SirA , positively regulates another regulatory gene , hilA .
A second formal possibility is that SirA activates expression of hilA .
For example , the response regulator SirA has been shown to activate hilA transcription in the presence of suitable environmental signals , providing us with tools for both an on - -LRB- S i r M i l A -RRB- .
For example , the response regulator SirA has been shown to activate hilA transcription in PhoPmediated prg response for invasion .
For example , the response regulator SirA has been shown to activate hilA transcription in off-switch for invasion .
In Salmonella , SirA also directly activates the horizontally acquired regulatory genes hilA .
-RRB- b-galactosidase Activity b-galactosidase Activit SirA induction of hilA requires HilD Previous evidence suggested that SirA required the HilC/HilD/RtsA binding sites in the hilA promoter to induce thus the entire SPI1 TTSS b-galactosidase Activity b-galactosidase Activit Fig. 5 .
-RRB- b-galactosidase Activity b-galactosidase Activit SirA induction of hilA requires HilD Previous evidence suggested that SirA required the HilC/HilD/RtsA binding sites in the hilA promoter to induce expression of hilA .
Therefore , our model predicts that SirA induces expression of hilA -LRB- and invF -RRB- via HilD .
We determined if SirA was still capable of inducing expression of hilA -- and invF -- lac fusions .
This suggests that SirA induction of hilA expression requires the presence of HilD .
In support of our model , we demonstrate that SirA induction of hilA requires the presence of HilD .
However , the data in Fig. 5 show that SirA , even overproduced , can activate neither hilA in the absence of HilD .
SirA does this by directly activating the hilA .
SirA controls these genes by directly activating the hilA .
Deletions of rtsA do not affect the induction of hilA by SirA .
Deletions of hilC do not affect the induction of hilA by SirA .
On the basis of these data , the authors concluded that SirA activates the system by direct action on hilA .
SirA , positively regulates the expression of hilA .
SirA , positively regulates the transcription of hilA .