EMD-3561
map of the RNA polymerase lambda-based antitermination complex solved by cryo-EM
EMD-3561
Single-particle9.8 Å
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Map released: 03/05/2017
Last modified: 15/05/2024
Sample Organism:
Escherichia coli K-12,
Escherichia coli,
Escherichia phage lambda
Sample: lambdaN-dependent antitermination complex
Fitted models: 5ms0 (Avg. Q-score: 0.069)
Deposition Authors: Said N
,
Krupp F
Sample: lambdaN-dependent antitermination complex
Fitted models: 5ms0 (Avg. Q-score: 0.069)
Deposition Authors: Said N
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Structural basis for lambda N-dependent processive transcription antitermination.
Said N
,
Krupp F
,
Anedchenko E,
Santos KF,
Dybkov O,
Huang YH,
Lee CT,
Loll B
,
Behrmann E
,
Burger J
,
Mielke T,
Loerke J
,
Urlaub H,
Spahn CMT,
Weber G
,
Wahl MC
(2017) Nat Microbiol , 2 , 17062 - 17062
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(2017) Nat Microbiol , 2 , 17062 - 17062
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 DNA:RNA 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.
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 DNA:RNA 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.