Disease relevance of virA

• Identification of a novel virulence gene, virA, on the large plasmid of Shigella, involved in invasion and intercellular spreading [1].
• Multiplex PCR amplification of invA and virA genes was developed enabling simultaneous detection in mussels of Salmonella spp. and Shigella spp., respectively [2].

High impact information on virA

• In this study, we have identified secreted proteins of 46 and 60 kDa as the products of virA and ipaH9.8, respectively, the latter being a member of the ipaH multigene family [3].
• Using lacZ transcriptional fusions, we found that transcription of virA and four ipaH genes, but not that of the ipaBCDA and mxi operons, was markedly increased during growth in the presence of Congo red and in an ipaD mutant, two conditions in which secretion through the Mxi-Spa machinery is enhanced [3].
• Inactivation of virA did not affect entry into epithelial cells [3].
• H-NS binding sites were determined by DNase I footprinting at the icsB and the virA promoters [4].
• The expression of virA was under the control of the virB gene, the positive regulator of the ipa, mxi and spa operons [1].

Biological context of virA

• The nucleotide sequence of the virA region revealed that the virA gene was located 528 bp upstream of the virG gene, in the opposite orientation [1].

Anatomical context of virA

• Degradation of microtubules by VirA was dependent on its alpha-tubulin-specific cysteine protease-like activity. virA mutants did not move within the host cytoplasm and failed to move into adjacent cells [5].

Other interactions of virA

• Promoter mapping and deletion analysis of the ipaH9.8. virA, and ospC1 promoters identified a 17-bp motif, the MxiE box, which overlaps the -35 region and is essential for the activation of these promoters [6].
• These results indicate that virA is a new member of the invasion regulon directed by virB and that the VirA function is involved in invasion and intercellular spreading [1].

Analytical, diagnostic and therapeutic context of virA

• Moreover, a multiplex PCR with specific (virA) and bacterium-restricted (16S ribosomal DNA) primers generated an amplification product of approximately 755 bp for all bacteria tested and an additional 215-bp product for Shigella and enteroinvasive E. coli [7].

References