Ancient diversification of eukaryotic MCM DNA replication proteins

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Genomics

Background:

• Eukaryotic DNA replication relies on the Mcm2-7 complex and Mcm10 protein.
• Archaea possess a simpler, single MCM homologue forming a homohexamer.
• Mcm8 and Mcm9 roles in eukaryotic DNA replication are not fully understood.

Purpose of the Study:

• To reconstruct the evolutionary history of the eukaryotic Mcm2-9 gene family.
• To understand the diversification and conservation patterns of MCM proteins across eukaryotes.

Main Methods:

• Comparative genomics
• Phylogenetic analysis

Main Results:

• The Mcm2-9 family arose from seven gene duplications predating the last eukaryotic common ancestor.
• Mcm2-7 paralogues are universally conserved in eukaryotes, indicating essential, non-redundant functions.
• Mcm8 and Mcm9 co-evolved and are widely distributed, though secondarily lost in some lineages.
• Mcm10 distribution shows no clear pattern with Mcm8 or Mcm9.

Conclusions:

• A complex, heterogeneous Mcm2-7 hexamer evolved early in eukaryotes, preceding their diversification.
• The conservation of Mcm2-7 subunits suggests unique functional roles within the hexamer.
• Mcm8 and Mcm9 likely have linked functions, evolving early in eukaryotic evolution.
• Drosophila Mcm8 divergence may limit its utility as a model for other eukaryotes.