Somatic Primary piRNA Biogenesis Driven by Cis-Acting RNA Elements and Trans- Acting Yb
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ABSTRACT:
ORGANISM(S): Drosophila melanogaster
SUBMITTER: Haruhiko Siomi
PROVIDER: E-GEOD-69625 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Primary piRNAs in Drosophila ovarian somatic cells arise from piRNA cluster transcripts and the 3′ UTRs of a subset of mRNAs, including Traffic jam (Tj) mRNA. However, it is unclear how these RNAs are determined as primary piRNA sources. Here, we identify a cis-acting 100-nt fragment in the Tj 3′ UTR that is sufficient for producing artificial piRNAs from unintegrated DNA. These artificial piRNAs were effective in endogenous gene transcriptional silencing. Yb, a core component of primary piRNA biogenesis center Yb bodies, directly bound the Tj-cis-element. Disruption of this interaction markedly reduced piRNA production. Thus, Yb is the trans-acting partner of the Tj-cis-element. Yb-CLIP revealed that Yb-binding correlated with somatic piRNA production but Tj-cis-element downstream sequences produced few artificial piRNAs. Thus, Yb determines primary piRNA sources by two modes of action; primary binding to cis-elements to specify substrates, and secondary binding to downstream regions to increase diversity in piRNA populations.
2015-06-05 | GSE69625 | GEO
Project description:piRNAs direct Piwi to repress transposons to maintain genome integrity in Drosophila ovarian somatic cells. piRNA maturation and association with Piwi occur at perinuclear Yb bodies, the centers of piRNA biogenesis. Here, we show that piRNA intermediates arising from the piRNA cluster flamenco (flam) concentrate into perinuclear foci adjacent to Yb bodies, termed Flam bodies. Although flam expression is not required for Yb body formation, Yb, the core component of Yb bodies, is required for Flam body formation. Abolishment of the RNA-binding activity of Yb disrupts both Yb bodies and Flam bodies. Loss of Zucchini, an endoribonuclease necessary for piRNA maturation, enlarges Flam bodies, which now superimpose with Yb bodies. Yb directly binds flam, but not neighboring protein-coding gene, transcripts. Thus, Yb integrates piRNA processing factors and piRNA intermediates into Yb bodies and Flam bodies, respectively, through direct binding to enhance piRNA biogenesis and formation of piRNA-inducing silencing complexes. HITS-CLIP was performed using OSC (Ovarian Somatic Cells). The antibody for Drosophila Yb, which was generated in this study, was used. Obtained CLIP tags were analyzed using illumina HiSeq200.
2014-06-24 | E-GEOD-54875 | biostudies-arrayexpress
Project description:In Drosophila, PIWI proteins and bound PIWI interacting RNAs (piRNAs) form the core of a small RNA mediated defense system against selfish genetic elements. Within germline cells piRNAs are processed from piRNA clusters and transposons to be loaded into Piwi/Aubergine/AGO3 and a subset of piRNAs undergoes target dependent amplification. In contrast, gonadal somatic support cells express only Piwi, lack signs of piRNA amplification and exhibit primary piRNA biogenesis from piRNA clusters. Neither piRNA processing/loading nor Piwi mediated target silencing is understood at the genetic, cellular or molecular level. We developed an in vivo RNAi assay for the somatic piRNA pathway and identified the RNA helicase Armitage, the Tudor domain containing RNA helicase Yb and the putative nuclease Zucchini as essential factors for primary piRNA biogenesis. Lack of any of these proteins leads to transposon de-silencing, to a collapse in piRNA levels and to a failure in Piwi nuclear accumulation. We show that Armitage and Yb interact physically and co-localize in cytoplasmic Yb-bodies, which flank P-bodies. Loss of Zucchini leads to an accumulation of Piwi and Armitage in Yb-bodies indicating that Yb-bodies are sites of primary piRNA biogenesis. small RNA libraries were prepared from Piwi immuno-precipitates of five different genotypes
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Project description:In animals, the piRNA pathway preserves the integrity of gametic genomes, guarding them against the activity of mobile genetic elements. This innate immune mechanism relies on distinct genomic loci, termed piRNA clusters, to provide a molecular definition of transposons, enabling their discrimination from genes. piRNA clusters give rise to long, single-stranded precursors which are processed into primary piRNAs through an unknown mechanism. These can engage in an adaptive amplification loop, the ping-pong cycle, to optimize the content of small RNA populations via the generation of secondary piRNAs. Many proteins have been ascribed functions in either primary biogenesis or the ping- pong cycle, though for the most part the molecular functions of proteins implicated in these pathways remain obscure. Here, we link shutdown, a gene previously shown to be required for fertility in Drosophila, to the piRNA pathway. Analysis of knockdown phenotypes in both the germ line and somatic compartments of the ovary demonstrate important roles for shutdown in both primary biogenesis and the ping-pong cycle. shutdown is a member of the FKBP family of immunophilins, with domains implicated in peptidyl-prolyl cis-trans isomerase activity and in the binding of HSP90-family chaperones. Though the relevance of these domains to piRNA biogenesis is unknown, evolutionary comparisons raise questions about the integrity of these functions in the shutdown protein. Examination of small RNA levels from nos-GAL4 or tj-GAL4 driven UAS-dsRNA knockdowns of white, shu and piwi in ovaries of Drosophila melanogaster by deep sequencing (using Illumina GAII).
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Project description:PIWI-interacting RNAs (piRNAs) repress transposons to maintain germline genome integrity. Previous studies showed that artificial tethering of Armitage (Armi) to reporter RNAs induced piRNA biogenesis. However, lack of female sterile (1) Yb (Yb) in Drosophila ovarian somatic cells (OSCs) impaired production of transposon-targeting piRNAs even in the presence of Armi. Here, we show that specific interaction of Armi with RNA transcripts of flamenco piRNA cluster, the primary source of transposon-targeting piRNAs in OSCs, is strictly regulated by Yb. Lack of Yb allowed Armi to bind RNAs promiscuously, leading to the production of piRNAs unrelated to transposon silencing. The ATP hydrolysis-defective mutants of Armi failed to unwind RNAs and were retained on them, abolishing piRNA production. These findings shed light on distinct and collaborative requirements of Yb and Armi in transposon-targeting piRNA biogenesis. We also provide evidence supporting the direct involvement of Armi but not Yb in Zucchini-dependent piRNA phasing.
2019-03-28 | GSE128924 | GEO
Project description:Small RNAs mediate gene silencing by binding Argonaute/Piwi proteins to regulate target RNAs. Here we describe small RNA profiling of the adult testes of Callithrix jacchus, the common marmoset. The most abundant class of small RNAs in the adult testis was piRNAs, while 353 novel miRNAs but few endo-siRNAs were also identified. MARWI, a marmoset homolog of mouse MIWI and a very abundant PIWI in adult testes, associates with piRNAs that show characteristics of mouse pachytene piRNAs. As in other mammals, most marmoset piRNAs are derived from conserved clustered regions in the genome, which are annotated as intergenic regions. However, some of these piRNA cluster regions contain antisense-orientated pseudogenes, suggesting regulation of parental functional protein-coding genes. More piRNAs map to transposable element (TE) subfamilies when they have copies in piRNA clusters. In addition, the strand-bias observed for piRNAs mapped to each TE subfamily correlates with the polarity of copies inserted in clusters. These findings suggest that pachytene piRNA clusters determine the abundance and strand-bias of TE-derived piRNAs, and also regulate protein-coding genes via pseudogene-derived piRNAs. small RNA levels in the adult marmoset testis, and MARWI-IP small RNA levels and RNA levels from the adult marmoset testis with two replicates.
2014-06-01 | E-GEOD-52927 | biostudies-arrayexpress
Project description:The piRNA pathway is a small RNA-based immune system that silences mobile genetic elements in animal germlines. In Drosophila ovaries, piRNAs are produced from discrete genomic loci, called piRNA clusters, which are composed of inactive transposon copies and fragments and thus constitute a genetically encoded memory of past transposon challenges. Two types of piRNA clusters exist in flies: dual-strand clusters, expressed only in the germline via a highly specialised machinery, and uni-strand cluster, which are predominantly expressed in the somatic follicle cells. Flamenco (flam) is the major uni-strand piRNA cluster in Drosophila, giving rise to the majority of somatic piRNAs. Flam resembles a canonical RNA polymerase II transcriptional unit, nonetheless it can be specifically recognised by the piRNA pathway and directed to the biogenesis machinery. Recent work has implicated the RNA helicase Yb in the licensing of somatic piRNA production, however a detailed understanding of the molecular mechanisms underlying flam export and specification is still lacking. Here, we show that flam export triggers the assembly of peri-nuclear condensates of Yb and provide evidence that piRNA production from flam specifically requires subunits of the Nuclear Pore Complex (NPC). In the absence of some NPC subunits, transposons become de-silenced and piRNA biogenesis is compromised exclusively from flam. We also show that Yb transiently associates with the NPC to promote flam export. Taken together, our data shed light on how the export of uni-strand cluster transcripts is achieved and suggest the evolution of a specialised machinery that couples transcription, nuclear export and piRNA production.
2021-04-16 | PXD019671 | Pride
Project description:The piRNA pathway is a small RNA-based immune system that silences mobile genetic elements in animal germlines. In Drosophila ovaries, piRNAs are produced from discrete genomic loci, called piRNA clusters, which are composed of inactive transposon copies and fragments and thus constitute a genetically encoded memory of past transposon challenges. Two types of piRNA clusters exist in flies: dual-strand clusters, expressed only in the germline via a highly specialised machinery, and uni-strand cluster, which are predominantly expressed in the somatic follicle cells. Flamenco (flam) is the major uni-strand piRNA cluster in Drosophila, giving rise to the majority of somatic piRNAs. Flam resembles a canonical RNA polymerase II transcriptional unit, nonetheless it can be specifically recognised by the piRNA pathway and directed to the biogenesis machinery. Recent work has implicated the RNA helicase Yb in the licensing of somatic piRNA production, however a detailed understanding of the molecular mechanisms underlying flam export and specification is still lacking. Here, we show that flam export triggers the assembly of peri-nuclear condensates of Yb and provide evidence that piRNA production from flam specifically requires subunits of the Nuclear Pore Complex (NPC). In the absence of some NPC subunits, transposons become de-silenced and piRNA biogenesis is compromised exclusively from flam. We also show that Yb transiently associates with the NPC to promote flam export. Taken together, our data shed light on how the export of uni-strand cluster transcripts is achieved and suggest the evolution of a specialised machinery that couples transcription, nuclear export and piRNA production.
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