MCM10 has been shown to be a component for the elongation step of chromosome replication in model organisms such as yeast. In the accompanying manuscript [J.H. Park, S.W. Bang, Y. Jeon, S. Kang, D.S. Hwang, Knockdown of human MCM10 exhibits delayed and incomplete chromosome replication, Biochem. Biophys. Res. Commun. (2007) 365 (2008) 575-582.], we reported that knockdown of human MCM10 protein exhibits delayed and incomplete chromosomal DNA replication. In this report, we examined the consequences of the delayed and incomplete chromosome replication in the cell cycle. Defective and incomplete chromosome replication by MCM10 knockdown activated a checkpoint pathway, composed of Chk1 and Cdc25, that inhibited Cdk1. Chk2 appeared not to be involved in the CdkI inhibition. The function of CdkI is necessary for the transition from G2 to mitotic phase, thereby CdkI inhibition by checkpoint arrested MCM10-knockdown cells in G2 phase. The prolonged depletion of MCM10 resulted in DNA damage followed by cell death. These results indicate that MCM10 protein is essential for maintaining genome integrity as well as cell cycle progression. (c) 2007 Elsevier Inc. All rights reserved.