Transcriptional regulation of xyn1, encoding xylanase I, in Hypocrea jecorina
Transcriptional regulation of xyn1, encoding xylanase I, in Hypocrea jecorina
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DOI：
10.1128/ec.5.3.447-456.2006
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发表时间：
2006-03-01
期刊：
影响因子：
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通讯作者：
Mach, RL
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文献类型：
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作者：
Rauscher, R;Würleitner, E;Mach, RL
丝状真菌红褐肉座菌（里氏木霉）的两种主要木聚糖酶（XYN I和XYN II）在木聚糖生长期间同时表达，但对低分子量诱导剂的反应不同。木聚糖酶1（xyn 1）启动子的体内足迹分析揭示了用于结合蛋白质的三种不同的核苷酸序列（5 '-GGCTAAATGCGACATCTTAGCC-3' [间隔10 bp的GGCTAA的反向重复]、5 '-CCAAT-3'和5 '-GGGGTCTAGACCCC-3' [相当于双Cre 1位点]）。仅在抑制条件下观察到与Cre 1位点的结合，而与其他两个基序的结合是组成性的。应用H. jecorina纤维素酶调节剂Ace 1和Ace 2以及木聚糖酶调节剂Xyr 1的差异表明Ace 1和Xyr 1而不是Ace 2接触两个GGCTAA基序。H.含有突变形式的xyn 1启动子的jecorina转化体，导致与左或右GGCTAA盒结合的蛋白质的消除，揭示了转录诱导的强烈降低或完全消除。消除Cre 1结合其目标释放葡萄糖阻遏的基础转录水平，但不影响xyn 1表达的诱导。CCAAT盒的突变阻止了体外Hap 2/3/5复合物的结合，并部分补偿了由右GGCTAA盒突变引起的转录损失。最后，Ace 1和Xyr 1的竞争的权利GGCTAA框的证据。这些数据促使我们假设xyn 1调控是基于Cre 1和Ace 1作为一般和特异性阻遏物与Xyr 1作为反式激活因子的相互作用。
Two major xylanases (XYN I and XYN II) of the filamentous fungus Hypocrea jecorina (Trichoderma reesei) are simultaneously expressed during growth on xylan but respond differently to low-molecular-weight inducers. In vivo footprinting analysis of the xylanase1 (xyn1) promoter revealed three different nucleotide sequences (5'-GGCTAAATGCGACATCTTAGCC-3' [an inverted repeat of GGCTAA spaced by 10 bp], 5'-CCAAT-3', and 5'-GGGGTCTAGACCCC-3' [equivalent to a double Cre1 site]) used to bind proteins. Binding to the Cre1 site is only observed under repressed conditions, whereas binding to the two other motifs is constitutive. Applying heterologously expressed components of the H. jecorina cellulase regulators Ace1 and Ace2 and the xylanase regulator Xyr1 suggests that Ace1 and Xyr1 but not Ace2 contact both GGCTAA motifs. H. jecorina transformants containing mutated versions of the xyn1 promoter, leading to elimination of protein binding to the left or the right GGCTAA box revealed either strongly reduced or completely eliminated induction of transcription. Elimination of Cre1 binding to its target released the basal transcriptional level from glucose repression but did not influence the inducibility of xyn1 expression. Mutation of the CCAAT box prevents binding of the Hap2/3/5 complex in vitro and is partially compensating for the loss of transcription caused by the mutation of the right GGCTAA box. Finally, evidence for a competition of Ace1 and Xyr1 for the right GGCTAA box is given. These data prompted us to hypothesize that xyn1 regulation is based on the interplay of Cre1 and Ace1 as a general and specific repressor with Xyr1 as transactivator.