Autoactivation of the AggR regulator of enteroaggregative Escherichia coli in vitro and in vivo.
Enteroaggregative Escherichia coli (EAEC) causes diarrhea in diverse populations worldwide. The AraC-like regulator AggR is a key virulence regulator in EAEC. AggR-regulated genes include those encoding the Aggregative Adherence Fimbria, the dispersin protein, and a type VI secretion system. This study characterizes the regulation of the aggR promoter (P(aggR)). Using primer extension analysis, the transcriptional start site of the aggR promoter was located 40 nucleotides upstream of the translational start. P(aggR) was found to be autoregulated and DNA footprinting revealed the presence of two AggR-binding sites: one upstream of the transcriptional start site and one downstream. Additionally, P(aggR) was found to be positively regulated by the DNA-binding protein FIS and negatively regulated by the global regulator H-NS. To further understand this complex regulation scheme, a bacterial luciferase reporter system was used with a mouse model of EAEC colonization. This allowed for the in vivo measurement of P(aggR), P(fis), and P(hns) activity. EAEC present in the mouse intestine possessed relatively high levels of P(fis) and P(aggR) activity and a low level of P(hns) when compared with in vitro experiments. The data provide significant insights into the regulation cascade leading to aggR expression in the mammalian intestine during EAEC infection.
Morin
Nicholas
N
Department of Pediatrics and Microbiology and Immunology, Center for Vaccine Development, University of Maryland, Baltimore, MD 21201, USA.
Tirling
Chelsea
C
Ivison
Sabine M
SM
Kaur
Ajinder Pal
AP
Nataro
James P
JP
Steiner
Theodore S
TS
D000818:Animals; D001483:Base Sequence; D003967:Diarrhea / Q000382:microbiology; D004195:Disease Models, Animal; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014774:Virulence
C088603:AggR protein, E coli; D029968:Escherichia coli Proteins; D015534:Trans-Activators