Tagetitoxin inhibits transcription by stabilizing pre-translocated state of the elongation complex.
Nucleic Acids Res
; 41(20): 9257-65, 2013 Nov.
Article
em En
| MEDLINE
| ID: mdl-23935117
ABSTRACT
Transcription elongation consists of repetition of the nucleotide addition cycle phosphodiester bond formation, translocation and binding of the next nucleotide. Inhibitor of multi-subunit RNA polymerase tagetitoxin (TGT) enigmatically slows down addition of nucleotides in a sequence-dependent manner, only at certain positions of the template. Here, we show that TGT neither affects chemistry of RNA synthesis nor induces backward translocation, nor competes with the nucleoside triphosphate (NTP) in the active center. Instead, TGT increases the stability of the pre-translocated state of elongation complex, thus slowing down addition of the following nucleotide. We show that the extent of inhibition directly depends on the intrinsic stability of the pre-translocated state. The dependence of translocation equilibrium on the transcribed sequence results in a wide distribution (~1-10(3)-fold) of inhibitory effects of TGT at different positions of the template, thus explaining sequence-specificity of TGT action. We provide biochemical evidence that, in pre-translocated state, TGT stabilizes folded conformation of the Trigger Loop, which inhibits forward and backward translocation of the complex. The results suggest that Trigger Loop folding in the pre-translocated state may serve to reduce back-tracking of the elongation complex. Overall, we propose that translocation may be a limiting and highly regulated step of RNA synthesis.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Compostos Organofosforados
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Inibidores da Síntese de Ácido Nucleico
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Ácidos Dicarboxílicos
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Elongação da Transcrição Genética
Idioma:
En
Revista:
Nucleic Acids Res
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Reino Unido