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eLife Volume 8 ,2019-12-03
Crl activates transcription by stabilizing active conformation of the master stress transcription initiation factor
Chromosomes and Gene Expression
Juncao Xu 1 , 2 Kaijie Cui 2 , 3 Liqiang Shen 1 , 2 Jing Shi 4 , 5 Lingting Li 1 , 2 Linlin You 1 , 2 Chengli Fang 1 , 2 Guoping Zhao 1 , 6 , 7 , 8 , 9 Yu Feng 4 , 5 Bei Yang 3 Yu Zhang 1
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Received 2019-08-07, accepted for publication 2019-12-03, Published 2019-12-03

σS is a master transcription initiation factor that protects bacterial cells from various harmful environmental stresses including antibiotic pressure. Although its mechanism remains unclear, it is known that full activation of σS-mediated transcription requires a σS-specific activator, Crl. In this study, we determined a 3.80 Å cryo-EM structure of an Escherichia coli transcription activation complex (E. coli Crl-TAC) comprising E. coli σS-RNA polymerase (σS-RNAP) holoenzyme, Crl, and a nucleic-acid scaffold. The structure reveals that Crl interacts with domain 2 of σS (σS2) and the RNAP core enzyme, but does not contact promoter DNA. Results from subsequent hydrogen-deuterium exchange mass spectrometry (HDX-MS) indicate that Crl stabilizes key structural motifs within σS2 to promote the assembly of the σS-RNAP holoenzyme and also to facilitate formation of an RNA polymerase–promoter DNA open complex (RPo). Our study demonstrates a unique DNA contact-independent mechanism of transcription activation, thereby defining a previously unrecognized mode of transcription activation in cells.


E. coli;stress response;sigma factor;transcription activation;Crl;RNA polymerase;transcription factors


© 2019, Xu et al
http://creativecommons.org/licenses/by/4.0/This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.


Juncao Xu,Kaijie Cui,Liqiang Shen,Jing Shi,Lingting Li,Linlin You,Chengli Fang,Guoping Zhao,Yu Feng,Bei Yang,Yu Zhang. Crl activates transcription by stabilizing active conformation of the master stress transcription initiation factor. eLife ,Vol.8(2019)



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