Wang, Z.-G.; Knowles, S.; Wang, F.; Chai, W.

DNA replication is a strictly regulated process during cell proliferation to ensure faithful duplication of the genome. Its firing and elongation can be arrested or temporally inhibited in response to a variety of internal and external causes. Inside cells numerous factors including cell cycle checkpoints, protein kinases, and others are involved in the control of this process to maintain genome integrity. Here, we describe that NuMA, a nuclear scaffolding protein, plays an important role in regulating DNA replication. We show that NuMA is present at active replication forks, and its deficiency impairs cell viability, reduces the replication fork speed and increases origin firing, leading to increased level of {gamma}H2AX and the activation of the ATM-CHK2 DNA damage response pathway. Mechanistically, our results show that NuMA depletion reduced the association of multiple key replisome proteins to replication forks, suggesting that NuMA is essential for efficient replisome proteins binding to ongoing forks. Our study uncovers a novel function of NuMA in maintaining genome stability, providing new insights into the important role of nuclear structural proteins in safeguarding DNA replication.