An RNA-binding protein acts as a major post-transcriptional modulator in Bacillus anthracis.

HitRS is a two-component system that responds to cell envelope damage in the human pathogen Bacillus anthracis. Here we identify an RNA-binding protein, KrrA, that regulates HitRS function by modulating the stability of the hitRS mRNA. In addition to hitRS, KrrA binds to over 70 RNAs and, directly or indirectly, affects the expression of over 150 genes involved in multiple processes, including genetic competence, sporulation, RNA turnover, DNA repair, transport, and cellular metabolism. KrrA does not exhibit detectable nuclease activity in vitro, and thus the mechanism by which it modulates mRNA stability remains unclear.