KaiA调控蓝藻生物钟的分子机制研究进展

蓝藻生物钟系统主要包括输入途径、核心振荡器和输出途径3部分,核心振荡器主要由时钟蛋白KaiA、KaiB、KaiC构成。3种蛋白之间的相互作用产生节律信号及调控输入、输出信号进而维持生物振荡的精确与稳定。文中围绕蓝藻生物钟核心振荡器及核心振荡器组成蛋白的结构、功能与相互作用特点,结合本实验室近期取得的研究成果,针对时钟蛋白KaiA调节KaiC的酶活性、介导核心振荡器的时相重置、与CikA竞争KaiB的结合位点等方面近年来的研究进展进行了综述。     

Life's 24-hour clock: molecular control of circadian rhythms in animal cells

Our sleep–wake cycles and many other 24-hour rhythms of behavior and physiology persist in the absence of environmental cues. Genetic and biochemical studies have shown that such rhythms are controlled by internal molecular clocks. These are assembled from the cycling RNA and protein products of a small group of genes that are conserved throughout the animal kingdom.     

Robust synchronization of coupled circadian and cell cycle oscillators in single mammalian cells

Circadian cycles and cell cycles are two fundamental periodic processes with a period in the range of 1 day. Consequently, coupling between such cycles can lead to synchronization. Here, we estimated the mutual interactions between the two oscillators by time‐lapse imaging of single mammalian NIH3T3 fibroblasts during several days. The analysis of thousands of circadian cycles in dividing cells clearly indicated that both oscillators tick in a 1:1 mode‐locked state, with cell divisions occurring tightly 5 h before the peak in circadian Rev‐Erbα‐YFP reporter expression. In principle, such synchrony may be caused by either unidirectional or bidirectional coupling. While gating of cell division by the circadian cycle has been most studied, our data combined with stochastic modeling unambiguously show that the reverse coupling is predominant in NIH3T3 cells. Moreover, temperature, genetic, and pharmacological perturbations showed that the two interacting cellular oscillators adopt a synchronized state that is highly robust over a wide range of parameters. These findings have implications for circadian function in proliferative tissues, including epidermis, immune cells, and cancer.     

Bmal1-deficient mouse fibroblast cells do not provide premature cellular senescence in vitro

Bmal1 is a core circadian clock gene. Bmal1^?/? mice show disruption of the clock and premature aging phenotypes with a short lifespan. However, little is known whether disruption of Bmal1 leads to premature aging at cellular level. Here, we established primary mouse embryonic fibroblast (MEF) cells derived from Bmal1^?/? mice and investigated its effects on cellular senescence. Unexpectedly, Bmal1^?/? primary MEFs that showed disrupted circadian oscillation underwent neither premature replicative nor stress-induced cellular senescence. Our results therefore uncover that Bmal1 is not required for in vitro cellular senescence, suggesting that circadian clock does not control in vitro cellular senescence.     

月经周期对女性睡眠-觉醒和静息-活动的影响

目前有关月经周期对睡眠影响的研究结果并不一致,而对月经周期中昼夜睡眠-觉醒及静息-活动节律尚缺乏系统性的研究.本研究旨在观察正常育龄期女性月经周期中睡眠-觉醒及静息-活动昼夜节律的变化.我们采用静息-活动监测仪(actigraphy)和睡眠日志,调查了12个自然生活状态下健康育龄期妇女在月经周期不同阶段,即行经期、围排卵期、黄体早期及黄体晚期中睡眠与活动节律的变化.结果显示,睡眠-觉醒节律参数在四期之间无统计学显著差异;而静息-活动节律方面,所有受试女性静息-活动节律的平均日周期长度为(24.01±0.29)h,并且四期之间无显著性差异.行经期日间稳定系数(interdaily stability,IS)比黄体早期显著增加(P＜0.05).黄体早期日间活动开始时间明显较黄体晚期提前(P＜0.05);黄体早期的活动峰值时相比围排卵期显著提前(P＜0.05).月经周期可以影响静息-活动昼夜节律时相.而总体静息-活动数量与质量未发生显著变化;健康育龄期妇女在月经周期的各阶段中睡眠-觉醒节律亦无明显变异.     

The circadian mutation PER2(S662G) is linked to cell cycle progression and tumorigenesis

Circadian oscillation and cell cycle progression are the two most essential rhythmic events present in almost all organisms. Circadian rhythms keep track of time and provide temporal regulation with a period of about 24 h. The cell cycle is optimized for growth and division, but not for time keeping. Circadian gated cell divisions are observed in nearly all organisms. However, the implications of this coupling to the physiology of mammals are unknown. A mutation (S662G) in the clock protein PERIOD2 (PER2) is responsible for familial advanced sleep phase syndrome in which sleep onset occurs in the early evening and wakefulness occurs in the early morning. Here, we provide evidence that the PER2^S662 mutation leads to enhanced resistance to X-ray-induced apoptosis and increased E1A- and RAS-mediated oncogenic transformation. Accordingly, the PER2^S662 mutation affects tumorigenesis in cancer-sensitized p53^R172H/+ mice. Finally, analyzing the clock-controlled cell cycle genes p21, c-Myc, Cyclin D1 and p27, we found that the relative phases between p21 and Cyclin D expression profiles have been changed significantly in these Per2 allele mutant mouse embryonic fibroblasts. This key role of the Per2-mediated phase alteration of p21 provides what we believe to be a novel mechanism in understanding cell cycle progression, its plasticity and its resistance to interference.     

The positive circadian regulators CLOCK and BMAL1 control G2/M cell cycle transition through Cyclin B1

We previously identified a tight bidirectional phase coupling between the circadian clock and the cell cycle. To understand the role of the CLOCK/BMAL1 complex, representing the main positive regulator of the circadian oscillator, we knocked down Bmal1 or Clock in NIH3T3^3C mouse fibroblasts (carrying fluorescent reporters for clock and cell cycle phase) and analyzed timing of cell division in individual cells and cell populations. Inactivation of Bmal1 resulted in a loss of circadian rhythmicity and a lengthening of the cell cycle, originating from delayed G2/M transition. Subsequent molecular analysis revealed reduced levels of Cyclin B1, an important G2/M regulator, upon suppression of Bmal1 gene expression. In complete agreement with these experimental observations, simulation of Bmal1 knockdown in a computational model for coupled mammalian circadian clock and cell cycle oscillators (now incorporating Cyclin B1 induction by BMAL1) revealed a lengthening of the cell cycle. Similar data were obtained upon knockdown of Clock gene expression. In conclusion, the CLOCK/BMAL1 complex controls cell cycle progression at the level of G2/M transition through regulation of Cyclin B1 expression.     

哺乳动物生物钟的遗传和表观遗传研究进展

生物钟对生物机体的生存与环境适应具有着重要意义,其相关研究近年来受到人们的广泛关注。生物钟的重要性质之一是内源节律的周期性,当前的研究认为这种周期性是由生物钟相关基因转录翻译的多反馈环路构成核心机制调控着近似24 h的节律振荡。哺乳动物的生物钟系统存在一个多层次的结构,包括位于视交叉上核的主时钟和外周器官和组织的子时钟。虽然主时钟和子时钟存在的组织不同,但是参与调节生物钟的分子机制是一致的。近年来,通过正向、反向遗传学方法和表观遗传学的研究方法,对生物钟的分子机制的解析和认知愈发深入。本文在简单回顾生物钟基因发现历史的基础上,重点从遗传学和表观遗传学两个方面,从振荡周期的角度,对哺乳动物生物钟分子机制的研究进展进行了综述性介绍,以期为靶向调节生物钟来改善机体的稳态系统的研究提供参考,同时希望能促进时间生物学领域与更多其他领域形成交叉研究。     

Pigment‐dispersing factor affects circadian molecular oscillations in the cricket Gryllus bimaculatus

Pigment‐dispersing factor (PDF) is an important neurotransmitter in insect circadian systems. In the cricket Gryllus bimaculatus, it affects nocturnal activity, the free‐running period and photic entrainment. In this study, to investigate whether these effects of PDF occur through a circadian molecular machinery, we measured mRNA levels of clock genes period (per) and timeless (tim) in crickets with pdf expression knocked‐down by pdf RNAi. The pdf RNAi decreased per and tim mRNA levels during the night to reduce the amplitude of their oscillation. The phase of the rhythm advanced by about 4 h in terms of trough and/or peak phases. On the other hand, pdf mRNA levels were little affected by per and tim RNAi treatment. These results suggest that PDF affects the circadian rhythm at least in part through the circadian molecular oscillation while the circadian clock has little effect on the pdf expression.     

Impaired light detection of the circadian clock in a zebrafish melanoma model

The circadian clock controls the timing of the cell cycle in healthy tissues and clock disruption is known to increase tumourigenesis. Melanoma is one of the most rapidly increasing forms of cancer and the precise molecular circadian changes that occur in a melanoma tumor are unknown. Using a melanoma zebrafish model, we have explored the molecular changes that occur to the circadian clock within tumors. We have found disruptions in melanoma clock gene expression due to a major impairment to the light input pathway, with a parallel loss of light-dependent activation of DNA repair genes. Furthermore, the timing of mitosis in tumors is perturbed, as well as the regulation of certain key cell cycle regulators, such that cells divide arhythmically. The inability to co-ordinate DNA damage repair and cell division is likely to promote further tumourigenesis and accelerate melanoma development.     

Dexamethasone induces high-amplitude rhythms in preadipocytes,But hinders circadian expression in differentiated adipocytes

Glucocorticoids induce circadian gene expression in cultured cells and change the phase of circadian gene expression in vivo. In addition, glucocorticoids induce differentiation of preadipocyte to adipocytes. We set out to test the effect of dexamethasone, a glucocorticoid receptor agonist, on circadian rhythms in 3T3-L1 differentiated adipocytes. Our results show that differentiated adipocytes exhibit robust circadian rhythms without dexamethasone. Dexamethasone induces phase changes and increases the amplitude of circadian gene expression in nondifferentiated 3T3-L1 preadipocytes. However, dexamethasone had an opposite effect on differentiated adipocytes, leading to low-amplitude circadian expression. In conclusion, although glucocorticoids reset circadian rhythms, once rhythms are reset, glucocorticoid administration hinders circadian expression.     

生物节律基因period3的研究进展

昼夜节律是所有真核生物和部分原核生物的基本特征,一组节律表达的生物钟基因形成24 h周期振荡的自主调节转录-翻译反馈回路。period（per）基因家族是生物钟反馈回路中重要组成成分,per3基因是period基因家族成员之一。人类的per3基因定位于染色体1p36,其编码区第18外显子中含有一个灵长类特有的串联重复序列（variable number tandem repeat,VNTR）。该VNTR包含一簇理论上的磷酸化位点,能影响PER3蛋白的磷酸化降解,影响PER3蛋白的功能。近年研究发现,per3基因多态性与睡眠结构、睡眠紊乱发病年龄、睡眠剥夺后次日清晨执行能力等密切相关。     

The microbiota coordinates diurnal rhythms in innate immunity with the circadian clock

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Circadian clock,cell cycle,and breast cancer: an updated review

Some key elements are common to two fundamental periodic regulatory processes; the circadian cycle and the cell cycle. Underlying mechanisms of coordination between the two processes are critical for proper cellular functioning and physiology. Disruption in the mechanisms of one process may affect the role of other that may direct critical physiological changes and may cause severe diseases like cancer, etc. More or less persuasive evidences evolve from the breast cancer research. In this mini review, we highlighted the molecular coordination’s of the elements of circadian cycle and the cell cycle and their altered expressions associated with the genesis and progression of breast cancer.