The function of TAF4 (TATA-box binding protein associated factor 4, Ensembl gene identifier ENSG00000130699) 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:10594036, PubMed:33795473, PubMed:8942982). TAF4 may maintain an association between the TFIID and TFIIA complexes, while bound to the promoter, together with TBP, during PIC assembly (PubMed:33795473). Potentiates transcriptional activation by the AF-2S of the retinoic acid, vitamin D3 and thyroid hormone (PubMed:9192867). {ECO:0000269|PubMed:10594036, ECO:0000269|PubMed:33795473, ECO:0000269|PubMed:8942982, ECO:0000269|PubMed:9192867}.