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Un solo aminoácido gobierna la actividad mejorada de las polimerasas de ADN DinB en plantillas dañadas
Daniel F Jarosz1, Veronica G Godoy, James C Delaney
1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Nature
|January 13, 2006
Resumen
DinB, una polimerasa de ADN conservada, evita con precisión los añadidos de ADN de N2-deoxiguanosina (dG). Este bypass de la lesión es más eficiente que la replicación del ADN no dañado, lo que explica DinB.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Genética La genética.
- La bioquímica es la bioquímica.
Sus antecedentes:
- La síntesis de traslación (TLS) por las polimerasas de ADN de la familia Y es crucial para la tolerancia al daño del ADN.
- El papel biológico de DinB, una polimerasa de la familia Y universalmente conservada, sigue sin estar claro.
- Ciertos agentes que dañan el ADN forman aductos en la posición N2 de la desoxiguanosina (dG).
Objetivo del estudio:
- Para investigar la función de Escherichia coli DinB en la tolerancia al daño del ADN.
- Para determinar el papel de DinB en eludir las adicciones de N2-deoxiguanosina (dG).
- Aclarar el mecanismo y la especificidad del TLS mediado por DinB.
Principales métodos:
- Evaluó el requisito del gen dinB para la resistencia a los agentes que dañan el ADN.
- Se midió la eficiencia catalítica de DinB y la ADN polimerasa kappa para la inserción de deoxicitidina (dC) frente a N2-furfuril-dG y dG no dañado.
- Utilizó mutagénesis dirigida al sitio para alterar el residuo de "puerta estérica" en DinB y su homólogo Dbh.
Principales resultados:
- Escherichia coli dinB es esencial para la resistencia a los agentes formadores de adductos N2-dG específicos.
- DinB (DNA polimerasa IV) realiza con precisión TLS sobre los aductos de N2-furfuril-dG.
- DinB y la ADN polimerasa kappa exhiben una eficiencia catalítica significativamente mayor para insertar dC frente a N2-furfuril-dG que la dG no dañada.
- La mutación del residuo de "puerta estérica" en DinB y Dbh desacopla el bypass de la lesión de la replicación de la plantilla no dañada.
- El bypass de lesión por DinB es más eficiente que la síntesis en plantillas de ADN no dañadas.
Conclusiones:
- DinB y sus ortólogos están especializados en TLS precisos sobre aductos ubicuos de N2-dG.
- La especificidad de la enzima para el bypass de la lesión puede implicar cambios conformacionales inducidos por la lesión.
- La naturaleza conservada de DinB sugiere un papel biológico fundamental en la reparación del ADN en todos los dominios de la vida.
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