CHOP/DDIT3 was identified as a C/EBP-homologous protein that inhibits C/EBP and LAP in a dominant-negative manner. CHOP expression is induced by certain cellular stresses including starvation and the induced CHOP suppresses cell cycle progression from G1 to S phase. Studies also found that CHOP mediates the activation of GADD34 and Ero1-Lα expression during ER stress. GADD34 in turn dephosphorylates phospho-Ser51 of eIF2α thereby stimulating protein synthesis. Ero1-Lα promotes oxidative stress inside the endoplasmic reticulum (ER). The role of CHOP in the programmed cell death of ER-stressed cells is correlated with its role promoting protein synthesis and oxidative stress inside the ER.
