State Key Laboratory of Microbial Technology, Shandong University, No. 72 Binhai Road, Qingdao, 266237, People's Republic of China.
Mol Microbiol. 2019 Oct;112(4):1145-1162. doi: 10.1111/mmi.14352. Epub 2019 Jul 25.
Cellulase gene expression in Trichoderma reesei is highly responsive to environmental cues and is under stringent regulation by multiple transcription factors. XYR1 (Xylanase regulator 1) has been identified as the most important transcriptional activator of cellulase/hemicellulase gene expression although the precise transactivating mechanism remains largely elusive. Here we show that the activation domain of XYR1 interacts with the T. reesei homolog of the TrSNF12 subunit of SWI/SNF complex. Deletion of Trsnf12 markedly impaired the induced cellulase gene expression. Individual loss of other SWI/SNF subunits including the catalytic subunit also severely compromised cellulase gene expression and interfered with loss of histone H4 in the cbh1 and eg1 promoters upon cellulose induction. In addition, we find that the SWI/SNF occupancy on cellulase gene promoters strictly required XYR1 and TrSNF12 but TrSNF12 was dispensable for the XYR1 binding to these promoters. These data suggest a model in which XYR1 recruits SWI/SNF through direct interactions with TrSNF12 to remodel chromatin at cellulase gene promoters, thereby activating cellulase gene expression to initiate the cellulolytic response in T. reesei.
木霉纤维二糖水解酶基因的表达对环境信号高度敏感，并受到多种转录因子的严格调控。虽然确切的转录激活机制在很大程度上仍不清楚，但 XYRI（木聚糖酶调节剂 1）已被确定为纤维二糖/半纤维素酶基因表达的最重要的转录激活因子。在这里，我们表明 XYR1 的激活结构域与 SWI/SNF 复合物的 TrSNF12 亚基的木霉同源物相互作用。Trsnf12 的缺失显著损害了诱导型纤维二糖水解酶基因的表达。单个缺失其他 SWI/SNF 亚基，包括催化亚基，也严重损害了纤维二糖水解酶基因的表达，并干扰了纤维素诱导时 cbh1 和 eg1 启动子中组蛋白 H4 的丢失。此外，我们发现纤维二糖水解酶基因启动子上的 SWI/SNF 占据严格需要 XYR1 和 TrSNF12，但 TrSNF12 对于 XYR1 结合到这些启动子上是可有可无的。这些数据表明了一个模型，即 XYR1 通过与 TrSNF12 的直接相互作用招募 SWI/SNF，从而重塑纤维二糖水解酶基因启动子上的染色质，从而激活纤维二糖水解酶基因的表达，从而启动木霉中的纤维降解反应。
