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The gene 32 single-stranded DNA-binding protein is not bound stably to the phage T4 presynaptic filament
H Jiang1, F Salinas, T Kodadek
1Department of Chemistry and Biochemistry, University of Texas at Austin 78712, USA.
Abstract:
A central reaction in homologous recombination is synapsis, which involves invasion of duplex DNA by a homologous single strand. A key intermediate in this process is the presynaptic filament, a protein-DNA complex composed of a "strand transferase" polymerized along the invading single strand. In this report, the organization and mechanism of assembly of the bacteriophage T4 presynaptic filament are explored. Three T4 proteins, encoded by the uvsX, uvsY and 32 genes, are involved in this process. It is demonstrated that a well-defined series of events involving multiple protein-DNA and protein-protein interactions is required to mediate a transition from an initial gene 32-DNA complex to a mature presynaptic filament in which the UvsX and UvsY proteins are in contact with the DNA and each other, while most or all of the gene 32 protein is removed from the complex.
Insights
The bacteriophage T4 presynaptic filament assembly involves specific protein interactions. Gene 32 protein is displaced during the formation of this key homologous recombination intermediate.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Homologous recombination is a fundamental DNA repair process.
- Synapsis, a crucial step, involves DNA strand invasion.
- The presynaptic filament is a key intermediate in synapsis.
Purpose of the Study:
- To investigate the organization and assembly mechanism of the bacteriophage T4 presynaptic filament.
- To understand the roles of T4 uvsX, uvsY, and 32 proteins in filament formation.
Main Methods:
- Analysis of protein-DNA complex formation.
- Characterization of presynaptic filament assembly intermediates.
- Study of protein-protein and protein-DNA interactions.
Main Results:
- Bacteriophage T4 presynaptic filament assembly follows a defined sequence of events.
- Multiple protein-DNA and protein-protein interactions orchestrate filament formation.
- Gene 32 protein is largely removed from the complex during mature filament assembly, with UvsX and UvsY proteins binding DNA.
Conclusions:
- The assembly of the T4 presynaptic filament is a highly regulated process.
- Specific protein dynamics, including gene 32 protein displacement, are essential for forming the functional presynaptic filament.