Crl activates transcription by stabilizing active conformation of the master stress transcription initiation factor

In this study, we determined a 3.80 Å cryo-EM structure of anEscherichia coli transcription activation complex (E. coli Crl-TAC) comprisingE. coliσS-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.
Source: eLife - Category: Biomedical Science Tags: Chromosomes and Gene Expression Source Type: research