Étude structurale et fonctionnelle de l’activité de relecture par GreA au cours de la transcription
Ayesha Eduljee · theses.fr (ABES) · 2021
The first step of gene expression, transcription of DNA to RNA, is carried outby DNA-dependent RNA polymerase (RNAP). During this process, an incorrectNTP substrate might be incorporated into the growing RNA molecule. Whenthis occurs, RNAP enters a backtracked state in which it cannot continue withelongation of the RNA. To rescue itself from this backtracked state, RNAP cuts offthe erroneous portion of the RNA in a catalytic process whose efficiency is increasedin the presence of specific cleavage factors (GreA in bacteria, TFIIS in eukaryotes).Cryo-EM structures of a complex backtracked by 1 nucleotide with and withoutthe cleavage factor GreA bound to the secondary channel were used to addressquestions related to the process of proofreading in E. coli RNAP, specifically thoseof the importance of the RNAP structural motif known as the trigger loop, andthe process of selection for GreA amongst other structurally similar transcriptionfactors. In addition to this, the structural data along with results from in vitrotranscription assays show that GreA participates in cleavage in multiple ways.Key words: RNA polymerase, transcription, proofreading, GreA, cryo-electronmicroscopy