Functional Analysis of EspM, an ESX-1-Associated Transcription Factor in Mycobacterium marinum

Kevin G. Sanchez, Rebecca J. Prest, Kathleen R. Nicholson, Konstantin V. Korotkov, Patricia A. Champion

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Pathogenic mycobacteria use the ESX-1 secretion system to escape the macrophage phagosome and survive infection. We demonstrated that the ESX-1 system is regulated by feedback control in Mycobacterium marinum, a nontuberculous pathogen and model for the human pathogen Mycobacterium tuberculosis. In the presence of a functional ESX-1 system, the WhiB6 transcription factor upregulates expression of ESX-1 substrate genes. In the absence of an assembled ESX-1 system, the conserved transcription factor, EspM, represses whiB6 expression by specifically binding the whiB6 promoter. Together, WhiB6 and EspM fine-tune the levels of ESX-1 substrates in response to the secretion system. The mechanisms underlying control of the ESX-1 system by EspM are unknown. Here, we conduct a structure and function analysis to investigate how EspM is regulated. Using biochemical approaches, we measured the formation of higher-order oligomers of EspM in vitro. We demonstrate that multimerization in vitro can be mediated through multiple domains of the EspM protein. Using a bacterial monohybrid system, we showed that EspM self-associates through multiple domains in Escherichia coli. Using this system, we performed a genetic screen to identify EspM variants that failed to self-associate. The screen yielded four EspM variants of interest, which we tested for activity in M. marinum. Our study revealed that the two helix-turn-helix domains are functionally distinct. Moreover, the helix bundle domain is required for wild-type multimerization in vitro. Our data support models where EspM monomers or hexamers contribute to the regulation of whiB6 expression.

Original languageEnglish
JournalJournal of Bacteriology
Issue number12
StatePublished - Dec 2022

Bibliographical note

Publisher Copyright:
Copyright © 2022 American Society for Microbiology. All Rights Reserved.


  • ESX-1
  • EspM
  • Mycobacterium
  • WhiB6
  • protein secretion
  • transcription

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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