The components of the replisome that preserve genomic stability by controlling 
the progression of eukaryotic DNA replication forks are poorly understood. Here, 
we show that the GINS (go ichi ni san) complex allows the MCM (minichromosome 
maintenance) helicase to interact with key regulatory proteins in large 
replisome progression complexes (RPCs) that are assembled during initiation and 
disassembled at the end of S phase. RPC components include the essential 
initiation and elongation factor, Cdc45, the checkpoint mediator Mrc1, the 
Tof1-Csm3 complex that allows replication forks to pause at protein-DNA 
barriers, the histone chaperone FACT (facilitates chromatin transcription) and 
Ctf4, which helps to establish sister chromatid cohesion. RPCs also interact 
with Mcm10 and topoisomerase I. During initiation, GINS is essential for a 
specific subset of RPC proteins to interact with MCM. GINS is also important for 
the normal progression of DNA replication forks, and we show that it is required 
after initiation to maintain the association between MCM and Cdc45 within RPCs.