Transcription initiation factor TFIID subunit 1 (TAF1) is the largest component and core scaffold of the TFIID basal transcription factor complex. TAF1 contains novel N- and C-terminal Ser/Thr kinase domains which can autophosphorylate or transphosphorylate other transcription factors. TAF1 phosphorylates TP53 on 'Thr-55' which leads to MDM2-mediated degradation of TP53. It also phosphorylates GTF2A1 and GTF2F1 on Ser residues. TAF1 possesses DNA-binding activity and is essential for progression of the G1 phase of the cell cycle [taken from the Universal Protein Resource (UniProt) www.uniprot.org/uniprot/P21675].