8b9a
S. cerevisiae replisome + Ctf4, bound by pol alpha primase. Complex engaged with a fork DNA substrate containing a 60 nucleotide lagging strand.
Structural highlights
FunctionMCM2_YEAST Acts as component of the MCM2-7 complex (MCM complex) which is the putative replicative helicase essential for 'once per cell cycle' DNA replication initiation and elongation in eukaryotic cells. The active ATPase sites in the MCM2-7 ring are formed through the interaction surfaces of two neighboring subunits such that a critical structure of a conserved arginine finger motif is provided in trans relative to the ATP-binding site of the Walker A box of the adjacent subunit. The six ATPase active sites, however, are likely to contribute differentially to the complex helicase activity; specifically the MCM2-MCM5 association is proposed to be reversible and to mediate a open ring conformation which may facilitate DNA loading. Once loaded onto DNA, double hexamers can slide on dsDNA in the absence of ATPase activity. Necessary for cell growth.[1] [2] Publication Abstract from PubMedDuring eukaryotic DNA replication, Pol alpha-primase generates primers at replication origins to start leading-strand synthesis and every few hundred nucleotides during discontinuous lagging-strand replication. How Pol alpha-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 alpha-primase, we reveal a conserved mechanism for the coordination of priming by the replisome. Pol alpha-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 alpha-primase to overcome competition from RPA to initiate primer synthesis. How Pol alpha-primase is targeted to replisomes to prime eukaryotic DNA replication.,Jones ML, Aria V, Baris Y, Yeeles JTP Mol Cell. 2023 Jul 27:S1097-2765(23)00511-7. doi: 10.1016/j.molcel.2023.06.035. PMID:37506699[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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