scholarly journals The Circadian Clock Modulates Global Daily Cycles of mRNA Ribosome Loading

2015 ◽  
Vol 27 (9) ◽  
pp. 2582-2599 ◽  
Author(s):  
Anamika Missra ◽  
Ben Ernest ◽  
Tim Lohoff ◽  
Qidong Jia ◽  
James Satterlee ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Daily Cycles

scholarly journals Melatonin rhythm and other outputs of the master circadian clock in the desert goat ( Capra hircus ) are entrained by daily cycles of ambient temperature

2020 ◽  
Vol 68 (3) ◽  
Author(s):  
Hicham Farsi ◽  
Driss Harti ◽  
Mohamed R. Achaâban ◽  
Mohammed Piro ◽  
Véronique Raverot ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Circadian Clock ◽  
Capra Hircus ◽  
Melatonin Rhythm ◽  
Daily Cycles

scholarly journals Temperature-modulated Alternative Splicing and Promoter Use in the Circadian Clock Gene frequency

2005 ◽  
Vol 16 (12) ◽  
pp. 5563-5571 ◽  
Author(s):  
Hildur V. Colot ◽  
Jennifer J. Loros ◽  
Jay C. Dunlap
Keyword(s):  
Alternative Splicing ◽  
Circadian Clock ◽  
Clock Gene ◽  
Transcription Unit ◽  
Central Component ◽  
Temperature Sensitive ◽  
Circadian Clock Gene ◽  
Mrna Species ◽  
Daily Cycles ◽  
Evolutionary Comparisons

The expression of FREQUENCY, a central component of the circadian clock in Neurospora crassa, shows daily cycles that are exquisitely sensitive to the environment. Two forms of FRQ that differ in length by 99 amino acids, LFRQ and SFRQ, are synthesized from alternative initiation codons and the change in their ratio as a function of temperature contributes to robust rhythmicity across a range of temperatures. We have found frq expression to be surprisingly complex, despite our earlier prediction of a simple transcription unit based on limited cDNA sequencing. Two distinct environmentally regulated major promoters drive primary transcripts whose environmentally influenced alternative splicing gives rise to six different major mRNA species as well as minor forms. Temperature-sensitive alternative splicing determines AUG choice and, as a consequence, the ratio of LFRQ to SFRQ. Four of the six upstream ORFs are spliced out of the vast majority of frq mRNA species. Alternative splice site choice in the 5′ UTR and relative use of two major promoters are also influenced by temperature, and the two promoters are differentially regulated by light. Evolutionary comparisons with the Sordariaceae reveal conservation of 5′ UTR sequences, as well as significant conservation of the alternative splicing events, supporting their relevance to proper regulation of clock function.

scholarly journals Biochemical Evidence for a Timing Mechanism in Prochlorococcus

2009 ◽  
Vol 191 (17) ◽  
pp. 5342-5347 ◽  
Author(s):  
Ilka M. Axmann ◽  
Ulf Dühring ◽  
Luiza Seeliger ◽  
Anne Arnold ◽  
Jens T. Vanselow ◽  
...  
Keyword(s):  
Gene Expression ◽  
Circadian Clock ◽  
Biological Activities ◽  
Circadian Oscillator ◽  
Biochemical Evidence ◽  
Timing Mechanism ◽  
The Third ◽  
Stable Environment ◽  
Daily Cycles

ABSTRACT Organisms coordinate biological activities into daily cycles using an internal circadian clock. The circadian oscillator proteins KaiA, KaiB, and KaiC are widely believed to underlie 24-h oscillations of gene expression in cyanobacteria. However, a group of very abundant cyanobacteria, namely, marine Prochlorococcus species, lost the third oscillator component, KaiA, during evolution. We demonstrate here that the remaining Kai proteins fulfill their known biochemical functions, although KaiC is hyperphosphorylated by default in this system. These data provide biochemical support for the observed evolutionary reduction of the clock locus in Prochlorococcus and are consistent with a model in which a mechanism that is less robust than the well-characterized KaiABC protein clock of Synechococcus is sufficient for biological timing in the very stable environment that Prochlorococcus inhabits.

scholarly journals Why Lungs Keep Time: Circadian Rhythms and Lung Immunity

2020 ◽  
Vol 82 (1) ◽  
pp. 391-412 ◽  
Author(s):  
Charles Nosal ◽  
Anna Ehlers ◽  
Jeffrey A. Haspel
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Respiratory System ◽  
Lung Diseases ◽  
Environmental Changes ◽  
Biological Processes ◽  
General Introduction ◽  
Daily Cycles ◽  
Ancient Times ◽  
Lung Immunity

Circadian rhythms are daily cycles in biological function that are ubiquitous in nature. Understood as a means for organisms to anticipate daily environmental changes, circadian rhythms are also important for orchestrating complex biological processes such as immunity. Nowhere is this more evident than in the respiratory system, where circadian rhythms in inflammatory lung disease have been appreciated since ancient times. In this focused review we examine how emerging research on circadian rhythms is being applied to the study of fundamental lung biology and respiratory disease. We begin with a general introduction to circadian rhythms and the molecular circadian clock that underpins them. We then focus on emerging data tying circadian clock function to immunologic activities within the respiratory system. We conclude by considering outstanding questions about biological timing in the lung and how a better command of chronobiology could inform our understanding of complex lung diseases.

Entrainment of the circadian clock by daily ambient temperature cycles in the camel (Camelus dromedarius)

2013 ◽  
Vol 304 (11) ◽  
pp. R1044-R1052 ◽  
Author(s):  
Khalid El Allali ◽  
Mohamed R. Achaâban ◽  
Béatrice Bothorel ◽  
Mohamed Piro ◽  
Hanan Bouâouda ◽  
...  
Keyword(s):  
Phase Shift ◽  
Ambient Temperature ◽  
Circadian Clock ◽  
Camelus Dromedarius ◽  
Systematic Effect ◽  
Continuous Darkness ◽  
Experimental Conditions ◽  
Daily Cycles ◽  
Desert Areas ◽  
The Mean

In mammals the light-dark (LD) cycle is known to be the major cue to synchronize the circadian clock. In arid and desert areas, the camel ( Camelus dromedarius) is exposed to extreme environmental conditions. Since wide oscillations of ambient temperature (Ta) are a major factor in this environment, we wondered whether cyclic Ta fluctuations might contribute to synchronization of circadian rhythms. The rhythm of body temperature (Tb) was selected as output of the circadian clock. After having verified that Tb is synchronized by the LD and free runs in continuous darkness (DD), we submitted the animals to daily cycles of Ta in LL and in DD. In both cases, the Tb rhythm was entrained to the cycle of Ta. On a 12-h phase shift of the Ta cycle, the mean phase shift of the Tb cycle ranged from a few hours in LD (1 h by cosinor, 4 h from curve peaks) to 7–8 h in LL and 12 h in DD. These results may reflect either true synchronization of the central clock by Ta daily cycles or possibly a passive effect of Ta on Tb. To resolve the ambiguity, melatonin rhythmicity was used as another output of the clock. In DD melatonin rhythms were also entrained by the Ta cycle, proving that the daily Ta cycle is able to entrain the circadian clock of the camel similar to photoperiod. By contrast, in the presence of a LD cycle the rhythm of melatonin was modified by the Ta cycle in only 2 (or 3) of 7 camels: in these specific conditions a systematic effect of Ta on the clock could not be evidenced. In conclusion, depending on the experimental conditions (DD vs. LD), the daily Ta cycle can either act as a zeitgeber or not.

scholarly journals Clock-in, clock-out: circadian timekeeping between tissues

2020 ◽  
Vol 42 (2) ◽  
pp. 6-10
Author(s):  
Jacob G. Smith ◽  
Paolo Sassone-Corsi
Keyword(s):  
Circadian Clock ◽  
Daily Activity ◽  
Biological Processes ◽  
Stored Energy ◽  
Conscious Thought ◽  
Complex Organism ◽  
The Earth ◽  
Daily Cycles ◽  
Rotation Of The Earth ◽  
Time Information

Life evolved in the presence of alternating periods of light and dark that accompany the daily rotation of the Earth on its axis. This offered an advantage for organisms able to regulate their physiology to anticipate these daily cycles. In each light-sensitive organism studied, spanning single-celled bacteria to complex mammals, there exist timekeeping mechanisms able to control physiology over the course of 24 hours. Endowed with internal timekeeping, organisms can put their previously stored energy to the most efficient use, selectively ramping up biological processes at specific times of day or night according to when they will be needed. Humans have evolved to be more active during the day (diurnal), likely due to the increased opportunities for foraging or hunting in our evolutionary past, and this daily activity is accompanied by an up-regulation of genes involved in metabolism to increase the energy available for such behaviours. Remarkably, this happens without conscious thought—due to a complex organism-wide signalling apparatus known as the circadian clock network, which conveys time information between cells and tissues.

The Circadian Clock Regulates Rhythmic Expression of Ucp2 in β Cells and Controls Daily Cycles of Insulin Secretion

2017 ◽  
Vol 41 (5) ◽  
pp. S70-S71
Author(s):  
Nivedita Seshadri ◽  
Tianna N. Flett ◽  
Michael Jonasson ◽  
Kristin Hunt ◽  
Bo Xiang ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Circadian Clock ◽  
Β Cells ◽  
Rhythmic Expression ◽  
Daily Cycles

scholarly journals Cryptochromes and the Circadian Clock: The Story of a Very Complex Relationship in a Spinning World

Genes ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 672
Author(s):  
Loredana Lopez ◽  
Carlo Fasano ◽  
Giorgio Perrella ◽  
Paolo Facella
Keyword(s):  
Circadian Clock ◽  
Cell Cycle Regulation ◽  
Molecular Mechanisms ◽  
Chloroplast Development ◽  
Complex Relationship ◽  
Physiological Processes ◽  
Environmental Light ◽  
Daily Cycles ◽  
Chromatin Organisation ◽  
Cycle Regulation

Cryptochromes are flavin-containing blue light photoreceptors, present in most kingdoms, including archaea, bacteria, plants, animals and fungi. They are structurally similar to photolyases, a class of flavoproteins involved in light-dependent repair of UV-damaged DNA. Cryptochromes were first discovered in Arabidopsis thaliana in which they control many light-regulated physiological processes like seed germination, de-etiolation, photoperiodic control of the flowering time, cotyledon opening and expansion, anthocyanin accumulation, chloroplast development and root growth. They also regulate the entrainment of plant circadian clock to the phase of light–dark daily cycles. Here, we review the molecular mechanisms by which plant cryptochromes control the synchronisation of the clock with the environmental light. Furthermore, we summarise the circadian clock-mediated changes in cell cycle regulation and chromatin organisation and, finally, we discuss a putative role for plant cryptochromes in the epigenetic regulation of genes.

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