Nhp6 facilitates Aft1 binding and Ssn6 recruitment, both essential for FRE2 transcriptional activation
Nhp6 facilitates Aft1 binding and Ssn6 recruitment, both essential for FRE2 transcriptional activation
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DOI：
10.1038/sj.emboj.7600043
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发表时间：
2004-01-28
期刊：
影响因子：
11.4
通讯作者：
Alexandraki, D
中科院分区：
文献类型：
--
作者：
Fragiadakis, GS;Tzamarias, D;Alexandraki, D
我们发现Nhp 6a/B酵母HMG盒染色质相关的结构因子和Ssn 6（Cyc 8）辅阻遏物是FRE 2基因的关键转录辅激活因子。编码质膜铁还原酶的FRE 2由铁响应性DNA结合转录激活因子Aft 1诱导。我们已经表明，Nhp 6直接与Aft 1 N-半，包括DNA结合区，以促进Aft 1在FRE 2 UAS的结合。Ssn 6也直接与Aft 1 N-半相互作用，并且仅在Aft 1和Nhp 6都存在的情况下在FRE 2启动子上募集。这种Nhp 6/Ssn 6在Aft 1介导的转录中的作用是FRE 2启动子环境特异性的，并且这两种调节剂都是激活依赖性染色质重塑所需的。我们的研究结果提供了第一个在体内的非序列特异性HMG盒蛋白促进招聘的酵母基因特异性反式激活因子的DNA靶位点和Nhp 6介导的Ssn 6启动子招聘的生化证据。Ssn 6仅在诱导时对FRE 2启动子具有明确的共激活作用。因此，转录激活响应铁的可用性涉及多种蛋白质之间的相互作用Aft 1铁响应DNA结合因子和全球监管机构，如Nhp 6和Ssn 6。
We found Nhp6a/b yeast HMG-box chromatin-associated architectural factors and Ssn6 (Cyc8) corepressor to be crucial transcriptional coactivators of FRE2 gene. FRE2 encoding a plasma membrane ferric reductase is induced by the iron-responsive, DNA-binding, transcriptional activator Aft1. We have shown that Nhp6 interacts directly with the Aft1 N-half, including the DNA-binding region, to facilitate Aft1 binding at FRE2 UAS. Ssn6 also interacts directly with the Aft1 N-half and is recruited on FRE2 promoter only in the presence of both Aft1 and Nhp6. This Nhp6/Ssn6 role in Aft1-mediated transcription is FRE2 promoter context specific, and both regulators are required for activation-dependent chromatin remodeling. Our results provide the first in vivo biochemical evidence for nonsequence-specific HMG-box protein-facilitated recruitment of a yeast gene-specific transactivator to its DNA target site and for Nhp6-mediated Ssn6 promoter recruitment. Ssn6 has an explicitly coactivating role on FRE2 promoter only upon induction. Therefore, transcriptional activation in response to iron availability involves multiple protein interactions between the Aft1 iron-responsive DNA-binding factor and global regulators such as Nhp6 and Ssn6.