C/EBP homologous protein (CHOP) is a transcription factor that regulates apoptosis in response to cellular stress. CHOP also known as growth arrest and DNA damage 153 (GADD153) was first cloned because of its induction in response to genotoxic stress such as UV irradiation. CHOP has now been shown to be induced mainly by ER-stress (1). CHOP is normally expressed at low levels and localizes to the cytoplasm. Cellular stress triggers an upregulation of CHOP levels and accumulation in the nucleus where it can act as either a transcriptional repressor or activator (1).
