The presence of an RNA:DNA hybrid that is prone to slippage promotes termination by T7 RNA polymerase.
J Mol Biol
; 426(18): 3095-3107, 2014 Sep 09.
Article
en En
| MEDLINE
| ID: mdl-24976131
Intrinsic termination signals for multisubunit bacterial RNA polymerases (RNAPs) encode a GC-rich stem-loop structure followed by a polyuridine [poly(U)] tract, and it has been proposed that steric clash of the stem-loop with the exit pore of the RNAP imposes a shearing force on the RNA in the downstream RNA:DNA hybrid, resulting in misalignment of the active site. The structurally unrelated T7 RNAP terminates at a similar type of signal (TΦ), suggesting a common mechanism for termination. In the absence of a hairpin (passive conditions), T7 RNAP slips efficiently in both homopolymeric A and U tracts, and we have found that replacement of the U tract in TΦ with a slippage-prone A tract still allows efficient termination. Under passive conditions, incorporation of a single G residue following a poly(U) tract (which is the situation during termination at TΦ) results in a "locked" complex that is unable to extend the transcript. Our results support a model in which transmission of the shearing force generated by steric clash of the hairpin with the exit pore is promoted by the presence of a slippery tracts downstream, resulting in alterations in the active site and the formation of a locked complex that represents an early step in the termination pathway.
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Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Transcripción Genética
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Proteínas Virales
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ARN Polimerasas Dirigidas por ADN
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Regiones Terminadoras Genéticas
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Bacteriófago T7
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Secuencias Invertidas Repetidas
Idioma:
En
Revista:
J Mol Biol
Año:
2014
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Países Bajos