Protein interactions in T7 DNA replisome inhibit the bypass of abasic site by DNA polymerase

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Abasic sites are common DNA lesions that impede DNA replication and increase mutation risk.
• The T7 DNA replisome, comprising DNA polymerase and helicase, is crucial for DNA replication and repair.
• Bypass of abasic sites by the T7 DNA replisome has not been previously studied.

Purpose of the Study:

• To investigate the ability of the T7 DNA replisome to replicate DNA containing an abasic site.
• To compare the abasic site bypass efficiency of T7 DNA polymerase alone versus the complete T7 DNA replisome.
• To elucidate the role of protein interactions in the T7 replisome during translesion DNA synthesis.

Main Methods:

• Utilized T7 DNA polymerase and the T7 DNA replisome as distinct models for studying DNA replication.
• Assessed DNA replication dynamics, including primer extension and strand-displacement synthesis, in the presence of abasic sites.
• Employed kinetic analysis to determine the impact of protein interactions on abasic site bypass efficiency.

Main Results:

• Abasic sites significantly inhibited primer extension and completely blocked strand-displacement synthesis by the T7 DNA replisome.
• The presence of an abasic site at the DNA fork impeded the binding of DNA polymerase and helicase.
• Unexpectedly, T7 DNA polymerase alone bypassed abasic sites more effectively than the complete replisome; gp2.5 further inhibited bypass at the fork.

Conclusions:

• Protein interactions within the T7 DNA replisome inhibit the bypass of DNA lesions, contrary to the general understanding that accessory proteins facilitate DNA damage tolerance.
• This finding offers novel insights into the mechanisms of translesion DNA synthesis by DNA replisomes.
• The study highlights a unique regulatory role of protein complex formation in managing DNA replication through damaged DNA templates.