Interaction between human Ctf4 and the Cdc45/Mcm2-7/GINS (CMG) replicative helicase

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Chromosome transmission fidelity 4 (Ctf4) is crucial for accurate DNA replication.
• The CMG (Cdc45/Mcm2-7/GINS) complex is the core replicative helicase.
• Understanding protein interactions within the replisome is vital for comprehending DNA replication fidelity.

Purpose of the Study:

• To investigate the interactions between human Ctf4 (hCtf4) and the human CMG (hCMG) complex.
• To characterize the biochemical properties and composition of the hCtf4-hCMG complex.
• To elucidate the role of hCtf4 in the DNA replication machinery.

Main Methods:

• In vitro interaction assays with purified proteins.
• Co-infection of insect cells (Spodoptera frugiperda) with recombinant viruses.
• Chromatin isolation from HeLa cells followed by nuclease digestion and immunoprecipitation.

Main Results:

• The hCtf4-hCMG complex was successfully isolated using multiple methods.
• Complex stability is dependent on hCtf4 interactions with multiple hCMG components.
• The hCtf4-hCMG complex exhibits salt-resistant DNA helicase activity, superior to the hCMG complex alone.
• The complex consists of homodimeric hCtf4 and monomeric hCMG, with hCtf4 potentially bridging polymerase alpha to hCMG.

Conclusions:

• hCtf4 forms a stable complex with the hCMG helicase.
• hCtf4 acts as a scaffold, linking polymerase alpha to the CMG complex.
• This interaction is critical for the function of the replisome and maintaining DNA replication fidelity.