that HilD are each capable of independently inducing expression of the hilD genes
We demonstrate that HilD are each capable of inducing expression of hilD .
We wanted to determine if HilD could induce expression of hilD in the absence of the other regulators .
HilD also induced expression of hilD .
HilD induced expression of hilD ~ 10-to 12-fold .
These data show that HilD are each capable of independently inducing expression of hilD , consistent with our model that HilD constitute a feed forward regulatory loop .
We show that HilD can each independently activate expression of the hilD genes .
HilD are clearly able to induce hilD transcription .
HilD are all also capable of activating expression of hilD independent of each other and comprise a complex feed forward regulatory loop .
not indirectly is it absolutely required for HilD to activate hilD transcription
not directly is it absolutely required for HilD to activate hilD transcription
This regulated induction of hilD eliminates the autoinduction of hilD expression by the HilD protein .
Other features that need to be taken in account when assessing hilD transcription are the presence of an intact hilD ORF , as the HilD protein positively regulates its own expression [ 15 ] and the presence of the newly described regulatory motif hilD 3 
Gre factors affect SPI-1 gene expression by modulating hilD expression The transcriptional expression of hilA is tightly modulated by three AraC activators , HilD , HilC and RtsA , which form an auto-inducing regulatory loop where each protein can activate its own expression , as well as expression of the other two regulators [ 15 ] .
hilD expression from the strain complemented with HilD was significantly higher than hilD expression from both the reporter strain alone and the reporter carrying the empty vector ( Fig. 5 ) , indicating that in S. Typhi HilD positively regulates its own transcription , either directly or indirectly .
Saini et al. demonstrated that the interaction of HilD with the hilD promoter is the trigger for inducing the expression of SPI1 through a stepwise increase of autoactivation .
Saini et al. demonstrated that the interaction of HilD with the hilD promoter is the trigger for inducing the expression of SPI1 through a stepwise increase of hilD promoter activity .