Regulation of Virulence Genes in PathogenicListeriaspp.

Abstract

Regulation of virulence genes in pathogenic bacteria must occur by mechanisms allowing the coordinate and differential expression of the virulence factors during infection. Although positive regulatory factor A (PrfA) and (to some extent) sigma factor B (SigB), are not specific for the pathogenic Listeria species, they have been so far shown by genetic and biochemical studies to be involved in the regulation of virulence genes. This chapter focuses on gene regulation by PrfA. Extensive molecular studies have been carried out with the cyclic AMP (cAMP)-binding factor Crp; since PrfA shares extended sequential and structural similarity with Crp, a short overview of the most essential features of Crp has been provided in this chapter for the understanding of PrfA. The three-dimensional structure of PrfA shows high structural similarity with Crp. The chapter discusses some evidence for the involvement of a low-molecular-weight effector(s) for PrfA that is distinct from cAMP. The results described in the chapter suggest that regulation of virulence genes mediated by PrfA involves environmental parameters, as well as additional bacterial factors. The transcriptional activator of the pathogenic Listeria species L. monocytogenes and L. ivanovii shares common properties with other members of the Crp/Fnr family to which it belongs, but it also possesses unique features. The precise knowledge of the mechanisms involved in the regulation of the listerial virulence genes will be crucial for the understanding of the pathogenesis of infections by pathogenic Listeria spp.