The capacity of target silencing by <i>Drosophila</i> PIWI and piRNAs

Post, Christina M.; Clark, Josef P.; Sytnikova, Yuliya A.; Chirn, Gung-Wei; Lau, Nelson C.

doi:10.1261/rna.046300.114

Cited by 87 publications

(102 citation statements)

References 61 publications

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“…In agreement with the study by Lau and colleagues (Post et al 2014), we found that recruitment of Piwi to a reporter construct via a sequence stretch complementary to endogenous piRNAs elicits potent reporter silencing in a Piwi-dependent and target orientation-dependent manner (Supplemental Fig. S1A).…”

Section: Recruitment Of Cg9754 To Rna or Dna Elicits Potent Transcripsupporting

confidence: 92%

“…Several studies indicate that binding of the Piwi-piRNA complex to a nascent target RNA causes heterochromatin formation and transcriptional silencing (e.g., Sarot et al 2004;Sienski et al 2012;Le Thomas et al 2013;Post et al 2014). In agreement with the study by Lau and colleagues (Post et al 2014), we found that recruitment of Piwi to a reporter construct via a sequence stretch complementary to endogenous piRNAs elicits potent reporter silencing in a Piwi-dependent and target orientation-dependent manner (Supplemental Fig.…”

Section: Recruitment Of Cg9754 To Rna or Dna Elicits Potent Transcripsupporting

confidence: 91%

“…In contrast, artificial recruitment (tethering) of Piwi via the λN-boxB system (thereby bypassing the requirement for piRNA target sites) to a reporter RNA expressed from a transiently transfected plasmid does not affect reporter expression (Supplemental Fig. S1B; Post et al 2014).…”

Section: Recruitment Of Cg9754 To Rna or Dna Elicits Potent Transcripmentioning

confidence: 99%

“…In turn, two proteins with largely unknown functions that are required for piRNA-guided transcriptional silencing in animals (Gtsf1/Asterix and Maelstrom) (Sienski et al 2012;Donertas et al 2013;Muerdter et al 2013;Ohtani et al 2013) are absent in S. pombe, highlighting significant molecular differences in these two systems. Moreover, the Piwi-piRNA complex fails to mediate transcriptional silencing if recruited artificially (not involving a piRNAtarget interaction) to a reporter RNA in a Drosophila cell culture model that expresses a fully functional piRNA pathway centered on nuclear Piwi (Post et al 2014). Whether this reflects the necessity for a conformational change in Piwi upon piRNA-target binding or is due to the requirement of a minimum threshold of target-engaged Piwi molecules to initiate silencing is unclear.…”

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confidence: 99%

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Silencio/CG9754 connects the Piwi–piRNA complex to the cellular heterochromatin machinery

et al. 2015

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The repression of transposable elements in eukaryotes often involves their transcriptional silencing via targeted chromatin modifications. In animal gonads, nuclear Argonaute proteins of the PIWI clade complexed with small guide RNAs (piRNAs) serve as sequence specificity determinants in this process. How binding of nuclear PIWIpiRNA complexes to nascent transcripts orchestrates heterochromatin formation and transcriptional silencing is unknown. Here, we characterize CG9754/Silencio as an essential piRNA pathway factor that is required for Piwimediated transcriptional silencing in Drosophila. Ectopic targeting of Silencio to RNA or DNA is sufficient to elicit silencing independently of Piwi and known piRNA pathway factors. Instead, Silencio requires the H3K9 methyltransferase Eggless/SetDB1 for its silencing ability. In agreement with this, SetDB1, but not Su(var)3-9, is required for Piwi-mediated transcriptional silencing genome-wide. Due to its interaction with the target-engaged PiwipiRNA complex, we suggest that Silencio acts as linker between the sequence specificity factor Piwi and the cellular heterochromatin machinery.[Keywords: H3K9 methylation; Piwi; transposon silencing; heterochromatin formation; piRNA pathway; transcriptional silencing] Supplemental material is available for this article. In fungi, plants, and animals, nuclear Argonaute proteins target nascent transcripts-RNAs that are still attached to their originating DNA locus via the transcribing RNA polymerase. This provides an opportunity for small RNA silencing pathways to connect to the various cellular chromatin-modifying activities for the sequence-specific formation of heterochromatin, typically at transposable element (TE) insertions (Castel and Martienssen 2013).Pioneering work in fission yeast has identified methylation of histone H3 at Lys9 (H3K9me2/3) and histone deacetylation as two major hallmarks that are required for small RNA-guided silencing and heterochromatin formation (Nakayama et al. 2001;Hall et al. 2002;Volpe et al. 2002;Yamada et al. 2005). A sequential order of events downstream from the recruitment of the Schizosaccharomyces pombe Ago1/siRNA complex to nascent RNA of centromeric repeats has been described. According to this, the Ago1/siRNA complex recruits the H3K9 methyltransferase Clr4 to chromatin, which results in H3K9 methylation (Noma et al. 2004;Verdel et al. 2004). This is believed to be a binding platform for the chromodomain-containing protein Swi6/HP1, which in turn recruits the major histone deacetylase and remodeling complex SHREC (Sugiyama et al. 2007). The final outcome of these events is the establishment of a nucleosome-dense region with low histone turnover, which effectively prevents the recruitment of RNA polymerase II (Pol II) to transcription initiation sites and hence transcription as such (e.g., Aygun et al. 2013).H3K9 methylation is also a hallmark of small RNAguided heterochromatin formation in plants, ciliates, and multicellular animals. In animal gonads, many TE insertions are methylated at...

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Section: Recruitment Of Cg9754 To Rna or Dna Elicits Potent Transcripsupporting

confidence: 92%

Section: Recruitment Of Cg9754 To Rna or Dna Elicits Potent Transcripsupporting

confidence: 91%

Section: Recruitment Of Cg9754 To Rna or Dna Elicits Potent Transcripmentioning

confidence: 99%

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confidence: 99%

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Silencio/CG9754 connects the Piwi–piRNA complex to the cellular heterochromatin machinery

et al. 2015

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“…S3B,C). Although other regulation patterns in the cytoplasm and nucleoplasm were more complicated, the up-regulated nascent RNA changes suggested a transcriptional gene silencing mechanism, which is discussed in greater detail below as well as tested in a second study (Post et al 2014).…”

Section: Recovery Of Te Transcripts Confirms Approach To Identify Piwmentioning

confidence: 95%

Transposable element dynamics and PIWI regulation impacts lncRNA and gene expression diversity in Drosophila ovarian cell cultures

et al. 2014

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Piwi proteins and Piwi-interacting RNAs (piRNAs) repress transposable elements (TEs) from mobilizing in gonadal cells. To determine the spectrum of piRNA-regulated targets that may extend beyond TEs, we conducted a genome-wide survey for transcripts associated with PIWI and for transcripts affected by PIWI knockdown in Drosophila ovarian somatic sheet (OSS) cells, a follicle cell line expressing the Piwi pathway. Despite the immense sequence diversity among OSS cell piRNAs, our analysis indicates that TE transcripts are the major transcripts associated with and directly regulated by PIWI. However, several coding genes were indirectly regulated by PIWI via an adjacent de novo TE insertion that generated a nascent TE transcript. Interestingly, we noticed that PIWI-regulated genes in OSS cells greatly differed from genes affected in a related follicle cell culture, ovarian somatic cells (OSCs). Therefore, we characterized the distinct genomic TE insertions across four OSS and OSC lines and discovered dynamic TE landscapes in gonadal cultures that were defined by a subset of active TEs. Particular de novo TEs appeared to stimulate the expression of novel candidate long noncoding RNAs (lncRNAs) in a cell lineage-specific manner, and some of these TE-associated lncRNAs were associated with PIWI and overlapped PIWI-regulated genes. Our analyses of OSCs and OSS cells demonstrate that despite having a Piwi pathway to suppress endogenous mobile elements, gonadal cell TE landscapes can still dramatically change and create transcriptome diversity.

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InsecticidalRNAinterference, thinking beyond longdsRNA

Flynt

2020

Pest Management Science

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Over 20 years ago double‐stranded RNA (dsRNA) was described as the trigger of RNAi interference (RNAi)‐based gene silencing. This paradigm has held since, especially for insect biopesticide technologies where dsRNAs, similar to those described in 1998, are used to inhibit gene expression. In the intervening years, investigation of RNAi pathways has revealed the small RNA effectors of RNAi are diverse and rapidly evolving. The rich biology of insect small RNAs suggests potential to use multiple RNAi modes for manipulating gene expression. By exploiting different RNAi pathways, the menu of options for pest control can be expanded and could lead to better tailored solutions. Fortunately, basic delivery strategies used for dsRNA such as direct application or transgenic expression will translate well between RNAs transiting different RNAi pathways. Importantly, further engineering of RNAi‐based biopesticides may provide an opportunity to address dsRNA insensitivity seen in some pests. Characterization of RNAi pathways unique to target species will be indispensable to this end and may require thinking beyond long dsRNA. © 2020 Society of Chemical Industry

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The capacity of target silencing by Drosophila PIWI and piRNAs

Cited by 87 publications

References 61 publications

Silencio/CG9754 connects the Piwi–piRNA complex to the cellular heterochromatin machinery

Silencio/CG9754 connects the Piwi–piRNA complex to the cellular heterochromatin machinery

Transposable element dynamics and PIWI regulation impacts lncRNA and gene expression diversity in Drosophila ovarian cell cultures

InsecticidalRNAinterference, thinking beyond longdsRNA

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