DNA Replication in Eukaryotes

OriC

Binds to start the replication process.

CDC6

Binds to the origin after OriC during initiation.

MCM2-7 helicase complex

Binds during G₁ phase.

Cdt1

Loads MCM2-7 and then dissociates.

Helicase binding

Binds double-stranded DNA after it is loaded.

DDK

Binds between the helicase units and phosphorylates both to activate helicase.

SLD2 and SLD3

Bind to the helicase after DDK phosphorylation.

CMG complex

Formed by CDC45 and GINS joining, making the helicase active during S phase entry.

Transition to S phase

Marked by the formation of the CMG complex and helicase activation.

RFC

Loads the sliding clamp (PCNA) and then leaves.

Pol α/primase

Lays down a short RNA primer (10-12 nucleotides) and ~100 DNA bases before falling off.

Pol δ

Synthesizes the lagging strand (uses clamp).

Pol ε

Synthesizes the leading strand (uses clamp).

Telomeres

DNA polymerase adds DNA after telomerase activity.

Primer removal in eukaryotes

Pol δ displaces the primer, and FEN (Flap Endonuclease) digests it.