[seminar] "Flexibility in Bacterial Replication Origins: Molecular Mechanisms and Evolutionary Implications" by Shogo Ozaki

 

Title: 

Flexibility in Bacterial Replication Origins: Molecular Mechanisms and Evolutionary Implications

 

Abstract:

Chromosomal DNA replication begins at a specific genomic locus, the replication origin (oriC). While the initiator protein DnaA is highly conserved among bacteria, replication origin sequences are remarkably diverse. This raises a fundamental question: how can bacterial replication initiation remain robust despite extensive evolutionary changes in origin architecture?

In this seminar, I will present our studies of DNA replication origins from evolutionarily distant bacteria, including Escherichia coli, the hyperthermophile Thermotoga maritima, and the alphaproteobacterium Caulobacter crescentus. Comparison of these species reveals striking differences in origin architecture, providing a unique opportunity to explore how replication initiation systems evolve while maintaining the same fundamental function. By combining biochemical, genetic, and comparative approaches, we uncovered unexpected flexibility in DnaA-dependent origin function.

Our findings reveal that bacterial replication origins can tolerate variation in the orientation of DnaA-binding sites, the sequence of unwound DNA, and the spacing between essential origin elements. Together, these observations suggest that DnaA-dependent initiation complexes possess intrinsic flexibility that enables replication origins to diversify during evolution while preserving reliable replication initiation. These findings provide new insight into the molecular mechanisms that underlie both the robustness and the evolutionary diversification of bacterial chromosome replication.