Ctf4p (chromosome transmission fidelity) has been reported to function in DNA 
metabolism and sister chromatid cohesion in Saccharomyces cerevisiae. In this 
study, a ctf4(S143F) mutant was isolated from a yeast genetic screen to identify 
replication-initiation proteins. The ctf4(S143F) mutant exhibits plasmid 
maintenance defects which can be suppressed by the addition of multiple origins 
to the plasmid, like other known replication-initiation mutants. We show that 
both ctf4(S143F) and ctf4Delta strains have defects in S phase entry and S phase 
progression at the restrictive temperature of 38 degrees C. Ctf4p localizes in 
the nucleus throughout the cell cycle but only starts to bind chromatin at the 
G1/S transition and then disassociates from chromatin after DNA replication. 
Furthermore, Ctf4p interacts with Mcm10p physically and genetically, and the 
chromatin association of Ctf4p depends on Mcm10p. Finally, deletion of CTF4 
destabilizes Mcm10p and Pol alpha in both mcm10-1 and MCM10 cells. These data 
indicate that Ctf4p facilitates Mcm10p to promote the DNA replication.