Accurate transcription initiation on TATA-containing class II genes involves the ordered assembly of RNA polymerase II (POLR2A, MIM 180660) and the general initiation factors TFIIA, TFIIB (MIM 189963), TFIID (MIM 313650), TFIIE (MIM 189962), TFIIF (MIM 189968), TFIIG/TFIIJ, and TFIIH (MIM 189972). The first step involves recognition of the TATA element by the TATA-binding subunit (TBP, MIM 600075) and may be regulated by TFIIA, a factor that interacts with both TBP and a TBP-associated factor (TAF, MIM 600475) in TFIID. TFIIA has 2 subunits (43 and 12 kD) in yeast and 3 subunits in higher eukaryotes. In HeLa extracts, it consists of a 35-kD alpha subunit and a 19-kD beta subunit encoded by the N- and C-terminal regions of GTF2A1 (MIM 600520), respectively, and a 12-kD gamma subunit encoded by GTF2A2 (DeJong et al., 1995 [PubMed 7724559]).