Direct transcriptional control of the plasminogen activator gene of Yersinia pestis by the cyclic AMP receptor protein

Department of Food Science and Technology, Microbiology Graduate Group, Section of Microbiology, University of California, Davis, CA; Department of Microbiology and Immunology, Department of Pathology, University of Texas Medical Branch, Galveston, TX

	Abstract

Horizontal gene transfer events followed by proper regulatory integration of a gene drive rapid evolution of bacterial pathogens. A key event in the evolution of the highly virulent plague bacterium Yersinia pestis was the acquisition of the plasmid pPCP1, which carries the plasminogen activator gene, pla. This promoted the bubonic form of the disease by increasing bacterial dissemination from flea-bite sites and incidentally enhanced replication in respiratory airways during pneumonic infection. We determined that expression of pla is controlled by the global regulator Crp. This transcription factor is well conserved among distantly related bacteria where it acts as a soluble receptor for the ubiquitous signaling molecule cyclic adenosine monophosphate (cAMP) and controls a global network of metabolic and stress-protective genes. Crp has a similar physiological role in Y. pestis since loss of its function resulted in an inability to metabolize a variety of non-glucose substrates. Activation of pla expression requires a transcription activation element of the pla promoter that serves as a Crp binding site. Crp interaction with this site was demonstrated to occur only in the presence of cAMP. Alteration of the Crp binding-site nucleotide sequence prevented the in vitro formation of Crp-DNA complexes and inhibited in vivo expression of pla. The placement of pla under direct regulatory control of Crp highlights how highly adapted pathogens integrate laterally acquired genes to coordinate virulence factor expression with global gene networks to maintain homeostasis though the infectious lifecycle.