Different Impacts of MucR Binding to the babR and virB Promoters on Gene Expression in Brucella abortus 2308.

Giorgia Borriello,Gaetano Verde,Ilaria Baglivo,Rubina Paradiso,Paolo Vincenzo Pedone,Marita Georgia Riccardi,Veronica Russo,Daniela Criscuolo,Giorgio Galiero,Rosangela Marasco

doi:10.3390/biom10050788

Giorgia Borriello, Gaetano Verde + Show 8 more

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https://doi.org/10.3390/biom10050788

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Abstract

The protein MucR from Brucella abortus has been described as a transcriptional regulator of many virulence genes. It is a member of the Ros/MucR family comprising proteins that control the expression of genes important for the successful interaction of α-proteobacteria with their eukaryotic hosts. Despite clear evidence of the role of MucR in repressing virulence genes, no study has been carried out so far demonstrating the direct interaction of this protein with the promoter of its target gene babR encoding a LuxR-like regulator repressing virB genes. In this study, we show for the first time the ability of MucR to bind the promoter of babR in electrophoretic mobility shift assays demonstrating a direct role of MucR in repressing this gene. Furthermore, we demonstrate that MucR can bind the virB gene promoter. Analyses by RT-qPCR showed no significant differences in the expression level of virB genes in Brucella abortus CC092 lacking MucR compared to the wild-type Brucella abortus strain, indicating that MucR binding to the virB promoter has little impact on virB gene expression in B. abortus 2308. The MucR modality to bind the two promoters analyzed supports our previous hypothesis that this is a histone-like protein never found before in Brucella.

Highlights

Brucella spp. are the bacteria responsible for one of the most widespread zoonoses worldwide
The results show that MucR is able to bind babR60 (Figure 2a) demonstrating that the babR promoter is a target of
Our findings in this paper demonstrate for the first time that MucR from B. abortus plays a direct role in regulating the expression of the Lux-like type regulator BabR by binding multiple target sites in the babR promoter

Summary

Introduction

Brucella spp. are the bacteria responsible for one of the most widespread zoonoses worldwide. We have demonstrated that the Mls and MucR form higher-order oligomers and interact mostly with the DNA minor groove recognizing AT-rich DNA sequences containing T–A steps. These findings led us to suggest that members of the Ros/MucR family could play the same role in α-proteobacteria in regulating virulence gene expression as the histone-like proteins H-NS in β- and γ-proteobacteria [12,13,14]. One of the gene whose expression is controlled by MucR in Brucella abortus is babR which encodes the corresponding LuxR-type quorum sensing regulator BabR [17], known as BlxR [18]. These effector proteins disrupt the normal endolysosomal trafficking of the Brucella-containing vacuoles (BCVs) in host cells and allow the brucellae to reach a specialized intracellular compartment known as the replicative BCV where they maintain their intracellular persistence [26]

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