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Las transcripciones que aumentan la procesividad y la tasa de alargamiento de la ARN polimerasa
R A King1, S Banik-Maiti, D J Jin
1Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institute of Health, Bethesda, Maryland 20892, USA.
Cell
|November 29, 1996
Resumen
El fago HK022 utiliza estructuras específicas de ARN en sitios de antiterminación (sitios de inserción) para controlar la expresión génica. Este proceso mejora la lectura y elongación de la transcripción sin necesidad de proteínas adicionales, lo que sugiere que el propio ARN regula la actividad de la polimerasa.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Virología Virología.
- Reglamento genético Reglamento genético.
Sus antecedentes:
- El fago lambdoide HK022 utiliza sitios de antiterminación de acción cis (sitios de inserción) para superar las señales de terminación de transcripción.
- La antiterminación es crucial para la expresión génica de los fagos, pero a menudo implica una compleja maquinaria proteica.
- El mecanismo preciso de la antiterminación HK022 y su dependencia de la estructura del ARN no fueron completamente esclarecidos.
Objetivo del estudio:
- Investigar el mecanismo de la antiterminación mediada por los sitios de puesta del fago HK022.2.
- Determinar el papel de la conformación del ARN y las proteínas celulares en este proceso.
- Para caracterizar el efecto de los sitios de inserción en el alargamiento y la pausa de la ARN polimerasa.
Principales métodos:
- Análisis de las mutaciones put que afectan a la formación del tallo de ARN predicho y su impacto en la antiterminación.
- Ensayos de transcripción in vitro utilizando polimerasa de ARN purificado, ADN de plantilla y sustratos.
- Mutagénesis dirigida al sitio de la subunidad beta' de la ARN polimerasa para evaluar su papel en la antiterminación.
Principales resultados:
- La actividad de antiterminación depende estrictamente de la formación de estructuras madre específicas de ARN dentro de las transcripciones put.
- En un sistema purificado se observaron lecturas de terminaciones dependientes de put y mayores tasas de alargamiento, lo que indica que no se requieren proteínas adicionales.
- Una mutación en la región del dedo de zinc de la subunidad beta' abolió los efectos mediados por put en la transcripción.
Conclusiones:
- La antiterminación HK022 es un mecanismo simple basado en ARN que no requiere proteínas accesorias.
- La conformación de la transcripción put modula directamente las propiedades de alargamiento de la ARN polimerasa, incluida la lectura y la supresión de la pausa.
- Este mecanismo centrado en el ARN ofrece una alternativa distinta a otras vías de antiterminación conocidas.
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