Together, these factors are responsible for promoter recognition and the formation of a transcription preinitiation complex (PIC) capable of initiating RNA synthesis from a DNA template.
[2][3] Interaction of TFIIA with TBP facilitates formation of and stabilizes the preinitiation complex.
The requirement for TFIIA in vitro transcription systems has been variable, and it can be considered either as a GTF and/or a loosely associated TAF-like coactivator.
Both genes are present in species ranging from humans to yeast, and their protein products interact to form a complex composed of a beta barrel domain and an alpha helical bundle domain.
A second gene encoding a large TFIIA subunit has been found in some higher eukaryotes.