Involved in the regulation of growth and apoptosis. Mediates activation of stress-responsive MTK1/MEKK4 MAPKKK. Undergoes concentration-dependent homodimerization, which is required for growth inhibititory activity and enhances interaction with PCNA. Interacts with GADD45GIP1. Interacts with PCNA. Two central helices mediate homodimerization through parallel packing. Belongs to the GADD45 family. GADD45G entry