Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea.
Department of Systems Biology, Institute of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea.
Mol Plant. 2021 Apr 5;14(4):647-663. doi: 10.1016/j.molp.2021.01.020. Epub 2021 Jan 29.
The precise regulation of microRNA (miRNA) biogenesis is crucial for plant development, which requires core microprocessors and many fine tuners to coordinate their miRNA processing activity/specificity in fluctuating cellular environments. During de-etiolation, light triggers a dramatic accumulation of core microprocessors and primary miRNAs (pri-miRNAs) but decreases pri-miRNA processing activity, resulting in relatively constant miRNA levels. The mechanisms underlying these seemingly contradictory regulatory changes remain unclear. In this study, we identified forkhead-associated domain 2 (FHA2) as a light-stabilized suppressor of miRNA biogenesis. We found that FHA2 deficiency increased the level of mature miRNAs, accompanied by a reduction in pri-miRNAs and target mRNAs. Biochemical assays showed that FHA2 associates with the core microprocessors DCL1, HYL1, and SE, forming a complex to suppress their pri-miRNA processing activity. Further analyses revealed that FHA2 promotes HYL1 binding but inhibits the binding of DCL1-PAZ-RNase-RNA-binding domains (DCL1-PRR) to miRNAs, whereas FHA2 does not directly bind to these RNAs. Interestingly, we found that FHA2 protein is unstable in the dark but stabilized by light during de-etiolation. Consistently, disruption of FHA led to defects in light-triggered changes in miRNA expression and reduced the survival rate of de-etiolated seedlings after prolonged light deprivation. Collectively, these data suggest that FHA2 is a novel light-stabilized suppressor of miRNA biogenesis and plays a role in fine-tuning miRNA processing during de-etiolation.
miRNA 生物发生的精确调控对于植物发育至关重要，这需要核心微处理器和许多微调因子来协调它们在不断变化的细胞环境中的 miRNA 加工活性/特异性。在去黄化过程中，光触发核心微处理器和初级 miRNA（pri-miRNA）的大量积累，但降低了 pri-miRNA 的加工活性，导致 miRNA 水平相对稳定。这些看似矛盾的调节变化的机制尚不清楚。在这项研究中，我们鉴定了 forkhead-associated domain 2（FHA2）作为 miRNA 生物发生的光稳定抑制因子。我们发现 FHA2 缺陷会增加成熟 miRNA 的水平，同时减少 pri-miRNA 和靶 mRNAs。生化分析表明，FHA2 与核心微处理器 DCL1、HYL1 和 SE 结合，形成一个复合物来抑制它们的 pri-miRNA 加工活性。进一步的分析表明，FHA2 促进 HYL1 的结合，但抑制 DCL1-PAZ-RNase-RNA 结合域（DCL1-PRR）与 miRNA 的结合，而 FHA2 不直接与这些 RNA 结合。有趣的是，我们发现 FHA2 蛋白在黑暗中不稳定，但在去黄化过程中会被光稳定。一致地，FHA 缺失导致光触发的 miRNA 表达变化缺陷，并降低了去黄化幼苗在长时间光照剥夺后的存活率。总之，这些数据表明 FHA2 是一种新型的光稳定的 miRNA 生物发生抑制剂，在去黄化过程中发挥作用，精细调节 miRNA 的加工。
