Conserved ESX-1 Substrates EspE and EspF Are Virulence Factors That Regulate Gene Expression

Mycobacterium tuberculosis , the cause of human tuberculosis, and Mycobacterium marinum , a nontubercular pathogen with a broad host range, require the ESX-1 secretion system for virulence. The ESX-1 system secretes proteins which cause phagosomal lysis within the macrophage via an unknown mechanism. As reported elsewhere (R. E. Bosserman et al., Proc Natl Acad Sci U S A 114:E10772–E10781, 2017, https://doi.org/10.1073/pnas.1710167114 ), we recently discovered that the ESX-1 system regulates gene expression in M. marinum This finding was confirmed in M. tuberculosis in reports by C.