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Un efecto de posición en el control de la transcripción en los loci tipo de apareamiento de la levadura

K A Nasmyth, K Tatchell, B D Hall

|January 22, 1981

Resumen

Los loci de tipo de apareamiento silencioso (HMRa y HML alfa) en la levadura no se transcriben a pesar de las secuencias de ADN idénticas. Esto sugiere que las secuencias reguladoras ubicadas muy lejos influyen en la expresión génica.

Área de la Ciencia:

Biología Molecular Biología Molecular
Genética de la levadura Genética de la levadura

Sus antecedentes:

Los loci de tipo de apareamiento (MATa y MAT alfa) en la levadura son cruciales para la reproducción sexual.
Estos loci producen ARNm específicos transcritos desde promotores centrales.
Las copias silenciosas, HMRa y HML alfa, comparten secuencias de ADN idénticas con loci expresados, pero no se transcriben.

Objetivo del estudio:

Para investigar el mecanismo detrás del silenciamiento transcripcional de HMRa y HML alfa loci.
Para entender cómo las secuencias de ADN distantes regulan la iniciación de la transcripción.

Principales métodos:

Análisis comparativo de secuencias de ADN entre loci de tipo de apareamiento expresado y silencioso.
Investigando el papel de las secuencias de flanqueo en la regulación transcripcional.

Principales resultados:

Las regiones transcritas idénticas en los loci silenciosos (HMRa, HML alfa) no se correlacionan con la expresión génica.
La transcripción se reprime en los loci silenciosos a pesar de la presencia del promotor.
La evidencia sugiere que las secuencias reguladoras ubicadas proximamente a la izquierda de HMRa (y probablemente HML alfa) son responsables del silenciamiento.

Conclusiones:

El silenciamiento transcripcional de los loci de tipo de apareamiento está regulado por efectos de posición.
Las secuencias de ADN distantes, ubicadas 700-1,400 pares de bases aguas arriba, juegan un papel crítico en la represión de la iniciación de la transcripción en HMRa y HML alfa.
Se propone un mecanismo potencial para este efecto de posición de largo alcance.

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