Fernandes M, Keller N P, Adams T H
Department of Plant Pathology and Microbiology, Texas A&M University, College Station 77843, USA.
Mol Microbiol. 1998 Jun;28(6):1355-65. doi: 10.1046/j.1365-2958.1998.00907.x.
The Aspergillus nidulans aflR gene is found within a 60 kb gene cluster that includes approximately 24 other genes that putatively function in the production of the aflatoxin-related mycotoxin sterigmatocystin. Previous work showed that AflR is a C6 zinc binuclear cluster protein that is conserved across Aspergillus spp. and functions as a pathway-specific transcription factor in activating expression of other cluster genes. In this report, we demonstrate that A. nidulans AflR (AnAflR) is a 45kDa protein that binds to the palindromic sequence 5'-TCG(N5)CGA-3' found in the promoter regions of several aflatoxin and sterigmatocystin cluster genes (stc genes). The in vivo relevance of this AnAflR binding site was assessed by examining the contribution of the three TCG(N5)CGA elements in the 1.1 kb promoter region of stcU using gene fusions with the bacterial uidA gene encoding beta-glucuronidase (GUS). By mutating one, two or all three of the AnAflR-binding elements and examining GUS activity in wild-type aflR or delta aflR A. nidulans strains, we found that stc gene activation required both AnAflR and at least one TCG(N5)CGA AflR binding site.
构巢曲霉的aflR基因位于一个60 kb的基因簇内，该基因簇包含大约24个其他基因，这些基因可能在黄曲霉毒素相关霉菌毒素柄曲霉素的产生中发挥作用。先前的研究表明，AflR是一种C6锌双核簇蛋白，在曲霉属物种中保守，并作为途径特异性转录因子激活其他簇基因的表达。在本报告中，我们证明构巢曲霉AflR（AnAflR）是一种45 kDa的蛋白质，它与几个黄曲霉毒素和柄曲霉素簇基因（stc基因）启动子区域中发现的回文序列5'-TCG(N5)CGA-3'结合。通过使用与编码β-葡萄糖醛酸酶（GUS）的细菌uidA基因的基因融合，检测stcU 1.1 kb启动子区域中三个TCG(N5)CGA元件的作用，评估了该AnAflR结合位点在体内的相关性。通过突变AnAflR结合元件中的一个、两个或全部三个，并检测野生型aflR或缺失aflR的构巢曲霉菌株中的GUS活性，我们发现stc基因的激活需要AnAflR和至少一个TCG(N5)CGA AflR结合位点。
