Abstract

IscR is a global transcriptional regulator that contributes to the pathogenesis of Vibrio vulnificus, a food-borne pathogen. In the present study, the regulatory mechanism for the iscR expression of V. vulnificus was evaluated. The expression of iscR was found to be upregulated by a transcriptional regu-lator AphA, a homologue of the low cell density regulator AphA of the Vibrio species, in the exponential phase of growth. The promoter activity of iscR appeared to be acti-vated and repressed by AphA and IscR, respectively. EMSA and DNase I protection assay showed that both AphA and IscR bind to the iscR regulatory region and the binding site for AphA overlapped with part of the binding site for IscR. Further mutational analysis suggested that AphA upregu-lates the iscR expression only in the presence of functional IscR. An examination of the roles of AphA and the binding sites revealed that the binding of AphA would hinder the IscR-mediated repression of the iscR transcription. The com-bined results show that V. vulnificus AphA upregulates iscR expression by antagonizing its negative autoregulation.

• Keywords: V. vulnificus AphA; V. vulnificus iscR