Transcription factor II A

{{Short description|Nuclear protein}} {{infobox protein | Name = [[GTF2A1|general transcription factor IIA, 1, 19/37kDa]] | caption = | image = | width = | HGNCid = 4646 | Symbol = [[GTF2A1]] | AltSymbols = | EntrezGene = 2957 | OMIM = 600520 | RefSeq = NM_201595 | UniProt = P52655 | PDB = | ECnumber = | Chromosome = 14 | Arm = q | Band = 31 | LocusSupplementaryData = }}{{infobox protein | Name = general transcription factor IIA, 2, 12kDa | caption = | image = | width = | HGNCid = 4647 | Symbol = GTF2A2 | AltSymbols = | EntrezGene = 2958 | OMIM = 600519 | RefSeq = NM_004492 | UniProt = P52657 | PDB = | ECnumber = | Chromosome = 15 | Arm = q | Band = 21.3 | LocusSupplementaryData = }}

'''Transcription factor TF_IIA''' is a [[cell nucleus|nuclear]] [[protein]] involved in the [[RNA polymerase II]]-dependent [[transcription (genetics)|transcription]] of [[DNA]].<ref name="pmid17560669">{{cite journal | vauthors = Høiby T, Zhou H, Mitsiou DJ, Stunnenberg HG | title = A facelift for the general transcription factor TFIIA | journal = Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression | volume = 1769 | issue = 7–8 | pages = 429–36 | year = 2007 | pmid = 17560669 | doi = 10.1016/j.bbaexp.2007.04.008 | hdl = 2066/34866 | hdl-access = free }}</ref> TF_IIA is one of several general (basal) [[transcription factor]]s ([[General transcription factor|GTF]]s) that are required for all transcription events that use RNA polymerase II. Other GTFs include [[Transcription factor II D|TF_IID]], a complex composed of the [[TATA binding protein]] TBP and TBP-associated factors (TAFs), as well as the factors [[Transcription factor II B|TF_IIB]], [[Transcription factor II E|TF_IIE]], [[Transcription factor II F|TF_IIF]], and [[Transcription factor II H|TF_IIH]]. Together, these factors are responsible for [[promoter (biology)|promoter]] recognition and the formation of a transcription [[Transcription preinitiation complex|preinitiation complex]] (PIC) capable of initiating [[RNA]] synthesis from a DNA template.

==Functions==

TF_IIA interacts with the [[TATA Binding Protein|TBP]] subunit of [[Transcription factor II D|TF_IID]] and aids in the binding of TBP to [[TATA box|TATA-box]] containing [[promoter (genetics)|promoter]] DNA.<ref>{{cite journal | vauthors = Tang H, Sun X, Reinberg D, Ebright RH | title = Protein-protein interactions in eukaryotic transcription initiation: structure of the preinitiation complex | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 93 | issue = 3 | pages = 1119–24 | date = February 1996 | pmid = 8577725 | pmc = 40041 | doi = 10.1073/pnas.93.3.1119 | bibcode = 1996PNAS...93.1119T | author4-link = Richard H. Ebright | doi-access = free }}</ref><ref>{{cite journal | vauthors = Louder RK, He Y, López-Blanco JR, Fang J, Chacón P, Nogales E | title = Structure of promoter-bound TFIID and model of human pre-initiation complex assembly | journal = Nature | volume = 531 | issue = 7596 | pages = 604–9 | date = March 2016 | pmid = 27007846 | doi = 10.1038/nature17394 | pmc=4856295| bibcode = 2016Natur.531..604L }}</ref> Interaction of TF_IIA with TBP facilitates formation of and stabilizes the [[Transcription preinitiation complex|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 [[transcription coregulator|coactivator]] for some transcriptional [[activator (genetics)|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]] has shown that TF_IIA is essential for viability.

==Structure==

TF_IIA is a heterodimer with two [[protein subunit|subunits]]: one large unprocessed (subunit 1, or alpha/beta; gene name {{gene|GTF2A1}}) and one small (subunit 2, or gamma; gene name {{gene|GTF2A2}}).<ref name="pmid8224848">{{cite journal | vauthors = DeJong J, Roeder RG | title = A single cDNA, hTFIIA/alpha, encodes both the p35 and p19 subunits of human TFIIA | journal = Genes & Development | volume = 7 | issue = 11 | pages = 2220–34 | date = November 1993 | pmid = 8224848 | doi = 10.1101/gad.7.11.2220 | doi-access = free }}</ref><ref name="pmid7958899">{{cite journal | vauthors = Ozer J, Moore PA, Bolden AH, Lee A, Rosen CA, Lieberman PM | title = Molecular cloning of the small (gamma) subunit of human TFIIA reveals functions critical for activated transcription | journal = Genes & Development | volume = 8 | issue = 19 | pages = 2324–35 | date = October 1994 | pmid = 7958899 | doi = 10.1101/gad.8.19.2324 | doi-access = free }}</ref> It was originally believed to be a heterotrimer of an alpha (p35), a beta (p19) and a gamma subunit (p12). In humans, the sizes of the encoded proteins are approximately 55&nbsp;[[Dalton (unit)|kD]] and 12&nbsp;kD. Both genes are present in species ranging from humans to yeast, and their protein products interact to form a [[protein complex|complex]] composed of a [[beta barrel]] [[protein domains|domain]] and an [[helix bundle|alpha helical bundle]] domain. It is the [[N-terminus|N-terminal]] and [[C-terminus|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 sequence|conserved]]. A second gene encoding a large TF_IIA subunit has been found in some higher [[eukaryote]]s. This gene, ALF/TFIIAtau (gene name {{gene|GTF2A1LF}}) is expressed only in [[oocyte]]s and [[spermatocyte]]s, suggesting it has a TF_IIA-like regulatory role for gene expression only in [[germ cell]]s.

== References == {{Reflist}}

== External links == * {{MeshName|Transcription+Factor+TFIIA}}

{{Transcription factors|g2}}

[[Category:Gene expression]] [[Category:Transcription factors]]