title: Critical sequences in the core of the P1 plasmid replication origin.
abstract: The core of the P1 plasmid replication origin consists of a series of 7-bp repeats and a G+C-rich stretch. Methylation of the GATC sequences in the repeats is essential. Forty different single-base mutations in the region were isolated and assayed for origin function. A single-base change within any 7-bp repeat could block the origin, irrespective of whether GATC bases were affected. The repeats themselves were critical, but the short intervals between them were not. Mutations in the G+C-rich region showed it to be a spacer whose exact length is important but whose sequence can vary considerably. It maintains a precise distance between the 7-bp repeats and binding sites for the P1 RepA initiator protein. It may also serve as a clamp to limit strand separation during initiation.
authors.affiliation: Laboratory of Chromosome Biology, NCI-Frederick Cancer Research and Development Center, Maryland 21702.
authors.forename: T
authors.initials: T
authors.lastname: Brendler
authors.forename: A
authors.initials: A
authors.lastname: Abeles
authors.forename: S
authors.initials: S
authors.lastname: Austin
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D001435:Bacteriophages / Q000235:genetics*; D001482:Base Composition; D001483:Base Sequence; D004265:DNA Helicases; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis* / Q000737:chemistry; D004268:DNA-Binding Proteins; D008745:Methylation; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010641:Phenotype; D010957:Plasmids; D011506:Proteins; D012091:Repetitive Sequences, Nucleic Acid; D012093:Replicon; D015534:Trans-Activators
chemical_list: D001426:Bacterial Proteins; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D011506:Proteins; D015534:Trans-Activators; C045264:replication initiator protein; D004265:DNA Helicases