Protein-DNA interactions in regulation of P1 plasmid replication.
The P1 RepA protein appears to play three roles in P1 plasmid replication: acting at the origin both as a specific initiator and as a repressor of transcription, and interacting with the copy-control locus incA to bring about a negative control of initiation. We have used the DNase I footprinting technique to show that RepA binds specifically to repeat units of a 19-base-pair consensus sequence present in both the origin and incA control regions. RNA polymerase was shown to bind to two specific regions within the origin repeats. One of these constitutes the known promoter sequence for the repA gene. We show evidence that the polymerase can be efficiently displaced from the promoter by subsequent RepA binding, thus providing a direct mechanism for RepA autoregulation. Under the conditions used, there were no obvious differences in the affinities of individual repeat sequences for the purified protein.
Abeles
A L
AL
Laboratory of Chromosome Biology, National Cancer Institute-Frederick Cancer Research Facility, Maryland 21701.
Reaves
L D
LD
Austin
S J
SJ
D001426:Bacterial Proteins / Q000502:physiology*; D001483:Base Sequence; D004265:DNA Helicases; D004261:DNA Replication; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics*; D008969:Molecular Sequence Data; D009710:Nucleotide Mapping; D010957:Plasmids; D011506:Proteins; D012091:Repetitive Sequences, Nucleic Acid; D012093:Replicon; D015183:Restriction Mapping; D015534:Trans-Activators
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D011506:Proteins; D015534:Trans-Activators; C045264:replication initiator protein; D004265:DNA Helicases