Transcription factor IIA, alpha/beta subunit (IPR004855)

Short name: TFIIA_asu/bsu

Overlapping homologous superfamilies


Family relationships



Transcription factor IIA (TFIIA) is one of several factors that form part of a transcription pre-initiation complex along with RNA polymerase II, the TATA-box-binding protein (TBP) and TBP-associated factors, on the TATA-box sequence upstream of the initiation start site. After initiation, some components of the pre-initiation complex (including TFIIA) remain attached and re-initiate a subsequent round of transcription. TFIIA binds to TBP to stabilise TBP binding to the TATA element. TFIIA also inhibits the cytokine HMGB1 (high mobility group 1 protein) binding to TBP [PMID: 12818428], and can dissociate HMGB1 already bound to TBP/TATA-box.

Human and Drosophila TFIIA have three subunits: two large subunits, LN/alpha and LC/beta, derived from the same gene, and a small subunit, S/gamma. Yeast TFIIA has two subunits: a large TOA1 subunit that shows sequence similarity to the N-terminal of LN/alpha and the C-terminal of LC/beta, and a small subunit, TOA2 that is highly homologous with S/gamma. The conserved regions of the large and small subunits of TFIIA combine to form two domains: a four-helix bundle (helical domain) composed of two helices from each of the N-terminal regions of TOA1 and TOA2 in yeast; and a beta-barrel (beta-barrel domain) composed of beta-sheets from the C-terminal regions of TOA1 and TOA2 [PMID: 8610010].

This entry represents the precursor that yields both the alpha and beta subunits of TFIIA. The TFIIA heterotrimer is an essential general transcription initiation factor for the expression of genes transcribed by RNA polymerase II [PMID: 11089979].

GO terms

Biological Process

GO:0006367 transcription initiation from RNA polymerase II promoter

Molecular Function

No terms assigned in this category.

Cellular Component

GO:0005672 transcription factor TFIIA complex

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.