Zinc finger homeodomain enhancer-binding protein (Zfhep/Zfhx1a) is a transcription factor essential for immune system development, skeletal patterning, and life. Regulation of the interleukin-2 gene in T cells has been suggested to depend on posttranslational processing of Zfhep, however. no modifications of Zfhep are known, Here we demonstrate that Zfhep is present in both hyperphosphorylated and hypophosphorylated forms. Western blot analysis demonstrates two forms of Zfhep with different mobilities. Differences in phosphorylation are sufficient to explain the difference in mobilities. Zfhep is primarily phosphorylated on Ser and Thr residues since PP2A dephosphorylates the slower mobility band. Treatment of nuclear extract with O-GlcNAcase did not detect O-linked sugar. Importantly, post-translational processing is cell-specific. Doublets of Zfhep were detected in Five cell lines, whereas 6 cell lines contain only. or predominantly. non-phosphorlated Zfhep. and Saos-2 cells contain predominantly the phosphorylated form. These data provide the first demonstration that Zfhep is post-translationally modified. (C) 2002 Elsevier Science (USA). All rights reserved.