The architecture of a eukaryotic replisome.

ABSTRACT: At the eukaryotic DNA replication fork, it is widely believed that the Cdc45-Mcm2-7-GINS (CMG) helicase is positioned in front to unwind DNA and that DNA polymerases trail behind the helicase. Here we used single-particle EM to directly image a Saccharomyces cerevisiae replisome. Contrary to expectations, the leading strand Pol ? is positioned ahead of CMG helicase, whereas Ctf4 and the lagging-strand polymerase (Pol) ?-primase are behind the helicase. This unexpected architecture indicates that the leading-strand DNA travels a long distance before reaching Pol ?, first threading through the Mcm2-7 ring and then making a U-turn at the bottom and reaching Pol ? at the top of CMG. Our work reveals an unexpected configuration of the eukaryotic replisome, suggests possible reasons for this architecture and provides a basis for further structural and biochemical replisome studies.

SUBMITTER: Sun J 

PROVIDER: S-EPMC4849863 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature