TATA box

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A TATA box (also called Hogness Box) is a DNA sequence (cis-element) found in the promoter region of most genes (it is considered to be a promoter sequence). It is the binding site of either transcription factors or histones (binding of a transcription factor blocks 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'-TATAA-3', which is usually followed by three or more adenine bases and has been highly conserved through evolution.

In eukaryotes, it is normally bound by the TATA Binding Protein (TBP) in the process of transcription, which melts the DNA, and bends it through 90°. The AT-rich sequence facilitates easy melting. The TBP is an unusual protein in that it binds the minor groove and binds with a β sheet.

The TATA box is essential for the binding of RNA polymerase in prokaryotes, and is usually found as the binding site of RNA polymerase II in eukaryotes. In eukaryotes the transcription factor TFIID binds to the TATA box, followed by TFIIA binding to the upstream part 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, however TBP is always involved and is forced to bind non-sequence specifically. Promotors lacking a TATA box are called TATA-less promotors and are suggested to make up 50% of all promotor sequences.

Binding of histones

The binding of histones involves the N-terminal tail of H4.

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