Biology subjects

Quarato, P.

Publications and source records attributed to Quarato, P..

4 recordsLinked to original sources

bioRxiv2025

Nuclear Argonaute HRDE-1 Sustains Chromatin-Independent Transcriptional Silencing and Epigenetic Inheritance

Epigenetic inheritance of transcriptional silencing is traditionally attributed to chromatin-based mechanisms in which Argonaute-small RNA complexes recruit histone-modifying enzymes. Here we show that, in Caenorhabditis elegans, the nuclear Argonaute HRDE-1 maintains germline transcriptional repression independently of canonical heterochromatin marks. Using inducible, germline-specific HRDE-1 depletion combined with nuclear sorting, CUT&Tag, and nascent transcription profiling, we identified endogenous genes that become transcriptionally activated upon loss of HRDE-1 despite retaining H3K9me3 and H3K23me3. HRDE-1 directly restrains RNA polymerase II (Pol II) while simultaneously promoting polyUG-dependent amplification of antisense 22G-RNAs in perinuclear condensates, thereby coupling nuclear transcriptional repression to small RNA biogenesis. HRDE-1 loss causes progressive erosion of 22G-RNAs and delays silencing re-establishment, revealing a transgenerational feedback loop in which small RNAs, and not chromatin modifications, constitute the primary heritable signal. These findings redefine nuclear Argonautes as active drivers of RNA-based epigenetic inheritance and broaden our understanding of how small RNA pathways maintain transcriptional silencing across generations.

molecular biology↗

bioRxiv2021

A virus-encoded microRNA contributes to evade innate immune response during SARS-CoV-2 infection

SARS-CoV-2 infection results in impaired interferon response in severe COVID-19 patients. However, how SARS-CoV-2 interferes with host immune response is incompletely understood. Here, we sequenced small RNAs from SARS-CoV-2-infected human cells and identified a micro-RNA (miRNA) encoded in a recently evolved region of the viral genome. We show that the virus-encoded miRNA produces two miRNA isoforms in infected cells by the enzyme Dicer and they are loaded into Argonaute proteins. Moreover, the predominant miRNA isoform targets the 3UTR of interferon-stimulated genes and represses their expression in a miRNA-like fashion. Finally, the two viral miRNA isoforms were detected in nasopharyngeal swabs from COVID-19 patients. We propose that SARS-CoV-2 employs a virus-encoded miRNA to hijack the host miRNA machinery and evade the interferon-mediated immune response.

molecular biology↗

bioRxiv2020

Translation and codon usage regulate Argonaute slicer activity to trigger small RNA biogenesis

In the Caenorhabditis elegans germline, thousands of mRNAs are concomitantly expressed with antisense 22G-RNAs, which are loaded into the Argonaute CSR-1. Despite their essential functions for animal fertility and embryonic development, how CSR-1 22G-RNAs are produced remains unknown. Here, we show that CSR-1 slicer activity is primarily involved in triggering the synthesis of small RNAs on the coding sequences of germline mRNAs and post-transcriptionally regulates a fraction of targets. CSR-1-cleaved mRNAs prime the RNA-dependent RNA polymerase, EGO-1, to synthesize 22G-RNAs in phase with ribosome translation in the cytoplasm, in contrast to other 22G-RNAs mostly synthesized in germ granules. Moreover, codon optimality and efficient translation antagonize CSR-1 slicing and 22G-RNAs biogenesis. We propose that codon usage differences encoded into mRNA sequences might be a conserved strategy in eukaryotes to regulate small RNA biogenesis and Argonaute targeting.

molecular biology↗

bioRxiv2020

Argonaute catalytic activity is required for maternal mRNA clearance in embryos

Inheritance and clearance of maternal mRNAs are two of the most critical events required for animal early embryonic development. However, the mechanisms regulating this process are still largely unknown. Here, we show that together with maternal mRNAs, C. elegans embryos inherit a complementary pool of small non-coding RNAs capable of triggering the cleavage and removal of hundreds of maternal mRNAs. These antisense small RNAs are loaded into the maternal catalytically-active Argonaute CSR-1 and cleave complementary mRNAs no longer engaged in translation in somatic blastomeres. Induced depletion of CSR-1 specifically during embryonic development leads to embryonic lethality in a slicer-dependent manner and impairs the degradation of CSR-1 embryonic mRNA targets. Given the conservation of Argonaute catalytic activity, we propose that a similar mechanism operates to clear maternal mRNAs during the maternal-to-zygotic transition across species.

developmental biology↗