It has been assumed that there is a direct correlation between hilA transcription , production of the HilA protein and HilA-activated gene expression .
These results suggest that repression of hilA transcription by oxygen leads to a decrease in HilA protein production , which in turn reduces the expression of HilA-activated genes , such as prgH .
These data demonstrated that the expression of the SPI-1 activator , hilA , as well as of the HilA-activated genes invF and sipC , was transcriptionally repressed by growth at 42 °C .