Related Experiment Videos
The ordered assembly of the phiX174-type primosome. III. PriB facilitates complex formation between PriA and DnaT
1Graduate Program in Molecular Biology, Cornell University Graduate School of Medical Sciences, New York, New York 10021, USA.
Insights
The protein PriB is essential for forming complexes between PriA and DnaT during phiX174-type primosome assembly. Mutant PriA proteins unable to bind PriB show replication defects that can be overcome by high DnaT concentrations.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- The phiX174-type primosome is a complex molecular machine essential for viral DNA replication.
- PriA, PriB, and DnaT are key proteins involved in primosome assembly.
- Understanding the roles of these proteins is crucial for elucidating viral replication mechanisms.
Purpose of the Study:
- To investigate the role of PriB in the assembly of the phiX174-type primosome.
- To characterize the function of mutant PriA proteins (PriA C439Y and PriA C445Y) in primosome formation.
- To determine how PriB influences the interaction between PriA and DnaT.
Main Methods:
- Utilized mutant PriA proteins (PriA C439Y and PriA C445Y) to study primosome assembly.
- Analyzed the formation of intermediate protein-DNA complexes.
- Assessed the effect of PriB on PriA binding to DNA and complex formation with DnaT.
Main Results:
- Mutant PriA proteins could not form stable PriA-PriB complexes on DNA, leading to replication defects.
- These defects were rescued by high concentrations of DnaT, enabling PriA-DnaT complex formation.
- PriB was found to stabilize wild-type PriA on DNA but not the mutant forms.
Conclusions:
- PriB plays a critical role in facilitating the formation of PriA-DnaT complexes during primosome assembly.
- The ability of PriB to interact with PriA is essential for efficient primosome formation.
- High DnaT concentrations can bypass the requirement for PriB-PriA interaction for replication.
Abstract:
The properties of two mutant PriA proteins, PriA C439Y and PriA C445Y have been used to reveal the role of PriB during assembly of the phiX174-type primosome. The replication defects of both mutant PriA proteins could be rescued by high concentrations of DnaT. Analysis of the formation of intermediate complexes in primosome assembly and the effect of PriB on PriA binding to DNA demonstrated that the mutant PriA proteins could not form a PriA-PriB complex on DNA carrying a primosome assembly site. Consequently, the mutant proteins also could not form PriA-PriB-DnaT complexes at concentrations of DnaT sufficient to form such a complex with wild-type PriA. In addition, PriB was found to stabilize wild-type but not mutant PriA proteins on DNA. At high concentrations of DnaT, both mutant and wild-type PriA proteins could form a PriA-DnaT complex and support PriB-independent phiX174 complementary strand DNA replication. Thus, during primosome assembly, PriB facilitates complex formation between PriA and DnaT.