Gai Kexin, Cao Xuemei, Dong Qing, Ding Zhaolan, Wei Yashang, Liu Yingchun, Liu Xiao, He Qun
State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, China.
Department of Physiology, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America.
PLoS Genet. 2017 Apr 12;13(4):e1006732. doi: 10.1371/journal.pgen.1006732. eCollection 2017 Apr.
Rhythmic activation and repression of the frequency (frq) gene are essential for normal function of the Neurospora circadian clock. WHITE COLLAR (WC) complex, the positive element of the Neurospora circadian system, is responsible for stimulation of frq transcription. We report that a C2H2 finger domain-containing protein IEC-1 and its associated chromatin remodeling complex INO80 play important roles in normal Neurospora circadian clock function. In iec-1KO strains, circadian rhythms are abolished, and the frq transcript levels are increased compared to that of the wild-type strain. Similar results are observed in mutant strains of the INO80 subunits. Furthermore, ChIP data show that recruitment of the INO80 complex to the frq promoter is IEC-1-dependent. WC-mediated transcription of frq contributes to the rhythmic binding of the INO80 complex at the frq promoter. As demonstrated by ChIP analysis, the INO80 complex is required for the re-establishment of the dense chromatin environment at the frq promoter. In addition, WC-independent frq transcription is present in ino80 mutants. Altogether, our data indicate that the INO80 complex suppresses frq transcription by re-assembling the suppressive mechanisms at the frq promoter after transcription of frq.
频率（frq）基因的节律性激活和抑制对于粗糙脉孢菌生物钟的正常功能至关重要。白领（WC）复合体是粗糙脉孢菌昼夜节律系统的正向元件，负责刺激frq转录。我们报道，一种含C2H2指状结构域的蛋白质IEC-1及其相关的染色质重塑复合体INO80在粗糙脉孢菌生物钟的正常功能中发挥重要作用。在iec-1基因敲除菌株中，昼夜节律被消除，与野生型菌株相比，frq转录本水平升高。在INO80亚基的突变菌株中也观察到类似结果。此外，染色质免疫沉淀（ChIP）数据表明，INO80复合体向frq启动子的募集依赖于IEC-1。WC介导的frq转录有助于INO80复合体在frq启动子处的节律性结合。如ChIP分析所示，在frq启动子处重新建立致密染色质环境需要INO80复合体。此外，在ino80突变体中存在不依赖WC的frq转录。总之，我们的数据表明，INO80复合体通过在frq转录后在frq启动子处重新组装抑制机制来抑制frq转录。
