CHOP (also known as growth arrest and DNA-damage-inducible protein GADD153) is a 27 kD member of the C/EBP transcription factor family containing a basic region involved in DNA binding and a leucine zipper domain. This nuclear protein functions as a dimer to inhibit the DNA-binding activity of C/EBP and LAP by forming heterodimers that cannot bind DNA target sequences. CHOP (GADD153) is induced by endoplasmic-reticulum stress and nutrient deprivation. Phosphorylation by p38-MAP kinase enhances activity of this protein while CK2 phosphorylation decreases activity. CHOP (GADD153) has been shown to interact with c-jun, c-fos, C/EBP, and LAP. The Poly6436 antibody has been shown to be useful for Western blotting of the human CHOP protein.