生物钟基因3及其表达的调节机制

众所周知 ,生物体的新陈代谢过程 ,细胞和细胞器官的生理功能 ,以及心理行为等生命活动往往随着昼夜循环而发生规律性的变化。就是在实验室恒定的条件下 ,消除一切环境因子的影响 ,生命活动仍表现出昼夜节律性的变化。这说明昼夜节律受体内的测时系统——生物钟的控制。从 5 0年代至今 ,人们对生物的昼夜节律及其调控机制进行了深入地研究 ,特别是应用生物化学和分子生物学的方法 ,使人们逐步了解了生物节律的特点 ,生物钟基因及其表达的调控机制。1　生物钟基因存在于不同生物体中的昼夜节律时钟都表现出 3个共同的特点 :1 )在恒定的环境条…     

果蝇昼夜节律的调控机制

40多年前的遗传筛选鉴定了第一个果蝇生物钟基因period,开启了果蝇生物钟调控机制的研究。随着更多生物钟基因被发现,一个由转录水平的调控及转录后水平的修饰组成的负反馈环路模型逐步形成,被认为是调控昼夜节律的核心分子机制。生物钟驱动果蝇脑内约150个神经元的活动,这些神经元在不同的环境条件下通过不同的方式互作,共同调控果蝇的行为节律。昼夜环境变化中最显著的是明暗变化。蓝光受体cryptochrome在光对昼夜节律的调控中起重要作用。     

果蝇昼夜节律生物钟机制研究进展

昼夜节律生物钟包括输入途径、生物钟本身和输出途径。果蝇作为昼夜节律生物钟研究的前沿模式生物需被进一步了解。本文对果蝇昼夜节律生物钟的钟基因、激酶和磷酸酶的调控、两个相互依赖的转录/翻译反馈环路、生物钟细胞和昼夜节律行为进行了综述。     

生物钟基因研究进展

昼夜节律是以大约24 h为周期波动的生物现象.这些节律包括血压、体温、激素水平、血中免疫细胞的数量、睡眠觉醒周期循环等.基因水平上的昼夜节律研究还只是刚起步,介绍不同物种控制昼夜行为的共同基因(如period 、timless 、clock基因等)的研究进展,特别是一些有关调控昼夜节律基因的转录因子的研究.同时讨论果蝇和人类生物钟调节的共同分子机制.     

拟南芥生物钟分子机制研究进展

本文主要概述了目前拟南芥生物钟分子机制的研究进展。生物钟通过调控导引节律的相位来调节植物的生理活动。拟南芥生物钟由CCA1、LHY和TOC1 3个主要基因构成了一个稳定的负反馈环,来调节昼夜节律中各个基因如APRR/TOC1 5重奏的作用, 从而调控昼夜节律的相位。在开花的光周期调控中, 提出了外协和模型, 其中的关键基因是CO , 它与拟南芥的开花时间直接相关。     

生物钟基因介导卵巢功能调控的分子机制研究

地球的自转产生了以24 h为周期的昼夜节律,因此生物的生理过程和行为活动大都呈现一个近似24 h的周期节律改变,以适应环境的不断变化。昼夜节律在整体水平是一个系统性的调控,它的产生、维持和调控依赖于细胞内生物钟基因的震荡型转录翻译负反馈环路。研究表明,生物钟在卵巢动情周期和生殖系统发育过程中发挥重要作用。本篇综述主要阐述了自卵巢生物钟发现后的种种研究成果,包括卵巢生物钟对类固醇激素生成及排卵的影响,生物钟基因对生育能力的影响,以及生物钟调控与女性生殖系统疾病的相关性。     

拟南芥生物钟分子机制研究进展

本文主要概述了目前拟南芥生物钟分子机制的研究进展.生物钟通过调控导引节律的相位来调节植物的生理活动.拟南芥生物钟由CCAJ、LHy和TOCJ 3个主要基因构成了一个稳定的负反馈环,来调节昼夜节律中各个基因如APRR/TOC15重奏的作用,从而调控昼夜节律的相位.在开花的光周期调控中,提出了外协和模型,其中的关键基因是CO,它与拟南芥的开花时间直接相关.     

生物钟基因及其表达的调节机制

众所周知,生物体的新陈代谢过程,细胞和细胞器官的生理功能,以及心理行为等生命活动往往随着昼夜循环而发生规律性的变化.就是在实验室恒定的条件下,消除一切环境因子的影响,生命活动仍表现出昼夜节律性的变化.这说明昼夜节律受体内的测时系统--生物钟的控制.从50年代至今,人们对生物的昼夜节律及其调控机制进行了深入地研究,特别是应用生物化学和分子生物学的方法,使人们逐步了解了生物节律的特点,生物钟基因及其表达的调控机制.     

哺乳动物昼夜节律的调控及其分子机制

昼夜节律是生物界普遍存在的一种生命现象,它由生物自身因素控制,并可对环境变化作出应对。综述哺乳动物昼夜节律调控的分子机制及全身组织器官生物钟同步化控制机制。     

生物钟节律与肝脏代谢稳态

生物钟(circadian clock)是机体内在的自主性计时系统,包括视交叉上核(suprachiasmatic nucleus, SCN)中枢生物钟与各组织外周生物钟。分子生物钟的核心机制包括CLOCK/BMAL1二聚体诱导抑制因子CRYs和PERs的转录,CRYs/PERs复合物反馈抑制前者转录活性,进而使这些生物钟核心因子以及节律输出基因的转录水平呈24 h振荡的反馈调节核心环路,以及REV-ERBα和RORα调控BMAL1转录的补充环路。机体大约80%的蛋白编码基因表达呈现明显的昼夜节律性特征,生物钟系统使生物能够适应地球自转所产生的昼夜节律(近日节律),使机体的代谢平衡与能量相互协同。生物钟与代谢稳态相互依存、互为基础,使机体能够高效利用能量,协同机体不同组织,快速适应内外环境变化。肝脏作为机体代谢的中枢器官,其进行的各种生理活动几乎都受到生物钟的控制。生物钟与肝脏代谢调控之间存在多重交互调控机制,两者的交互平衡失调是代谢性疾病的高风险因素。本文主要就肝脏的糖、脂和蛋白质代谢的节律性调控进行了综述,并强调了线粒体功能的振荡,讨论了肝脏代谢对生物钟的反馈调节,并对生物钟研究方法和应用进行展望。     

Circadian rhythms in plants: Strategies for analysis

Molecular mechanism of the circadian clock which regulates the circadian rhythms has been believed to be common in different organisms. However, recent topic about multiple oscillators in a cell is thought to suggest other possibility. We may need to reconsider effectiveness of strategies for understanding molecular mechanism of the circadian clock.     

Tales from the crypt(ochromes)

Cryptochromes are a family of flavoproteins found in organisms ranging from Arabidopsis to man. Across phylogeny, these proteins have been used for pleiotropic functions ranging from blue-light-dependent development in plants and blue-light-mediated phase shifting of the circadian clock in insects to a core circadian clock component in mammals. Review of the roles of cryptochromes in model organisms reveals several common themes: Multiple cryptochrome family members within individual organisms have redundant functions; cryptochromes used in photic entrainment pathways of the circadian clock are partially redundant with other photopigments; and cryptochromes may function in circadian phototransduction and core clock mechanisms in the same organism, with different functions in different tissues. The present review summarizes recent research on the functions of cryptochrome in the circadian timekeeping and photic entrainment pathways.     

A TEMPERATURE-COMPENSATED ULTRADIAN CLOCK OF TETRAHYMENA: OSCILLATIONS IN RESPIRATORY ACTIVITY AND CELL DIVISION

Both a circadian clock and an ultradian clock (period 4—5 h) have previously been described for the ciliated protozoon Tetrahymena. The present communication demonstrates the existence of yet another cellular clock: an ultradian rhythm with a period of about 30 min. The period was found to be well temperature-compensated over the range studied, i.e., between 19°C and 33°C. Ultradian rhythmicity was initiated by dilution of stationary-phase cultures, which were kept previously in a light-dark cycle, into fresh medium. LD treatment during stationary phase was an absolute requirement, since cultures kept in either LL or DD did not produce the ultradian rhythmicity after refeeding. The clock exerts control over respiration; the observed oscillation in oxygen uptake is just a hand of the clock: after a limitation of oxygen supply had ended, the rhythm resumed with the same phase and period as that in control cultures. The clock exerts temporal control also over cell division; in the refed culture cell division resumed with an oscillation in the number of dividing organisms. The period of this oscillation corresponded to that of the rhythm in respiratory activity, indicating that the same ultradian clock may exert control over different cellular functions. Analysis of a second Tetrahymena strain indicates that period length of the ultradian clock is a strain-specific characteristic.     

Understanding circadian rhythmicity in Neurospora crassa: from behavior to genes and back again

Circadian clocks have been described in organisms ranging in complexity from unicells to mammals, in which they function to control daily rhythms in cellular activities and behavior. The significance of a detailed understanding of the clock can be appreciated by its ubiquity and its established involvement in human physiology, including endocrine function, sleep/wake cycles, psychiatric illness, and drug tolerances and effectiveness. Because the clock in all organisms is assembled within the cell and clock mechanisms are evolutionarily conserved, simple eukaryotes provide appropriate experimental systems for dissecting the clock. Significant progress has been made in deciphering the circadian system in Neurospora crassa using both genetic and molecular approaches, and Neurospora has contributed greatly to our understanding of (1) the feedback cycle that comprises a circadian oscillator, (2) the mechanisms by which the clock is kept in synchrony with the environment, and (3) the genes that reside in rhythmic output pathways. Importantly, the lessons learned in Neurospora are relevant to our understanding of clocks in higher eukaryotes.     

Riding tandem: circadian clocks and the cell cycle

The circadian clock, which governs metabolic and physiological rhythms in diverse organisms, shares common features with the cell cycle. Yet, these two oscillatory systems seem to be fully independent of each other. Recent studies now reveal that some essential regulatory elements are common to both the cell cycle and circadian clock.     

Circadian rhythms from multiple oscillators: lessons from diverse organisms

The organization of biological activities into daily cycles is universal in organisms as diverse as cyanobacteria, fungi, algae, plants, flies, birds and man. Comparisons of circadian clocks in unicellular and multicellular organisms using molecular genetics and genomics have provided new insights into the mechanisms and complexity of clock systems. Whereas unicellular organisms require stand-alone clocks that can generate 24-hour rhythms for diverse processes, organisms with differentiated tissues can partition clock function to generate and coordinate different rhythms. In both cases, the temporal coordination of a multi-oscillator system is essential for producing robust circadian rhythms of gene expression and biological activity.     

生物钟基因研究新进展

生物钟基因普遍存在于生物界,其作用在于产生和控制昼夜节律的运转。生物钟基因及其编码的蛋白质组成反馈回路,维持振荡系统持续进行并与环境周期保持同步。各级进化水平物种生物钟的基因组成和控制途径有同有异。此文主要介绍蓝细菌、脉孢菌、果蝇、鼠和人昼夜钟的分子运作机制以及研究钟基因的意义和展望。 Abstract:The circadian clock genes,which generate and control the running of the circadian rhythms,exist in organisms ranging from prokaryotes to mammals.The oscillator genes and its coding proteins compose the feedback loops of circadian system.The kind,number and regulating route of clock genes are characterized by living things at different evolution levels.The molecular mechanism of the run of circadian clock genes in cyanobacteria,neurospore,fruit fly,mouse and human being is introduced in this article.