The function of TAF9 (TATA-box binding protein associated factor 9, Ensembl gene identifier ENSG00000273841) is as follows. The TFIID basal transcription factor complex plays a major role in the initiation of RNA polymerase II (Pol II)-dependent transcription (PubMed:33795473). TFIID recognizes and binds promoters with or without a TATA box via its subunit TBP, a TATA-box-binding protein, and promotes assembly of the pre-initiation complex (PIC) (PubMed:33795473). The TFIID complex consists of TBP and TBP-associated factors (TAFs), including TAF1, TAF2, TAF3, TAF4, TAF5, TAF6, TAF7, TAF8, TAF9, TAF10, TAF11, TAF12 and TAF13 (PubMed:33795473). TAF9 is also a component of the TBP-free TAFII complex (TFTC), the PCAF histone acetylase complex and the STAGA transcription coactivator-HAT complex (PubMed:15899866). TAF9 and its paralog TAF9B are involved in transcriptional activation as well as repression of distinct but overlapping sets of genes (PubMed:15899866). Essential for cell viability (PubMed:15899866). May have a role in gene regulation associated with apoptosis (PubMed:15899866). .