However , we provide evidence that LeuO mainly exerts SPI-1 repression by an indirect mechanism , hitherto unsuspected : LeuO activates transcription of the hilE gene .
LeuO downregulates SPI-1 expression via hilE Because SPI-1 expression is responsive to multiple regulators , we devised a genetic screen to ascertain whether a single cell function might transmit LeuO-mediated regulation to SPI-1 .
Furthermore , even though a hilD mutation was epistatic over hilE , moderate repression of SPI-1 by LeuO was still observed in a HilD − HilE − background .
A genetic screen for loss-of-function mutations provided evidence that the hilE gene is necessary for LeuOmediated repression of an hypothesis confirmed upon directed construction of a HilE − muta .
A genetic screen for loss-of-function mutations provided evidence that the hilE gene is necessary for LeuOmediated repression of SPI-1 .