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Bases estructurales de la iniciación de la transcripción de la ARN polimerasa I

Christoph Engel¹, Tobias Gubbey¹, Simon Neyer¹

¹Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.

|March 25, 2017

Resumen

La ARN polimerasa I (Pol I) y los factores de iniciación Rrn3 y el factor central (CF) son esenciales para la transcripción de genes de ARN ribosomal. Los estudios estructurales revelan cómo la CF se acopla a Pol I-Rrn3, carga el ADN y facilita la iniciación de la transcripción.

Área de la Ciencia:

Biología molecular
Biología estructural
La bioquímica

Sus antecedentes:

La síntesis de ARN ribosomal (ARNr) es crucial para el crecimiento celular y requiere ARN polimerasa I (Pol I).
La iniciación de la transcripción por Pol I incluye los factores de iniciación Rrn3 y el factor central (CF).
La comprensión de los mecanismos estructurales de la iniciación de la transcripción Pol I es clave para descifrar la regulación génica.

Objetivo del estudio:

Para aclarar el mecanismo molecular de la iniciación de la transcripción de la ARN polimerasa basal I.
Determinar la base estructural del reconocimiento del promotor y la carga de ADN por el complejo Pol I-Rrn3-CF.

Principales métodos:

Cristalografía de rayos X
Microscopía criolectrónica (cryo-EM)
Modelado estructural

Principales resultados:

Se obtuvo un modelo molecular para la iniciación de Pol I basal mediante la combinación de cristalografía de rayos X y crio-EM.
El factor de núcleo de tres subunidades (CF) se une al ADN promotor aguas arriba y se acopla al complejo Pol I-Rrn3.
El ADN se carga en la hendidura central activa de la polimerasa, lo que lleva a la contracción de la hendidura y una conformación activa para la síntesis de ARN.

Conclusiones:

El modelo estructural revela el proceso paso a paso de carga y desenrollo del ADN durante la iniciación de la transcripción Pol I.
La especificidad del promotor está determinada por las características de la secuencia de ADN ("flexibilidad" y "fusión") que permiten las interacciones con los factores de iniciación y la polimerasa.
Este estudio proporciona información fundamental sobre la regulación de la transcripción génica del ARNr por la ARN polimerasa I.

Palabras clave:

La ARN polimerasa I Cristalografía de rayos X Factor del núcleo Crio-EM promotor de ARN ribosómico Iniciación de la transcripción

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