The Ubiquitin-Proteasome System (UPS) is a cellular mechanism that regulates protein degradation. It tags unwanted or damaged proteins with a small protein called ubiquitin, marking them for destruction. This process is essential for maintaining cellular health and function by removing proteins that could be harmful if allowed to accumulate. Once tagged, the proteins are directed to the proteasome, a large protein complex that breaks them down into smaller peptides. This recycling process not only helps control protein levels but also plays a crucial role in various cellular processes, including the cell cycle, immune response, and stress responses.