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Compensatory evolution in NusG improves fitness of drug-resistant M. tuberculosis.

ABSTRACT: Drug-resistant bacteria are emerging as a global threat, despite frequently being less fit than their drug-susceptible ancestors^1-8. Here we sought to define the mechanisms that drive or buffer the fitness cost of rifampicin resistance (RifR) in the bacterial pathogen Mycobacterium tuberculosis (Mtb). Rifampicin inhibits RNA polymerase (RNAP) and is a cornerstone of modern short-course tuberculosis therapy^9,10. However, RifR Mtb accounts for one-quarter of all deaths due to drug-resistant bacteria^11,12. We took a comparative functional genomics approach to define processes that are differentially vulnerable to CRISPR interference (CRISPRi) inhibition in RifR Mtb. Among other hits, we found that the universally conserved transcription factor NusG is crucial for the fitness of RifR Mtb. In contrast to its role in Escherichia coli, Mtb NusG has an essential RNAP pro-pausing function mediated by distinct contacts with RNAP and the DNA¹³. We find this pro-pausing NusG-RNAP interface to be under positive selection in clinical RifR Mtb isolates. Mutations in the NusG-RNAP interface reduce pro-pausing activity and increase fitness of RifR Mtb. Collectively, these results define excessive RNAP pausing as a molecular mechanism that drives the fitness cost of RifR in Mtb, identify a new mechanism of compensation to overcome this cost, suggest rational approaches to exacerbate the fitness cost, and, more broadly, could inform new therapeutic approaches to develop drug combinations to slow the evolution of RifR in Mtb.

SUBMITTER: Eckartt KA

PROVIDER: S-EPMC10990936 | biostudies-literature | 2024 Apr

REPOSITORIES: biostudies-literature

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Compensatory evolution in NusG improves fitness of drug-resistant M. tuberculosis.

Eckartt Kathryn A KA Delbeau Madeleine M Munsamy-Govender Vanisha V DeJesus Michael A MA Azadian Zachary A ZA Reddy Abhijna K AK Chandanani Joshua J Poulton Nicholas C NC Quiñones-Garcia Stefany S Bosch Barbara B Landick Robert R Campbell Elizabeth A EA Rock Jeremy M JM

Nature 20240320 8006

Drug-resistant bacteria are emerging as a global threat, despite frequently being less fit than their drug-susceptible ancestors<sup>1-8</sup>. Here we sought to define the mechanisms that drive or buffer the fitness cost of rifampicin resistance (RifR) in the bacterial pathogen Mycobacterium tuberculosis (Mtb). Rifampicin inhibits RNA polymerase (RNAP) and is a cornerstone of modern short-course tuberculosis therapy<sup>9,10</sup>. However, RifR Mtb accounts for one-quarter of all deaths due to ...[more]

PMID: 38509362

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Project description:BackgroundRifampicin (RIF) is a key first-line drug used to treat tuberculosis, a primarily pulmonary disease caused by Mycobacterium tuberculosis. RIF resistance is caused by mutations in rpoB, at the cost of slower growth and reduced transcription efficiency. Antibiotic resistance to RIF is prevalent despite this fitness cost. Compensatory mutations in rpoABC genes have been shown to alleviate the fitness cost of rpoB:S450L, explaining how RIF resistant strains harbor this mutation can spread so rapidly. Unfortunately, the full set of RIF compensatory mutations is still unknown, particularly those compensating for rarer RIF resistance mutations.ObjectivesWe performed an association study on a globally representative set of 4,309 whole genome sequenced clinical M. tuberculosis isolates to identify novel putative compensatory mutations, determine the prevalence of known and previously reported putative compensatory mutations, and determine which RIF resistance markers associate with these compensatory mutations.Results and conclusionsOf the 1,079 RIF resistant isolates, 638 carried previously reported putative and high-probability compensatory mutations. Our strict criteria identified 46 additional mutations in rpoABC for which no strong prior evidence of their compensatory role exists. Of these, 35 have previously been reported. As such, our independent corroboration adds to the mounting evidence that these 35 also carry a compensatory role. The remaining 11 are novel putative compensatory markers, reported here for the first time. Six of these 11 novel putative compensatory mutations had two or more mutation events. Most compensatory mutations appear to be specifically compensating for the fitness loss due to rpoB:S450L. However, an outbreak of 22 closely related isolates each carried three rpoB mutations, the rare RIFR markers D435G and L452P and the putative compensatory mutation I1106T. This suggests compensation may require specific combinations of rpoABC mutations. Here, we report only mutations that met our very strict criteria. It is highly likely that many additional rpoABC mutations compensate for rare resistance-causing mutations and therefore did not carry the statistical power to be reported here. These findings aid in the identification of RIF resistant M. tuberculosis strains with restored fitness, which pose a greater risk of causing resistant outbreaks.

Dataset Information

Compensatory evolution in NusG improves fitness of drug-resistant M. tuberculosis.

Publications

Compensatory evolution in NusG improves fitness of drug-resistant M. tuberculosis.

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