DDI1 (DNA-Damage Inducible 1 Homolog 1) is a protein involved in key cellular processes such as DNA repair, cell cycle regulation, and the ubiquitin-proteasome system. It plays a critical role in responding to DNA damage by acting as a ubiquitin-dependent protease, helping degrade specific proteins to maintain cellular health. Due to its multifunctional roles, DDI1 is important for protecting cells from stress and may be linked to cancer and other diseases related to DNA damage and repair.