Understanding the cyclic di AMP signaling network in DNA damage repair in Mycobacterium

Abstract

The double-stranded break (DSB) of chromosomes is lethal to cells because it compromises their replication. Every living organism from unicellular bacteria to higher eukaryotes have developed elegant pathways to repair them. Mycobacteria have three pathways to repair DNA DSB: homologous recombination (HR), non-homologous end joining (NHEJ), and single-strand annealing (SSA). DNA repair in mycobacteria is unique in many ways compared to the usual bacterial DNA repair pathways and provides an interesting and simple system to study them. Mycobacterium repairs the DNA breaks when the cells are not replicating through NHEJ and utilizes SSA to fix the breaks between the repeated sequences. Understanding the mechanism and regulation of these pathways will reveal the survival strategies and pathogenesis of Mycobacterium tuberculosis, a highly pathogenic agent, and will help in devising ways to contain the pathogen. newlineRecA protein plays a central role in DNA recombination processes in bacteria including Mycobacterium, even though recombination can also occur through RecA-independent pathways. The activity of RecA is carefully controlled to avoid unnecessary genetic rearrangements that could result in instability of the genome. Interestingly, and#916;disA M. smegmatis cells are sensitive to different DNA clastogens suggesting the involvement of cyclic di-AMP in DNA damage repair. My thesis work is to study the role of cyclic di-AMP in DSB repair in Mycobacterium. I have organized my work into two main sections. The first part of the thesis focuses on establishing two reporter constructs to investigate the involvement of cyclic di-AMP in the repair of double-stranded breaks (DSB) in Mycobacterium. The second part is dedicated to comprehending how cyclic di-AMP regulates the function of RecA and the regulation of SOS response. My work provides evidence that cyclic di-AMP is crucial for preserving the stability of the genome in Mycobacterium. newline newline