Transposon silencing in the Drosophila female germline ensures genome stability in progeny embryos

AbstractThe piRNA pathway functions in transposon control in the germ line of metazoans. The conserved RNA helicase Vasa is an essential piRNA pathway component, but has additional important developmental functions. Here we address the importance of Vasa-dependent transposon control in the Drosophila female germline and early embryos. We find that transient loss of vasa expression during early oogenesis leads to transposon up-regulation in supporting nurse cells of the fly egg-chamber. We show that elevated transposon levels have dramatic consequences, as de-repressed transposons accumulate in the oocyte where they cause DNA damage. We find that suppression of Chk2-mediated DNA damage signaling in vasa mutant females restores oogenesis and egg production. Damaged DNA and up-regulated transposons are transmitted from the mother to the embryos, which sustain severe nuclear defects and arrest development. Our findings reveal that the Vasa-dependent protection against selfish genetic elements in the nuage of nurse cell is essential to prevent DNA damage-induced arrest of embryonic development.

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Transposon silencing in the Drosophila female germline is essential for genome stability in progeny embryos

Life Science Alliance ◽

10.26508/lsa.201800179 ◽

2018 ◽

Vol 1 (5) ◽

pp. e201800179 ◽

Cited By ~ 7

Author(s):

Zeljko Durdevic ◽

Ramesh S Pillai ◽

Anne Ephrussi

Keyword(s):

Dna Damage ◽

Genome Stability ◽

Egg Production ◽

Nurse Cells ◽

Selfish Genetic Elements ◽

Dna Damage Signaling ◽

Transposon Silencing ◽

Early Embryos ◽

Transient Loss ◽

Female Germline

The Piwi-interacting RNA pathway functions in transposon control in the germline of metazoans. The conserved RNA helicase Vasa is an essential Piwi-interacting RNA pathway component, but has additional important developmental functions. Here, we address the importance of Vasa-dependent transposon control in the Drosophila female germline and early embryos. We find that transient loss of vasa expression during early oogenesis leads to transposon up-regulation in supporting nurse cells of the fly egg-chamber. We show that elevated transposon levels have dramatic consequences, as de-repressed transposons accumulate in the oocyte where they cause DNA damage. We find that suppression of Chk2-mediated DNA damage signaling in vasa mutant females restores oogenesis and egg production. Damaged DNA and up-regulated transposons are transmitted from the mother to the embryos, which sustain severe nuclear defects and arrest development. Our findings reveal that the Vasa-dependent protection against selfish genetic elements in the nuage of nurse cell is essential to prevent DNA damage–induced arrest of embryonic development.

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AMPK blocks chromatin activation and consequent R-loop formation to protect genome stability following acute starvation

10.21203/rs.3.rs-378687/v1 ◽

2021 ◽

Author(s):

Bing Sun ◽

McLean Sherrin ◽

Richard Roy

Keyword(s):

Dna Damage ◽

Genome Stability ◽

Germ Line ◽

Critical Role ◽

Significant Proportion ◽

Loop Formation ◽

C Elegans ◽

Chromatin Activation ◽

Acute Starvation

Abstract During periods of starvation organisms must modify both gene expression and metabolic pathways to adjust to the energy stress. We previously reported that C. elegans that lack AMPK have transgenerational reproductive defects that result from abnormally elevated H3K4me3 levels in the germ line following recovery from acute starvation1. Here we show that H3K4me3 is dramatically increased at promoters, driving aberrant transcription elongation that results in the accumulation of R-loops in the starved AMPK mutants. DRIP-seq analysis demonstrated that a significant proportion of the genome was affected by R-loop formation with a dramatic expansion in the number of R-loops at numerous loci, most pronounced at the promoter-TSS regions of genes in the starved AMPK mutants. The R-loops are transmissible into subsequent generations, likely contributing to the transgenerational reproductive defects typical of these mutants following starvation. Strikingly, AMPK null germ lines show considerably more RAD-51 foci at sites of R-loop formation, potentially sequestering it from its critical role at meiotic breaks and/or at sites of induced DNA damage. Our study reveals a previously unforeseen role of AMPK in maintaining genome stability following starvation, where in its absence R-loops accumulate, resulting in reproductive compromise and DNA damage hypersensitivity.

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Assembly and Function of Gonad-Specific Non-Membranous Organelles in Drosophila piRNA Biogenesis

Non-Coding RNA ◽

10.3390/ncrna5040052 ◽

2019 ◽

Vol 5 (4) ◽

pp. 52 ◽

Cited By ~ 3

Author(s):

Shigeki Hirakata ◽

Mikiko C. Siomi

Keyword(s):

Dna Damage ◽

Gonadal Development ◽

Mitochondrial Membranes ◽

Animal Life ◽

Transposon Silencing ◽

Dna Elements ◽

Non Coding Rnas ◽

And Function ◽

Pirna Pathway

PIWI-interacting RNAs (piRNAs) are small non-coding RNAs that repress transposons in animal germlines. This protects the genome from the invasive DNA elements. piRNA pathway failures lead to DNA damage, gonadal development defects, and infertility. Thus, the piRNA pathway is indispensable for the continuation of animal life. piRNA-mediated transposon silencing occurs in both the nucleus and cytoplasm while piRNA biogenesis is a solely cytoplasmic event. piRNA production requires a number of proteins, the majority of which localize to non-membranous organelles that specifically appear in the gonads. Other piRNA factors are localized on outer mitochondrial membranes. In situ RNA hybridization experiments show that piRNA precursors are compartmentalized into other non-membranous organelles. In this review, we summarize recent findings about the function of these organelles in the Drosophila piRNA pathway by focusing on their assembly and function.

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Role of Deubiquitinating Enzymes in DNA Repair

Molecular and Cellular Biology ◽

10.1128/mcb.00847-15 ◽

2015 ◽

Vol 36 (4) ◽

pp. 524-544 ◽

Cited By ~ 34

Author(s):

Younghoon Kee ◽

Tony T Huang

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Mammalian Cells ◽

Genome Stability ◽

Regulatory Mechanisms ◽

Deubiquitinating Enzymes ◽

Genome Maintenance ◽

Dna Damage Signaling ◽

Damage Response

Both proteolytic and nonproteolytic functions of ubiquitination are essential regulatory mechanisms for promoting DNA repair and the DNA damage response in mammalian cells. Deubiquitinating enzymes (DUBs) have emerged as key players in the maintenance of genome stability. In this minireview, we discuss the recent findings on human DUBs that participate in genome maintenance, with a focus on the role of DUBs in the modulation of DNA repair and DNA damage signaling.

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RDC complex executes a dynamic piRNA program during Drosophila spermatogenesis to safeguard male fertility

PLoS Genetics ◽

10.1371/journal.pgen.1009591 ◽

2021 ◽

Vol 17 (9) ◽

pp. e1009591

Author(s):

Peiwei Chen ◽

Yicheng Luo ◽

Alexei A. Aravin

Keyword(s):

Sexually Dimorphic ◽

Common Belief ◽

Germline Stem Cells ◽

Male Germline ◽

Pirna Cluster ◽

Transposon Silencing ◽

Normal Spermatogenesis ◽

The Common ◽

Pirna Pathway ◽

Female Germline

piRNAs are small non-coding RNAs that guide the silencing of transposons and other targets in animal gonads. In Drosophila female germline, many piRNA source loci dubbed “piRNA clusters” lack hallmarks of active genes and exploit an alternative path for transcription, which relies on the Rhino-Deadlock-Cutoff (RDC) complex. RDC was thought to be absent in testis, so it remains to date unknown how piRNA cluster transcription is regulated in the male germline. We found that components of RDC complex are expressed in male germ cells during early spermatogenesis, from germline stem cells (GSCs) to early spermatocytes. RDC is essential for expression of dual-strand piRNA clusters and transposon silencing in testis; however, it is dispensable for expression of Y-linked Suppressor of Stellate piRNAs and therefore Stellate silencing. Despite intact Stellate repression, males lacking RDC exhibited compromised fertility accompanied by germline DNA damage and GSC loss. Thus, piRNA-guided repression is essential for normal spermatogenesis beyond Stellate silencing. While RDC associates with multiple piRNA clusters in GSCs and early spermatogonia, its localization changes in later stages as RDC concentrates on a single X-linked locus, AT-chX. Dynamic RDC localization is paralleled by changes in piRNA cluster expression, indicating that RDC executes a fluid piRNA program during different stages of spermatogenesis. These results disprove the common belief that RDC is dispensable for piRNA biogenesis in testis and uncover the unexpected, sexually dimorphic and dynamic behavior of a core piRNA pathway machinery.

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The role of ATXR6 expression in modulating genome stability and transposable element repression in Arabidopsis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2115570119 ◽

2022 ◽

Vol 119 (3) ◽

pp. e2115570119

Author(s):

Magdalena E. Potok ◽

Zhenhui Zhong ◽

Colette L. Picard ◽

Qikun Liu ◽

Truman Do ◽

...

Keyword(s):

Dna Damage ◽

Genome Stability ◽

Null Allele ◽

Epigenetic Changes ◽

Germline Development ◽

Tissue Specific ◽

Damage Response ◽

Female Germline

ARABIDOPSIS TRITHORAX-RELATED PROTEIN 5 (ATXR5) AND ATXR6 are required for the deposition of H3K27me1 and for maintaining genomic stability in Arabidopsis. Reduction of ATXR5/6 activity results in activation of DNA damage response genes, along with tissue-specific derepression of transposable elements (TEs), chromocenter decompaction, and genomic instability characterized by accumulation of excess DNA from heterochromatin. How loss of ATXR5/6 and H3K27me1 leads to these phenotypes remains unclear. Here we provide extensive characterization of the atxr5/6 hypomorphic mutant by comprehensively examining gene expression and epigenetic changes in the mutant. We found that the tissue-specific phenotypes of TE derepression and excessive DNA in this atxr5/6 mutant correlated with residual ATXR6 expression from the hypomorphic ATXR6 allele. However, up-regulation of DNA damage genes occurred regardless of ATXR6 levels and thus appears to be a separable process. We also isolated an atxr6-null allele which showed that ATXR5 and ATXR6 are required for female germline development. Finally, we characterize three previously reported suppressors of the hypomorphic atxr5/6 mutant and show that these rescue atxr5/6 via distinct mechanisms, two of which involve increasing H3K27me1 levels.

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