title: Identification of iron-activated and -repressed Fur-dependent genes by transcriptome analysis of Neisseria meningitidis group B.
abstract: Iron is limiting in the human host, and bacterial pathogens respond to this environment by activating genes required for bacterial virulence. Transcriptional regulation in response to iron in Gram-negative bacteria is largely mediated by the ferric uptake regulator protein Fur, which in the presence of iron binds to a specific sequence in the promoter regions of genes under its control and acts as a repressor. Here we describe DNA microarray, computational and in vitro studies to define the Fur regulon in the human pathogen Neisseria meningitidis group B (strain MC58). After iron addition to an iron-depleted bacterial culture, 153 genes were up-regulated and 80 were down-regulated. Only 50% of the iron-regulated genes were found to contain Fur-binding consensus sequences in their promoter regions. Forty-two promoter regions were amplified and 32 of these were shown to bind Fur by gel-shift analysis. Among these genes, many of which had never been described before to be Fur-regulated, 10 were up-regulated on iron addition, demonstrating that Fur can also act as a transcriptional activator. Sequence alignment of the Fur-binding regions revealed that the N. meningitidis Fur-box encompasses the highly conserved (NATWAT)3 motif. Cluster analysis was effective in predicting Fur-regulated genes even if computer prediction failed to identify Fur-box-like sequences in their promoter regions. Microarray-generated gene expression profiling appears to be a very effective approach to define new regulons and regulatory pathways in pathogenic bacteria.
authors.affiliation: Chiron SpA, Siena, Italy.
authors.forename: Renata
authors.initials: R
authors.lastname: Grifantini
authors.forename: Shite
authors.initials: S
authors.lastname: Sebastian
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Frigimelica
authors.forename: Monia
authors.initials: M
authors.lastname: Draghi
authors.forename: Erika
authors.initials: E
authors.lastname: Bartolini
authors.forename: Alessandro
authors.initials: A
authors.lastname: Muzzi
authors.forename: Rino
authors.initials: R
authors.lastname: Rappuoli
authors.forename: Guido
authors.initials: G
authors.lastname: Grandi
authors.forename: Caroline Attardo
authors.initials: CA
authors.lastname: Genco
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D002455:Cell Division; D016000:Cluster Analysis; D015536:Down-Regulation; D005786:Gene Expression Regulation; D006801:Humans; D007501:Iron / Q000378:metabolism*; D008969:Molecular Sequence Data; D009345:Neisseria meningitidis / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D040081:Protein Array Analysis; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D015854:Up-Regulation
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; D007501:Iron