Angermayr M, Bandlow W
Institut für Genetik und Mikrobiologie der Universität München, Maria-Ward-Str. 1a, 80638 Munich, Germany.
J Biol Chem. 1997 Dec 12;272(50):31630-5. doi: 10.1074/jbc.272.50.31630.
The yeast genes, GCY1 and RIO1, are transcribed divergently from the 869-base pair intergenic region. GCY1 is inducible by galactose about 25-fold due to Gal4p-binding to a single UASGAL, whereas RIO1 is constitutively expressed. GCY1 has a TATA box obeying the consensus TATAAA, whereas the RIO1 5'-upstream region lacks such a motif. In vitro mutagenesis of the TATA motif of GCY1, on the one hand, and introduction of a TATA-element into the promoter of RIO1, on the other hand, as well as inversion of the intergenic region have revealed that transcription of GCY1 and RIO1 is only regulated by Gal4p when a consensus TATA motif is included in their core promoters but not in its absence. The data imply that only transcription complexes that assemble at a consensus TATA box are compatible with specific transactivators, such as Gal4p. As a result, the adjacent gene is subject to regulated expression. By contrast, if a consensus TATA sequence is absent, the initiation complex does not respond to regulatory transcription factors, and consequently, the respective gene is constitutively transcribed. On the other hand, we show that two blocks of homo-oligomeric (dA.dT) sequences do not function as boundary sequences that might confine regulatory action of Gal4p to GCY1.
酵母基因GCY1和RIO1从869个碱基对的基因间隔区反向转录。由于Gal4p与单个UASGAL结合，GCY1可被半乳糖诱导约25倍，而RIO1则组成型表达。GCY1有一个符合TATAAA共有序列的TATA盒，而RIO1的5'上游区域缺乏这样的基序。一方面，对GCY1的TATA基序进行体外诱变，另一方面，在RIO1的启动子中引入TATA元件，以及对基因间隔区进行倒置，结果表明，只有当它们的核心启动子中包含共有TATA基序时，GCY1和RIO1的转录才受Gal4p调控，否则不受其调控。数据表明，只有在共有TATA盒处组装的转录复合物才与特定的反式激活因子（如Gal4p）兼容。因此，相邻基因受到调控表达。相比之下，如果没有共有TATA序列，起始复合物就不会对调控转录因子作出反应，因此，相应的基因就会组成型转录。另一方面，我们表明，两段同聚寡聚（dA.dT）序列并不作为边界序列发挥作用，这些边界序列可能会将Gal4p的调控作用限制在GCY1上。
