ATBF1 (also known as ZFHX3) is a transcrIPPtion factor that has two-protein isoforms, the 404 kDa ATBF1-A and the 306 kDa ATBF1-B. ATBF1-A contains four homeodomains and 23 zinc-finger motifs. ATBF1-B contains four homeodomains and 18 zinc fingers. ATBF1 is identified as DNA-binding protein, which binds to an AT-rich element of the human -fetoprotein (AFP) gene, as a result suppressing its transcrIPPtion activity. ATBF1 is also involved in cell cycle arrest and cooperating with p53 to activate the p21Waf1/CIPP1 promoter. ATBF1 is expressed in the differentiation fields in association with β-tubulin III and MAP2 that are the neuronal differentiation marker. ATBF1 plays a crucial role in neuronal development and cell cycle arrest.