Transcription factor II A

general transcription factor IIA, 1, 19/37kDa
Identifiers
Symbol	GTF2A1
Entrez	2957
HUGO	4646
OMIM	600520
RefSeq	NM_201595
UniProt	P52655
Other data
Locus	Chr. 14 q31

general transcription factor IIA, 2, 12kDa
Identifiers
Symbol	GTF2A2
Entrez	2958
HUGO	4647
OMIM	600519
RefSeq	NM_004492
UniProt	P52657
Other data
Locus	Chr. 15 q21.3

Transcription factor TFIIA is a nuclear protein involved in the RNA polymerase II-dependent transcription of DNA.^[1] TFIIA is one of several general (basal) transcription factors (GTFs) that are required for all transcription events that use RNA polymerase II. Other GTFs include TFIID, a complex composed of the TATA binding protein TBP and TBP-associated factors (TAFs), as well as the factors TFIIB, TFIIE, TFIIF, and TFIIH. 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.

Functions

TFIIA interacts with the TBP subunit of TFIID and aids in the binding of TBP to TATA-box containing promoter DNA.^[2] Interaction of TFIIA with TBP facilitates formation of and stabilizes the preinitiation complex. Interaction of TFIIA with TBP also results in the exclusion of negative (repressive) factors that might otherwise bind to TBP and interfere with PIC formation. TFIIA also acts as a coactivator for some transcriptional activators, assisting with their ability to increase, or activate, transcription. 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. Genetic analysis in yeast has shown that TFIIA is essential for viability.

TFIIA genes

TFIIA is encoded by two separate genes, one of which encodes a large subunit (TFIIAalpha/beta, TFIIAL, TOA1; gene name GTF2A1)^[3] and another which encodes a small subunit (TFIIAgamma, TFIIAS, TOA2; gene name GTF2A2).^[4] In humans, the sizes of the encoded proteins are approximately 55 kD and 12 kD. 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. 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. The large subunit is often observed to be proteolytically processed into two smaller subunits (alpha and beta) of approximately 35 kD and 19 kD. A second gene encoding a large TFIIA 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 TFIIA-like regulatory role for gene expression only in germ cells.

References

1. Høiby T, Zhou H, Mitsiou DJ, Stunnenberg HG (2007). "A facelift for the general transcription factor TFIIA". Biochim. Biophys. Acta 1769 (7-8): 429–36. doi:10.1016/j.bbaexp.2007.04.008. PMID 17560669.
2. Tang H, Sun X, Reinberg D, Ebright RH (1996). "Protein-protein interactions in eukaryotic transcription initiation: structure of the preinitiation complex". Proc. Natl. Acad. Sci. U.S.A. 93 (3): 1119–24. doi:10.1073/pnas.93.3.1119. PMC 40041. PMID 8577725.
3. DeJong J, Roeder RG (1993). "A single cDNA, hTFIIA/alpha, encodes both the p35 and p19 subunits of human TFIIA". Genes Dev. 7 (11): 2220–34. doi:10.1101/gad.7.11.2220. PMID 8224848.
4. Ozer J, Moore PA, Bolden AH, Lee A, Rosen CA, Lieberman PM (1994). "Molecular cloning of the small (gamma) subunit of human TFIIA reveals functions critical for activated transcription". Genes Dev. 8 (19): 2324–35. doi:10.1101/gad.8.19.2324. PMID 7958899.

External links

• Transcription Factor TFIIA at the US National Library of Medicine Medical Subject Headings (MeSH)