TAF4 (TATA-box binding protein associated factor 4) is a crucial subunit of the TFIID complex that plays essential roles in RNA polymerase II-mediated transcription initiation and cellular differentiation. As part of TFIID, TAF4 facilitates preinitiation complex assembly by maintaining associations between TFIID and TFIIA complexes at promoters 1. The protein contains a conserved hTAF4-TAFH domain that undergoes alternative splicing to regulate cellular fate decisions 23. During stem cell differentiation, TAF4 isoforms lacking the hTAF4-TAFH domain promote chondrogenic and neuronal differentiation while suppressing proliferation 23. TAF4 also functions as a transcriptional coactivator, being recruited by YAP/TAZ to enhance oncogenic programs in cancer cells 4. Clinically, de novo loss-of-function variants in TAF4 cause intellectual developmental disorder, characterized by intellectual disability, behavioral abnormalities, and facial dysmorphisms 5. The protein's alternative splicing patterns vary across brain regions and developmental stages, suggesting tissue-specific regulatory functions 3. TAF4's dual role in transcriptional regulation and differentiation control makes it a potential therapeutic target for both developmental disorders and cancer treatment.