CDC16 controls initiation at chromosome replication origins

Area of Science:

• Cell biology
• Molecular genetics
• Yeast genetics

Background:

• Cdc28p cyclin-dependent kinase regulates DNA replication initiation and prevents rereplication.
• CDC16 gene mutations in budding yeast lead to DNA rereplication despite G2 arrest and high Cdc28p activity.

Purpose of the Study:

• To investigate the nature of DNA accumulation in cdc16 mutants.
• To determine the mechanism by which CDC16 prevents DNA rereplication.

Main Methods:

• Two-dimensional DNA electrophoresis to analyze DNA replication origins.
• Density transfer experiments to track DNA synthesis.
• Analysis of initiation proteins Cdc6p and Cdc46/Mcm5p.

Main Results:

• Accumulated DNA in cdc16 mutants is primarily chromosomal.
• cdc16 mutants reinitiate DNA synthesis from normal replication origins.
• Rereplication requires initiation proteins Cdc6p and Cdc46/Mcm5p, which are normally inactivated by Cdc28p.

Conclusions:

• CDC16 is essential for preventing the inappropriate firing of DNA replication origins.
• The findings challenge the established model of Cdc28p-mediated control of DNA replication.
• CDC16 acts as a critical regulator to ensure proper cell cycle progression and prevent DNA rereplication.