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Función de la E. coli ARN polimerasa sigma factor sigma 70 en la pausa promotor-proximal del promotor
B Z Ring1, W S Yarnell, J W Roberts
1Section of Biochemistry, Molecular and Cell Biology Cornell University Ithaca, New York 14853, USA.
Cell
|August 9, 1996
Resumen
El factor sigma 70 en la polimerasa de ARN de E. coli induce pausas de transcripción durante el alargamiento. Esta pausa está mediada por secuencias específicas de ADN y requiere la unión de sigma 70 a la cadena de ADN no modelo.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Genética La genética.
- La bioquímica es la bioquímica.
Sus antecedentes:
- Sigma 70 (σ70) es una subunidad crucial de la ARN polimerasa de E. coli, conocida principalmente por su papel en la iniciación de la transcripción.
- Las funciones precisas de σ70 más allá de la iniciación, particularmente durante la fase de alargamiento, siguen siendo áreas de investigación activa.
Objetivo del estudio:
- Para investigar el papel de sigma 70 en la inducción de pausas de transcripción durante el alargamiento temprano.
- Para identificar las señales de ADN y las regiones sigma 70 involucradas en la inducción de pausa.
- Para dilucidar el mecanismo por el cual sigma 70 interactúa con el ADN durante la pausa.
Principales métodos:
- Análisis de la pausa de la transcripción en la ARN polimerasa de E. coli.
- Identificación de las secuencias de ADN responsables de la inducción de pausa.
- Pruebas bioquímicas para determinar el papel de las regiones sigma 70 en la pausa.
- Caracterización de la presencia de sigma 70 dentro de complejos de transcripción en pausa.
Principales resultados:
- Sigma 70 induce la pausa de la transcripción en una etapa temprana de la elongación, lo que facilita la actividad del antiterminador del gen Q de los fagos lambda.
- Se identificó una secuencia de ADN que se asemeja al consenso del promotor sigma 70 -10 como la señal que induce la pausa.
- Las regiones 2 y 3 de sigma 70 son suficientes para inducir la pausa.
- Sigma 70 es esencial para la pausa y permanece unido dentro del complejo de transcripción en pausa.
- La pausa es inducida por el reconocimiento específico de la base de la cadena de ADN de cadena única no modelo.
Conclusiones:
- Sigma 70 juega un doble papel en la transcripción, actuando tanto en la iniciación como en el alargamiento temprano para regular la expresión génica.
- El mecanismo implica que sigma 70 reconozca la cadena de ADN no modelo dentro de la burbuja de transcripción.
- Sigma 70 probablemente permanece asociado con la ARN polimerasa del núcleo después del aclaramiento del promotor y se reubica en el sitio de pausa.
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