ELOB (elongin B) is a core scaffolding subunit of multiple cullin-RING E3 ubiquitin ligase complexes that regulate protein stability across diverse cellular processes. As a component of Cul2-RING and Cul5-RING complexes, ELOB catalyzes ubiquitination and proteasomal degradation of numerous substrates 1. In transcription, ELOB heterodimerizes with ELOC to form the Elongin complex, which binds RNA polymerase II and allosterically regulates the polymerase active center to stimulate elongation 2. During HIV-1 infection, the Vif protein hijacks the Cul5-ELOB-ELOC complex to ubiquitinate and degrade APOBEC3 antiviral proteins, facilitating viral replication 3. Beyond viral defense, ELOB participates in developmental signaling by promoting nuclear SMAD1 degradation to restrict BMP signaling 4, and regulates target-directed miRNA degradation through CRL3 complex assembly 5. ELOB dysregulation promotes cancer progression: elevated ELOB in breast cancer cells triggers p14/ARF degradation, enhancing proliferation and chemoresistance 1, while high ELOB expression correlates with radiotherapy resistance in triple-negative breast cancer 6. Additionally, ELOB participates in reproductive function through regulation of hydrogen sulfide metabolism 7. These multifaceted roles establish ELOB as a central regulator of protein stability with significant implications for development, immunity, and cancer biology.