The effects of CDC45 mutations on DNA replication and genome stability

Cdc45 is a non-catalytic subunit of the CMG helicase complex and is recruited to the autonomously replicating sequence at the onset of DNA replication. Cdc45 protein is required for the initiation of the DNA replication process as well as for the nascent DNA strand synthesis. It interacts with Mcm2 and Psf1 elements of CMG helicase, as well as with Sld3, and initiation factor, and Pol2, the catalytic subunit of DNA polymerase epsilon (Pol ε). In this study, we analyzed the effects of amino acid substitutions in Cdc45 regions involved in the interaction of this protein with Mcm2-7 (Cdc45-1), Psf1 (Cdc45-26), and Sld3 (Cdc45-25, Cdc45-35). We found that mutations in CDC45 result in defective DNA replication. At the restrictive temperature, mutant cells are unable to initiate DNA replication, while in permissive conditions, they demonstrate DNA synthesis delay. Moreover, we observed increased mutation rates, mainly dependent on DNA polymerase zeta (Pol ζ), as well as increased incidence of replication errors. These findings contribute to our understanding of Cdc45’s function in eukaryotic cells. Changes in the cell functioning observed in this study, related to the defect in Cdc45 function, may be helpful in understanding some diseases associated with CDC45 .