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EMD-34475

Single-particle
4.5 Å
EMD-34475 Deposition: 09/10/2022
Map released: 04/10/2023
Last modified: 30/10/2024
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links

EMD-34475

Cryo-EM structure of the full transcription activation complex NtcA-NtcB-TAC

EMD-34475

Single-particle
4.5 Å
EMD-34475 Deposition: 09/10/2022
Map released: 04/10/2023
Last modified: 30/10/2024
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Sample Organism: Anabaena
Sample: full transcription activation complex with two activators NtcA and NtcB
Fitted models: 8h3v (Avg. Q-score: 0.191)

Deposition Authors: Han SJ , Jiang YL , You LL, Shen LQ, Wu XX, Yang F, Kong WW , Chen ZP, Zhang Y , Zhou CZ
DNA looping mediates cooperative transcription activation.
Han SJ , Jiang YL , You LL, Shen LQ, Wu X , Yang F, Cui N, Kong WW , Sun H, Zhou K, Meng HC, Chen ZP, Chen Y , Zhang Y , Zhou CZ
(2024) Nat Struct Mol Biol , 31 , 293 - 299
PUBMED: 38177666
DOI: doi:10.1038/s41594-023-01149-7
ISSN: 1545-9985
Abstract:
Transcription factors respond to multilevel stimuli and co-occupy promoter regions of target genes to activate RNA polymerase (RNAP) in a cooperative manner. To decipher the molecular mechanism, here we report two cryo-electron microscopy structures of Anabaena transcription activation complexes (TACs): NtcA-TAC composed of RNAP holoenzyme, promoter and a global activator NtcA, and NtcA-NtcB-TAC comprising an extra context-specific regulator, NtcB. Structural analysis showed that NtcA binding makes the promoter DNA bend by ∼50°, which facilitates RNAP to contact NtcB at the distal upstream NtcB box. The sequential binding of NtcA and NtcB induces looping back of promoter DNA towards RNAP, enabling the assembly of a fully activated TAC bound with two activators. Together with biochemical assays, we propose a 'DNA looping' mechanism of cooperative transcription activation in bacteria.