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Updated: May 8, 2026
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Repressing Gene Transcription by Redirecting Cellular Machinery with Chemical Epigenetic Modifiers
Published on: September 20, 2018
Superar una barrera nucleosómica para la transcripción
V M Studitsky1, D J Clark, G Felsenfeld
1Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0540, USA.
Cell
|October 6, 1995
Resumen
La ARN polimerasa transcribe el ADN nucleosómico, deteniéndose en una barrera antes de llegar a la díada. Esta pausa se debe a la dificultad de transcribir el ADN en bucle, no romper los contactos histona-ADN.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- La epigenética es la epigenética.
- Expresión génica de la expresión génica.
Sus antecedentes:
- Los nucleosomas son unidades fundamentales del empaque del ADN en los eucariotas.
- La transcripción a través de los nucleosomas es un paso crítico en la regulación génica.
- Comprender el mecanismo de la transcripción a través de los nucleosomas es esencial para descifrar el control de la expresión génica.
Objetivo del estudio:
- Para investigar la cinética de la transcripción de la ARN polimerasa (RNAP) a través de un núcleo nucleosómico.
- Para identificar los factores que causan la pausa durante la transcripción del ADN nucleosómico.
- Para dilucidar el mecanismo de transferencia de octámero de histona durante la transcripción.
Principales métodos:
- Ensayos de transcripción in vitro utilizando nucleosomas purificados y ARN polimerasa.
- Análisis de la cinética de la transcripción y sitios de pausa.
- Investigando el papel de la accesibilidad del ADN y las interacciones histona-ADN.
Principales resultados:
- La RNAP transcribe rápidamente los ~25 bp iniciales de ADN nucleosómico, luego encuentra una barrera y se ralentiza.
- La barrera desaparece en la díada nucleosómica, con una rápida reanudación de la transcripción, lo que indica una transferencia completa de octámero de histona.
- La eliminación de ADN detrás de RNAP retrasa la aparición de la barrera; las plantillas más largas reducen la barrera, lo que sugiere que el bucle de ADN influye en la pausa.
Conclusiones:
- La pausa de RNAP durante la transcripción del nucleosoma es causada por la dificultad de transcribir el ADN dentro de un bucle, no por romper los contactos histona-ADN.
- La transferencia de octámero de histona alrededor de la polimerasa se completa en el momento en que el RNAP llega a la díada.
- El bucle de ADN intranucleosómico es un intermedio clave en la transferencia de octámero de histona e influye en la cinética de la transcripción.
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