Germ granule dysfunction is a hallmark and mirror of Piwi mutant sterility

AbstractIn several species, Piwi/piRNA genome silencing defects cause immediate sterility that correlates with transposon expression and transposon-induced genomic instability. In C. elegans, mutations in the Piwi-related gene (prg-1) and other piRNA deficient mutants cause a transgenerational decline in fertility over a period of several generations. Here we show that the sterility of late generation piRNA mutants correlates poorly with increases in DNA damage signaling. Instead, sterile individuals consistently exhibit altered perinuclear germ granules. We show that disruption of germ granules does not activate transposon expression but induces multiple phenotypes found in sterile prg-1 pathway mutants. Furthermore, loss of the germ granule component pgl-1 enhances prg-1 mutant infertility. Environmental restoration of germ granule function for sterile pgl-1 mutants restores their fertility. We propose that Piwi mutant sterility is a reproductive arrest phenotype that is characterized by perturbed germ granule structure and is phenocopied by germ granule dysfunction, independent of genomic instability.

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A reproductive arrest program triggered by defects in Piwi and germ granules

10.1101/276782 ◽

2018 ◽

Author(s):

Maya Spichal ◽

Bree Heestand ◽

Katherine Kretovich Billmyre ◽

Stephen Frenk ◽

Shawn Ahmed

Keyword(s):

Dna Damage ◽

Genomic Instability ◽

Germ Cells ◽

C Elegans ◽

Multiple Phenotypes ◽

Germ Granules

AbstractIn several species, Piwi/piRNA genome silencing defects lead to immediate sterility accompanied by heterochromatin dysfunction and transposon-induced genomic instability, which may cause Piwi mutant sterility. InC. elegans,Piwi pathway mutants transmit a heritable stress through germ cells that induces sterility after growth for several generations. We found that sterile Piwi pathway mutant germ cells displayed inconsistent increases in DNA damage but consistently altered perinuclear germ granules that are known to promote fertility. Germ granule dysfunction did not elicit transposon expression but was sufficient to induce multiple phenotypes found in sterile Piwi silencing mutants, including germline atrophy and regrowth. Furthermore, loss of the germ granule component PGL-1 accelerated sterility in response to deficiency forprg-1/Piwi. Restoration of germ granule function to sterilepgl-1mutants restored their fertility. Together, our results suggest that germ granule defects may promote an adult reproductive arrest phenotype that is responsible for Piwi/piRNA mutant sterility.

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Hsp90 induces increased genomic instability toward DNA-damaging agents by tuning down RAD53 transcription

Molecular Biology of the Cell ◽

10.1091/mbc.e15-12-0867 ◽

2016 ◽

Vol 27 (15) ◽

pp. 2463-2478 ◽

Cited By ~ 9

Author(s):

Nidhi Khurana ◽

Shyamasree Laskar ◽

Mrinal K. Bhattacharyya ◽

Sunanda Bhattacharyya

Keyword(s):

Dna Damage ◽

Genomic Instability ◽

Transcriptional Repression ◽

Strand Break ◽

Dependent Manner ◽

Loss Of Function ◽

Checkpoint Activation ◽

Dna Damage Signaling ◽

Dna Damaging Agents ◽

G1 Cells

It is well documented that elevated body temperature causes tumors to regress upon radiotherapy. However, how hyperthermia induces DNA damage sensitivity is not clear. We show that a transient heat shock and particularly the concomitant induction of Hsp90 lead to increased genomic instability under DNA-damaging conditions. Using Saccharomyces cerevisiae as a model eukaryote, we demonstrate that elevated levels of Hsp90 attenuate efficient DNA damage signaling and dictate preferential use of the potentially mutagenic double-strand break repair pathway. We show that under normal physiological conditions, Hsp90 negatively regulates RAD53 transcription to suppress DNA damage checkpoint activation. However, under DNA damaging conditions, RAD53 is derepressed, and the increased level of Rad53p triggers an efficient DNA damage response. A higher abundance of Hsp90 causes increased transcriptional repression on RAD53 in a dose-dependent manner, which could not be fully derepressed even in the presence of DNA damage. Accordingly, cells behave like a rad53 loss-of-function mutant and show reduced NHEJ efficiency, with a drastic failure to up-regulate RAD51 expression and manifestly faster accumulation of CLN1 and CLN2 in DNA-damaged G1, cells leading to premature release from checkpoint arrest. We further demonstrate that Rad53 overexpression is able to rescue all of the aforementioned deleterious effects caused by Hsp90 overproduction.

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DNA damage signaling regulates cohesin stabilization and promotes meiotic chromosome axis morphogenesis

10.1101/2021.08.28.458025 ◽

2021 ◽

Author(s):

Zhouliang Yu ◽

Abby F Dernburg

Keyword(s):

Dna Damage ◽

Mammalian Cells ◽

Meiotic Chromosome ◽

Proliferating Cells ◽

Linear Arrays ◽

C Elegans ◽

Homolog Pairing ◽

Dna Damage Signaling ◽

Damage Response ◽

Chromosome Axis

A hallmark of meiosis is the reorganization of chromosomes as linear arrays of chromatin loops around a chro- mosome axis comprised of cohesins and regulatory proteins. Defective axis morphogenesis impairs homolog pairing, synapsis, and recombination. We find that axis assembly in C. elegans is promoted by DNA Damage Response (DDR) signaling activated at meiotic entry. Central to this regulation is downregulation of the cohesin release factor WAPL-1 by the DDR transducer kinase ATM-1, which is activated by the meiotic kinase CHK- 2. Additional cohesin regulators, including ECO-1 and PDS-5, also contribute to stabilizing axis-associated cohesins. We find that downregulation of WAPL by ATM also promotes cohesin enrichment at DNA damage foci in cultured mammalian cells. Our findings reveal that the DDR and Wapl play conserved roles in cohesin regulation in meiotic prophase and proliferating cells.

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