HrcA is a negative regulator of the dnaK and groESL operons of Streptococcus pyogenes.

Abstract The genome of Streptococcus pyogenes , an important human pathogen, encodes homologs of the principal bacterial heat shock proteins DnaK and GroES, -EL, as well as HrcA, a negative regulator of dnaK and groESL expression in other Gram-positive bacteria. Using nuclease protection assays to measure dnaK/groESL mRNA abundance and a “non-polar” insertion to disrupt hrcA , we demonstrate that heat shock triggers a 4- to 8-fold increase in dnaK and groESL -specific mRNAs within 5 min of the temperature shift and that HrcA is a negative regulator of S. pyogenes dnaK/groESL mRNA abundance in unstressed S. pyogenes . Although the loss of HrcA elevated dnaK and groESL mRNA levels under non-heat shock conditions, the relative abundance of these RNAs increased further in heat shocked S. pyogenes , suggesting an additional element contributing to their synthesis or stability.