Replisome dynamics in M tuberculosis_linking persistence to genetic resistance

University Of Cape Town, Rondebosch

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Abstract

? DESCRIPTION (provided by applicant): A major goal of tuberculosis (TB) drug discovery programs is the development of compounds that will reduce the duration of therapy, simultaneously limiting the emergence of drug-resistant strains of the causative agent, Mycobacterium tuberculosis (Mtb). The current six-month regimen is thought to result from the inability of existing anti-tuberculars to eliminate a sub-population of Mtb bacilli that are refracory to killing despite retaining full genetic susceptibility to the applied drugs. The existence of thee Mtb persisters, together with the increasing emergence of drug-resistant clinical isolates, in turn raises a critical question: is there a functional link between (non-genetic) persistence and the development of genetic drug resistance? Here, we will test the hypothesis that, by controlling functions involved in DNA repair and damage tolerance, the mycobacterial SOS response plays a key role in the inherent heterogeneity of Mtb populations and, therefore, contributes to the ability of Mtb to persist in the face of lethal stresses including drug treatmen. We will also evaluate the notion that the SOS-regulated imuA'-imuB/dnaE2 mutasome, which was previously implicated in Mtb survival and drug-resistance in vivo, drives mutagenesis in antibiotic-exposed persister populations and so links persistence and genetic resistance. Finally, we will utilize biochemical and target-based whole-cell (TB-WCS) screens to identify novel chemical inhibitors which sensitize Mtb to genotoxic stress and eliminate the emergence of resistance under drug-selective pressure in vitro. This fully collaborative proposal will utilize biochemical, genetic, and microbiological techniques that will require both partners to develop and apply. Moreover, it is predicated on the open transfer of scientific insight and technical expertise as part of a new collaboration designed to create a long-term partnership around the investigation of fundamental aspects of mycobacterial DNA replication and repair as an underexplored target for novel anti-TB agents.