Regulation of protein secretion by ... protein secretion?

Mycobacterium tuberculosis (Mtb) requires an alternative protein secretion system, ESX1, for virulence. Recently, Raghavan et al. (2008) reported a new regulatory circuit that may explain how ESX1 activity is controlled during infection. Mtb appears to regulate ESX1 by modulating transcription of associated genes rather than structural components of the secretion system itself.