Estructura y mecanismo del remodelador Swi2/Snf2 Mot1 en complejo con su sustrato TBP
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Petra Wollmann1, Sheng Cui, Ramya Viswanathan
1Department of Biochemistry, Ludwig-Maximilians University, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.
Nature
|July 8, 2011
Resumen
Mot1, una enzima Swi2 / Snf2, actúa como un abridor de botellas para liberar la proteína de unión TATA del ADN. Este mecanismo combina las actividades motoras y de acompañamiento para una regulación precisa de la transcripción.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- Biología Molecular Biología Molecular
Sus antecedentes:
- Las ATPasas tipo Swi2 / Snf2 son cruciales para los procesos del genoma como la transcripción, la replicación y la reparación.
- La comprensión de cómo estas enzimas interactúan con los complejos proteína-ADN está limitada por la falta de datos estructurales de alta resolución.
- Mot1 (modificador de transcripción 1) es una enzima modelo ideal para estudiar los mecanismos Swi2/Snf2 debido a su estructura polipéptida única y sustrato simple.
Objetivo del estudio:
- Para aclarar el mecanismo por el cual Mot1 (BTAF1) interrumpe los complejos TATA-binding protein (TBP) -DNA.
- Proporcionar información estructural de alta resolución sobre la interacción entre una enzima remodeladora y su sustrato.
- Para entender cómo Mot1 logra la especificidad funcional en la regulación de la transcripción.
Principales métodos:
- La cristalografía de rayos X y la microscopía electrónica se utilizaron para determinar las estructuras de los complejos Mot1-TBP de Encephalitozoon cuniculi.
- Se realizaron estudios bioquímicos para validar los hallazgos estructurales y los mecanismos funcionales.
- Análisis de las repeticiones HEAT de Mot1 y las interacciones de dominio Swi2/Snf2 con TBP y ADN.
Principales resultados:
- Mot1 se envuelve alrededor de TBP, utilizando una serie de repeticiones HEAT en forma de resorte para agarrar el lado distal del ADN de TBP.
- El dominio Swi2 / Snf2 se une al ADN aguas arriba, lo que facilita la translocación del ADN y debilita la interacción TBP-ADN.
- Un mecanismo de "cerrojo" dentro de Mot1 bloquea la ranura de unión al ADN de TBP, actuando como un acompañante para garantizar el despeje del promotor.
Conclusiones:
- Mot1 emplea un mecanismo único de "abrebotas" que involucra la translocación de ADN y un pestillo parecido a un chaperón para desplazar TBP.
- Este estudio revela cómo las enzimas remodeladoras combinan las actividades motoras y de acompañamiento para la interrupción específica de los complejos proteína-ADN.
- Los hallazgos ofrecen una comprensión más profunda de la familia de enzimas Swi2 / Snf2 y su papel en la regulación de la transcripción a nivel mundial.
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