Mechanism of asymmetric polymerase assembly at the eukaryotic replication fork.

ABSTRACT: Eukaryotes use distinct polymerases for leading- and lagging-strand replication, but how they target their respective strands is uncertain. We reconstituted Saccharomyces cerevisiae replication forks and found that CMG helicase selects polymerase (Pol) ? to the exclusion of Pol ? on the leading strand. Even if Pol ? assembles on the leading strand, Pol ? rapidly replaces it. Pol ?-PCNA is distributive with CMG, in contrast to its high stability on primed ssDNA. Hence CMG will not stabilize Pol ?, instead leaving the leading strand accessible for Pol ? and stabilizing Pol ?. Comparison of Pol ? and Pol ? on a lagging-strand model DNA reveals the opposite. Pol ? dominates over excess Pol ? on PCNA-primed ssDNA. Thus, PCNA strongly favors Pol ? over Pol ? on the lagging strand, but CMG over-rides and flips this balance in favor of Pol ? on the leading strand.

SUBMITTER: Georgescu RE 

PROVIDER: S-EPMC4482249 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature