CdcA3 (Cell division cycle-associated protein 3), also known as TOME1 (Trigger of mitotic entry protein 1) and GRCC8 (Gene-rich cluster protein C8), is a 268 amino acid cytoplasmic protein that is required for entry into mitosis. By participating with E3 ligase complexes, CdcA3 is involved in ubiquination and degradation of the mitosis-inhibitory kinase Wee 1, leading to the dephosphorylation of Cdc2 in the late G2 phase. CdcA3 itself is targeted for destruction by anaphase promoting complex (APC) in the G1 phase of the cell cycle, then allowing for Wee 1 accumulation during interphase.