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RNAi-dependent Polycomb repression controls transposable elements in Tetrahymena [small RNA-seq]

ABSTRACT: RNA interference (RNAi) and Polycomb repression play evolutionarily conserved and often coordinated roles in transcriptional silencing. Here we show that in the protozoan Tetrahymena thermophila, germ line-specific internally eliminated sequences (IES)—many related to transposable elements (TE)—are transcriptionally activated in mutants deficient in the RNAi-dependent Polycomb repression pathway. Mobilization of recently duplicated TE also dramatically increases in these mutants. Importantly, transcriptional silencing and activation of TE-related sequences are accompanied by switching between noncoding RNA (ncRNA) and mRNA production, which can be affected by co-transcriptional processing as well as RNAi and Polycomb repression. We posit that interplay between RNAi and Polycomb repression is a widespread phenomenon, whose ancestral role is epigenetic silencing of TE.

ORGANISM(S): Tetrahymena thermophila

PROVIDER: GSE118198 | GEO | 2019/03/01

REPOSITORIES: GEO

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RNAi-dependent Polycomb repression controls transposable elements in Tetrahymena [RNA-seq]

Project description:RNA interference (RNAi) and Polycomb repression play evolutionarily conserved and often coordinated roles in transcriptional silencing. Here we show that in the protozoan Tetrahymena thermophila, germ line-specific internally eliminated sequences (IES) - many related to transposable elements (TE) - are transcriptionally activated in mutants deficient in the RNAi-dependent Polycomb repression pathway. Mobilization of recently duplicated TE also dramatically increases in these mutants. Importantly, transcriptional silencing and activation of TE-related sequences are accompanied by switching between noncoding RNA (ncRNA) and mRNA production, which can be affected by co-transcriptional processing as well as RNAi and Polycomb repression. We posit that interplay between RNAi and Polycomb repression is a widespread phenomenon, whose ancestral role is epigenetic silencing of TE.

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2022-10-13 | PXD036548 | Pride

VAL1 acts as an assembly platform co-ordinating co-transcriptional repression and chromatin regulation at Arabidopsis FLC

Project description:Polycomb (PcG) silencing is crucial for development, but how targets are specified remains incompletely understood. The cold-induced Polycomb Repressive Complex 2 (PRC2) silencing of Arabidopsis thaliana FLOWERING LOCUS C (FLC) provides an excellent system to elucidate PcG regulation. Association of the DNA binding protein VAL1 to the PcG nucleationregion at FLC is an important step. VAL1 interacts with APOPTOSIS AND SPLICING ASSOCIATED PROTEIN (ASAP) complex and PRC1. Here, we show that ASAP and PRC1 are necessary for co-transcriptional repression and chromatin regulation during FLC silencing. ASAP mutants affect FLC transcription in warm conditions, but the rate of FLC silencing in the cold is unaffected. PRC1-mediated H2Aub accumulates at FLC nucleation region during cold, but unlike the PRC2-delivered H3K27me3 does not spread across the locus. H2Aub thus marks the transition to epigenetic silencing, while H3K27me3 is necessary for long-term epigenetic memory. Overall, our work highlights the importance of VAL1 as an assembly platform co-ordinating the co-transcriptional repression and chromatin regulation necessary for the epigenetic silencing of FLC.

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H2A ubiquitination is essential for Polycomb Repressive Complex 1-mediated gene regulation in Marchantia polymorpha

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Investigation of the timing of secondary small RNA biogenesis during programmed DNA elimination in Tetrahymena

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An RNAi-dependent Polycomb Repression Pathway Is Required for Co-transcriptional Silencing of Transposable Elements

Project description:An RNAi-dependent Polycomb Repression Pathway Is Required for Co-transcriptional Silencing of Transposable Elements

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RNAi-dependent Polycomb repression controls transposable elements in Tetrahymena

Project description:RNAi-dependent Polycomb repression controls transposable elements in Tetrahymena

| PRJNA484827 | ENA

Identification of new regulators of the three dimensional Polycomb organization by a microscopy-based genome-wide RNAi screen

Project description:Polycomb group (PcG) proteins dynamically define cellular identities through epigenetic repression of key developmental genes. PcG target gene repression can be stabilized through the interaction in the nucleus at PcG foci. Here, we report the results of a high-resolution microscopy genome-wide RNAi screen that identifies 129 genes that regulate the nuclear organization of Pc foci. Candidate genes include PcG components and chromatin factors, as well as many novel protein-modifying enzymes, including components of the SUMOylation pathway. In the absence of SUMO Pc foci coagulate into larger aggregates. Conversely, loss of function of the SUMO peptidase velo disperses Pc foci. Moreover, SUMO and velo colocalize with PcG proteins at PREs and Pc SUMOylation affects its chromatin targeting, suggesting that the dynamic regulation of Pc SUMOylation regulates PcG-mediated silencing by modulating the kinetics of Pc binding to chromatin as well as its ability to form Polycomb foci. ChIP-Seq mapping of Polycomb (PC), SUMO and Velo on Drosophila Melanogaster

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