Biol. Pharm. Bull. 29(9) 1830—1835 (2006)

homeodomain motifs. Drosophila ZFH-1 contains one homeodomain and 9 zinc fingers, and Drosophila ZFH-2 contains 3 homeodomains and 16 zinc fingers Human ATBF1 (AT motif binding factor 1) has four homeodomains and 23 zinc fingers. The first three homeodomains in ATBF1 and ZFH-2 are highly homologous and arranged collinearly. ATBF1 was initially isolated as a transcription factor inhibiting the enhancer activity of the human alphafetoprotein gene. The mouse ATBF1 protein shares 93% amino acid identity with human ATBF1. Studies of ATBF1 expression in developing murine brain suggest that ATBF1 has a role in early development of the central nervous system. ATBF1 has also been reported to be involved in the maintenance of the undifferentiated state of myoblasts. Recently, various ATBF1 binding proteins have been identified which include Myb, PIAS3, and p53. Jointly with these proteins, ATBF1 regulates various genes important for cell cycle and growth. Zfhx4 is a homeodomain-zinc finger protein most recently identified in mice. ( Other aliases of mouse Zfhx4 are Zfh-4 or Zfh4.) It carries four homeodomains and 22 zinc fingers and is most similar to ATBF1 among the known homeodomain-zinc finger proteins. The expression of Zfhx4 is prominent in developing brain and muscle. McMullan et al. (2002) have identified a chromosomal breakpoint in the human homolog in a patient with congenital bilateral isolated ptosis. Here, we report molecular cloning of the human homolog of Zfhx4 cDNA and genomic organization of the ZFHX4.