Transcription factor TFIIA is a
nuclearprotein 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][3] 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.
Structure
TFIIA is a heterodimer with two
subunits: one large unprocessed (subunit 1, or alpha/beta; gene name GTF2A1) and one small (subunit 2, or gamma; gene name GTF2A2).[4][5] 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
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 barreldomain 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 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
^Høiby T, Zhou H, Mitsiou DJ, Stunnenberg HG (2007). "A facelift for the general transcription factor TFIIA". Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression. 1769 (7–8): 429–36.
doi:
10.1016/j.bbaexp.2007.04.008.
hdl:2066/34866.
PMID17560669.
Transcription factor TFIIA is a
nuclearprotein 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][3] 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.
Structure
TFIIA is a heterodimer with two
subunits: one large unprocessed (subunit 1, or alpha/beta; gene name GTF2A1) and one small (subunit 2, or gamma; gene name GTF2A2).[4][5] 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
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 barreldomain 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 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
^Høiby T, Zhou H, Mitsiou DJ, Stunnenberg HG (2007). "A facelift for the general transcription factor TFIIA". Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression. 1769 (7–8): 429–36.
doi:
10.1016/j.bbaexp.2007.04.008.
hdl:2066/34866.
PMID17560669.