FACT-(H3-H4) complex stimulates Pol α activity to coordinate DNA synthesis with nucleosome assembly

Deficiencies in replication-coupled (RC) nucleosome assembly often lead to reduced DNA replication rate, but the precise mechanism underlying this process remains unsolved. Here, we discovered that H3-H4, but not H2A-H2B, mediates the interaction between FACT and the primase-polymerase complex DNA Pol α. This interaction stimulates the DNA polymerase activity of Pol α, and is indispensable for Okazaki fragment synthesis and replication fork progression. Moreover, the Pol1-N domain of Pol α provides a specific binding site for FACT and H3-H4. Furthermore, CAF-1 and Rtt106-mediated replication-coupled nucleosome assembly pathways regulate this interaction. Together, we propose that the FACT-(H3-H4)-Pol α interaction acts as a “Pre-Warning System” that regulates DNA replication, ensuring proper coordination between DNA synthesis and nucleosome assembly.