Structural basis for λN-dependent processive transcription antitermination.
Nat Microbiol
; 2: 17062, 2017 Apr 28.
Article
em En
| MEDLINE
| ID: mdl-28452979
ABSTRACT
λN-mediated processive antitermination constitutes a paradigmatic transcription regulatory event, during which phage protein λN, host factors NusA, NusB, NusE and NusG, and an RNA nut site render elongating RNA polymerase termination-resistant. The structural basis of the process has so far remained elusive. Here we describe a crystal structure of a λN-NusA-NusB-NusE-nut site complex and an electron cryo-microscopic structure of a complete transcription antitermination complex, comprising RNA polymerase, DNA, nut site RNA, all Nus factors and λN, validated by crosslinking/mass spectrometry. Due to intrinsic disorder, λN can act as a multiprotein/RNA interaction hub, which, together with nut site RNA, arranges NusA, NusB and NusE into a triangular complex. This complex docks via the NusA N-terminal domain and the λN C-terminus next to the RNA exit channel on RNA polymerase. Based on the structures, comparative crosslinking analyses and structure-guided mutagenesis, we hypothesize that λN mounts a multipronged strategy to reprogram the transcriptional machinery, which may include (1) the λN C terminus clamping the RNA exit channel, thus stabilizing the DNARNA hybrid; (2) repositioning of NusA and RNAP elements, thus redirecting nascent RNA and sequestering the upstream branch of a terminator hairpin; and (3) hindering RNA engagement of termination factor ρ and/or obstructing ρ translocation on the transcript.
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Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
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Transcrição Gênica
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RNA Polimerases Dirigidas por DNA
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Regiões Terminadoras Genéticas
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Proteínas de Ligação a RNA
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article