S100A3, also known as Protein S-100E and S100 calcium-binding protein A3, belongs to the S-100 family of proteins containing 2 EF-hand calcium-binding motifs. The S100 proteins act as multifactional signaling factors that are involved in the regulation of diverse cellular processes such as cell cycle progression and differentiation. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells.