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Identification of two replicons in phage-plasmid P4
A Tocchetti1, S Serina, S Terzano
1Dipartimento di Genetica e di Biologia dei Microrganismi, Università di Milano, Italy.
Virology
|June 24, 1998
Summary
Bacteriophage P4 DNA replication utilizes two origins, ori1 and ori2, and requires the P4 alpha gene product. The Cnr protein regulates replication from ori1 and also silences the alternative ori2 origin.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bacteriophage P4 DNA replication is a complex process.
- Replication initiates bidirectionally from the ori1 site.
- A second cis-acting region, crr, is also essential for replication.
Purpose of the Study:
- To investigate the mechanisms of P4 DNA replication.
- To identify and characterize additional replication origins.
- To understand the role of the Cnr protein in replication control.
Main Methods:
- Plasmid complementation tests were used to assess replication.
- Deletion mapping was employed to identify essential DNA regions.
- Analysis of P4 gene products and their functions.
Main Results:
- Two distinct replicons dependent on the P4 alpha gene product were identified.
- A novel replication origin, ori2, was mapped within the P4 alpha gene.
- The Cnr protein negatively regulates replication from ori1 and silences ori2.
Conclusions:
- P4 DNA replication can initiate from at least two distinct origins (ori1 and ori2).
- The P4 alpha gene product possesses primase and helicase activities essential for replication.
- The Cnr protein plays a crucial role in controlling P4 plasmid copy number by regulating both ori1 and ori2.