Structural insights into Rhino-mediated germline piRNA cluster formation.
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ABSTRACT:
SUBMITTER: Yu B
PROVIDER: S-EPMC4387552 | biostudies-literature | 2015 Apr
REPOSITORIES: biostudies-literature
Publications
Structural insights into Rhino-mediated germline piRNA cluster formation.
Yu Bowen B Cassani Madeline M Wang Min M Liu Mofang M Ma Jinbiao J Li Guohong G Zhang Zhao Z Huang Ying Y
Cell research 20150123 4
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Project description:PIWI-interacting RNAs (piRNAs) silence transposons in germ cells to maintain genome stability and animal fertility. Rhino, a rapidly evolving heterochromatin protein 1 (HP1) family protein, binds Deadlock in a species-specific manner and so defines the piRNA-producing loci in the Drosophila genome. Here, we determine the crystal structures of Rhino-Deadlock complex in Drosophila melanogaster and simulans In both species, one Rhino binds the N-terminal helix-hairpin-helix motif of one Deadlock protein through a novel interface formed by the beta-sheet in the Rhino chromoshadow domain. Disrupting the interface leads to infertility and transposon hyperactivation in flies. Our structural and functional experiments indicate that electrostatic repulsion at the interaction interface causes cross-species incompatibility between the sibling species. By determining the molecular architecture of this piRNA-producing machinery, we discover a novel HP1-partner interacting mode that is crucial to piRNA biogenesis and transposon silencing. We thus explain the cross-species incompatibility of two sibling species at the molecular level.
| S-EPMC6030695 | biostudies-literature
Project description:In a broad range of organisms, Piwi-interacting RNAs (piRNAs) have emerged as core components of a surveillance system that protects the genome by silencing transposable and repetitive elements. A vast proportion of piRNAs is produced from discrete genomic loci, termed piRNA clusters, which are generally embedded in heterochromatic regions. The molecular mechanisms and the factors that govern their expression are largely unknown. Here, we show that Cutoff (Cuff), a Drosophila protein related to the yeast transcription termination factor Rai1, is essential for piRNA production in germline tissues. Cuff accumulates at centromeric/pericentromeric positions in germ-cell nuclei and strongly colocalizes with the major heterochromatic domains. Remarkably, we show that Cuff is enriched at the dual-strand piRNA cluster 1/42AB and is likely to be involved in regulation of transcript levels of similar loci dispersed in the genome. Consistent with this observation, Cuff physically interacts with the Heterochromatin Protein 1 (HP1) variant Rhino (Rhi). Our results unveil a link between Cuff activity, heterochromatin assembly and piRNA cluster expression, which is critical for stem-cell and germ-cell development in Drosophila.
| S-EPMC3243597 | biostudies-literature
Project description:PIWI-interacting RNAs (piRNAs) guide transposable element repression in animal germ lines. In Drosophila, piRNAs are produced from heterochromatic loci, called piRNA clusters, which act as information repositories about genome invaders. piRNA generation by dual-strand clusters depends on the chromatin-bound Rhino-Deadlock-Cutoff (RDC) complex, which is deposited on clusters guided by piRNAs, forming a positive feedback loop in which piRNAs promote their own biogenesis. However, how piRNA clusters are formed before cognate piRNAs are present remains unknown. Here, we report spontaneous de novo piRNA cluster formation from repetitive transgenic sequences. Cluster formation occurs over several generations and requires continuous trans-generational maternal transmission of small RNAs. We discovered that maternally supplied small interfering RNAs (siRNAs) trigger de novo cluster activation in progeny. In contrast, siRNAs are dispensable for cluster function after its establishment. These results reveal an unexpected interplay between the siRNA and piRNA pathways and suggest a mechanism for de novo piRNA cluster formation triggered by siRNAs.
| S-EPMC10846595 | biostudies-literature
Project description:BackgroundFor species survival, the germline must faithfully transmit genetic information to the progeny. Transposable elements (TEs) constitute a significant threat to genome stability due to their mobility. In the metazoan germline, their mobilization is limited by a class of small RNAs called PIWI-interacting RNAs (piRNAs) produced by dedicated genomic loci called piRNA clusters. Although the piRNA pathway is an adaptive genomic immunity system, it remains unclear how the germline gains protection from a new transposon invasion.ResultsTo address this question, we analyze Drosophila melanogaster lines harboring a deletion within flamenco, a major piRNA cluster specifically expressed in somatic follicular cells. This deletion leads to derepression of the retrotransposon ZAM in the somatic follicular cells and subsequent germline genome invasion. In this mutant line, we identify de novo production of sense and antisense ZAM-derived piRNAs that display a germinal molecular signature. These piRNAs originated from a new ZAM insertion into a germline dual-strand piRNA cluster and silence ZAM expression specifically in germ cells. Finally, we find that ZAM trapping in a germinal piRNA cluster is a frequent event that occurs early during the isolation of the mutant line.ConclusionsTransposons can hijack the host developmental process to propagate whenever their silencing is lost. Here, we show that the germline can protect itself by trapping invading somatic-specific TEs into germline piRNA clusters. This is the first demonstration of "auto-immunization" of a germline endangered by mobilization of a surrounding somatic TE.
| S-EPMC6587276 | biostudies-literature
Project description:In order to control transposable element (TE) activity, PIWI-interacting RNAs (piRNAs) have been evolved to silence TE transcriptionally and post-transcriptionally, and produced from heterochromatic genomic loci, called piRNA cluster. Maternal inherited piRNAs transmission is considered as the key step of piRNA cluster maintenance and induction of de nove piRNA cluster formation, however, how the original piRNAs were produced without maternal piRNAs deposition remains unclear. In this paper, we created a repetitive GFP reporter and found a Rhino-dependent piRNA cluster conversion spontaneously occurs to the reporter over generations. Importantly, this conversion is reversible by removal of maternal piRNAs of GFP reporter. Taking advantage of this reversible GFP reporter piRNA cluster, we found that siRNA is able to initiate piRNA cluster formation epigenetically, even when only maternal siRNA presence is capable to do so. Our results suggest the importance of siRNA on initiation of piRNA biogenesis and describe a whole picture of initiation and maintenance of piRNA cluster.
2024-01-05 | GSE193091 | GEO
Project description:PIWI proteins and their guiding Piwi-interacting (pi-) RNAs direct the silencing of target nucleic acids in the animal germline and soma. Although in mammal testes fetal piRNAs are involved in extensive silencing of transposons, pachytene piRNAs have additionally been shown to act in post-transcriptional gene regulation. The bulk of pachytene piRNAs is produced from large genomic loci, named piRNA clusters. Recently, the presence of reversed pseudogenes within piRNA clusters prompted the idea that piRNAs derived from such sequences might direct regulation of their parent genes. Here, we examine primate piRNA clusters and integrated pseudogenes in a comparative approach to gain a deeper understanding about mammalian piRNA cluster evolution and the presumed gene-regulatory role of pseudogene-derived piRNAs. Initially, we provide a broad analysis of the evolutionary relationships of piRNA clusters and their differential activity among six primate species. Subsequently, we show that pseudogenes in reserve orientation relative to piRNA cluster transcription direction generally do not exhibit signs of selection pressure and cause weakly conserved targeting of homologous genes among species, suggesting a lack of functional constraints and thus only a minor significance for gene regulation in most cases. Finally, we report that piRNA-producing loci generally tend to be located in active genomic regions with elevated gene and pseudogene density. Thus, we conclude that the presence of most pseudogenes in piRNA clusters might be regarded as a byproduct of piRNA cluster generation, whereas this does not exclude that some pseudogenes nevertheless play critical roles in individual cases.
| S-EPMC6461890 | biostudies-literature
Project description:PIWI interacting RNAs (piRNAs) provide defense against transposable element (TE) expansion in the germline of metazoans. piRNAs are processed from the transcripts encoded by specialized heterochromatic clusters enriched in damaged copies of transposons. How these regions are recognized as a source of piRNAs is still elusive. The aim of this study is to determine how transgenes that contain a fragment of the LINE-like I transposon lead to an acquired TE resistance in Drosophila. We show that such transgenes, being inserted in unique euchromatic regions which normally do not produce small RNAs, become de novo bidirectional piRNA clusters that silence I-element activity in the germline. Strikingly, small RNAs of both polarities are generated from the entire transgene and flanking genomic sequences — not only from the transposon fragment. Chromatin immunoprecipitation analysis shows that in ovaries the trimethylated histone 3 lysine 9 (H3K9me3) mark associates with transgenes producing piRNAs. We show that transgene-derived hsp70 piRNAs stimulate in trans cleavage of cognate endogenous transcripts with subsequent processing of the non-homologous parts of these transcripts into piRNAs. The fractions of small RNAs (19-29 nt) from ovaries of wild type and 11 transgenic lines of Drosophila melanogaster were sequenced using Illumina HiSeq 2000.
2013-04-25 | E-GEOD-41780 | biostudies-arrayexpress
Project description:PIWI interacting RNAs (piRNAs) provide defense against transposable element (TE) expansion in the germline of metazoans. piRNAs are processed from the transcripts encoded by specialized heterochromatic clusters enriched in damaged copies of transposons. How these regions are recognized as a source of piRNAs is still elusive. The aim of this study is to determine how transgenes that contain a fragment of the LINE-like I transposon lead to an acquired TE resistance in Drosophila. We show that such transgenes, being inserted in unique euchromatic regions which normally do not produce small RNAs, become de novo bidirectional piRNA clusters that silence I-element activity in the germline. Strikingly, small RNAs of both polarities are generated from the entire transgene and flanking genomic sequences — not only from the transposon fragment. Chromatin immunoprecipitation analysis shows that in ovaries the trimethylated histone 3 lysine 9 (H3K9me3) mark associates with transgenes producing piRNAs. We show that transgene-derived hsp70 piRNAs stimulate in trans cleavage of cognate endogenous transcripts with subsequent processing of the non-homologous parts of these transcripts into piRNAs.
2013-04-25 | GSE41780 | GEO
Project description:Germline silencing of transposable elements is essential for the maintenance of genome integrity. Recent results indicate that this repression is largely achieved through a RNA silencing pathway that involves Piwi-interacting RNAs (piRNAs). However the repressive mechanisms are not well understood. To address this question, we used the possibility to disrupt the repression of the Drosophila I element retrotransposon by hybrid dysgenesis. We show here that the repression of the functional I elements that are located in euchromatin requires proteins of the piRNA pathway, and that the amount of ovarian I element piRNAs correlates with the strength of the repression in the female germline. Antisense RNAs, which are likely used to produce antisense piRNAs, are transcribed by heterochromatic defective I elements, but efficient production of these antisense small RNAs requires the presence in the genome of euchromatic functional I elements. Finally, we demonstrate that the piRNA-induced silencing of the functional I elements is at least partially posttranscriptional. In a repressive background, these elements are still transcribed, but some of their sense transcripts are kept in nurse cell nuclear foci together with those of the Doc retrotransposon. In the absence of I element piRNAs, either in dysgenic females or in mutants of the piRNA silencing pathway, sense I element transcripts are transported toward the oocyte where retrotransposition occurs. Our results indicate that piRNAs are involved in a posttranscriptional gene-silencing mechanism resulting in RNA nuclear accumulation.
| S-EPMC2567476 | biostudies-literature
Project description:In a broad range of organisms, Piwi-interacting RNAs (piRNAs) have emerged as core components of a surveillance system that protects the genome by silencing transposable and repetitive elements. A vast proportion of piRNAs is produced from discrete genomic loci, termed piRNA clusters. The molecular mechanisms and the factors that govern the expression of these loci are largely unknown. We have preciously shown the Cutoff (Cuff), a protein with similarity to yeast Rai1, is a component of the piRNA pathway. In order to understand the function of the Cuff protein in piRNA production, we produced small RNA libraries from cn, bw (wt) and cuffwm25 mutant ovaties. The analysis of these libraries revealed that approximately 80% of the total piRNA population is depleted in the absence of a functional Cuff protein. We also determined that Cuff is mostly a nuclear protein and is enriched at the level of certain piRNA clusters. Our results point to a role for Cuff in the transcriptional regulation of piRNA generating loci and in the production of the proper piRNA complement during Drosophila oogenesis. piRNA profiling in ovaries from cn, bw and cuffwm25 mutant ovaries
2013-06-07 | E-GEOD-47738 | biostudies-arrayexpress