Required for initiation of chromosomal DNA replication. Associated with ORC2. Interacts with HELB (PubMed:25933514). Component of the CMG helicase complex, composed of the MCM2-7 complex, the GINS complex and CDC45 (By similarity). Widely expressed, highest levels are found in adult testis and thymus and in fetal liver. Transcript peaks at G1-S transition, but total protein remains constant throughout the cell cycle. Expressed in multiple tissues during embryogenesis, including neural crest-derived structures. The disease is caused by variants affecting the gene represented in this entry. Belongs to the CDC45 family.