InvF are sufficient to activate transcription of sicA ± lacZYA in E : coli CC118lpir .
InvF activates a promoter upstream of sicA , causing additional expression of sicAsipBCDA .
Our RNA-seq data show strong upregulation of sicA by InvF ( see of RcsB .
As the sicA promoter has the longest relaxation time for SPI-1 , induction of sic/sip by InvF represents a key commitment step to the associated burden of producing effector proteins .
As the sicA promoter has the longest relaxation time for SPI-1 , induction of sic/sip by InvF represents a key commitment step to virulence .