AFF4 (ALF transcription elongation factor 4) serves as a central scaffolding protein in the super elongation complex (SEC), which enhances RNA polymerase II transcription elongation by suppressing polymerase pausing 1. AFF4 recruits other SEC components through direct interactions with ELL proteins and the P-TEFb complex, facilitating transcriptional elongation of target genes 1. The protein plays critical roles in cellular differentiation processes, promoting osteogenic differentiation of mesenchymal stem cells through regulation of ID1 expression and BMP2 signaling 2, while also enhancing adipogenic differentiation by targeting autophagy-related genes ATG5 and ATG16L1 3. In disease contexts, AFF4 mutations cause CHOPS syndrome, a disorder of transcriptional regulation characterized by cognitive impairment and developmental abnormalities 45. AFF4 also contributes to cancer progression, particularly in lung adenocarcinoma where it promotes glycolysis and cisplatin resistance through PTEN/PI3K/AKT/mTOR pathway modulation 6. Additionally, AFF4 facilitates HIV-1 replication by forming complexes with viral Tat protein and P-TEFb, making it a potential therapeutic target 1. The protein's diverse functions highlight its importance in transcriptional control, development, and pathological processes.