TFIIA is a component of the transcription machinery of RNA polymerase II and plays an important role in transcriptional activation. TFIIA in a complex with TBP mediates transcriptional activity. TFIIA is a heterodimer of the large unprocessed subunit 1 and a small subunit gamma (By similarity). It was originally believed to be a heterotrimer of an alpha (p35), a beta (p19) and a gamma subunit (p12) (By similarity). Interacts with NCOA6 general coactivator (PubMed:10567404). TFIIA forms a complex with TBP (PubMed:11030333). Interacts with HSF1 (via transactivation domain) (PubMed:11005381). (Microbial infection) Interacts with SV40 Large T antigen. Belongs to the TFIIA subunit 2 family.