title: The cyclic-AMP receptor protein (CRP) regulon in Aggregatibacter actinomycetemcomitans includes leukotoxin.
abstract: The cyclic-AMP receptor protein (CRP) acts as a global regulatory protein among bacteria. Here, the CRP regulon has been defined in Aggregatibacter actinomycetemcomitans using microarray analysis of A. actinomycetemcomitans strain JP2 wild type cells compared to an isogenic crp deletion mutant. Genes whose expression levels changed at least 2-fold with p≤0.05 were considered significant. Of the 300 genes identified as being CRP-regulated, 139 were CRP-activated, including leukotoxin, with the remaining being CRP-repressed. The 300 genes represent 14.2% of ORFs probed which is significantly higher than what has been reported for CRP regulons in other bacteria. If the CRP-regulated genes are put into 17 functional classes, all 17 categories had at least 1 CRP-regulated gene. Several functional categories, mainly transport and binding proteins and energy metabolism proteins, were disproportionately represented in the CRP-regulated subset of genes relative to their overall representation in the genome. This is similar to the patterns seen in other bacteria. Finally, quantitative RT-PCR was used to show that the leukotoxin RNA levels were repressed 16-fold in the CRP mutant indicating that CRP activates leukotoxin transcription. However, this regulation appears to be acting through another regulatory protein since the leukotoxin promoter, unlike ∼129 other promoters of CRP-regulated genes, does not have a match to the consensus CRP-binding site. Several candidate genes for this intermediary transcription factor have been identified in the CRP regulon.
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, Mail Code 7758, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
authors.forename: Leigh A
authors.initials: LA
authors.lastname: Feuerbacher
authors.forename: Alex
authors.initials: A
authors.lastname: Burgum
authors.forename: David
authors.initials: D
authors.lastname: Kolodrubetz
mesh_terms: D002373:Cyclic AMP Receptor Protein / Q000378:metabolism*; D005098:Exotoxins / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D046228:Microarray Analysis; D015661:Pasteurellaceae / Q000235:genetics* / Q000378:metabolism*; D018085:Regulon; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D002373:Cyclic AMP Receptor Protein; D005098:Exotoxins; C018579:leukotoxin