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C. elegans piRNAs are processed from capped-small RNAs transcribed at promoters throughout the genome

ABSTRACT: 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.

ORGANISM(S): Caenorhabditis elegans Mus musculus

PROVIDER: GSE40053 | GEO | 2012/12/22

SECONDARY ACCESSION(S): PRJNA172751

REPOSITORIES: GEO

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C. elegans piRNAs are processed from capped-small RNAs transcribed at promoters throughout the genome

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.

2012-12-22 | E-GEOD-40053 | biostudies-arrayexpress

C. elegans piRNAs mediate the genome-wide surveillance of germline transcripts

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.

2012-09-01 | GSE38723 | GEO

C. elegans piRNAs mediate the genome-wide surveillance of germline transcripts

2012-09-01 | E-GEOD-38723 | biostudies-arrayexpress

A Genome-wide RNAi screen identifies factors required for distinct stages of C. elegans piRNA biogenesis

Project description:In animals, piRNAs, and their associated Piwi proteins, guard germ cell genomes against mobile genetic elements via an RNAi-like mechanism. In C. elegans, 21U-RNAs comprise the piRNA class and these collaborate with 22G RNAs, via unclear mechanisms, to discriminate self from non-self and selectively and heritably silence the latter. Recent work indicates that 21U-RNAs are post-transcriptional processing products of individual transcription units that produce ~26 nucleotide capped precursors. Yet, nothing is known of how the expression of precursors is controlled or of how primary transcripts give rise to mature small RNAs. We conducted a genome-wide RNAi screen to identify components of the 21U biogenesis machinery. Screening by direct, qPCR-based measurements of mature 21U-RNA levels, we identified 22 genes important for 21U-RNA production, termed TOFUs (Twenty-One-u Fouled Up). We also identified 7 genes that normally repress 21U production. By measuring mature 21U-RNA and precursor levels for the 7 strongest hits from the screen, we have assigned factors to discrete stages of 21U-RNA production. Our work has identified factors separately required for the transcription of 21U precursors, and the processing of these precursors into mature 21U-RNAs, thereby providing an essential resource for studying the biogenesis of this important small RNA class. Small RNA and capped small RNA sequencing from total RNA of C. elegans subjected to different RNAi and different C. elegans mutants

2014-04-01 | E-GEOD-53970 | biostudies-arrayexpress

A Genome-wide RNAi screen identifies factors required for distinct stages of C. elegans piRNA biogenesis

2014-04-01 | GSE53970 | GEO

The IDR-containing protein PID-2 affects Z granules and is required for piRNA-induced silencing in the embryo

Project description:In Caenorhabditis elegans, the piRNA (21U RNA) pathway is required to establish proper gene regulation and an immortal germline. To achieve this, PRG-1-bound 21U RNAs trigger silencing mechanisms mediated by RNA-dependent RNA polymerase (RdRP)-synthetized 22G RNAs. This silencing can become PRG-1-independent, and heritable over many generations. This state is named RNAe. It is unknown how and when RNAe is established, and how it is maintained. We show that maternally provided 21U RNAs can be sufficient to trigger RNAe in embryos. Additionally, we identify the IDR-containing protein PID-2, as a factor required to establish and maintain RNAe. PID-2 interacts with two novel, partially redundant, eTudor domain proteins, PID-4 and PID-5. Additionally, PID-5 has a domain related to the X-prolyl aminopeptidase protein APP-1, and binds APP-1, implicating N-terminal proteolysis in RNAe. All three proteins are required for germline immortality, localize to perinuclear foci and affect Z granules, and are required for balancing of 22G RNA populations. Overall, our study identifies three new proteins with crucial functions in the C. elegans small RNA silencing network.

2020-09-21 | PXD018402 | Pride

Comparative analysis of piRNA sequences, targets and functions in Caenorhabditis nematodes

Project description:Piwi proteins and Piwi-interacting RNAs (piRNAs) are best known for their roles in suppressing transposons and promoting fertility. Yet piRNA biogenesis and its mechanisms of action differ widely between distantly related species. To better understand the evolution of piRNAs, we characterized the piRNA pathway in C. briggsae, a sibling species of the model organism C. elegans. Our analyses define 25,883 piRNA producing-loci in C. briggsae. piRNA sequences in C. briggsae are extremely divergent from their counterparts in C. elegans, yet both species adopt similar genomic organization and transcription program that drive piRNA expression. By examining production of Piwi-dependent secondary small RNAs, we identified a set of protein-coding genes that are evolutionarily conserved piRNA targets. In contrast to C. elegans, small RNAs mapped to ribosomal RNAs or histone transcripts are not hyper-accumulated in C. briggsae. Instead, we found that fewer introns in transcripts are associated with hyper-accumulation of small RNAs. Together our work highlights evolutionary conservation and divergence of the nematode piRNA pathway and provides insights into its role in endogenous gene regulation.

2022-08-23 | GSE203297 | GEO

The RNA Polymerase II subunit RPB-9 directs transcriptional elongation at piRNA loci in C. elegans

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.

2020-12-07 | PXD018657 | Pride

PID-1 is a novel factor that operates during 21U RNA biogenesis in Caenorhabditis elegans

Project description:Animal germ cells employ small RNA-based mechanisms to recognize and silence DNA that invades their genome. One of these pathways is named the Piwi:piRNA pathway. Biogenesis of piRNAs is poorly understood. In C. elegans, the piRNA (21U-RNA)-binding Argonaute protein PRG-1 is the only known player acting downstream of pre-cursor transcription. From a screen aimed at the isolation of ‘piRNA-induced silencing defective’ mutations we identified, amongst known Piwi-pathway components like MUT-7, RDE-3 and HRDE-1, PID-1 as a novel player. PID-1 is essential for 21U RNA biogenesis and affects an early step in the processing or transport of 21U precursor transcripts.

2014-03-17 | GSE55309 | GEO

The expression of small RNAs after prg-1 mutation

Project description:Piwi-related Argonaute proteins play important roles in maintaining germline integrity and fertility and have been linked to a class of germline-enriched small RNAs termed piRNAs. Caenorhabditis elegans encodes two Piwi family proteins called PRG-1 and PRG-2, and PRG-1 interacts with the C. elegans piRNAs (21U-RNAs). Previous studies found that the prg-1 mutation causes a marked reduction in the expression of 21U-RNAs, temperature-sensitive defects in fertility and other phenotypic defects.To systematically demonstrate the function of PRG-1 on regulating small RNAs and their targets. We use recent advances in high-throughput sequencing technology to show that expression of non-coding small RNAs in six stages(embryo,L1,L2,L3,L4,young audlt) and mRNAs in four stages (L1,L2,L3,L4) after prg-1 mutation. prg-1 mutation can not only lead to a decrease in the expression of 21U-RNAs, but also cause 35~40% of miRNAs to be significantly down-regulated; approximately 3% (6.00% in L4) of protein-coding genes are differentially expressed after mutating prg-1, and 60~70% of these substantially changed protein-coding genes are up-regulated.

2014-06-09 | GSE56272 | GEO

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