Interaction between heat shock transcription factor and transcription initiation complex.

转录激活子的转录激活信号通过中介因子如Mediator和TAF(TBP相关因子)传递到转录起始复合体。该起始复合体由RNA聚合酶II和通用转录因子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)的活性对于一些应激反应基因如热休克基因的激活是必不可少的，它使RNA聚合酶II的羧基末端结构域(CTD)磷酸化。在这项研究中，我已经证明了热诱导基因的Kin28非依赖性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对于铜诱导的编码铜金属硫蛋白的CUP1基因的转录是必不可少的。CUP1的转录受HSFL和AOE-1(铜诱导激活因子)的调控。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的非TFIIE激活是由介体复合体的某些组分介导的。2)另一个已知的中介因子TAFs的募集参与了HSFL对Kin28的非依赖性转录。3)HSFL的C末端部分具有将TAFs招募到启动子并独立于Kin28进行转录的活性。4)HSFL的C-末端含有一个新的结构域，调控HSFL的热诱导磷酸化。这些结果表明，另一种转录反应途径，其中激活剂的特定结构域在取消对作为转录反应主要途径的先决条件的一般转录因子子集的要求方面起着关键作用。

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.