Equilibrium between nascent and parental MCM proteins protects replicating genomes

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Minichromosome maintenance proteins (MCMs) are essential for DNA replication, forming pre-replication complexes (pre-RCs) at origins.
• Cells produce a large excess of MCMs, but the purpose of this surplus and its regulation remain unclear.
• Reduced MCM levels compromise genome integrity, yet the underlying mechanisms are not fully understood.

Purpose of the Study:

• To investigate the mechanisms behind the surplus of MCM proteins during DNA replication.
• To understand how cells sustain MCM pools across generations for error-free DNA replication.
• To elucidate the role of MCMBP in stabilizing and translocating nascent MCMs.

Main Methods:

• Analysis of MCM protein pools (parental vs. nascent) in mother and daughter cells.
• Investigating the interaction between MCMs and MCMBP.
• Assessing the impact of MCMBP deficiency on DNA replication fork dynamics and genome integrity.

Main Results:

• Cells build nuclear MCM pools by recycling parental and synthesizing nascent MCMs.
• Parental MCMs preferentially form stable pre-RCs and mature into CMG helicases.
• MCMBP stabilizes nascent MCMs (except MCM2) and facilitates their nuclear translocation, safeguarding genome replication.

Conclusions:

• A surplus of MCMs, regulated by recycling, synthesis, and MCMBP chaperoning, ensures robust and error-free DNA replication.
• MCMBP prevents rapid proteolysis of nascent MCMs, ensuring sufficient pre-RCs for genome duplication.
• The regulation of MCM pools and replication fork speed by MCMBP is crucial for maintaining genome stability and preventing DNA damage.