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Secuencia de nucleótidos de Xenopus borealis oocyte 5S ADN: comparación de secuencias que flanquean varios genes
Cell
|December 1, 1978
Resumen
El análisis genómico del ADN de Xenopus borealis 5S revela grupos de genes con números genéticos variables y espaciadores ricos en AT. Los elementos promotores, incluidos los oligonucleótidos conservados, impulsan la transcripción por la ARN polimerasa III.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- La genómica es la genómica.
- Biología del desarrollo Biología del desarrollo.
Sus antecedentes:
- El ADN 5S (Xbo) genómico de Xenopus borealis específico del ovocito (Xbo) presenta grupos de genes de ARNr 5S con diferentes números de genes y espaciadores ricos en AT.
- La heterogeneidad de la longitud del ADN espaciador se debe en parte a las secuencias repetidas en tándem.
Objetivo del estudio:
- Caracterizar la organización genómica y la regulación transcripcional de los genes de ARNr 5S de Xenopus borealis.
- Para identificar los elementos promotores conservados involucrados en la transcripción de la ARN polimerasa III.
Principales métodos:
- Secuenciación de ADN de un fragmento de ADN Xbo 5S clonado (Xbo1).
- Análisis de secuencia de ADN genómico y regiones flanqueantes.
- Ensayos de transcripción in vitro con extractos de núcleos de ovocitos de Xenopus laevis.
Principales resultados:
- Xbo1 contiene tres genes de ARNr 5S, con el gen 3 que muestra una divergencia de secuencia significativa, pero es un componente abundante.
- Los 80 nucleótidos que preceden a cada gen 5S son suficientes para la función promotora in vitro.
- Los oligonucleótidos conservados (AAAAG, AGAAG, GAC) en las regiones flanqueantes del 5' funcionan como elementos promotores clave para la transcripción de la ARN polimerasa III.
- Las regiones flanqueantes de 3' exhiben características similares a los sitios de terminación de la transcripción procariota, incluida la simetría de la díada rica en GC y los cúmulos T ricos en AT.
Conclusiones:
- Las secuencias 5' flanqueantes de los genes de Xenopus 5S contienen elementos promotores esenciales para la iniciación de la transcripción.
- La conservación de la secuencia en las regiones promotoras destaca su importancia funcional a pesar de las variaciones en el ADN espaciador.
- Las señales de promotor y terminación identificadas proporcionan información sobre la regulación de la expresión génica del ARNr 5S en Xenopus.
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