Biochemical studies on replication of the genome in eukaryotes (27.1)

Our primary goal has been to understand how chromosomes are duplicated during the cell division cycle to ensure faithful inheritance of genetic information in eukaryotes. By initially investigating SV40 DNA replication, we reconstituted the entire process of DNA replication from the SV40 origin and in so doing discovered how the replication fork is assembled. Later, from studies on replication of DNA from chromosomal origins of DNA replication in eukaryotic cells, we discovered an ATP‐dependent protein machine, the Origin Recognition Complex (ORC) that is required to form a pre‐Replicative Complex (pre‐RC) at all origins of DNA replication prior to S phase. The process of pre‐RC assembly at origins of DNA replication licenses chromosomes for subsequent DNA replication during the S phase of the cell cycle. Pre‐RC assembly has been reconstituted in vitro with purified proteins and structural studies have revealed a conserved mechanism of protein assembly on origin DNA. Activation of DNA replication requires multiple protein kinase signaling systems, including the Cyclin‐Dependent Protein Kinase (CDK), the Cdc7‐Dbf4 Protein Kinase (DDK) and the Mec1 (ATM/ATR) checkpoint kinase. The presentation will focus on both the mechanism and regulation of the initiation of DNA replication.