Phosphopeptide binding by Sld3 links Dbf4‐dependent kinase to MCM replicative helicase activation

Abstract

The initiation of eukaryotic DNA replication requires the assembly of active CMG (Cdc45‐MCM‐GINS) helicases at replication origins by a set of conserved and essential firing factors. This process is controlled during the cell cycle by cyclin‐dependent kinase (CDK) and Dbf4‐dependent kinase (DDK), and in response to DNA damage by the checkpoint kinase Rad53/Chk1. Here we show that Sld3, previously shown to be an essential CDK and Rad53 substrate, is recruited to the inactive MCM double hexamer in a DDK‐dependent manner. Sld3 binds specifically to DDK‐phosphorylated peptides from two MCM subunits (Mcm4, 6) and then recruits Cdc45. MCM mutants that cannot bind Sld3 or Sld3 mutants that cannot bind phospho‐MCM or Cdc45 do not support replication. Moreover, phosphomimicking mutants in Mcm4 and Mcm6 bind Sld3 without DDK and facilitate DDK‐independent replication. Thus, Sld3 is an essential “reader” of DDK phosphorylation, integrating signals from three distinct protein kinase pathways to coordinate DNA replication during S phase.

Cited by papers we hold 4

• Cell cycle-dependent TICRR/TRESLIN and MTBP chromatin binding mechanisms and patterns · 2025
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• Structure of DNA-CMG-Pol epsilon elucidates the roles of the non-catalytic polymerase modules in the eukaryotic replisome · 2018
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• How the Eukaryotic Replisome Achieves Rapid and Efficient DNA Replication · 2017
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• Chromosome Duplication in Saccharomyces cerevisiae · 2016
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