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Analysis of replicative intermediates produced during bacteriophage phi 29 DNA replication in vitro
C Gutiérrez1, J M Sogo, M Salas
1Centro de Biología Molecular (CSIC-UAM), Universidad Autónoma de Madrid, Spain.
Journal of Molecular Biology
|December 20, 1991
Summary
Bacteriophage phi 29 DNA replication initiates at both ends using a strand-displacement mechanism. In vitro studies reveal two intermediate types, suggesting type II intermediates form when replication forks from opposite ends merge.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bacteriophage phi 29 DNA replication is a complex process.
- Understanding replication intermediates is key to deciphering viral DNA synthesis.
- Strand-displacement replication is a known mechanism in some viruses.
Purpose of the Study:
- To analyze replicative intermediates of bacteriophage phi 29 DNA replication in vitro.
- To characterize the types and formation kinetics of these intermediates.
- To elucidate the mechanism of type II intermediate formation.
Main Methods:
- In vitro bacteriophage phi 29 DNA replication system.
- Electron microscopy for visualizing replicative intermediates.
- Analysis of recombinant DNA templates lacking terminal protein.
Main Results:
- Two types of replicative intermediates (type I and type II) were observed in vitro, mirroring in vivo findings.
- Type I intermediates showed preferential, non-simultaneous initiation at both DNA ends.
- Type II intermediates appeared early and were dependent on the presence of terminal protein at both ends, suggesting a merge of replication forks.
Conclusions:
- The in vitro system accurately replicates bacteriophage phi 29 DNA intermediates.
- Type II intermediates are formed by the merging of two replication forks originating from opposite ends of the DNA molecule.
- Terminal protein is crucial for the formation of type II intermediates, likely facilitating fork convergence.