Trichoderma reeseiXYR1 activates cellulase gene expression via interaction with the Mediator subunit TrGAL11 to recruit RNA polymerase II
Trichoderma reeseiXYR1 activates cellulase gene expression via interaction with the Mediator subunit TrGAL11 to recruit RNA polymerase II
复制标题
里氏木霉 XYR1 通过与介体亚基 TrGAL11 相互作用来招募 RNA 聚合酶 II，从而激活纤维素酶基因表达。
DOI：
10.1371/journal.pgen.1008979
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发表时间：
2020-09-01
期刊：
影响因子：
4.5
通讯作者：
Liu, Weifeng
中科院分区：
文献类型：
--
作者：
Zheng, Fanglin;Cao, Yanli;Liu, Weifeng
子囊菌里氏木霉（Trichoderma reesei）是一种高产纤维素酶产生菌。虽然XYR1（Xylanase regulator 1）已被确定为里氏木霉纤维素酶基因表达的主要激活因子，但其精确的转录激活机制仍知之甚少。在本研究中，TrGAL 11，一个组成部分的调解人尾部模块，被确定为一个假定的相互作用的合作伙伴XYR1。Trgal 11的缺失显著损害了大多数（半）纤维素酶基因的诱导表达，但不是主要的β-葡萄糖苷酶编码基因。TrGAL 11在纤维素酶基因的完全诱导中的这种差异参与通过其核心启动子上的RNA聚合酶II（Pol II）募集来反映，表明TrGAL 11是大多数纤维素酶基因的有效转录起始所需的。此外，我们发现，TrGAL 11招募纤维素酶基因启动子主要发生在XYR1依赖的方式。尽管没有TrGAL 11时XYR1的表达显著下调，但XYR1与纤维素酶基因启动子的结合不需要TrGAL 11。这些结果表明，TrGAL 11代表XYR1的一个直接体内靶点，并可能在促进介体和随后的RNA Pol II募集以确保诱导的纤维素酶基因expression.Author摘要作为一种模式纤维素分解真菌，T. reeseis能够快速产生大量的（半）纤维素酶当适当的底物存在。这一特性使里氏木霉在工业上成为纤维素酶的主要生产者，也是研究真核生物基因表达的模式生物。这些水解酶编码基因在里氏木霉中的表达受到一系列转录因子的精确调控。其中，转录激活因子XYR 1已被确定为激活几乎所有纤维素酶基因表达所必需的。然而，它的确切作用机制在很大程度上仍然未知。在真核生物中，多亚基介体复合物已被证明是至关重要的表达，如果不是所有的，蛋白质编码基因的基础转录机制，通过传递调控信息。在这里，我们发现XYR1与介体尾模块亚基TrGAL 11相互作用，TrGAL 11有助于纤维二糖水解酶（cbh）和内切葡聚糖酶（eg）基因的表达，但不影响β-葡萄糖苷酶（bgl）基因的表达。因此，诱导的XYR1与纤维素酶基因启动子的结合导致TrGAL 11和RNA Pol II募集到这些启动子。这些结果表明，TrGAL 11代表了XYR 1的定向体内靶点，并提供了证据，不仅在进化上保守的Mediator功能，但也存在一些微妙的差异，其行动，以介导基因表达在不同的真核生物。
The ascomyceteTrichoderma reeseiis a highly prolific cellulase producer. While XYR1 (Xylanase regulator 1) has been firmly established to be the master activator of cellulase gene expression inT.reesei, its precise transcriptional activation mechanism remains poorly understood. In the present study, TrGAL11, a component of the Mediator tail module, was identified as a putative interacting partner of XYR1. Deletion ofTrgal11markedly impaired the induced expression of most (hemi)cellulase genes, but not that of the major beta-glucosidase encoding genes. This differential involvement of TrGAL11 in the full induction of cellulase genes was reflected by the RNA polymerase II (Pol II) recruitment on their core promoters, indicating that TrGAL11 was required for the efficient transcriptional initiation of the majority of cellulase genes. In addition, we found that TrGAL11 recruitment to cellulase gene promoters largely occurred in an XYR1-dependent manner. Althoughxyr1expression was significantly tuned down without TrGAL11, the binding of XYR1 to cellulase gene promoters did not entail TrGAL11. These results indicate that TrGAL11 represents a directin vivotarget of XYR1 and may play a critical role in contributing to Mediator and the following RNA Pol II recruitment to ensure the induced cellulase gene expression.Author summary As a model cellulolytic fungus,T.reeseiis capable of rapidly producing a large quantity of (hemi)cellulases when appropriate substrates are present. This outstanding characteristic has madeT.reeseia prominent producer of cellulase in industry and also a model organism for studying eukaryotic gene expression. The expression of these hydrolytic enzymes encoding genes inT.reeseiis precisely regulated at a transcriptional level and controlled by a suite of transcription factors. Among others, the transcription activator XYR1 has been firmly established to be absolutely necessary for activating the expression of almost all cellulase genes. However, the precise mechanism it acts remains largely unknown. In eukaryotes, the multisubunit Mediator complex has been shown to be critical for expression of most, if not all, protein-coding genes by conveying regulatory information to the basal transcription machinery. Here, we find that XYR1 interacts with the Mediator tail module subunit, TrGAL11, which contributes to cellobiohydrolase (cbh) and endoglucanase (eg)genes but not beta-glucosidase (bgl) genes expression. Thus, the induced XYR1 binding to cellulase gene promoters led to TrGAL11 and RNA Pol II recruitment to these promoters. These results show that TrGAL11 represents a directin vivotarget of XYR1 and provide evidence for not only the evolutionarily conserved function of Mediator, but also for the existence of some subtle difference in its action to mediate gene expression in different eukaryotes.