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Bases estructurales de la transcripción: selección de nucleótidos por rotación en el centro activo de la ARN
Kenneth D Westover1, David A Bushnell, Roger D Kornberg
1Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
Cell
|November 13, 2004
Resumen
La ARN polimerasa II utiliza un nuevo mecanismo de dos pasos para la selección de nucleótidos, que implica un sitio de entrada antes del sitio activo. Este hallazgo redefine la comprensión de las grandes polimerasas de ARN multisubunitaria.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Biología Estructural Biología estructural.
- La bioquímica es la bioquímica.
Sus antecedentes:
- La ARN polimerasa II es crucial para la transcripción génica en los eucariotas.
- Comprender el mecanismo preciso de la selección de nucleótidos es clave para regular la expresión génica.
Objetivo del estudio:
- Para dilucidar el mecanismo de selección de nucleótidos por la ARN polimerasa II.
- Caracterizar la base estructural de la unión y incorporación de nucleótidos.
Principales métodos:
- Se empleó cristalografía de rayos X para visualizar el complejo de transcripción de la ARN polimerasa II.
- Análisis de los sitios de unión de nucleótidos y las orientaciones dentro de la enzima.
Principales resultados:
- Se reveló un mecanismo de selección de nucleótidos en dos pasos, que involucra un sitio de entrada (E) y un sitio de adición (A).
- Los nucleótidos no coincidentes se unen en una orientación invertida en el sitio E antes de la rotación potencial.
- Un tercer sitio de unión de nucleótidos potencialmente regula el retroceso del ARN; el desenrollo del ADN precede al centro activo.
Conclusiones:
- Los hallazgos establecen un nuevo paradigma para la selección de nucleótidos en las grandes polimerasas de ARN multisubunitaria, distintas de las enzimas de una sola subunidad.
- El estudio proporciona información a nivel atómico sobre la función y regulación de la ARN polimerasa II.
- La cristalografía de alta resolución avanzó en la comprensión de la dinámica de las enzimas y la interacción del ADN.
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