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Defense of thesis Fan CHEN

FAn Chen

PhD defence entitled “ Exploring the role of 5’UTRs in the regulation of gene expression using synthetic and native libraries“, supervised by Laurence Girbal and Sébastien Nouaille.

The PhD defense will be on July 6 at 2 pm in visioconference.

Abstract

When facing changing environments, bacteria have to adapt their metabolism by modifying the expression pattern of their gene repertoire. The goal of my PhD was to provide additional fundamental insights into gene expression regulation in bacteria. We have focused our work on the role of 5’UTRs in gene expression regulation in E. coli. 5’UTRs are the transcribed but untranslated sequences located in the 5’ends of the mRNAs.

We first developed an approach using synthetic 5’UTR sequences to analyze their role at three levels, namely translation, transcription, and mRNA degradation. We confirmed the multilevel contribution of 5’UTRs in the control of gene expression at the level of translation initiation, transcription, and/or mRNA stability and showed the degree of dependence on the downstream reporter gene sequence. Then we played with the 5’UTR-mediated translation regulation and showed the consequences on mRNA concentration and stability.

How 5’UTRs regulate gene expression in response to environmental changes is still only partially understood. We designed and constructed a full-size library of 2547 native 5’UTR sequences from E. coli fused to a fluorescent reporter gene. The role of native 5’UTRs was explored by challenging the native 5’UTR library to grow in changing environmental conditions. We demonstrated that the 5’UTRs directly and efficiently regulate downstream gene expression and thus contribute to the E. coli adaption to changing environments.

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