PMID:9150205

Citation	Pesci, EC, Pearson, JP, Seed, PC and Iglewski, BH (1997) Regulation of las and rhl quorum sensing in Pseudomonas aeruginosa. J. Bacteriol. 179:3127-32
Abstract	The production of several virulence factors by Pseudomonas aeruginosa is controlled according to cell density through two quorum-sensing systems, las and rhl. The las system is comprised of the transcriptional activator protein LasR and of LasI, which directs the synthesis of the autoinducer PAI-1. Similarly, the rhl system consists of the transcriptional activator protein RhlR and of RhlI, which directs synthesis of the autoinducer PAI-2 (formerly referred to as factor 2). To study the interrelation between the two P. aeruginosa quorum-sensing systems, we fused a lacZ reporter gene to lasR, rhlR, and rhlA and monitored expression of these three genes under various conditions. Our data indicate that lasR and rhlR are expressed in a growth-dependent manner, with activation of each gene occurring during the last half of log-phase growth. We also show that the las quorum-sensing system controls the rhl quorum-sensing system in two ways. First, we found that LasR and PAI-1 activated rhlR transcription. Second, we showed that PAI-1 blocked PAI-2 from binding to RhlR, thereby inhibiting the expression of rhlA. Our data thus indicate that the las system exerts two levels of control on RhlR, transcriptional and posttranslational.
Links	PubMed PMC179088
Keywords	4-Butyrolactone/analogs & derivatives; 4-Butyrolactone/pharmacology; Bacterial Proteins/genetics; DNA-Binding Proteins/genetics; DNA-Binding Proteins/pharmacology; Genes, Bacterial/drug effects; Protein Processing, Post-Translational/drug effects; Protein Processing, Post-Translational/genetics; Pseudomonas aeruginosa/genetics; Pseudomonas aeruginosa/growth & development; Trans-Activators/genetics; Trans-Activators/pharmacology; Transcription, Genetic/drug effects
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
PSEAE:LASR		GO:0009372: quorum sensing	ECO:0000314:		P		Figure 3a shows almost a two-fold increase in lasR expression under the presence of autoinducers, PAI-1 and PAI-2, showing that lasR is involved in quorum sensing in P. aeruginosa	complete
PSEAE:LASR		GO:0045893: positive regulation of transcription, DNA-dependent	ECO:0000314:		P		Figure 4. In the absence of LasR or PAI-1, rhlR expression remained at background level, but in the presence of both LasR and PAI-1, rhlR expression increased approximately threefold, indicating that rhlR was directly controlled by LasR and PAI-1.	complete CACAO 5863
PSEAE:LASR	involved_in	GO:0045893: positive regulation of transcription, DNA-templated	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete
PSEAE:RHLR		GO:0009372: quorum sensing	ECO:0000314:		P		Figure 1A and B show that rhlR is mroe strongly induced when in the presence of autoinducers which shows that rhlR is involved in quorum sensing of P. aeruginosa.	complete

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