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GLH/VASA helicases promote germ granule formation to ensure the fidelity of piRNA-mediated transcriptome surveillance

ABSTRACT: The ability to distinguish non-self from self is the key characteristic for any defense system. piRNAs function as guardians of the genome by silencing non-self nucleic acids and transposable elements in animals. Many piRNA factors are enriched in perinuclear germ granules, but whether their localization is required for piRNA biogenesis or function is not known. Here we show that GLH/VASA helicase mutants exhibit defects in forming perinuclear condensates containing PIWI and other small RNA cofactors. These mutant animals produce largely normal levels of piRNA but are defective in triggering piRNA silencing. Strikingly, while many piRNA targets are activated in GLH mutants, we observed that hundreds of endogenous genes are aberrantly silenced by piRNAs. This defect in self versus non-self recognition was also observed in other mutants where perinuclear P granules are disrupted. Together, our results argue that perinuclear germ granules function critically to promote the fidelity of piRNA-based transcriptome surveillance in C. elegans and preserve self versus non-self distinction.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Caenorhabditis Elegans

TISSUE(S): Whole Body

SUBMITTER: Donglei Zhang

LAB HEAD: Donglei Zhang

PROVIDER: PXD033506 | Pride | 2022-08-05

REPOSITORIES: Pride

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			Action	DRS
	GLH-1_repeat_1.raw	Raw
	GLH-1_repeat_1.xlsx	Xlsx
	GLH-1_repeat_2.raw	Raw
	GLH-1_repeat_2.xlsx	Xlsx
	N2.raw	Raw

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Project description:Formation of biomolecular condensates have emerged as a critical mechanism for compartmentation in living cells. Despite interactions between distinct condensates have been reported, the biological relevance of such interactions remains elusive. In germ cells, small RNA silencing factors are enriched in germ granules, which distinct factors are organized into sub-compartments with specific functions linked to genome surveillance or transgenerational gene silencing. Here we showed that perinuclear germ granules are coated by P body, another condensate known for housing untranslated mRNAs and mRNA degradation factors. Disruption of P body factors, including CGH-1/DDX6 and CAR-1/LSM14, lead to dispersal of small RNA factors from perinuclear germ granules and disorganization of sub-compartments within germ granules. We further showed that CAR-1 promote the interactions between CGH-1 with germ granule factors and such interactions are critical for CGH-1’s ability to promote piRNA-mediated gene silencing. Importantly, we observed that cgh-1 mutants are competent in triggering gene silencing but exhibit defects in maintaining gene silencing effects in the subsequent generations. Small RNA sequencing further showed that cgh-1 mutants exhibit defects in amplifying secondary small RNAs, a known carrier of gene silencing memory. Together, our results uncover the function of P body factors in small RNA-mediated transgenerational gene silencing and highlight how the formation and function of one condensate can be regulated by an adjacent, interacting condensate in cells.

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