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La estructura cristalina del ADN-PKcs revela una gran cuna de anillo abierto compuesta por repeticiones de CALOR

Bancinyane L Sibanda¹, Dimitri Y Chirgadze, Tom L Blundell

¹Department of Biochemistry, University of Cambridge, Old Addenbrooke's site, 80 Tennis Court Road, Cambridge CB2 1GA, UK. lynn@cryst.bioc.cam.ac.uk

|December 22, 2009

Resumen

Se determinó la estructura cristalina de la subunidad catalítica de proteína quinasa dependiente del ADN humano (ADN-PKcs), revelando su papel en la reparación de la ruptura de doble hebra del ADN. Este hallazgo ofrece información sobre el mecanismo de la estabilidad genómica y la prevención del cáncer.

Área de la Ciencia:

Biología Molecular Biología Molecular
Biología Estructural Biología estructural.
La bioquímica es la bioquímica.

Sus antecedentes:

Las rupturas de doble hebra del ADN (DSB) son lesiones críticas del ADN que surgen de fuentes endógenas y exógenas.
Los DSB no reparados o mal reparados pueden conducir a inestabilidad genómica, muerte celular o cáncer.
La proteína quinasa dependiente del ADN (ADN-PK), una holoenzima que incluye ADN-PKcs y Ku70/Ku80, es fundamental para la unión de extremos no homólogos (NHEJ) para la reparación de DSB.

Objetivo del estudio:

Para dilucidar la base estructural de la función de ADN-PKcs en la reparación de la ruptura de doble cadena de ADN.
Proporcionar la primera estructura cristalina del ADN humano-PKcs, detallando su plegado general y la organización del dominio.

Principales métodos:

Se empleó cristalografía de rayos X para determinar la estructura del ADN humano-PKcs.
Se realizó un análisis estructural de alta resolución (6.6 Å) para visualizar el plegamiento de la proteína.

Principales resultados:

La estructura cristalina del ADN-PKcs humano revela un pliegue único caracterizado por numerosas repeticiones HEAT alfa-helicas.
Estas repeticiones HEAT facilitan la flexión de la cadena polipeptídica en una estructura circular hueca.
El dominio de la quinasa carboxiterminal está posicionado en la parte superior de esta estructura, con un dominio de repetición HEAT de unión al ADN localizado internamente.

Conclusiones:

La estructura determinada del ADN-PKcs presenta una conformación flexible parecida a una cuna esencial para promover la reparación de la ruptura de doble hebra del ADN.
La comprensión de la estructura del ADN-PKcs proporciona información mecanicista sobre la vía NHEJ y la respuesta al daño del ADN.
Esta información estructural puede informar estrategias para apuntar a las vías de reparación del ADN en la terapia del cáncer.

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