PMID:16385041

Citation	Will, WR and Frost, LS (2006) Characterization of the opposing roles of H-NS and TraJ in transcriptional regulation of the F-plasmid tra operon. J. Bacteriol. 188:507-14
Abstract	The transfer (tra) operon of the conjugative F plasmid of Escherichia coli is a polycistronic 33-kb operon which encodes most of the proteins necessary for F-plasmid transfer. Here, we report that transcription from PY, the tra operon promoter, is repressed by the host nucleoid-associated protein, H-NS. Electrophoretic mobility shift assays indicate that H-NS binds preferentially to the tra promoter region, while Northern blot and transcriptional fusion analyses indicate that transcription of traY, the first gene in the tra operon, is derepressed in an hns mutant throughout growth. The plasmid-encoded regulatory protein TraJ is essential for transcription of the tra operon in wild-type Escherichia coli; however, TraJ is not necessary for plasmid transfer or traY operon transcription in an hns mutant. This indicates that H-NS represses transcription from PY directly and not indirectly via its effects on TraJ levels. These results suggest that TraJ functions to disrupt H-NS silencing at PY, allowing transcription of the tra operon.
Links	PubMed PMC1347297 Online version:10.1128/JB.188.2.507-514.2006
Keywords	Bacterial Outer Membrane Proteins/genetics; Bacterial Proteins/genetics; Base Sequence; DNA-Binding Proteins/genetics; Escherichia coli/genetics; Escherichia coli/growth & development; Escherichia coli Proteins/genetics; F Factor/genetics; Gene Expression Regulation, Bacterial; Molecular Sequence Data; Operon/genetics; Promoter Regions, Genetic; Repressor Proteins/genetics; Transcription, Genetic
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:HNS		GO:0016481: negative regulation of transcription	ECO:0000314:		P		See Fig 3. The preferential binding to the Py region shows that H-NS down-regulates transcription from Py	complete

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