High throughput sequencing of small RNAs from Drosophila cells infected with a panel of viruses
Ontology highlight
ABSTRACT:
ORGANISM(S): Drosophila melanogaster
SUBMITTER: Sara Cherry
PROVIDER: E-GEOD-43031 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Background: RNA silencing pathways play critical roles in gene regulation, virus infection, and transposon control. RNA interference (RNAi) is mediated by small interfering RNAs (siRNAs), which are liberated from double stranded (ds) RNA precursors by Dicer and direct the RNA-induced silencing complex (RISC) to target transcripts. Recent efforts have uncovered important principles governing small RNA (smRNA) sorting into RISC, yet mechanisms defining substrate selection by Dicer proteins remain uncharacterized. Methodology: To better characterize Dicer-2 substrates in Drosophila, we examined the antiviral RNAi response, which generates virus-derived siRNAs from viral RNA. Using high-throughput sequencing, we found that diverse viruses were uniquely targeted; substrates included dsRNA replication intermediates and intramolecular RNA stem loops. smRNA distribution patterns from viral and synthetic dsRNA precursors were highly reproducible, and machine learning techniques identified characteristics of precursor molecules and smRNA duplexes important in determining relative smRNA abundance. Significance: To our knowledge, this study provides the first description of the rules governing Dicer-2 substrate selection, which has important implications for exogenous RNA silencing technologies and the development of smRNA-based antiviral therapeutics. virus-derived siRNA (vsiRNA) expression comparison between control and 4 different virus-infected cells in control as well as 5 different RNAi pathway protein knock-downs in Drosophila dl1 cells
2013-01-31 | E-GEOD-28957 | biostudies-arrayexpress
Project description:RNAi, a gene-silencing pathway triggered by double-stranded RNA, is conserved in diverse eukaryotic species but has been lost in the model budding yeast, Saccharomyces cerevisiae. We report that RNAi is present in other budding-yeast species, including Saccharomyces castellii and Candida albicans. These species use noncanonical Dicer proteins to generate siRNAs, which mostly correspond to transposable elements and YM-BM-4 subtelomeric repeats. In S. castellii, RNAi mutants are viable but have excess YM-BM-4 mRNA levels. In S. cerevisiae, introducing Dicer and Argonaute of S. castellii restores RNAi, and the reconstituted pathway silences endogenous retrotransposons. These results identify a novel class of Dicer proteins, bring the tool of RNAi to the study of budding yeasts, and bring the tools of budding yeast to the study of RNAi. Employ high-throughput sequencing of endogenous small RNAs from the budding yeasts Saccharomyces castellii, Kluyveromyces polysporus, Candida albicans, Saccharomyces cerevisiae, and Saccharomyces bayanus.
2009-09-10 | E-GEOD-17871 | biostudies-arrayexpress
Project description:Transcriptional gene silencing controls transposons and other repetitive elements through RNA-directed DNA methylation (RdDM) and heterochromatin formation. A key component of the Arabidopsis RdDM pathway is ARGONAUTE4 (AGO4), which associates with sizs to mediate DNA methylation. Here, we show that AGO4 preferentially targets transposable elements embedded within promoters of protein-coding genes. This pattern of AGO4 binding cannot be simply explained by the sequences of AGO4-bound siRNAs; instead, AGO4 binding to specific gene promoters is also mediated by long non-coding RNAs (lncRNAs) produced by RNA polymerase V. lncRNA-mediated AGO4 binding to gene promoters directs asymmetric DNA methylation to these genomic regions and is involved in regulating the expression of targeted genes. Finally, AGO4 binding overlaps sites of DNA methylation affected by the biotic stress response. Based on these findings, we propose that the targets of AGO4-directed RdDM are regulatory units responsible for controlling gene expression under specific environmental conditions. ChIP-seq experiments using AGO4 antibody of WT (Col-0) and ago4 or nrpe1 mutant plants of Arabidopsis thaliana
2012-10-17 | E-GEOD-35381 | biostudies-arrayexpress
Project description:The PiwiM-bM-^@M-^SpiRNA complex (PiwiM-bM-^@M-^SpiRISC) in Drosophila ovarian somatic cells represses transposons transcriptionally to maintain genome integrity; however, the underlying mechanisms remain obscure. We performed mRNA-seq analysis from OSCs transfected with siRNAs against CG3893, the known piRNA pathway genes, Piwi, Maelstrom, HP1a and Armitage, and the control (EGFP), and PolII ChIP-seqanalysis from OSCs transfected with siRNAs against CG3893, Piwi, Mael and the control (EGFP). This result indicates that CG3893 is a novel factor for primary piRNA pathway in OSCs. RNA levels in wild-type (EGFP control knock-down) ovarian somatic cells (OSC) and RNAi knock-downs of Piwi, Armi, Mael, CG3893, and HP1a. RNA Polymerase II occupancy in wild-type (EGFP control knock-down) ovarian somatic cells (OSC) and RNAi knock-downs of Piwi, Mael, and CG3893.
2013-08-01 | E-GEOD-47006 | biostudies-arrayexpress
Project description:Using a crucifer-infecting strain of Tobacco Mosaic Virus (TMV-Cg) and Arabidopsis thaliana as a model system, we analyzed the viral small RNA profile in wild-type plants as well as rdr mutants by applying small RNA deep sequencing technology. Over 100,000 TMV-Cg-specific small RNA reads, mostly of 21- (78.4%) and 22-nucleotide (12.9%) in size and originating predominately (79.9%) from the genomic sense RNA strand, were captured at an early infection stage, yielding the first high-resolution small RNA map for a plant virus. The TMV-Cg genome harbored multiple, highly reproducible small RNA-generating hot spots that corresponded to regions with no apparent local hairpin-forming capacity. Significantly, both the rdr1 and rdr6 mutants exhibited globally reduced levels of viral small RNA production as well as reduced strand bias in viral small RNA population, revealing an important role for these host RDRs in viral siRNA biogenesis. In addition, an informatics analysis showed that a large set of host genes could be potentially targeted by TMV-Cg-derived siRNAs for posttranscriptional silencing, raising the interesting possibility for a hidden layer of widespread virus-host interactions that may contribute to viral pathogenicity and host specificity. Profiling of TMV-Cg derived small RNAs in systemically infected tissues of wild type (Col-0) Arabidopsis as well as the rdr1and rdr6 mutants, at 3 days post-infection.
2009-03-24 | E-GEOD-12918 | biostudies-arrayexpress
Project description:Background: The majority of plant transposable elements (TEs) are found in a silenced state that is epigenetically propagated by the maintenance of symmetrical DNA methylation. TE methylation is established and reinforced by a mechanism of RNA-dependent DNA methylation, which is dependent on transcription of the PolIV RNA polymerase. Recently, a pathway has been described that initiates de novo DNA methylation dependent on components of the RNAi post-transcriptional silencing pathway, independent of PolIV. To define the function of this new pathway, we have focused on the RDR6 protein, which plays a central role in the pathway we refer to as RDR6-dependent RNA-directed DNA Methylation (RDR6-RdDM). Methods: We have sequenced total small RNAs from wild-type and three mutant genotypes: ddm1, ddm1/rdr6, and rdr6. Conclusions: We demonstrate that RDR6-RdDM utilizes 21 and 22 nucleotide siRNAs to de novo methylate actively transcribing TEs. In addition, we find that the RDR6-RdDM pathway functions in the efficient initiation and re-establishment of TE transcriptional silencing, while it is not necessary to maintain trans-generational epigenetic silencing. Examination of flower bud small RNAs from wild-type and 3 mutant genotypes
2013-04-11 | E-GEOD-41755 | biostudies-arrayexpress
Project description:Background: Transposable element 24 nucleotide small RNAs are not efficiently incorporated into the AGO1 protein, which is involved in endogenous RNAi and gene regulation through the microRNA and tasiRNA pathways. Results: The AGO1 protein incorporates large quantities of transposable element siRNAs when transposable elements are epigenetically activated and transcribed. The incorporation of transposable element siRNAs is at the expense of the most abundant microRNAs. These transposable element siRNAs can act as tasiRNAs, regulating genes that they have partial complementarity to. Conclusion: Transposable element small RNAs are more dynamic than previously thought. They can be incorporated into AGO1 and regulate genes. Three biological replicates of small RNA sequencing from two genotypes
2014-04-07 | E-GEOD-45990 | biostudies-arrayexpress
Project description:Drosophila Argonaute-1 and Argonaute-2 differ in function and small RNA content. AGO2 binds to siRNAs, whereas AGO1 is almost exclusively occupied by microRNAs. microRNA duplexes are intrinsically asymmetric, with one strand, the miR strand, preferentially entering AGO1 to recognize and regulate the expression of target mRNAs. The other strand, miR*, has been viewed as a by-product of microRNA biogenesis. Here, we show that miR*s are often loaded as functional species into AGO2. This indicates that each microRNA precursor can potentially produce two mature small RNA strands that are differentially sorted within the RNAi pathway. miR* biogenesis depends upon the canonical microRNA pathway, but loading into AGO2 is mediated by factors traditionally dedicated to siRNAs. By inferring and validating hierarchical rules that predict differential AGO loading, we find that intrinsic determinants, including structural and thermodynamic properties of the processed duplex, regulate the fate of each RNA strand within the RNAi pathway. These were independently processed and sequenced using the Illumina GAII platform. In total, five libraries were analyzed.
2009-11-15 | E-GEOD-17734 | biostudies-arrayexpress
Project description:MicroRNA (miRNA) and endogenous siRNA (endo-siRNA) are two essential classes of small noncoding RNAs (sncRNAs) in eukaryotic organisms. The class of miRNA is diverse and there exist noncanonical miRNAs that bypass the canonical miRNA biogenesis pathway. In order to identify noncanonical miRNAs and endo-siRNAs responding to virus infection and study their potential function, we sequenced small-RNA species from cells lytically infected with murine gammaherpesvirus 68. In addition to 3 novel canonical miRNAs in mouse, two antisense miRNAs in virus and 25 novel noncanonical miRNAs, including miRNAs derived from tRNAs, snoRNAs and introns, in the host were identified. These noncanonical miRNAs exhibited features distinct from canonical miRNAs in the lengths and structures of miRNA hairpins as well as base pairings and first nucleotide preference. Many of the novel miRNAs are conserved in mammals. In addition to several known murine endo-siRNAs detected by the sequencing profiling, a novel locus in the mouse genome was identified to give rise to endo-siRNAs. This novel endo-siRNA locus is comprised of two tandem inverted B4 short interspersed nuclear elements (SINEs). Unexpectedly, the SINE-derived endo-siRNAs were found in a variety of sequencing data as well as virus-infected cells. Moreover, a murine miRNA was up-regulated more than 35 fold in infected than in mock-treated cells. The putative target genes of the viral and the up-regulated murine miRNAs were potentially involved in processes of gene transcription and protein phosphorylation and localized to membranes, suggesting their role in manipulating the host basal immune system during lytic infection. Our results extended the number of noncanonical miRNAs in mammals and shed new lights on their potential functions of lytic infection of MHV68. Mouse NIH 3T12 cells infectd with MHV68 (3 samples) and mock-treated (2 samples) were examined. Noncanonical microRNAs and endogenous siRNAs discovery in lytic infection of murine gammaherpesvirus MHV68 (NC_001826.2).
2012-12-31 | E-GEOD-36639 | biostudies-arrayexpress
Project description:The piRNA machinery is known for its role in mediating epigenetic silencing of transposons. Recent studies suggest that this function also involves piRNA-guided cleavage of transposon-derived transcripts. As many piRNAs also appear to have the capacity to target diverse mRNAs, this raises the intriguing possibility that piRNAs may act extensively as siRNAs to degrade specific mRNAs. To directly test this hypothesis, we compared mouse PIWI (MIWI)-associated piRNAs with experimentally identified cleaved mRNA fragments from mouse testes, and observed cleavage sites that predominantly occur at position 10 from the 5' end of putative targeting piRNAs. We also noted strong biases for U and A residues at nucleotide positions 1 and 10, respectively, in both piRNAs and mRNA fragments, features that resemble the pattern of piRNA amplification by the 'ping-pong' cycle. Through mapping of MIWI-RNA interactions by CLIP-seq and gene expression profiling, we found that many potential piRNA-targeted mRNAs directly interact with MIWI and show elevated expression levels in the testes of Miwi catalytic mutant mice. Reporter-based assays further revealed the importance of base pairing between piRNAs and mRNA targets and the requirement for both the slicer activity and piRNA-loading ability of MIWI in piRNA-mediated target repression. Importantly, we demonstrated that proper turnover of certain key piRNA targets is essential for sperm formation. Together, these findings reveal the siRNA-like function of the piRNA machinery in mouse testes and its central requirement for male germ cell development and maturation. CLIP-Seq (Crosslinking Immunoprecipitation coupled with high-throughput sequencing) experiments targeting Miwi in isolated round spermatids from mouse testis.
2015-04-09 | E-GEOD-67683 | biostudies-arrayexpress