Identification of two small regulatory RNAs linked to virulence in Brucella abortus 2308

Department of Microbiology and Immunology, East Carolina University School of Medicine, Greenville, NC 27834, USA.
Molecular Microbiology (Impact Factor: 4.42). 06/2012; 85(2):345-60. DOI: 10.1111/j.1365-2958.2012.08117.x
Source: PubMed


Hfq is an RNA-binding protein that functions in post-transcriptional gene regulation by mediating interactions between mRNAs and small regulatory RNAs (sRNAs). Two proteins encoded by BAB1_1794 and BAB2_0612 are highly over-produced in a Brucella abortus hfq mutant compared with the parental strain, and recently, expression of orthologues of these proteins in Agrobacterium tumefaciens was shown to be regulated by two sRNAs, called AbcR1 and AbcR2. Orthologous sRNAs (likewise designated AbcR1 and AbcR2) have been identified in B. abortus 2308. In Brucella, abcR1 and abcR2 single mutants are not defective in their ability to survive in cultured murine macrophages, but an abcR1 abcR2 double mutant exhibits significant attenuation in macrophages. Additionally, the abcR1 abcR2 double mutant displays significant attenuation in a mouse model of chronic Brucella infection. Quantitative proteomics and microarray analyses revealed that the AbcR sRNAs predominantly regulate genes predicted to be involved in amino acid and polyamine transport and metabolism, and Northern blot analyses indicate that the AbcR sRNAs accelerate the degradation of the target mRNAs. In an Escherichia coli two-plasmid reporter system, overexpression of either AbcR1 or AbcR2 was sufficient for regulation of target mRNAs, indicating that the AbcR sRNAs from B. abortus 2308 perform redundant regulatory functions.

Download full-text


Available from: K. Sayood, Dec 11, 2014
  • Source
    • "Several experimental evidences suggest that the A. tumefaciens and S. meliloti AbcR1 and AbcR2 sRNAs act independently to regulate nutrient uptake whereas their Brucella homologs have a rather redundant function (Wilms et al. 2011; Caswell et al. 2012; Torres-Quesada et al. 2013; Overlöper et al. 2014). "
    [Show abstract] [Hide abstract]
    ABSTRACT: High-throughput transcriptome profiling (RNAseq) has uncovered large and heterogeneous populations of small noncoding RNA species (sRNAs) with potential regulatory roles in bacteria. These sRNAs act mostly by protein-assisted base-pairing with target mRNAs to fine-tune post-transcriptional reprogramming of gene expression underlying bacterial responses to changing environments. Riboregulation impacts virtually any physiological process, and has been shown to largely influence virulence of pathogenic bacteria. Here, we review our current knowledge on the structure, conservation and function of the noncoding transcriptome of the α-rhizobia Sinorhizobium meliloti, the nitrogen-fixing symbiotic partner of alfalfa and related medics. Several RNAseq-based surveys in S. meliloti have shown abundant transcription from hitherto regarded as noncoding intergenic regions (IGRs), strikingly high numbers of mRNA-derived RNAs and pervasive antisense transcription of protein-coding genes. sRNAs encoded within IGRs constitute the most extensively studied group of bacterial riboregulators. They are differentially expressed and modulate translation and/or stability of trans-encoded target mRNAs by short antisense interactions that, in enteric model bacteria, are facilitated by the RNA chaperone Hfq. Among symbiotic rhizobia, regulatory sRNAs have been functionally characterized only in S. meliloti to date. The trans-sRNAs AbcR1 and AbcR2 are examples of Hfq-dependent sRNAs whereas EcpR1 does not bind Hfq. We will provide insights into the transcriptional regulation and activity mechanisms of these sRNAs for the targeting and control of multiple mRNAs involved in nutrient uptake (AbcR1/2) and cell cycle progression (EcpR1).
    Full-text · Article · Oct 2015 · Symbiosis
  • Source
    • "Previous reports have shown that half of all known sRNAs in Escherichia [80] and Salmonella [81] associate with Hfq. Little is known about sRNAs in Brucella except for abcR1 and abcR2, which were recently reported by Caswell et al [82]. Our work reveals potential target genes for sRNAs regulation in B. melitensis. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Brucella melitensis is a facultative intracellular bacterium that replicates within macrophages. The ability of brucellae to survive and multiply in the hostile environment of host macrophages is essential to its virulence. The RNA-binding protein Hfq is a global regulator that is involved in stress resistance and pathogenicity. Here we demonstrate that Hfq is essential for stress adaptation and intracellular survival in B. melitensis. A B. melitensis hfq deletion mutant exhibits reduced survival under environmental stresses and is attenuated in cultured macrophages and mice. Microarray-based transcriptome analyses revealed that 359 genes involved in numerous cellular processes were dysregulated in the hfq mutant. From these same samples the proteins were also prepared for proteomic analysis to directly identify Hfq-regulated proteins. Fifty-five proteins with significantly affected expression were identified in the hfq mutant. Our results demonstrate that Hfq regulates many genes and/or proteins involved in metabolism, virulence, and stress responses, including those potentially involved in the adaptation of Brucella to the oxidative, acid, heat stress, and antibacterial peptides encountered within the host. The dysregulation of such genes and/or proteins could contribute to the attenuated hfq mutant phenotype. These findings highlight the involvement of Hfq as a key regulator of Brucella gene expression and facilitate our understanding of the role of Hfq in environmental stress adaptation and intracellular survival of B. melitensis.
    Full-text · Article · Aug 2013 · PLoS ONE
  • Source
    • "Similar approaches also identified several ABC transporter mRNAs as AbcR1 and AbcR2 targets in A. tumefaciens and B. abortus [20], [21]. Preliminary computational predictions have rendered long and partially overlapping lists of target candidates for AbcR1 and AbcR2 in S. meliloti, with 35–45% of the top scoring hits corresponding to ABC transporter genes [11]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The legume symbiont Sinorhizobium meliloti expresses a plethora of small noncoding RNAs (sRNAs) whose function is mostly unknown. Here, we have functionally characterized two tandemly encoded S. meliloti Rm1021 sRNAs that are similar in sequence and structure. Homologous sRNAs (designated AbcR1 and AbcR2) have been shown to regulate several ABC transporters in the related α-proteobacteria Agrobacterium tumefaciens and Brucella abortus. In Rm1021, AbcR1 and AbcR2 exhibit divergent unlinked regulation and are stabilized by the RNA chaperone Hfq. AbcR1 is transcribed in actively dividing bacteria, either in culture, rhizosphere or within the invasion zone of mature alfalfa nodules. Conversely, AbcR2 expression is induced upon entry into stationary phase and under abiotic stress. Only deletion of AbcR1 resulted into a discrete growth delay in rich medium, but both are dispensable for symbiosis. Periplasmic proteome profiling revealed down-regulation of the branched-chain amino acid binding protein LivK by AbcR1, but not by AbcR2. A double-plasmid reporter assay confirmed the predicted specific targeting of the 5'-untranslated region of the livK mRNA by AbcR1 in vivo. Our findings provide evidences of independent regulatory functions of these sRNAs, probably to fine-tune nutrient uptake in free-living and undifferentiated symbiotic rhizobia.
    Full-text · Article · Jul 2013 · PLoS ONE
Show more