<Li> Four hydrogen bonds form between polar side chains on TBP amino acid residues and bases in the minor groove . </Li> <Li> Numerous hydrophobic interactions form between TBP residues and DNA bases, including van der Waals forces . </Li> <P> Additionally, binding of TBP is facilitated by stabilizing interactions with DNA flanking the TATA box, which consists of G-C rich sequences . These secondary interactions induce bending of the DNA and helical unwinding . The degree of DNA bending is species and sequence dependent . For example, one study used the adenovirus TATA promoter sequence (5' - CGCTATAAAAGGGC - 3') as a model binding sequence and found that human TBP binding to the TATA box induced a 97 ° bend toward the major groove while the yeast TBP protein only induced an 82 ° bend . X-ray crystallography studies of TBP / TATA - box complexes generally agree that the DNA goes through an ~ 80 ° bend during the process of TBP - binding . </P> <P> The conformational changes induced by TBP binding to the TATA box allows for additional transcription factors and RNA polymerase II to bind to the promoter region . TFIID first binds to the TATA box, facilitated by TFIIA binding to the upstream part of the TFIID complex . TFIIB then binds to the TFIID - TFIIA - DNA complex through interactions both upstream and downstream of the TATA box . RNA polymerase II is then recruited to this multi-protein complex with the help of TFIIF . Additional transcription factors then bind, first TFIIE and then TFIIH . This completes the assembly of the preinitiation complex for eukaryotic transcription . Generally, the TATA box is found at RNA polymerase II promoter regions, although some in vitro studies have demonstrated that RNA polymerase III can recognize TATA sequences . </P>

What is the significance of the tata box in eukaryotic promoters