Ago2-Mediated Recruitment of HP1a on Transposable Elements in Drosophila Brain
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PROVIDER: PRJNA1301249 | ENA |
REPOSITORIES: ENA
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Project description:In Drosophila gonads, transposable elements (TEs) are repressed by Piwi-interacting RNA (piRNA) pathway operating both co-transcriptionally and post-transcriptionally. In the non-gonadal tissues, TEs are mainly repressed by short interfering RNA (siRNA) pathway with Argonaute2 (Ago2) as an effector protein. It is generally assumed that this pathway acts at the post-transcriptional level. However, recent data point to its involvement in the co-transcriptional silencing. Here, using DamID, we found drastic decrease of HP1a on TEs (especially on the LTR-containing retrotransposons) and other heterochromatin regions in Ago2-mutant Drosophila brain. HP1a reduction is accompanied by the increased chromatin accessibility of TEs, indicating their derepression. Consistent with these findings, several LTR-containing retrotransposons were up-regulated in larval brain upon Ago2 mutation. Moreover, upon knock-down of lamin Dm0 in neurons, HP1a was increased predominantly on the same set of TEs that have the reduced HP1a binding upon Ago2 mutation. We hypothesize that, since Ago2 was revealed in the common complex with lamin Dm0, the depletion of the latter may release Ago2 in the nucleoplasm, thus enhancing the recruitment of HP1a on TEs. Our findings support the model that TEs in Drosophila brain are partially silenced through Ago2-mediated recruitment of HP1a.
2025-09-08 | GSE304397 | GEO
Project description: Not available
| S-EPMC12427935 | biostudies-literature
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:Transposable elements study for Fritillaria imperialis
| PRJEB104641 | ENA
Project description:Transposable Elements in Frontotemporal Lobar Degeneration
| PRJNA561865 | ENA
Project description:Transposable Elements in Frontotemporal Lobar Degeneration
| PRJNA561866 | ENA
Project description:Transposable elements (TEs) are usually silenced by DNA methylation and H3K9me2, but in the absence of DNA methylation they can instead acquire the Polycomb-associated mark H3K27me3. Here, we initially set out to test whether DNA methylation and H3K27me3 compete during TE silencing establishment in Arabidopsis. Although we observe this competition at one newly inserted transgenic TE, we unexpectedly find that H3K27me3 deposition at another neo-inserted TE requires the de novo methyltransferase DRM2, revealing that DNA methylation can also promote Polycomb recruitment. Genome-wide H3K27me3 profiling in drm2, met1, and rdd mutants shows that DNA methylation either antagonizes or promotes H3K27me3 in a locus-specific manner, and that DNA demethylation also shapes H3K27me3 levels in vegetative tissues. Targeted methylation experiments demonstrate that DNA methylation directly influences PcG recruitment, and analyses using a drm2 catalytic mutant further confirm that this effect depends on DNA methylation itself rather than on DNA the methylation machinery. Overall, our work reveals an unexpected, cooperative crosstalk between DNA methylation and Polycomb pathways that maintains genome and epigenome integrity in eukaryotes.
2026-05-22 | GSE331299 | GEO
Project description:Heterochromatin protein 1a (HP1a) is a well-known component of pericentromeric and telomeric heterochromatin in Drosophila. However, its role and the mechanisms of its binding in the chromosome arms (ChAs) remain largely unclear. Here, we identified HP1a-interacting domains in the somatic cells of Drosophila ovaries using a DamIDseq approach and compared them with insertion sites of transposable elements (TEs) revealed by genome sequencing. Although HP1a domains cover only 13% of ChAs, they non-randomly associate with 42% of TE insertions. Furthermore, HP1a propagates from TE insertions at distances up to 10-kb. These data confirm the role of TEs in formation of HP1a islands in ChAs. However, only 18% of HP1a domains have adjacent TEs, indicating the existence of other mechanisms of HP1a domain formation besides spreading from TEs. In particular, many TE-independent HP1a domains correspond to the regions attached to the nuclear pore complexes (NPCs), or contain active gene promoters. Surprisingly, HP1a occupancy on the promoters of these genes does not lead to their repression. However, the steady-state transcript level of many genes located outside of HP1a domains was altered upon HP1a knockdown in the somatic cells of ovaries, thus pointing to the strong indirect effect of HP1a depletion. Collectively, our results support an existence of at least three different mechanisms of HP1a domain emergence in ChAs: spreading from TE insertions, interaction with the chromatin located near NPCs and targeting to the promoters of moderately expressed genes.
2020-05-26 | GSE132756 | GEO
Project description:Heterochromatin protein 1 (HP1) proteins are important regulators of heterochromatin mediated gene silencing and chromosome structure and it is well known as the reader of the heterochromatin mark methylation of histone H3 lysine 9 (H3K9me). In Drosophila three different histone lysine methyl transferases (HKMTs) are associated with the methylation of H3K9; Su(var)3-9, Setdb1 and G9a. To gain insights on the dependence of HP1a on the three different HKMTs, the division of labor between these methyl transferases and the dependence of HP1a on H3K9me we have studied HP1a binding in relation to H3K9me in mutants of these HKMTs. We show that Su(var)3-9 is responsible for the HP1a H3K9me-dependent binding in pericentromeric regions while Setdb1 controls the HP1a H3K9me-dependent binding to cytological region 2L:31 and together with POF chromosome 4. HP1a binds to the promoters and within gene bodies of active genes in these three regions. More importantly, HP1a bound at promoters of active genes are independent of H3K9me and POF and is associated to heterochromatin protein 2 (HP2) and open chromatin. Our results supports a model where HP1a nucleates with high affinity independent of H3K9me in promoters of active genes and then spreads via H3K9 methylation and transient looping contacts with those H3K9me target sites.
2012-12-21 | GSE38366 | GEO
Project description:Transposable elements function as mechanical sensors [HiCAR]
| PRJNA1108187 | ENA