Synergism between CMG helicase and leading strand DNA polymerase at replication fork

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The eukaryotic replisome is a complex molecular machine responsible for DNA replication.
• It comprises the Cdc45-MCM-GINS (CMG) helicase and DNA polymerases, essential for unwinding and copying DNA.

Purpose of the Study:

• To elucidate the structural mechanism of yeast replisome coordination.
• To understand how the CMG helicase interacts with the leading-strand polymerase Polε during DNA replication.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine high-resolution structures of the yeast replisome.
• Structural analysis of the CMG helicase, Polε polymerase, and accessory factors bound to forked DNA.

Main Results:

• Identified two distinct positions of Polε relative to the CMG helicase, correlating with DNA translocation.
• Revealed that Psf1 acts as a hinge, maintaining stable coupling between Polε and CMG.
• Demonstrated that Polε-CMG coupling is crucial for replication initiation and leading-strand synthesis.

Conclusions:

• The study elucidates a mechanism for coordinating CMG helicase and Polε polymerase activities during DNA replication.
• This coordination facilitates DNA translocation and helps overcome replication roadblocks, DNA damage, and epigenetic modifications.