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PIWI-interacting RNAs, or piRNAs, are the most abundant short non-coding RNAs. More than 20,000 genes have been found in humans that code for piRNAs while only 2000 genes have been found for miRNAs. piRNAs can act at the transcriptional and post-transcriptional levels and have a vital role in silencing transposable elements present in germ cells. They are also involved in epigenetic silencing and activation. Previously, they were thought to function only in germ cells but new evidence suggests...
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RNA Interference01:23

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RNA interference (RNAi) is a process in which a small non-coding RNA molecule blocks the post-transcriptional expression of a gene by binding to its messenger RNA (mRNA) and preventing the protein from being translated.
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RNA interference (RNAi) is a cellular mechanism that inhibits gene expression by suppressing its transcription or activating the RNA degradation process. The mechanism was discovered by Andrew Fire and Craig Mello in 1998 in plants. Today, it is observed in almost all eukaryotes, including protozoa, flies, nematodes, insects, parasites, and mammals. This precise cellular mechanism of gene silencing has been developed into a technique that provides an efficient way to identify and determine the...
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Small interfering RNAs, or siRNAs, are short regulatory RNA molecules that can silence genes post-transcriptionally, as well as the transcriptional level in some cases. siRNAs are important for protecting cells against viral infections and silencing transposable genetic elements.
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Protein domains are small structurally independent units that are part of a single amino acid chain.  Although these domains are often structurally independent, they may rely on synergistic effects to perform their functions as part of a larger protein. Protein domains may be conserved within the same organism, as well as across different organisms.
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Updated: Sep 8, 2025

In Situ Detection of Ribonucleoprotein Complex Assembly in the C. elegans Germline using Proximity Ligation Assay
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Un complejo de silenciamiento PIWI conservado detecta el compromiso con el objetivo piRNA

Dipayan De1, Sucharita Sarkar1, Luca F R Gebert1

  • 1Department of Integrative Structural and Computational Biology, Scripps Research, La Jolla, CA, USA.

Molecular cell
|September 5, 2025
PubMed
Resumen

Las proteínas PIWI usan piRNAs para defenderse de los elementos genéticos egoístas. Este estudio revela un complejo asociado a PIWI conservado que reconoce y divide los ARN transposones, proporcionando un mecanismo de defensa crucial en los animales.

Palabras clave:
GTSF1 (en inglés)Maelstrom también.Piwi también.Siwi también.El piRNAsilenciamientoElemento transponibleel transposón

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Área de la Ciencia:

  • Biología molecular
  • La genética
  • Biología estructural

Sus antecedentes:

  • Las proteínas PIWI y los ARN que interactúan con PIWI (piRNA) son esenciales para silenciar los elementos genéticos egoístas en las células germinales animales.
  • El mecanismo preciso por el cual el reconocimiento del transposón guiado por piRNA activa las proteínas PIWI para la defensa sigue siendo incompleto.

Objetivo del estudio:

  • Para aclarar el mecanismo molecular de reconocimiento y silenciamiento del transposón por las proteínas PIWI.
  • Identificar el complejo proteico involucrado en la defensa mediada por piRNA contra los transposones.

Principales métodos:

  • Ensayos bioquímicos para caracterizar las interacciones proteína-proteína y la actividad enzimática.
  • Microscopía criolectrónica (crio-EM) para determinar la base estructural del complejo.
  • Las predicciones estructurales para evaluar la conservación evolutiva.

Principales resultados:

  • Identificación de un nuevo complejo de reconocimiento de transposones que comprende Siwi, GTSF1 y Maelstrom en gusanos de seda.
  • Demostración de que el emparejamiento extendido de piRNA con el objetivo induce una conformación específica de Siwi, lo que permite el reclutamiento de GTSF1 y Maelstrom.
  • El análisis estructural reveló que Maelstrom y GTSF1 activan cooperativamente la actividad de la endonucleasa de Siwi, lo que lleva a la escisión del ARN objetivo y el reclutamiento de Spindle-E.

Conclusiones:

  • El estudio define un complejo conservado asociado a PIWI (PIWI*) como un efector clave en la defensa del transposón mediada por piRNA.
  • Este mecanismo de ensamblaje y activación de PIWI* se conserva en todos los metazoos, desde las esponjas hasta los humanos.
  • Los hallazgos proporcionan un marco estructural y mecanicista para comprender cómo los animales defienden sus genomas contra elementos genéticos móviles.