The circadian clock is based on a transcriptional feedback loop with an essential time delay before feedback inhibition. Previous work has shown that PERIOD (PER) proteins generate circadian time cues through rhythmic nuclear accumulation of the inhibitor complex and subsequent interaction with the activator complex in the feedback loop. Although this temporal manifestation of the feedback inhibition is the direct consequence of PER’s cytoplasmic trafficking before nuclear entry, how this spatial regulation of the pacemaker affects circadian timing has been largely unexplored. Here we show that circadian rhythms, including wake-sleep cycles, are lengthened and severely unstable if the cytoplasmic trafficking of PER is disrupted by any disease condition that leads to increased congestion in the cytoplasm. Furthermore, we found that the time delay and robustness in the circadian clock are seamlessly generated by delayed and collective phosphorylation of PER molecules, followed by synchronous nuclear entry. These results provide clear mechanistic insight into why circadian and sleep disorders arise in such clinical conditions as metabolic and neurodegenerative diseases and aging, in which the cytoplasm is congested.

昼夜节律时钟基于转录反馈环，该环在反馈抑制之前具有必要的时间延迟。先前的研究表明，PERIOD（PER）蛋白通过抑制剂复合物的有节奏核积累以及随后在反馈环中与活化剂复合物的相互作用产生昼夜时间提示。尽管反馈抑制的这种暂时性表现是核进入前PER胞质运输的直接结果，但起搏器的这种空间调节如何影响昼夜节律的时间尚未得到充分探讨。在这里，我们显示，如果PER的胞质运输受到导致胞质充血增加的任何疾病状况的干扰，昼夜节律（包括觉醒-睡眠周期）将延长且严重不稳定。此外，我们发现，昼夜节律时钟中的时间延迟和鲁棒性是由PER分子的延迟和集体磷酸化以及随后的同步核进入无缝地产生的。这些结果提供了清晰的机械原理，以了解为什么在代谢性和神经退行性疾病以及衰老等细胞质充血的临床情况下会发生昼夜节律和睡眠障碍。