Interaction between heat shock transcription factor and transcription initiation complex.

转录激活因子的转录激活信号通过中介因子如Mediator和TAF（TBP-associated factor）传递到转录起始复合体。起始复合物由RNA聚合酶II和一般转录因子TBP、TFIIB、TFIIE、TFIIF和TFIIH组成。利用酵母分子遗传学的方法，已经揭示了TFIIH激酶（由KIN28基因编码）的活性，其磷酸化RNA聚合酶II的羧基末端结构域（CTD），对于激活一些应激反应基因如热休克基因是必不可少的。在这项研究中，我已经证明了kin28独立的热诱导基因的激活是由热休克交易因子Hsfl介导的。此外，调节Kin28激酶活性的通用转录因子IIE对于铜诱导的铜金属硫蛋白编码CUP1基因的转录是必不可少的。CUP1的转录受Hsfl和aoe1（铜诱导激活剂）调控。我进一步分析了kin28和tfiie独立的转录机制，揭示了以下内容。1) CUP1不依赖于tfiie的激活是由Mediator复合物的某些成分介导的。2)另一个众所周知的中介因子TAFs的募集参与了Hsfl独立于Kin28的转录。3)Hsfl的c端一半具有将TAFs募集到启动子并独立于Kin28进行转录的活性。4) Hsfl的c端区含有一个新的结构域，该结构域调节Hsfl的热诱导磷酸化。这些结果表明，在转录反应的主要途径中，激活因子的特定区域在消除对一般转录因子子集的需求方面起着关键作用，而这些转录因子子集是转录反应的先决条件。

The transcription activation signals of transcription activators are transmitted to the transcription initiation complex via intermediary factors such as Mediator and TAF(TBP-associated factor). The initiation complex consists of RNA polymerase II and the general transcription factors TBP,TFIIB,TFIIE,TFIIF,and TFIIH. By using the methods of yeast molecular genetics, it has been disclosed that activity of the TFIIH kinase(encoded by the KIN28 gene), which phosphorylates the carboxy-terminal domain(CTD) of RNA polymerase II, is dispensable for activation of several stress responsive genes such as heat shock genes. In this study, I have shown that the Kin28-independent activation of the heat-inducible genes is mediated by the heat shock transaction factor Hsfl. In addition, the general transcription factor IIE, which regulates the kinase activity of Kin28, was dispensable for copper-induced transcription of the CUP1 gene encoding copper metallothionein. Transcription of CUP1 is regulated by Hsfl and Aoe 1(copper-inducible activator). I further analyzed the Kin28-and TFIIE-independent transcription mechanisms and revealed the following. 1)The TFIIE-independent activation of CUP1 is mediated by oertain components of the Mediator complex. 2)The recruitment of TAFs, another well-known intermediary factor, is involved in the Kin28-independent transcription by Hsfl. 3) The C-terminal half of Hsfl has activities to recruit TAFs to a promoter and to undergo transcription independently of Kin28. 4)The C-terminal region of Hsfl contains a novel domain that regulates heat-inducible phosphorylation of Hsfl. These results illustrated that an alternate pathway of transcription reaction, in which a specific domain of activator plays a critical role in abrogation of requirement for subset of general transcription factors that are prerequisites in the main pathway of the transcription reaction.