GINS maintains association of Cdc45 with MCM in replisome progression complexes at eukaryotic DNA replication forks

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.