生物鐘控制著生命活動的內(nèi)在節(jié)律,，過去人們一直認(rèn)為它的“驅(qū)動齒輪”是基因。而英國研究人員在新一期《自然》雜志上報告說,，他們發(fā)現(xiàn)了獨立于基因的生物鐘機(jī)制,，這種與新陳代謝有關(guān)的機(jī)制構(gòu)成了生物鐘的“第二齒輪”。
英國劍橋大學(xué)研究人員報告說,，首次發(fā)現(xiàn)人類血液紅細(xì)胞中也存在生物鐘,。與其他細(xì)胞擁有脫氧核糖核酸（DNA）等遺傳物質(zhì)不同，紅細(xì)胞中沒有DNA,，因此它不會像過去認(rèn)為的那樣,，根據(jù)基因發(fā)出的信號來調(diào)整活動節(jié)律。研究人員探測發(fā)現(xiàn),，紅細(xì)胞中一種名為peroxiredoxin的抗氧化蛋白的含量會出現(xiàn)24小時的周期性起落,，這說明有另一種生物鐘機(jī)制在起作用。
英國愛丁堡大學(xué)等機(jī)構(gòu)的研究人員在同期《自然》雜志上發(fā)表另一份研究報告說,，他們在海藻中也發(fā)現(xiàn)了類似現(xiàn)象,。雖然海藻細(xì)胞中有DNA等遺傳物質(zhì)，但在黑暗環(huán)境中其DNA不會作為生物鐘的“驅(qū)動齒輪”而轉(zhuǎn)動,。研究人員在黑暗環(huán)境中也探測到海藻細(xì)胞中同一種抗氧化蛋白的含量有周期性起落現(xiàn)象,。
這兩項研究說明，除了基因以外,，還存在驅(qū)動生物鐘運行的“第二齒輪”,。由于這種抗氧化蛋白在細(xì)胞新陳代謝中扮演著重要角色，研究人員認(rèn)為“第二齒輪”的驅(qū)動力應(yīng)該來自新陳代謝機(jī)制本身,。
愛丁堡大學(xué)的安德魯·米勒教授說,，海藻是一種極為古老的生物，因此這種與新陳代謝有關(guān)的生物鐘機(jī)制很可能已經(jīng)存在數(shù)十億年之久,，并在進(jìn)化中成為人類等生物體內(nèi)普遍存在的現(xiàn)象,。這一發(fā)現(xiàn)還說明生物鐘比人們以前所知更精密、更復(fù)雜,，需要更多深入研究,。
此前研究發(fā)現(xiàn)，如果生物鐘因坐飛機(jī),、上夜班等原因被擾亂,，常會引起新陳代謝紊亂和不舒服，甚至有可能導(dǎo)致糖尿病等疾病，本次研究進(jìn)展將有助于相關(guān)領(lǐng)域的進(jìn)一步探索,。（生物谷Bioon.com）
生物谷推薦原文出處：
Nature doi:10.1038/nature09702
Circadian clocks in human red blood cells
John S. O’Neill& Akhilesh B. Reddy
Circadian (~24 hour) clocks are fundamentally important for coordinated physiology in organisms as diverse as cyanobacteria and humans. All current models of the molecular circadian clockwork in eukaryotic cells are based on transcription–translation feedback loops. Non-transcriptional mechanisms in the clockwork have been difficult to study in mammalian systems. We circumvented these problems by developing novel assays using human red blood cells, which have no nucleus (or DNA) and therefore cannot perform transcription. Our results show that transcription is not required for circadian oscillations in humans, and that non-transcriptional events seem to be sufficient to sustain cellular circadian rhythms. Using red blood cells, we found that peroxiredoxins, highly conserved antioxidant proteins, undergo ~24-hour redox cycles, which persist for many days under constant conditions (that is, in the absence of external cues). Moreover, these rhythms are entrainable (that is, tunable by environmental stimuli) and temperature-compensated, both key features of circadian rhythms. We anticipate that our findings will facilitate more sophisticated cellular clock models, highlighting the interdependency of transcriptional and non-transcriptional oscillations in potentially all eukaryotic cells.
Nature doi:10.1038/nature09654
Circadian rhythms persist without transcription in a eukaryote
John S. O’Neill,Gerben van Ooijen,Laura E. Dixon,Carl Troein,Florence Corellou,Fran?ois-Yves Bouget,Akhilesh B. Reddy& Andrew J. Millar
Circadian rhythms are ubiquitous in eukaryotes, and coordinate numerous aspects of behaviour, physiology and metabolism, from sleep/wake cycles in mammals to growth and photosynthesis in plants1, 2. This daily timekeeping is thought to be driven by transcriptional–translational feedback loops, whereby rhythmic expression of ‘clock’ gene products regulates the expression of associated genes in approximately 24-hour cycles. The specific transcriptional components differ between phylogenetic kingdoms3. The unicellular pico-eukaryotic alga Ostreococcus tauri possesses a naturally minimized clock, which includes many features that are shared with plants, such as a central negative feedback loop that involves the morning-expressed CCA1 and evening-expressed TOC1 genes4. Given that recent observations in animals and plants have revealed prominent post-translational contributions to timekeeping5, a reappraisal of the transcriptional contribution to oscillator function is overdue. Here we show that non-transcriptional mechanisms are sufficient to sustain circadian timekeeping in the eukaryotic lineage, although they normally function in conjunction with transcriptional components. We identify oxidation of peroxiredoxin proteins as a transcription-independent rhythmic biomarker, which is also rhythmic in mammals6. Moreover we show that pharmacological modulators of the mammalian clock mechanism have the same effects on rhythms in Ostreococcus. Post-translational mechanisms, and at least one rhythmic marker, seem to be better conserved than transcriptional clock regulators. It is plausible that the oldest oscillator components are non-transcriptional in nature, as in cyanobacteria7, and are conserved across kingdoms.
