Figure 2.

Thermoregulation of Ysc-Yop type III secretion by Yersinia. Thermoregulation of Ysc-Yop type III secretion is mediated through control of the transcriptional activator, LcrF. (A) At ambient temperature, transcription of the yscW-lcrF operon is inhibited by the YmoA DNA binding protein. Furthermore, post-transcriptional inhibition occurs as a result of stem-loop formation of mRNA within the intergenic region between the two alleles. (B) De-regulation occurs at elevated temperature because YmoA affinity for the yscW-lcrF operon promoter is dramatically diminished, and this promotes operon transcription. Moreover, elevate temperature resolves the stem-loop structure in mRNA transcripts, so that translation into LcrF can proceed. This results in a positive auto-regulatory cascade that enhances lcrF transcription. Accumulated LcrF can then transcriptionally activate responsive ysc and yop promoters. This illustration is inspired in part from Bohme et al. (2012) and initial artistic work of Tiago Costa.