SeqA, the Escherichia coli origin sequestration protein, is also a specific transcription factor.
The SeqA protein is a negative regulator of initiation of DNA replication in the Escherichia coli chromosome. Here, we demonstrate that SeqA stimulates transcription from the bacteriophage lambda pR promoter both in vivo and in vitro. The activity of the lambda pL promoter was found not to be affected by this protein. SeqA-mediated stimulation of pR was dependent on the state of template methylation: transcription was activated on fully methylated and hemimethylated templates but not on an unmethylated template. Using electrophoretic mobility shift assay and electron microscopy, we demonstrated that SeqA interacts specifically with a pR promoter region located on both fully methylated and hemimethylated DNA molecules, but not on unmethylated DNA. The activity of SeqA was found to affect the initiation of lambda plasmid replication positively in vivo, probably via pR-dependent expression of lambda replication genes and transcriptional activation of ori lambda. We conclude that, apart from its function in the control of DNA replication, SeqA is also a specific transcription factor.
Slomińska
M
M
Department of Molecular Biology, University of Gdańsk, Kladki 24, 80-822 Gdańsk, Poland.
Wegrzyn
A
A
Konopa
G
G
Skarstad
K
K
Wegrzyn
G
G
D001425:Bacterial Outer Membrane Proteins; D010582:Bacteriophage lambda / Q000235:genetics; D004268:DNA-Binding Proteins; D004586:Electrophoresis / Q000379:methods; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D018628:Gene Dosage; D009154:Mutation; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D001425:Bacterial Outer Membrane Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C089746:SeqA protein, E coli; D014157:Transcription Factors