Abstract TATA-box binding protein-associated factor 1 (TAF1) is the largest component of transcription factor IID, a fundamental multi-protein complex for RNA polymerase II-mediated transcription. TAF1 is essential for promoter recognition, coactivator interaction and normal development. Mutations in TAF1 cause developmental disorders and the lethal neurodegenerative disease X-linked dystonia-Parkinsonism. Our previous work suggested that this approximately 170 kb gene has a more complex set of