Premium
Conjugal transfer of the virulence plasmid of Salmonella enterica is regulated by the leucine‐responsive regulatory protein and DNA adenine methylation
Author(s) -
Camacho Eva M.,
Casadesús Josep
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.02981.x
Subject(s) - operon , biology , repressor , plasmid , transcription (linguistics) , dna methylation , microbiology and biotechnology , gene , activator (genetics) , promoter , regulation of gene expression , genetics , salmonella enterica , gene expression , mutant , escherichia coli , linguistics , philosophy
Summary Host‐encoded functions that regulate the transfer operon ( tra ) in the virulence plasmid of Salmonella enterica (pSLT) were identified with a genetic screen. Mutations that decreased tra operon expression mapped in the lrp gene, which encodes the leucine‐responsive regulatory protein (Lrp). Reduced tra operon expression in an Lrp − background is caused by lowered transcription of the traJ gene, which encodes a transcriptional activator of the tra operon. Gel retardation assays indicated that Lrp binds a DNA region upstream of the traJ promoter. Deletion of the Lrp binding site resulted in lowered and Lrp‐independent traJ transcription. Conjugal transfer of pSLT decreased 50‐fold in a Lrp − background. When a FinO − derivative of pSLT was used, conjugal transfer from an Lrp − donor decreased 1000‐fold. Mutations that derepressed tra operon expression mapped in dam , the gene encoding Dam methyltransferase. Expression of the tra operon and conjugal transfer remain repressed in an Lrp − Dam − background. These observations support the model that Lrp acts as a conjugation activator by promoting traJ transcription, whereas Dam methylation acts as a conjugation repressor by activating FinP RNA synthesis. This dual control of conjugal transfer may also operate in other F‐like plasmids such as F and R100.