Transcription initiation factor TFIID subunit 1, also known as transcription initiation factor TFIID 250 kDa subunit (TAFII-250) or TBP-associated factor 250 kDa (p250), is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
that in humans is encoded by the ''TAF1''
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
Function
Initiation of
transcription by
RNA polymerase II
RNA polymerase II (RNAP II and Pol II) is a Protein complex, multiprotein complex that Transcription (biology), transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. It is one of the three RNA pol ...
requires the activities of more than 70 polypeptides. The protein that coordinates these activities is the basal transcription factor
TFIID, which binds to the core promoter to position the polymerase properly, serves as the scaffold for assembly of the remainder of the transcription complex, and acts as a channel for regulatory signals. TFIID is composed of the TATA-binding protein (
TBP) and a group of evolutionarily conserved proteins known as TBP-associated factors or TAFs. TAFs may participate in basal transcription, serve as
coactivators, function in promoter recognition or modify general transcription factors (GTFs) to facilitate complex assembly and transcription initiation. This gene encodes the largest subunit of TFIID. This subunit binds to core
promoter sequences encompassing the transcription start site. It also binds to activators and other transcriptional regulators, and these interactions affect the rate of transcription initiation. This subunit contains two independent
protein kinase
A protein kinase is a kinase which selectively modifies other proteins by covalently adding phosphates to them ( phosphorylation) as opposed to kinases which modify lipids, carbohydrates, or other molecules. Phosphorylation usually results in a f ...
domains at the N and C-terminals, but also possesses
acetyltransferase activity and can act as a
ubiquitin
Ubiquitin is a small (8.6 kDa) regulatory protein found in most tissues of eukaryotic organisms, i.e., it is found ''ubiquitously''. It was discovered in 1975 by Gideon Goldstein and further characterized throughout the late 1970s and 19 ...
-activating/conjugating enzyme. Two transcripts encoding different isoforms have been identified for this gene.
Histones are often acetylated to open DNA for transcription. TAF1 contains two bromodomains, which each can bind one of two acetyllysine residues at position 5 and 12 in the H4 tail, to stabilize the TBP-TATA box complex.
Clinical significance
A mutation in TAF1 was identified that contributes to a phenotype with severe intellectual disability (ID), a characteristic intergluteal crease, and distinctive facial features, including a broad, upturned nose, sagging cheeks, downward sloping palpebral fissures, prominent periorbital ridges, deep-set eyes, relative hypertelorism, thin upper lip, a high-arched palate, prominent ears with thickened helices, and a pointed chin This is a non-synonymous change in TAF1 that results in an isoleucine (hydrophobic) to threonine (polar) change on the 1337th amino acid residue in the protein (NP_001273003.1). Two other mutations were reported in TAF1 in two families with intellectual disability, although further clinical details were not reported.
Interactions
TAF1 has been shown to
interact with:
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CSNK2A1,
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CCND1,
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GTF2F1,
See also
* Transcription factor II D
References
Further reading
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External links
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GeneReviews/NCBI/NIH/UW entry on X-Linked Dystonia-Parkinsonism
* http://biorxiv.org/content/early/2015/01/21/014050
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