DNA Replication Mechanisms in Eukaryotic Cells

DNA replication in eukaryotic cells is a highly coordinated, multi-step process that ensures precise duplication of the genome prior to cell division. In late mitosis and early G1 phase, the Origin Recognition Complex (ORC) binds to replication origins and, in concert with Cdc6 and Cdt1, loads an inactive double hexamer of the Mcm2-7 helicase onto chromatin—a process known as licensing. Upon entry to S phase, cyclin-dependent kinase (CDK) and Dbf4-dependent kinase (DDK) trigger recruitment of Cdc45 and the GINS complex to form the active CMG (Cdc45–Mcm2-7–GINS) helicase. This assembly unwinds parental DNA, enabling recruitment of DNA polymerases for leading- and lagging-strand synthesis. Replication forks traverse chromatin in association with a large multiprotein replisome, which coordinates unwinding, synthesis and nucleosome reassembly. Checkpoint kinases monitor fork integrity and can delay cell-cycle progression in response to stress. Spatial and temporal regulation of origin firing, influenced by chromatin context and higher-order genome structure, underpins genomic stability and avoids collisions between replication and transcription machinery. Defects in any stage of licensing, activation or fork progression can lead to genome instability, developmental disease or cancer.

Research from Nature Portfolio

Recent studies using chromatinised templates and single-molecule approaches have shown that nucleosomes markedly reduce the mobility of ORC along DNA without impairing its ability to recruit Mcm2-7. The constrained dynamics of ORC and the local retention of Mcm2-7 at nucleosomal origins are proposed to facilitate efficient replisome assembly in vivo. Structural analyses have further illuminated how Cdt1 stabilises an open conformation of the Mcm2-7 ring, acting as a brace that holds the helicase loader in a spiral arrangement poised for DNA entry. These models integrate X-ray crystallography and electron microscopy data to reveal how ATP-dependent transitions drive Cdt1 ejection and ring closure, providing a mechanistic basis for origin licensing at the molecular level.

DNA Replication Mechanisms in Eukaryotic Cells publication trend

The graph below shows the total number of articles in dna replication mechanisms in eukaryotic cells across all publications each year (not limited to Nature Index journals).

Technical terms

Origin Recognition Complex (ORC): A six-subunit protein assembly that marks replication origins and initiates helicase loading.

Mcm2-7: A heterohexameric ATPase motor that forms the core of the eukaryotic replicative helicase.

CMG complex: The active replicative helicase comprising Cdc45, Mcm2-7 and GINS, which unwinds DNA at replication forks.

Replisome: The multiprotein machinery at replication forks that coordinates DNA unwinding, synthesis and chromatin reassembly.

Cyclin-dependent kinase (CDK) and Dbf4-dependent kinase (DDK): Cell-cycle kinases that phosphorylate initiation factors to trigger helicase activation.

References

1. A chromatinized origin reduces the mobility of ORC and MCM through interactions and spatial constraint. Nature Communications (2023).
2. DONSON facilitates Cdc45 and GINS chromatin association and is essential for DNA replication initiation. Nucleic Acids Research (2023).
3. The structural mechanism of dimeric DONSON in replicative helicase activation. Molecular Cell (2023).
4. Changing protein–DNA interactions promote ORC binding-site exchange during replication origin licensing. Proceedings of the National Academy of Sciences of the United States of America (2023).
5. Cdt1 stabilizes an open MCM ring for helicase loading. Nature Communications (2017).