Transcription factor II A

promoter recognition and the formation of a transcription preinitiation complex (PIC) capable of initiating RNA

TBP subunit of TF_IID and aids in the binding of TBP to TATA-box containing promoter DNA.^[2][3] Interaction of TF_IIA with TBP facilitates formation of and stabilizes the preinitiation complex. Interaction of TF_IIA with TBP also results in the exclusion of negative (repressive) factors that might otherwise bind to TBP and interfere with PIC formation. TF_IIA also acts as a coactivator for some transcriptional activators, assisting with their ability to increase, or activate, transcription. The requirement for TF_IIA in vitro transcription systems has been variable, and it can be considered either as a GTF and/or a loosely associated TAF-like coactivator. Genetic analysis in yeast

domain and an alpha helical bundle domain. It is the N-terminal and C-terminal regions of the large subunit that participate in interactions with the small subunit. These regions are separated by another domain whose sequence is always present in large subunits from various species but whose size varies and whose sequence is poorly conserved. A second gene encoding a large TF_IIA subunit has been found in some higher eukaryotes. This gene, ALF/TFIIAtau (gene name GTF2A1LF) is expressed only in oocytes and spermatocytes, suggesting it has a TF_IIA-like regulatory role for gene expression only in germ cells