Ubiquitin plays a central role in the regulation of protein degradation within cells. It is primarily used by cells to tag damaged or unneeded proteins for destruction by the proteasome, a key component of the cellular waste disposal system. This tagging process, known as ubiquitination, helps maintain protein balance and supports normal cell function. In research, ubiquitin is widely used to study protein turnover, signal transduction, and DNA repair mechanisms. It is also crucial in understanding diseases linked to protein misfolding and impaired degradation, such as Parkinson’s, Alzheimer’s, and certain cancers. Scientists use ubiquitin probes and assays to track protein degradation pathways and to develop targeted therapies, including proteolysis-targeting chimeras (PROTACs), which harness the ubiquitin system to eliminate disease-causing proteins. Additionally, ubiquitin pathways are explored in drug development, especially in oncology, where modulating protein stability can control the levels of oncogenic or tumor-suppressor proteins. Its role in immune regulation and inflammation also makes it a focus in immunology research.