Functional analysis of TAND (TAF N-terminal domain) that inhibits TBP : DNA interactions

TFIID是由TBP和几种TAFls组成的多蛋白复合物。果蝇TAF 11230（dTAF 11230）和酵母TAF 11145（yTAF 11145）的小N-末端片段（TAND ; TAF N-末端结构域）与TBP强烈结合，从而抑制TBP：DNA相互作用。dTAF 11230 TAND（dTAND）和yTAF 11145 TAND（yTAND）进一步分为两个亚结构域，分别为dTANDI（18-77 aa）& II（118-143 aa）和yTANDI（10-37 aa）& II（46-71 aa），它们协同发挥功能。更重要的是，TANDI和TANDII分别与活化剂和TFIIA竞争TBP结合。我们还证明了激活结构域和TANDI之间的功能保守性，当与DNA结合结构域融合时，TANDI在酵母中作为激活结构域发挥作用。相反，当TANDI被TEIID中的激活结构域取代时，激活结构域的功能就像TANDI一样。此外，我们还发现与TBP凹面的相互作用对激活子和TAN DI的功能都是至关重要的。这些结果表明，转录激活步骤包括转录激活子抑制TANDI的抑制活性。

TFIID is a multiprotein complex comprised of TBP and several TAFlls. Small N-terminal segments (TAND ; TAF N-terminal Domain) of Drosophila TAFll23O (dTAFll230) and yeast TAFll145 (yTAFll145) bind strongly to TBP and thereby inhibit TBP : DNA interactions. dTAFll230 TAND (dTAND) and yTAFll145 TAND (yTAND) were further divided into two subdomains, dTANDI (18-77 aa) & II(118-143 aa), and yTANDI (10-37 aa) & II(46-71 aa), respectively, that function cooperatively. More importantly, TANDI and TANDII compete with activators and TFIIA, respectively, for TBP binding. We also demonstrated the functional conservation between activation domains and TANDI.When fused to the DNA-binding domain, TANDI functions as an activation domain in yeast. Conversely, activation domains function as TANDI when TANDI is replaced with activation domains within TEIID.Furthermore, we show that the interaction with the concave surface of TBP is crucial for the functions of both activators and TAN DI.These results indicate that transcriptional activation steps include suppression of the inhibitory activity of TANDI by transcriptional activators.