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Bases estructurales del silenciamiento: Dominio Sir3 BAH en complejo con un nucleosoma a una resolución de 3.0 Å
Karim-Jean Armache1, Joseph D Garlick, Daniele Canzio
1Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA.
Science (New York, N.Y.)
|November 19, 2011
Resumen
El silenciamiento de genes en eucariotas se basa en las interacciones de la proteína Sir3 con los nucleosomas. La estructura cristalina revela cómo estas interacciones y modificaciones forman dominios de cromatina silenciados, cruciales para el destino celular.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Biología de la cromatina Biología de la cromatina
- Biología Estructural Biología estructural.
Sus antecedentes:
- El silenciamiento de genes es vital para la regulación del destino de las células eucariotas.
- La arquitectura de la cromatina juega un papel clave en el mantenimiento de los estados silenciados.
- Las proteínas reguladoras de información silenciosa (Sir), incluida la Sir3, son cruciales para regular el tipo de apareamiento en la levadura.
Objetivo del estudio:
- Para determinar la estructura cristalina de la levadura, el dominio Sir3 BAH complejo con la partícula del núcleo del nucleosoma.
- Para dilucidar las interacciones moleculares responsables de la generación de dominios de cromatina silenciados.
- Comprender cómo las modificaciones específicas de las histonas influyen en la formación de complejos silenciadores.
Principales métodos:
- Cristalografía de rayos X con una resolución de 3.0 angstroms.
- Análisis estructural del dominio Sir3 BAH y del complejo de partículas del núcleo del nucleosoma.
- Mapeo de mutaciones genéticas a las interacciones moleculares observadas.
Principales resultados:
- La estructura cristalina revela extensas interacciones moleculares entre el dominio Sir3 BAH y la superficie del nucleosoma.
- Las interacciones observadas explican numerosas mutaciones genéticas documentadas que afectan el silenciamiento de genes.
- Se identificaron reordenamientos estructurales tanto en el nucleosoma como en el dominio BAH.
- La estructura proporciona información sobre cómo las modificaciones covalentes H4K16 y H3K79 regulan la formación de complejos silenciadores.
Conclusiones:
- El dominio Sir3 BAH interactúa directamente con el nucleosoma para establecer la cromatina silenciada.
- La estructura determinada proporciona una base molecular para la comprensión de los mecanismos de silenciamiento de genes.
- Las modificaciones de las histonas son reguladores críticos de la formación y función del complejo Sir3-nucleosoma.
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