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Diferentes fases del silenciamiento de Polycomb para mantener la memoria epigenética del frío en Arabidopsis

Hongchun Yang¹, Scott Berry^1,2, Tjelvar S G Olsson²

¹Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.

Science (New York, N.Y.)

|August 19, 2017

Resumen

Los complejos de policombos inician el silenciamiento genético en el gen FLOWERING LOCUS C (FLC) en Arabidopsis. Los distintos factores de Polycomb crean un silenciamiento epigenético metastable y luego estable, crucial para el desarrollo de las plantas.

Área de la Ciencia:

Biología molecular de las plantas
La epigenética
Regulación de la cromatina

Sus antecedentes:

Los complejos policombos son esenciales para el desarrollo eucariótico, regulando la expresión génica a través de mecanismos epigenéticos.
El gen FLOWERING LOCUS C (FLC) en Arabidopsis está epigenéticamente reprimido por el frío, sirviendo como modelo para estudiar el silenciamiento de Polycomb.
Comprender el inicio y el mantenimiento del silenciamiento de Polycomb es clave para descifrar los procesos de desarrollo.

Objetivo del estudio:

Investigar las distintas fases y mecanismos moleculares subyacentes al silenciamiento epigenético mediado por Polycomb en el locus FLC en Arabidopsis.
Identificar los factores específicos del complejo represivo Polycomb 2 (PRC2) implicados en el silenciamiento de la nucleación.
Para aclarar cómo el silenciamiento metastable se convierte en memoria epigenética estable.

Principales métodos:

Inmunoprecipitación de la cromatina para detectar los niveles de H3K27me3 en el locus FLC.
Análisis de los cambios en la expresión génica en respuesta al tratamiento en frío.
Investigar las funciones de los componentes específicos del complejo Polycomb en la iniciación y el mantenimiento del silenciamiento.

Principales resultados:

Un subconjunto de factores PRC2 nuclea el silenciamiento de Polycomb dentro de una región específica de FLC, aumentando H3K27me3.
Este silenciamiento inicial es metastable y se hereda a través de la memoria de cromatina local.
Los factores Polycomb separados promueven la propagación de H3K27me3 a través del locus FLC, convirtiendo el silenciamiento metastable en estable después de la exposición al frío.

Conclusiones:

El silenciamiento por policombos en FLC implica fases mecánicamente distintas: la nucleación de un silenciamiento metastable seguido de un silenciamiento epigenético estable.
La especialización de los componentes de Polycomb permite el establecimiento secuencial de la memoria epigenética transitoria y a largo plazo.
Este estudio proporciona información sobre la regulación dinámica de los estados epigenéticos durante el desarrollo de las plantas.

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