Résumé
As constitutive cofactors of bacterial RNA polymerase (RNAP), sigma70 and sigma54 areinvolved in the regulation of transcription initiation for different genes in prokaryotic cells, respectively. sigma70 is responsible for the spontaneous transcription initiation of housekeeping genes, while sigma54blocks DNA from entering RNAP by way of steric blockade and inhibits the initiation of gene transcriptionafter forming a complex with RNAP. When the cell environment changes, specific stress signals willinduce conformational changes of sigma54 through the bacterial enhancer binding protein (bEBP), release the inhibition of sigma54 on RNAP, and initiate sigma54-dependent gene transcription. Recentstructural biology studies have revealed the structures of several complexes for sigma54-dependenttranscription initiation, including holoenzyme, closed complex, two intermediate complexes and opencomplex. By analyzing the structure of these transcription initiation complexes, we introduce the structuralchanges of the complex during transcription initiation in this article. The functions of sigma54 and bEBPin the process of transcription initiation are described and analyzed. This article is helpful to understandthe changes of transcription initiation on molecular level, and provides a reference for deep understandingof the molecular mechanism of sigma54 and bEBP in promoting transcription initiation.