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La fosforilación multisite y la cuenta regresiva para la fase S

R J Deshaies¹, J E Ferrell

¹Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA. deshaies@its.caltech.edu

|January 10, 2002

Resumen

La ubiquitina ligasa SCF ((Cdc4) se dirige específicamente a Sic1 con seis fosfatos, no con cinco. Este hallazgo revela un mecanismo de conteo molecular, que convierte señales analógicas en salidas digitales para los nanoprocesadores de proteínas.

Área de la Ciencia:

Biología Molecular Biología Molecular
La bioquímica es la bioquímica.
Regulación de las comunicaciones celulares.

Sus antecedentes:

Sic1 es un inhibidor del ciclo celular regulado por la fosforilación.
SCF ((Cdc4) es una ligasa de ubiquitina E3 involucrada en la progresión del ciclo celular.
Los niveles de fosforilación a menudo dictan la función y la degradación de las proteínas.

Objetivo del estudio:

Para investigar el umbral de fosforilación preciso reconocido por SCF ((Cdc4) para la ubiquitinación de Sic1.
Aclarar el mecanismo por el cual SCF ((Cdc4) distingue entre diferentes estados de fosforilación de Sic1.
Comprender cómo las señales de fosforilación analógica se convierten en salidas digitales en un contexto biológico.

Principales métodos:

Ensayos de unión in vitro utilizando variantes purificadas de SCF ((Cdc4) y Sic1 con estados de fosforilación definidos.
Los ensayos de ubiquitinación monitorean la modificación de Sic1 por el SCF (Cdc4).
Espectrometría de masas para confirmar los sitios de fosforilación y estequiometría en Sic1.

Principales resultados:

SCF ((Cdc4) se une selectivamente y ubiquitinates Sic1 fosforilado en seis sitios, pero no en cinco.
Esta ubiquitinación dependiente de la fosforilación desencadena la degradación de Sic1.
El estudio demuestra un claro interruptor "digital" basado en una entrada "analógica" (número de fosfatos).

Conclusiones:

SCF ((Cdc4) actúa como un contador molecular, utilizando un umbral de fosforilación preciso para el reconocimiento del sustrato.
Este mecanismo proporciona una salida digital (ubiquitinación / degradación) de una entrada analógica (varios niveles de fosforilación).
Comprender esta arquitectura de nanoprocesador de proteínas ofrece información sobre la regulación celular precisa y la transducción de señales.

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