Minichromosome maintenance protein 3 (MCM3) is a protein essential for the initiation of DNA replication. MCM3-associated protein (MCM3AP), also known as GANP or MAP80, is a 1980 amino acid protein which binds to MCM3. MCM3AP is an acetyltransferase that acetylates MCM3, thereby playing an indirect role in DNA replication. MCM3AP is also believed to be involved in the nuclear localization of MCM3. Localized to the nucleus and the cytoplasm, GANP (MCM3AP) is thought to have phosphorylation-dependent DNA-primase activity that is up-regulated in germinal center regions. MCM3AP contains a nuclear localization signal, a coiled-coil structure and four LXXLL motifs.