Role of Hfq in iron-dependent and -independent gene regulation in Neisseria meningitidis

Abstract

In Neisseria meningitidis, iron-responsive gene regulation is mediated primarily by the ferric uptake regulator (Fur) protein. When complexed with iron, Fur represses gene expression by preventing transcription initiation. Fur can also indirectly activate gene expression via the repression of regulatory small RNAs (sRNA). One such Fur- and iron-regulated sRNA, NrrF, was previously identified in N. meningitidis and shown to repress expression of the sdhA and sdhC genes encoding subunits of the succinate dehydrogenase complex. In the majority of Gram-negative bacteria, sRNA-mediated regulation requires a cofactor RNA-binding protein (Hfq) for proper gene regulation and stabilization. In this study, we examined the role of Hfq in NrrF-mediated regulation of the succinate dehydrogenase genes in N. meningitidis and the effect of an hfq mutation on iron-responsive gene regulation more broadly. We first demonstrated that the stability of NrrF, as well as the regulation of sdhC and sdhA in vivo, was unaltered in the hfq mutant. Secondly, we established that iron-responsive gene regulation of the Fur-regulated sodB gene was dependent on Hfq. Finally, we demonstrated that in N. meningitidis, Hfq functions in a global manner to control expression of many ORFs and intergenic regions via iron-independent mechanisms. Collectively these studies demonstrate that in N. meningitidis, iron- and NrrF-mediated regulation of sdhC and sdhA can occur independently of Hfq, although Hfq functions more globally to control regulation of other N. meningitidis genes primarily by iron-independent mechanisms.

Analysis of the Regulated Transcriptome of Neisseria meningitidis in Human Blood Using a Tiling Array

“…These findings extend our knowledge of the whole transcriptome of N. meningitidis; previously, other research groups had shown the expression in N. meningitidis of small regulatory RNAs with a role in bacterial pathogenesis (14,35,38), and proteomic and transcriptomic analysis of Hfq deletion mutants suggested the presence of a small-RNA network in the bacterium (13,36,45). Here, we reported a panel of expressed small RNAs that could be involved in the adaptation of N. meningitidis to the human blood environment.…”

“…Moreover, an antisense transcript for prpB and prpC was detected (Fig. 3B), and the PrpB and PrpC proteins were deregulated in an Hfq deletion mutant (13,36,45).…”

“…2C), the sequence was probably transcribed as a single transcript and then processed. Interestingly, Bns3b is predicted to base pair with NMB0607 (see Table S6 in the supplemental material), which codes for a protein export protein, SecD, that was not regulated in blood but was downregulated in an Hfq deletion mutant (36).…”

Loving the poison: the methylcitrate cycle and bacterial pathogenesis

“…Hfq-dependent repression of prpB expression was subsequently shown to be mediated by two trans-acting sRNAs, RcoF1 and RcoF2 [27]. Northern blot analysis revealed that both the single prpB and the bicistronic prpB-prpC mRNAs were up-regulated upon the deletion of hfq or a double deletion of rcoF1 and rcoF2 [28], thereby confirming the genetic link between RcoF1/2, Hfq and prp gene expression. By regulating prpB, RcoF1 and RcoF2 appear to be the first trans-acting sRNAs with a direct host-associated function in N. meningitidis [27].…”

Fur-Mediated Activation of Gene Transcription in the Human Pathogen Neisseria gonorrhoeae

“…The sRNAs, RyhB of Escherichia coli and Vibrio cholerae (42), PrrF1 and PrrF2 of Pseudomonas aeruginosa (53), FsrA of Bacillus subtilis (29), and nrrF in Neisseria meningitidis (43,44) were found to be repressed by iron-bound Fur, indicating that the target genes of these small RNAs were indirectly activated by Fur. In Salmonella enterica serovar Typhimurium, Fur represses a repressor protein, the histone-like nucleoid structuring protein (H-NS), which negatively regulates hilA, resulting in indirect activation of hilA by Fur (52).…”