results: We used cloned human embryonic kidney cells (HEK293) followed by short RNAseq to investigate the small genic RNA transcriptome. 378 genes gave rise to short RNA reads that mapped to exons of RefSeq genes. The length profile of short RNAs showed a broad peak of 20-24 nucleotides, indicative of endo-siRNAs. Collapsed reads mapped predominantly to the first and the last exon of genes (74%). RNAs reads were intersected with sequences occupied by RNAPolII or bound to Argonaute (AGO1 by crosslinking, ligation, and sequencing of hybrids, CLASH). In the first exon, 94% of the reads correlated with PolII occupancy with an average density of 130 (relative units); this decreased to 65%/20 in middle exons and 54%/12 in the last exon. CLASH reads mapping to multi-exon genes showed little distribution bias with an average of about 5 CLASH reads overlapping with 60% of the endo-siRNA reads. However, endo-siRNAs (21-25 nt) intersecting with CLASH reads were enriched at the 5'end and decreased towards the 3'end. We then investigated the 378 genes with particular focus on features indicative for short RNA production; however, found that endo-siRNA numbers did not correlate with gene structures that favor convergent transcription. In contrast, our gene set was found notably over-represented in the NATsDB sense/antisense group as compared to non-overlapping and non-bidirectional groups. Moreover, read counts showed no correlation with the steady-state levels of the related mRNAs and the pattern of endo-siRNAs proved reproducible after an induced mutagenic insult. Conclusions: Our results suggest that antisense transcripts contribute to low levels of endo-siRNAs in fully differentiated human cells. A characteristic endo-siRNA footprint is being produced at sites of RNAPolII transcription which is also related to AGO1. This endo-siRNA signature represents an intriguing finding and its reproducibility suggests that the production of endo-siRNAs is a regulated process with potential homoeostatic impact. Size selected RNASeq of 3 human embryonic kidney cell (HEK293) samples. 1 control and 2 samples exposed to 100 μg/ml ethyl methanesulfonate for 24 hrs.
2014-02-28 | E-GEOD-52996 | biostudies-arrayexpress
Project description:The Arabidopsis ARGONAUTE (AGO) protein AGO1 associates with microRNA (miRNA) and specific classes of short-interfering RNA (siRNA). AGO1-small RNA complexes recognize target RNA transcripts through base-pairing interactions and inhibit translation of target RNAs through endonucleolytic cleavage (slicing) or non-degradative mechanisms. The PIWI domain of AGO1 contains a metal-coordinating triad [Asp-Asp-His] (DDH) that is required for slicer activity. Here, we compared the activities of wild type (DDH) and slicer active-site defective (DAH) forms of AGO1 by sequencing small RNA and target transcript RNAs that co-immunoprecipitated with hemagglutinin (HA)-tagged AGO1 proteins. We found that the population of miRNA that associated with both AGO1-DDH and AGO1-DAH proteins largely overlapped, suggesting that cleavage activity does not affect miRNA maturation. In contrast, slicer-defective AGO1-miRNA complexes associated with target RNA more effectively than did wild type AGO1-miRNA. These data indicate that slicer-defective AGO proteins can be used as an approach to capture AGO-small RNA-target RNA ternary complexes more efficiently for genome-wide analyses. AGO1-DDH (wild type) AGO1-DAH (slicer mutant) proteins were immunoprecipitated (N-terminal 3xHA) from Arabidopsis (Columbia) flower (stages 1-12) lysate. Immunoprecipitations were also done from control plants transformed with vector only. Small RNA from immunoprecipitate fractions of vector, AGO1-DDH and AGO1-DAH were sequenced.
2012-09-28 | E-GEOD-40258 | biostudies-arrayexpress
Project description:We provide evidence of the generation of Rdp1-mediated secondary siRNAs in vivo in fission yeast. Secondly, we show that the presence of Ago1-associated siRNAs does not guarantee robust silencing. We obtained sequences from gel purified small RNAs of wt and rdp1delta fission yeast cells and FLAG-ago1 associated small RNAs.
2010-02-15 | E-GEOD-20330 | biostudies-arrayexpress
Project description:Efforts to catalogue eukaryotic transcripts have uncovered a set of species derived from the termini and exon/intron boundaries of protein-coding loci. The biogenesis pathways of these small RNAs (sRNAs) are largely unknown, but a mechanism depending on backtracking of RNA polymerase II (RNAPII) has been suggested. Moreover, the functional relevance, if any, of these sRNAs remains elusive. By sequencing 12-100nt transcripts from cells depleted of major RNA degradation enzymes as well as RNAs associated with the effector-proteins Argonaute (AGO) 1/2, we provide mechanistic models for sRNA production and utilization. We suggest that neither splice site associated (SSa)- nor transcription start site associated (TSSa)-RNAs arise from RNAPII backtracking. Instead SSa-RNAs are largely degradation products of mRNA splicing intermediates, while TSSa-RNAs likely derive from nascent RNA protected by stalled RNAPII against nucleolysis. We also reveal new AGO1/2-associated RNAs, including such derived from 3'ends of introns (5'tailed miRtrons) and from mRNA 3'UTRs. Interestingly, both appear to draw from non-canonical microRNA (miRNA) biogenesis pathways. 10 samples all from HeLa in three size ranges: 12-20, 18-30 and 30-100. 1 from 12-20: nuclear; 6 from 18-30: WT, nuclear, RRP40 knockdown, Ago1&2 IP, RRP40 knockdown and Ago1&2 IP, XRN1&2 knockdown; 3 from 30-100: WT, of RRP40 knockdown, XRN1&2 knockdown.
2011-07-31 | E-GEOD-29116 | biostudies-arrayexpress
Project description:Using a high-throughput sequencing approach we quantitatively analyzed the content of viroid-derived siRNAs of an infected tree. Our results show that the entire PLMVd genome is found in the siRNA population. Also both polarities are susceptible to be targeted by the RNAi machinery but specific regions for each polarity are over represented. Those regions, that are not the same for each polarity, do not necessarily correlate with double stranded regions that could be substrate for Dicer-like enzymes. Finally the analysis of the first 5’ nucleotide revealed a bias toward a C or a U in viroid-derived siRNAs, indicating that at least AGO5 and AGO1 can recruit these small RNAs. Analysis of siRNAs population from RNA sample isolated from a viroid-infected tree
2010-02-20 | E-GEOD-18764 | biostudies-arrayexpress
Project description:The goal of this study was to identify AGO1-dependent miRNA and tasiRNA in Arabidopsis by sequencing small RNA from wild type (Col-0) and ago1-25 plants. Keywords: Small RNA Sequencing-by-synthesis technology was used to sequence small RNA from flower tissue (stages 1-12) from wild-type (Col-0) and ago1-25 Arabidopsis thaliana plants. Three biological replicates were sequenced for both Col-0 and ago1-25.
2008-11-17 | E-GEOD-13605 | biostudies-arrayexpress