Structure of a human replisome shows the organisation and interactions of a DNA replication machine

The human replisome is an elaborate arrangement of molecular machines responsible for accurate chromosome replication. At its heart is the CDC45-MCM-GINS (CMG) helicase, which, in addition to unwinding the parental DNA duplex, arranges many proteins including the leading-strand polymerase Pol epsilon, together with TIMELESS-TIPIN, CLASPIN and AND-1 that have key and varied roles in maintaining smooth replisome progression. How these proteins are coordinated in the human replisome is poorly understood. We have determined a 3.2 angstrom cryo-EM structure of a human replisome comprising CMG, Pol epsilon, TIMELESS-TIPIN, CLASPIN and AND-1 bound to replication fork DNA. The structure permits a detailed understanding of how AND-1, TIMELESS-TIPIN and Pol epsilon engage CMG, reveals how CLASPIN binds to multiple replisome components and identifies the position of the Pol epsilon catalytic domain. Furthermore, the intricate network of contacts contributed by MCM subunits and TIMELESS-TIPIN with replication fork DNA suggests a mechanism for strand separation.

Automated summary

This study determined the structure of a human replisome containing multiple proteins, revealing their interactions and providing insights into the working mechanism of the replisome and how it maintains smooth replication progression.