UBAP1 (Ubiquitin-associated protein 1) is a conserved eukaryotic protein implicated in ubiquitin-dependent cellular processes, primarily through its role in the endosomal sorting complex required for transport (ESCRT) pathway. As a subunit of ESCRT-I, UBAP1 facilitates the sorting of ubiquitinated cargo proteins into intraluminal vesicles of multivesicular bodies (MVBs), a critical step in lysosomal degradation, receptor downregulation, and viral budding. Structurally, it contains a ubiquitin-binding UBA domain, enabling recognition of ubiquitinated substrates, and a central coiled-coil region mediating ESCRT-I assembly. Dysregulation of UBAP1 has been linked to cancer progression, neurodegenerative disorders, and immune regulation. For instance, reduced UBAP1 expression correlates with poor prognosis in malignancies like hepatocellular carcinoma, while mutations are associated with hereditary spastic paraplegia. UBAP1 antibodies are essential tools for studying its expression, localization, and interactions in these contexts. They are widely used in techniques such as Western blotting, immunofluorescence, and co-immunoprecipitation to elucidate UBAP1’s role in membrane trafficking, autophagy, and disease mechanisms. Recent studies also explore UBAP1’s potential as a therapeutic target, particularly in cancers exploiting ESCRT dysfunction.