Characterization of the oriI and oriII Origins of Replication in Phage-Plasmid P4
AUTOR(ES)
Tocchetti, Arianna
FONTE
American Society for Microbiology
RESUMO
In the Escherichia coli phage-plasmid P4, two partially overlapping replicons with bipartite ori sites coexist. The essential components of the oriI replicon are the α and cnr genes and the ori1 and crr sites; the oriII replicon is composed of the α gene, with the internal ori2 site, and the crr region. The P4 α protein has primase and helicase activities and specifically binds type I iterons, present in ori1 and crr. Using a complementation test for plasmid replication, we demonstrated that the two replicons depend on both the primase and helicase activities of the α protein. Moreover, neither replicon requires the host DnaA, DnaG, and Rep functions. The bipartite origins of the two replicons share the crr site and differ for ori1 and ori2, respectively. By deletion mapping, we defined the minimal ori1 and ori2 regions sufficient for replication. The ori1 site was limited to a 123-bp region, which contains six type I iterons spaced regularly close to the helical periodicity, and a 35-bp AT-rich region. Deletion of one or more type I iterons inactivated oriI. Moreover, insertion of 6 or 10 bp within the ori1 region also abolished replication ability, suggesting that the relative arrangement of the iterons is relevant. The ori2 site was limited to a 36-bp P4 region that does not contain type I iterons. In vitro, the α protein did not bind ori2. Thus, the α protein appears to act differently at the two origins of replication.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=104256Documentos Relacionados
- Cnr interferes with dimerization of the replication protein α in phage-plasmid P4
- Characterization of a phage-plasmid hybrid (phasyl) with two independent origins of replication isolated from Escherichia coli.
- Transplacement mutagenesis: a novel in situ mutagenesis system using phage-plasmid recombination.
- Phage P4 DNA replication in vitro.
- A novel replicon occurring naturally in Escherichia coli is a phage-plasmid hybrid.