Single-Molecule Imaging Reveals the Mechanism of Bidirectional Replication Initiation in Higher Eukaryotes

Chromosomes are copied from thousands of origins. At each origin, two replicative DNA helicases are first assembled, then activated to begin unwinding DNA. Several replication proteins are subsequently recruited to the active helicase, forming a replisome. The helicase must undergo dramatic conformational changes during its activation and this process is poorly understood, especially in metazoa. How the metazoan replicative helicase is activated, and which proteins promote this essential process are long-standing questions. Using a combination of single-molecule imaging and ensemble biochemistry, we systematically dissected how two replicative DNA helicases are first assembled, then activated at each replication origins. Our findings reveal a surprisingly dynamic mechanism of initiation, help resolve long-standing contradictions in the field, and overturn long-held views about the roles of key replication initiation factors.

Speaker: Gheorghe Chistol, Stanford School of Medicine