<scp>LeuO</scp>, a dormant sentinel for <scp>SPI</scp>‐1?

SummaryA new mechanism for the turning‐off of gene expression in Salmonella Pathogenicity Island 1 (SPI‐1) is proposed by Espinosa and Casadesús, which involves the action of the LeuO quiescent regulator, by two different pathways. A major one through the activation of the hilE gene, where the HilE protein would in turn inactivate HilD, a major positive transcriptional regulator of SPI‐1; and a minor HilE‐HilD‐independent pathway. This could constitute a back‐up or an aid for the turn‐off of SPI‐1 genes mediated by the nucleoid protein H‐NS.