Interdependent recruitment of CYC8/TUP1 and the transcriptional activator XYR1 at target promoters is required for induced cellulase gene expression in Trichoderma reesei.
Interdependent recruitment of CYC8/TUP1 and the transcriptional activator XYR1 at target promoters is required for induced cellulase gene expression in Trichoderma reesei.
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里氏木霉中诱导纤维素酶基因表达需要 CYC8/TUP1 和转录激活因子 XYR1 在靶启动子处相互依赖的募集
DOI：
10.1371/journal.pgen.1009351
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发表时间：
2021-03
期刊：
影响因子：
4.5
通讯作者：
Liu W
中科院分区：
文献类型：
--
作者：
Wang L;Zhang W;Cao Y;Zheng F;Zhao G;Lv X;Meng X;Liu W
丝状真菌里氏木霉的纤维素酶生产对各种环境信号高度响应，涉及多个正负调控因子。XYR1(木聚糖酶调节因子1)是里氏木霉纤维素酶基因表达的关键转录激活子。然而，XYR1实现纤维素酶基因转录激活的确切机制仍不完全清楚。在这里，我们确定TrCyC8/Tup1复合体是里氏木霉中一种新的XYR1共激活因子。CyC8/Tup1是第一个在酿酒酵母中发现的转录辅阻遏子复合体，介导多种基因的转录抑制。Trcyc8或Trtup1基因的敲除导致里氏木霉纤维素酶基因的表达明显受损。我们发现TrCyC8/Tup1在纤维素酶基因启动子诱导下被募集到纤维素酶基因启动子上，并且这种募集依赖于XYR1。我们进一步观察到，抑制Trtup1或Trcyc8的表达导致了XYR1在纤维素酶基因启动子上的占位和组蛋白H4的丢失。过表达XYR1不能克服Trtup1或Trcyc8抑制细胞中XYR1结合缺陷和靶基因转录激活的缺陷。我们的结果揭示了TrCyC8/Tup1在激活剂结合水平上的新的共激活功能，并提示了XYR1和TrCyC8/Tup1相互依赖地募集到纤维素酶基因启动子的机制是确保纤维素酶基因表达的重要调节电路。这些发现有助于揭示XYR1介导的纤维素酶基因激活的复杂调控机制，也为进一步提高里氏木霉的纤维素酶产量提供了重要线索。
Cellulase production in filamentous fungus Trichoderma reesei is highly responsive to various environmental cues involving multiple positive and negative regulators. XYR1 (Xylanase regulator 1) has been identified as the key transcriptional activator of cellulase gene expression in T. reesei. However, the precise mechanism by which XYR1 achieves transcriptional activation of cellulase genes is still not fully understood. Here, we identified the TrCYC8/TUP1 complex as a novel coactivator for XYR1 in T. reesei. CYC8/TUP1 is the first identified transcriptional corepressor complex mediating repression of diverse genes in Saccharomyces cerevisiae. Knockdown of Trcyc8 or Trtup1 resulted in markedly impaired cellulase gene expression in T. reesei. We found that TrCYC8/TUP1 was recruited to cellulase gene promoters upon cellulose induction and this recruitment is dependent on XYR1. We further observed that repressed Trtup1 or Trcyc8 expression caused a strong defect in XYR1 occupancy and loss of histone H4 at cellulase gene promoters. The defects in XYR1 binding and transcriptional activation of target genes in Trtup1 or Trcyc8 repressed cells could not be overcome by XYR1 overexpression. Our results reveal a novel coactivator function for TrCYC8/TUP1 at the level of activator binding, and suggest a mechanism in which interdependent recruitment of XYR1 and TrCYC8/TUP1 to cellulase gene promoters represents an important regulatory circuit in ensuring the induced cellulase gene expression. These findings thus contribute to unveiling the intricate regulatory mechanism underlying XYR1-mediated cellulase gene activation and also provide an important clue that will help further improve cellulase production by T. reesei.
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