Complex Genetic Interactions between Piwi and HP1a in the Repression of Transposable Elements and Tissue-Specific Genes in the Ovarian Germline
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ABSTRACT:
PROVIDER: PRJNA776528 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR16642923.fastq.gz | Fastqsanger.gz | |||
| SRR16642924.fastq.gz | Fastqsanger.gz | |||
| SRR16642925.fastq.gz | Fastqsanger.gz | |||
| SRR16642926.fastq.gz | Fastqsanger.gz | |||
| SRR16642927.fastq.gz | Fastqsanger.gz |
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Project description:Insertions of transposable elements (TEs) in eukaryotic genomes are usually associated with repressive chromatin, which spreads to neighbouring genomic sequences. In ovaries of Drosophila melanogaster, the Piwi-piRNA pathway plays a key role in the transcriptional silencing of TEs considered to be exerted mostly through the establishment of H3K9me3 histone marks recruiting Heterochromatin Protein 1a (HP1a). Here, using RNA-seq, we investigated the expression of TEs and the adjacent genomic regions upon Piwi and HP1a germline knockdowns sharing a similar genetic background. We found that the depletion of Piwi and HP1a led to the derepression of only partially overlapping TE sets. Several TEs were silenced predominantly by HP1a, whereas the upregulation of some other TEs was more pronounced upon Piwi knockdown and, surprisingly, was diminished upon a Piwi/HP1a double-knockdown. We revealed that HP1a loss influenced the expression of thousands of protein-coding genes mostly not adjacent to TE insertions and, in particular, downregulated a putative transcriptional factor required for TE activation. Nevertheless, our results indicate that Piwi and HP1a cooperatively exert repressive effects on the transcription of euchromatic loci flanking the insertions of some Piwi-regulated TEs. We suggest that this mechanism controls the silencing of a small set of TE-adjacent tissue-specific genes, preventing their inappropriate expression in ovaries.
2021-12-22 | GSE186867 | GEO
Project description:Insertions of transposable elements (TEs) in eukaryotic genomes are usually associated with repressive chromatin, which spreads to neighbouring genomic sequences. In ovaries of Drosophila melanogaster, the Piwi-piRNA pathway plays a key role in the transcriptional silencing of TEs considered to be exerted mostly through the establishment of H3K9me3 histone marks recruiting Heterochromatin Protein 1a (HP1a). Here, using RNA-seq, we investigated the expression of TEs and the adjacent genomic regions upon Piwi and HP1a germline knockdowns sharing a similar genetic background. We found that the depletion of Piwi and HP1a led to the derepression of only partially overlapping TE sets. Several TEs were silenced predominantly by HP1a, whereas the upregulation of some other TEs was more pronounced upon Piwi knockdown and, surprisingly, was diminished upon a Piwi/HP1a double-knockdown. We revealed that HP1a loss influenced the expression of thousands of protein-coding genes mostly not adjacent to TE insertions and, in particular, downregulated a putative transcriptional factor required for TE activation. Nevertheless, our results indicate that Piwi and HP1a cooperatively exert repressive effects on the transcription of euchromatic loci flanking the insertions of some Piwi-regulated TEs. We suggest that this mechanism controls the silencing of a small set of TE-adjacent tissue-specific genes, preventing their inappropriate expression in ovaries.
| S-EPMC8707237 | biostudies-literature
Project description:The piRNA-interacting Piwi protein is involved in transcriptional silencing of transposable elements in ovaries of D. melanogaster. Here we characterized the genome-wide effect of nuclear Piwi elimination on the presence of the heterochromatic H3K9me3 mark and HP1a, as well as on the transcription-associated mark H3K4me2. Our results demonstrate that a significant increase in the H3K4me2 level upon nuclear Piwi loss is not accompanied by the alterations in H3K9me3 and HP1a levels for several germline-expressed transposons, suggesting that in this case Piwi prevents transcription by a mechanism distinct from H3K9 methylation. We found that the targets of Piwi-dependent chromatin repression are mainly related to the elements that display a higher level of H3K4me2 modification in the absence of silencing, i.e. most actively transcribed elements. We also show that Piwi-guided silencing does not significantly influence the chromatin state of dual-strand piRNA-producing clusters. In addition, host protein-coding gene expression is essentially not affected due to the nuclear Piwi elimination, but we noted an increase in small nuclear spliceosomal RNAs abundance and propose Piwi involvement in their posttranscriptional regulation. Our work reveals new aspects of transposon silencing in Drosophila, indicating that transcription of transposons can underpin their Piwi dependent silencing, while canonical heterochromatin marks are not obligatory for their repression.
2014-05-19 | GSE56347 | GEO
Project description:The piRNA-interacting Piwi protein is involved in transcriptional silencing of transposable elements in ovaries of D. melanogaster. Here we characterized the genome-wide effect of nuclear Piwi elimination on the presence of the heterochromatic H3K9me3 mark and HP1a, as well as on the transcription-associated mark H3K4me2. Our results demonstrate that a significant increase in the H3K4me2 level upon nuclear Piwi loss is not accompanied by the alterations in H3K9me3 and HP1a levels for several germline-expressed transposons, suggesting that in this case Piwi prevents transcription by a mechanism distinct from H3K9 methylation. We found that the targets of Piwi-dependent chromatin repression are mainly related to the elements that display a higher level of H3K4me2 modification in the absence of silencing, i.e. most actively transcribed elements. We also show that Piwi-guided silencing does not significantly influence the chromatin state of dual-strand piRNA-producing clusters. In addition, host protein-coding gene expression is essentially not affected due to the nuclear Piwi elimination, but we noted an increase in small nuclear spliceosomal RNAs abundance and propose Piwi involvement in their posttranscriptional regulation. Our work reveals new aspects of transposon silencing in Drosophila, indicating that transcription of transposons can underpin their Piwi dependent silencing, while canonical heterochromatin marks are not obligatory for their repression. Examination of histone modifications in ovaries from two different fly lines- piwiNt/piwi2 (mutant) and piwi/+ (wildtype)
2014-05-19 | E-GEOD-56347 | biostudies-arrayexpress
Project description:PIWI-interacting RNAs (piRNAs) mediate transposable element (TE) silencing at the transcriptional or post-transcriptional level in animal gonads. In the Drosophila ovary, Piwi–piRNA complexes (Piwi–piRISCs) repress TE transcription by modifying the chromatin state, such as H3K9me3 marks. Here, we demonstrate that Piwi physically interacts with linker histone H1. Depletion of Piwi decreases H1 density on target loci, leading to TE derepression. Loss of H1 results in gain of chromatin accessibility at target loci without affecting H3K9me3 and heterochromatin protein 1a (HP1a) density at the same loci. Piwi-mediated TE silencing also requires HP1a by regulating chromatin accessibility through its association with target loci. Thus, Piwi–piRISCs require both H1 and HP1a to repress TEs, and the silencing is correlated with the state of chromatin formation rather than H3K9me3 marks. These findings suggest that Piwi–piRISCs regulate the interaction of chromatin components with target loci to maintain silencing of the TE state through the modulation of chromatin accessibility.
2016-06-30 | GSE81434 | GEO
Project description:Transposable elements (TEs) can damage genomes, thus organisms employ a variety of mechanisms to repress TE expression. The PIWI-piRNA pathway is a small RNA pathway that represses TE expression in the germline of animals. Here we explore the function of the pathway in the somatic stem cells of Hydra, a long-lived freshwater cnidarian. Hydra have three stem cell populations, all of which express PIWI proteins; endodermal and ectodermal epithelial stem cells are somatic, whereas the interstitial stem cells have germline competence. To study somatic function of the pathway we isolated piRNAs from Hydra that lack the interstitial lineage and found that these somatic piRNAs map predominantly to TE transcripts and display the conserved sequence signatures typical of germline piRNAs. Three lines of evidence suggest that the PIWI-piRNA pathway represses TEs in Hydra epithelial stem cells. First, epithelial knockdown of the Hydra piwi gene hywi resulted in upregulation of TE expression. Second, degradome sequencing revealed evidence of PIWI-mediated cleavage of TE RNAs in epithelial cells using the ping-pong mechanism. Finally, we demonstrated a direct association between Hywi protein and TE transcripts in epithelial cells using RNA immunoprecipitation. Altogether, our data reveal that the PIWI-piRNA pathway represses TE expression in the somatic cell lineages of Hydra, which we propose contributes to the extreme longevity of the organism. Furthermore, our results, in combination with others, suggest that somatic TE repression is an ancestral function of the PIWI-piRNA pathway.
2019-08-07 | GSE135440 | GEO
Project description:Eukaryotic genomes are colonized by transposable elements whose uncontrolled activity results in genomic instability. The piRNA pathway silences transposons in animal gonads, yet how this is achieved molecularly remains controversial. We assign an essential role to the HMG protein Maelstrom in the process of Piwi mediated silencing in Drosophila. Genome wide assays revealed highly correlated changes in RNA Polymerase II recruitment, nascent RNA output and steady state RNA levels of transposons upon loss of Piwi or Maelstrom. Our data demonstrate piRNA-mediated trans- silencing of hundreds of transposon copies at the transcriptional level. We show that Piwi is required for establishing heterochromatic H3K9me3 marks on transposons and their genomic surrounding. In contrast, loss of Maelstrom impacts transposon H3K9me3 patterns only marginally yet leads to increased heterochromatin spreading, suggesting that Maelstrom acts downstream of or in parallel to H3K9me3. Our work uncovers the widespread influence of transposons and the piRNA pathway on chromatin patterns and gene expression programs. RNA Polymerase II and H3K9me3 occupancy, and steady-state and nascent RNA levels in wild-type ovarian somatic cells (OSC) and RNAi knock-downs of the piRNA pathway components. RNA Polymerase II occupancy in tissue-specific knockdowns of tejas (control) and armi in somatic cells of Drosophila ovary.
2012-11-26 | E-GEOD-41729 | biostudies-arrayexpress
Project description:PIWI-interacting RNAs (piRNAs) mediate transposable element (TE) silencing at the transcriptional or post-transcriptional level in animal gonads. In the Drosophila ovary, Piwiâ??piRNA complexes (Piwiâ??piRISCs) repress TE transcription by modifying the chromatin state, such as H3K9me3 marks. Here, we demonstrate that Piwi physically interacts with linker histone H1. Depletion of Piwi decreases H1 density on target loci, leading to TE derepression. Loss of H1 results in gain of chromatin accessibility at target loci without affecting H3K9me3 and heterochromatin protein 1a (HP1a) density at the same loci. Piwi-mediated TE silencing also requires HP1a by regulating chromatin accessibility through its association with target loci. Thus, Piwiâ??piRISCs require both H1 and HP1a to repress TEs, and the silencing is correlated with the state of chromatin formation rather than H3K9me3 marks. These findings suggest that Piwiâ??piRISCs regulate the interaction of chromatin components with target loci to maintain silencing of the TE state through the modulation of chromatin accessibility. RNA levels, H1 and H3K9me3 occupancy, chromatin accessibility, and Piwi-associated small RNA levels in ovarian somatic cells (OSC) depleted of piRNA pathway components and H1.
2016-06-30 | E-GEOD-81434 | biostudies-arrayexpress
Project description:Eukaryotic genomes are colonized by transposable elements whose uncontrolled activity results in genomic instability. The piRNA pathway silences transposons in animal gonads, yet how this is achieved molecularly remains controversial. We assign an essential role to the HMG protein Maelstrom in the process of Piwi mediated silencing in Drosophila. Genome wide assays revealed highly correlated changes in RNA Polymerase II recruitment, nascent RNA output and steady state RNA levels of transposons upon loss of Piwi or Maelstrom. Our data demonstrate piRNA-mediated trans- silencing of hundreds of transposon copies at the transcriptional level. We show that Piwi is required for establishing heterochromatic H3K9me3 marks on transposons and their genomic surrounding. In contrast, loss of Maelstrom impacts transposon H3K9me3 patterns only marginally yet leads to increased heterochromatin spreading, suggesting that Maelstrom acts downstream of or in parallel to H3K9me3. Our work uncovers the widespread influence of transposons and the piRNA pathway on chromatin patterns and gene expression programs.
2012-11-26 | GSE41729 | GEO
Project description:In the Metazoan germline, piwi proteins and associated piwi-interacting RNAs (piRNAs) provide a defense system against the expression of transposable elements. In the cytoplasm, piRNA sequences guide piwi complexes to destroy complementary transposon transcripts by endonucleolytic cleavage. However, some piwi family members are nuclear, raising the possibility of alternative pathways for piRNA-mediated regulation of gene expression. We found that Drosophila Piwi is recruited to chromatin, co-localizing with RNA polymerase II on polytene chromosomes. Knockdown of Piwi in the germline increases expression of transposable elements that are targeted by piRNAs, whereas protein-coding genes remain largely unaffected. De-repression of transposons upon Piwi depletion correlates with increased occupancy of RNA polymerase II on their promoters. Expression of piRNAs that target a reporter construct results in a decrease in Pol II occupancy and an increase in repressive H3K9me3 marks and HP1 on the reporter locus. Our results indicate that Piwi identifies targets complementary to the associated piRNA and induces transcriptional repression by establishing a repressive chromatin state when correct targets are found. Examination of mRNA levels, Pol II occupancy, and chromatin repressive state in D. melanogaster ovaries upon Piwi knockdown and Piwi mutation. This records present the sequencing data related to Piwi knockdown study portion.
2013-02-11 | E-GEOD-43829 | biostudies-arrayexpress