Project description:piRNAs are required to maintain germline integrity and fertility but their mechanism of action is poorly understood. Here we demonstrate that C. elegans piRNAs silence transcripts in trans through imperfectly complementary sites. We find that target silencing is independent of Piwi endonuclease activity or “slicing”. Instead, we show that piRNAs initiate a localized secondary endogenous small interfering RNA (endo-siRNA) response. Endogenous protein-coding gene, pseudogene and transposon transcripts exhibit Piwi-dependent endo-siRNAs at sites complementary to piRNAs and are derepressed in Piwi mutants. Genomic loci of piRNA biogenesis are depleted of protein-coding genes but not pseudogenes or transposons. Our data suggest that nematode piRNA clusters are evolving to generate piRNAs against active mobile elements. Thus, piRNAs provide heritable, sequence-specific triggers for RNAi in C. elegans. Affymetrix mRNA expression data from wild-type and two independent prg-1;prg-2 double mutant C. elegans strains (mRNA)
Project description:piRNAs are required to maintain germline integrity and fertility but their mechanism of action is poorly understood. Here we demonstrate that C. elegans piRNAs silence transcripts in trans through imperfectly complementary sites. We find that target silencing is independent of Piwi endonuclease activity or “slicing”. Instead, we show that piRNAs initiate a localized secondary endogenous small interfering RNA (endo-siRNA) response. Endogenous protein-coding gene, pseudogene and transposon transcripts exhibit Piwi-dependent endo-siRNAs at sites complementary to piRNAs and are derepressed in Piwi mutants. Genomic loci of piRNA biogenesis are depleted of protein-coding genes but not pseudogenes or transposons. Our data suggest that nematode piRNA clusters are evolving to generate piRNAs against active mobile elements. Thus, piRNAs provide heritable, sequence-specific triggers for RNAi in C. elegans.
Project description:piRNAs are required to maintain germline integrity and fertility but their mechanism of action is poorly understood. Here we demonstrate that C. elegans piRNAs silence transcripts in trans through imperfectly complementary sites. We find that target silencing is independent of Piwi endonuclease activity or “slicing”. Instead, we show that piRNAs initiate a localized secondary endogenous small interfering RNA (endo-siRNA) response. Endogenous protein-coding gene, pseudogene and transposon transcripts exhibit Piwi-dependent endo-siRNAs at sites complementary to piRNAs and are derepressed in Piwi mutants. Genomic loci of piRNA biogenesis are depleted of protein-coding genes but not pseudogenes or transposons. Our data suggest that nematode piRNA clusters are evolving to generate piRNAs against active mobile elements. Thus, piRNAs provide heritable, sequence-specific triggers for RNAi in C. elegans.
Project description:piRNAs are required to maintain germline integrity and fertility but their mechanism of action is poorly understood. Here we demonstrate that C. elegans piRNAs silence transcripts in trans through imperfectly complementary sites. We find that target silencing is independent of Piwi endonuclease activity or “slicing”. Instead, we show that piRNAs initiate a localized secondary endogenous small interfering RNA (endo-siRNA) response. Endogenous protein-coding gene, pseudogene and transposon transcripts exhibit Piwi-dependent endo-siRNAs at sites complementary to piRNAs and are derepressed in Piwi mutants. Genomic loci of piRNA biogenesis are depleted of protein-coding genes but not pseudogenes or transposons. Our data suggest that nematode piRNA clusters are evolving to generate piRNAs against active mobile elements. Thus, piRNAs provide heritable, sequence-specific triggers for RNAi in C. elegans. 7 small RNA libraries were sequenced as part of 25 flow cell lanes on the Illumina GA II platform. Samples were treated with tobacco acid pyrophosphatase to allow cloning of small RNAs with a 5'-triphosphate. Samples were labelled for multiplexing using 4-bp 5'-barcodes or barcodes included in Illumina TruSeq adapters. In most cases a single flow cell lane included several multiplexed libraries.
Project description:To explore the roles of piRNAs and WAGO-class 22G-RNAs in regulating gene expression and transposon silencing in Caenorhabditis elegans, we used RNA-seq to assess changes in small RNA and mRNA levels in prg-1 and mut-16 mutants, which disable the piRNA and WAGO-class 22G-RNA pathways respectively. We identified numerous roles for piRNAs and WAGO-class 22G-RNAs in regulating germline genes, including transposons, histones, and spermatogenic and oogenic transcripts.
Project description:PIWI-interacting RNAs (piRNAs) are genomically-encoded small RNAs that regulate germ cell development and guarantee germline integrity. Mature piRNAs engage Piwi Argonaute proteins to silence complementary transcripts, including transposable elements and endogenous genes. To date, piRNA biogenesis mechanisms are still unclear. Here, we show that the RNA Polymerase II subunit RPB-9 is required to promote transcription elongation at piRNA loci. Through genetic and biochemical experiments, we demonstrate that rpb-9-mediated piRNA production is needed to repress two DNA transposon families and a subset of somatic genes in the C. elegans germline.
Project description:Piwi-interacting (pi) RNAs are a class of germline-expressed small RNAs that have been linked to epigenetic programming in metazoa. C. elegans piRNAs known as 21U-RNAs are defined by more than 15,000 genome-encoded species. To explore the origin of 21U-RNAs we employed methods to enrich the 5' ends of Pol II transcripts. We show that a species of capped-short (cs) RNA is frequently expressed bidirectionally at Pol II loci in C. elegans. Interestingly, at annotated 21U-RNA loci, csRNAs originate precisely 2 nt upstream of the mature piRNA species suggesting that csRNAs are piRNA precursors. In addition, we show that csRNAs associated with TS sites genome-wide define a previously overlooked class of 21U-RNA loci, and nearly double the number of piRNA species available for genome surveillance. Our methods should be of general utility in TS site identification and 5' anchored RNA-expression profiling. Identification of capped RNA including capped small RNA and long capped RNA in C. elegans. The mouse data are independent data to test the CapSeq sequencing protocol.
Project description:Piwi-interacting (pi) RNAs are a class of germline-expressed small RNAs that have been linked to epigenetic programming in metazoa. C. elegans piRNAs known as 21U-RNAs are defined by more than 15,000 genome-encoded species. To explore the origin of 21U-RNAs we employed methods to enrich the 5' ends of Pol II transcripts. We show that a species of capped-short (cs) RNA is frequently expressed bidirectionally at Pol II loci in C. elegans. Interestingly, at annotated 21U-RNA loci, csRNAs originate precisely 2 nt upstream of the mature piRNA species suggesting that csRNAs are piRNA precursors. In addition, we show that csRNAs associated with TS sites genome-wide define a previously overlooked class of 21U-RNA loci, and nearly double the number of piRNA species available for genome surveillance. Our methods should be of general utility in TS site identification and 5' anchored RNA-expression profiling.
Project description:Piwi Argonautes and Piwi-interacting RNAs (piRNAs) mediate genome defense by targeting transposons. However, many piRNA species lack obvious sequence complementarity to transposons or other loci. For example, only one C. elegans transposon is a known piRNA target. Here we show that, in mutants lacking the Piwi Argonaute PRG-1 and associated piRNAs (21U-RNAs), many silent loci in the germline exhibit increased levels of mRNA expression and depletion of an amplified RNAdependent RNA polymerase (RdRP)-derived species of small RNA termed 22G-RNAs. Sequences depleted of 22G-RNAs are enriched nearby potential target sites that base pair imperfectly but extensively to 21U-RNAs. We show that PRG-1 is required to initiate, but not to maintain, silencing of transgenes engineered to contain complementarity to endogenous 21U-RNAs. Our findings support a model in which C. elegans piRNAs utilize their enormous repertoire of targeting capacity to scan the germline transcriptome for foreign sequences, while endogenous germline-expressed genes are actively protected from piRNA-induced silencing. Examine small RNA population changes in prg-1 and rescued strains