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A TATA box (also called Goldberg-Hogness box) is a DNA sequence (cis-regulatory element) found in the promoter region of most genes in eukaryotes. Considered to be the core promoter sequence, it is the binding site of either transcription factors or histones (the binding of a transcription factor blocks the binding of a histone and vice versa) and is involved in the process of transcription by RNA polymerase. It has the core DNA sequence 5'-TATAAA-3' or a variant, which is usually followed by three or more adenine bases. The TATA box is usually located 25 base pairs upstream to the transcription site. The sequence has been highly conserved through evolution.
It is normally bound by the TATA Binding Protein (TBP) in the process of transcription, which unwinds the DNA, and bends it through 80°. The AT-rich sequence facilitates easy unwinding (due to 2 hydrogen bonds between bases as opposed to 3 between GC pairs). The TBP is an unusual protein in that it binds the minor groove and binds with a β sheet.
The TATA box is usually found as the binding site of RNA polymerase II. The transcription factor TFIID binds to the TATA box, followed by TFIIA binding to the upstream part of TFIID. TFIIB can then bind to the downstream part of TFIID. The polymerase can then recognise this multi-protein complex and bind to it, along with various other transcription factors such as TFIIF, TFIIE and TFIIH. Transcription is then initiated, and the polymerase moves along the DNA strand, leaving TFIID and TFIIA bound to the TATA box. These can then facilitate the binding of additional RNA polymerase II molecules.
This cluster of RNA polymerase II and various transcription factors is known as a basal transcriptional complex (BTC). In this state, it only gives a low level of transcription. Other factors must stimulate the BTC to increase transcription levels. One such example of a BTC stimulating region of DNA is the CAAT box.
Many genes lack a TATA box and use an initiator element or downstream core promoter instead. Nevertheless, TBP is always involved and is forced to bind without sequence specificity. Promoters lacking a TATA box are called TATA-less promoters and are suggested to make up 50% of all promoter sequences.
Binding of histones
The binding of histones involves the N-terminal tail of H4.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "TATA_box". A list of authors is available in Wikipedia.|