The eukaryotic replisome is a crucial determinant of genome stability, but its 
structure is still poorly understood. We found previously that many regulatory 
proteins assemble around the MCM2-7 helicase at yeast replication forks to form 
the replisome progression complex (RPC), which might link MCM2-7 to other 
replisome components. Here, we show that the RPC associates with DNA polymerase 
alpha that primes each Okazaki fragment during lagging strand synthesis. Our 
data indicate that a complex of the GINS and Ctf4 components of the RPC is 
crucial to couple MCM2-7 to DNA polymerase alpha. Others have found recently 
that the Mrc1 subunit of RPCs binds DNA polymerase epsilon, which synthesises 
the leading strand at DNA replication forks. We show that cells lacking both 
Ctf4 and Mrc1 experience chronic activation of the DNA damage checkpoint during 
chromosome replication and do not complete the cell cycle. These findings 
indicate that coupling MCM2-7 to replicative polymerases is an important feature 
of the regulation of chromosome replication in eukaryotes, and highlight a key 
role for Ctf4 in this process.