G1 is an important phase of the cell cycle where the decision whether to enter the next round of DNA replication and cell division is made. Most cells spend a large portion of G1 preparing to replicate their DNA. Replication initiates from regions in the chromosomal DNA called replication origins. Preparation for replication is a multi-staged process, involving the recruitment of a series of different proteins to the origins. The assembly of a multi-subunit complex finally results in the separation of the two DNA strands, loading of the DNA polymerase, and initiation of DNA replication We are most interested in the regulation of the processes leading up to the initiation of DNA replication, both in unperturbed cell cycle and in response to cellular stress.