How Pol ?-primase is targeted to replisomes to prime eukaryotic DNA replication.

During eukaryotic DNA replication, Pol ?-primase generates primers at replication origins to start leading-strand synthesis and every few hundred nucleotides during discontinuous lagging-strand replication. How Pol ?-primase is targeted to replication forks to prime DNA synthesis is not fully understood. Here, by determining cryoelectron microscopy (cryo-EM) structures of budding yeast ...
and human replisomes containing Pol ?-primase, we reveal a conserved mechanism for the coordination of priming by the replisome. Pol ?-primase binds directly to the leading edge of the CMG (CDC45-MCM-GINS) replicative helicase via a complex interaction network. The non-catalytic PRIM2/Pri2 subunit forms two interfaces with CMG that are critical for in vitro DNA replication and yeast cell growth. These interactions position the primase catalytic subunit PRIM1/Pri1 directly above the exit channel for lagging-strand template single-stranded DNA (ssDNA), revealing why priming occurs efficiently only on the lagging-strand template and elucidating a mechanism for Pol ?-primase to overcome competition from RPA to initiate primer synthesis.
Mesh Terms:
Cryoelectron Microscopy, DNA Helicases, DNA Primase, DNA Replication, DNA, Single-Stranded, Humans, Saccharomyces cerevisiae
Mol Cell
Date: Aug. 17, 2023
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