• Development and Reproduction
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• v.7 no.1
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• pp.1-7
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• 2003

Most animals, including human beings, live in a cyclic pattern of lift that is influenced by the ambient changes of environment. The regular changes occurred by rotation of the Earth itself its revolving around the Sun, and the local environment, are reflected by the distinct behavior in the living organisms. These regular changes of environment have been imprinted into the genes within the living organisms through the evolutionary process over a long period of time. The genes are expressed by rhythms during the process of fetal development followed by growth. The environmental modifications ultimately are settled in genes, serving as a biological clock that is located putatively in the hypothalamus. Thus the biological clock governs a large number of rhythms and affects the time of birth and death lift expectancy, behavior, physiology, cell division, biochemical reaction, etc. The rhythms are readjusted to the changes of environmental cues. The biological clock has the great advantage of predicting and preparing the regular changes of environment.

• Journal of Life Science
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• v.22 no.8
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• pp.999-1008
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• 2012

The circadian clock is a self-sustaining 24-hour timekeeper that allows organisms to anticipate daily-changing environmental time cues. Circadian clock genes are regulated by a transcriptional-translational feedback loop. In Arabidopsis, LATE ELONGATED HYPOCOTYL (LHY) and CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) transcripts are highly expressed in the morning. Translated LHY and CCA1 proteins repress the expression of the TIMING OF CAB EXPRESSION 1 (TOC1) transcripts, which peaks in the evening. The TOC1 protein elevates the expression of the LHY and CCA1 transcripts, forming a negative feedback loop that is believed to constitute the oscillatory mechanism of the clock. In mammals, the transcription factor protein CLOCK, which is a central component of the circadian clock, was reported to have an intrinsic histone acetyltransferase (HAT) activity, suggesting that histone acetylation is important for core clock mechanisms. However, little is known about the components necessary for the histone acetylation of the Arabidopsis clock-related genes. Here, I report that DET1 (De-Etiolated1) functions as a negative regulator of a key component of the Arabidopsis circadian clock gene LHY in constant dark phases (DD) and is required for the down-regulation of LHY expression through the acetylation of histone 3 (H3Ac). However, the HATs directly responsible for the acetylation of H3 within LHY chromatin need to be identified, and a link connecting the HATs and DET1 protein is still absent.

• Journal of Plant Biotechnology
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• v.44 no.4
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• pp.438-447
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• 2017

Flowering is one of the most important development traits related to the production of Brassica rapa crops. After planting, a sudden low temperature triggers premature flowering, which leads to a reduction in the yield and quality of harvested production. Therefore, understanding the mechanism of flowering control is important in the agricultural productivity for preventing Brassica rapa crops. Vernalization is generally known as the main factor of flowering in the Brassica plant. However, in the subspecies of Brassica rapa, some accession such as Yellow sarson and Komatsuna display the flowering phenotype without vernalization. Circadian genes, which diurnally regulate plant physiology, have a role for photoperiodic flowering but are related to the regulation of the vernalizarion mechanism. In this report, the 22 B. rapa accession were divided into two groups, vernalization and non-vernalization, and the sequenced circadian gene, BrPRR1s. Among them, the BrPRR1b gene was found to have deletion regions, which could classify the two groups. The PCR primer was designed to amplify a short band of 422bp in the vernalization type and a long band of 451bp in the non-vernalization type. This primer set was applied to distinguish the flowering types in the 43 B. rapa accession and 4 Brassica genus crop, Broccoli, cabbage, mustard, and rape. The PCR analysis results and flowering time information of each crop demonstrated that the primer set can be used as marker to discern the flowering type in Brassica crops. This marker system can be applied to the B. rapa breeding when selecting the flowering character of new progenies or introducing varieties at an early stage. In addition, these results displayed that the circadian clock genes can be a good strategy for the flowering control of B. rapa crops.

• Journal of Korean Biological Nursing Science
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• v.18 no.4
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• pp.305-317
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• 2016

Purpose: Recent studies demonstrated disruption of the circadian clock gene is associated with the development of obesity and metabolic syndrome. Obesity is often caused by the high calorie intake, In addition, the chronic stress tends to contribute to the increased risk for obesity. To evaluate the molecular mechanisms, we examined the expression of circadian clock genes in high fat diet-induced mice models with the chronic stress. Methods: C57BL/6J mice were fed with a 45% or 60% high fat diet for 8 weeks. Daily immobilization stress was applied to mice fed with a 45% high fat for 16 weeks. We compared body weight, food consumption, hormone levels and metabolic variables in blood. mRNA expression levels of metabolic and circadian clock genes in both fat and liver were determined by quantitative RT-PCR. Results: The higher fat content induced more severe hyperglycemia, hyperlipidemia and hyperinsulinemia, and these results correlated with their relevant gene expressions in fat and liver tissues. Chronic stress had only minimal effects on metabolic variables, but it altered the expression patterns of metabolic and circadian clock genes. Conclusion: These results suggest that the fat metabolism regulates the function of the circadian clock genes in peripheral tissues, and stress hormones may contribute to its regulation.

• The Korean Journal of Mycology
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• v.41 no.1
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• pp.1-8
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• 2013

COP9 signalosome (CSN), which is originally identified as the regulator of the photomorphogenic development in plant, is highly conserved protein complex in diverse eukaryotic organisms. Most eukaryotic CSN complex is composed of 8 subunits, which is structurally and functionally similar to the lid subunit of 26S proteasome and eIF3 translation initiation complex. CSN play important functions in the regulation of cell cycle and checkpoint response by controlling Cullin-Ring E3 ubiquitin ligases (CRL) activities. CSN exhibits an isopeptidase activity which cleaves the neddylated moiety of cullin components. In fission yeast, S-phase cell cycle progression was delayed and the sensitivity to g-ray or UV was increased in CSN1 and CSN2 deletion mutants, indicating that yeast CSN is also involved in the checkpoint regulation. CSN in fungal system more closely resembles that of the higher organisms in the structure and assembly of their components. Functionally, CSN is associated with the regulation of conidiation rhythms in Neurospora crassa and the sexual development in Aspsergillus nidulans. Recent studies also revealed that CSN functions as an essential cell cycle regulator, playing key roles in the regulation of DNA replication and DNA damage response in Aspergillus. Overall, CSN of microorganisms, such as fission yeast and fungi, share functionally common aspects with higher organisms, implying that they can be useful tools to study the role of CSN in the CRL-mediated diverse cellular activities.