Stepwise assembly of initiation complexes at budding yeast replication origins during the cell cycle

Area of Science:

• Molecular Biology
• Cell Cycle Regulation
• DNA Replication

Background:

• DNA replication is a critical, tightly regulated process in eukaryotic cell cycles.
• Initiation of DNA replication depends on cell cycle completion and commitment during G1 phase.
• Understanding protein factors involved in initiation is key to cell cycle regulation.

Purpose of the Study:

• To characterize protein factors essential for initiating DNA replication.
• To elucidate the multi-stage assembly of initiation complexes.
• To understand the role of Dbf4 and Cdc7 in cell cycle regulation.

Main Methods:

• Characterization of protein factors involved in DNA replication initiation.
• Analysis of Origin Recognition Complex (ORC) binding to replication origins.
• Investigation of pre-replicative complex (pre-RC) assembly and Dbf4-origin interactions.

Main Results:

• Origin Recognition Complex (ORC) binds replication origins via a bipartite sequence (ACS and B1 element).
• A pre-replicative complex (pre-RC) assembles at origins post-mitosis and persists until replication.
• Dbf4 interacts with origins through ORC and activates the Cdc7 kinase, crucial for the G1-S transition.

Conclusions:

• DNA replication initiation involves sequential assembly of ORC, pre-RC, and Dbf4-Cdc7 complex.
• Dbf4 acts as a scaffold, recruiting Cdc7 kinase to replication origins for activation.
• This coordinated process ensures proper cell cycle progression from G1 to S phase.