Zhu Aijun, Chen Muyan, Zhang Xiumei, Storey Kenneth B
Fisheries College, Ocean University of China, Qingdao, PR China; The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, PR China.
Fisheries College, Ocean University of China, Qingdao, PR China; The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, PR China.
Gene. 2016 Dec 5;594(1):82-88. doi: 10.1016/j.gene.2016.09.006. Epub 2016 Sep 4.
The sea cucumber, Apostichopus japonicus, is a good model for studying environmentally-induced aestivation by a marine invertebrate. One of the central requirements of aestivation is the repression of energy-expensive cellular processes such as cell cycle progression. The present study identified the gene structure of the cell cycle regulator, cyclin B, and detected the expression levels of this gene over three stages of the annual aestivation-arousal cycle. Furthermore, the DNA methylation characteristics of cyclin B were analyzed in non-aestivation and deep-aestivation stages of sea cucumbers. We found that the cyclin B promoter contains a CpG island, three CCAAT-boxes and three cell cycle gene homology regions (CHRs). Application of qRT-PCR analysis showed significant downregulation of cyclin B transcript levels during deep-aestivation in comparison with non-aestivation in both intestine and longitudinal muscle, and these returned to basal levels after arousal from aestivation. Methylation analysis of the cyclin B core promoter revealed that its methylation level showed significant differences between non-aestivation and deep-aestivation stages (p<0.05) and interestingly, a positive correlation between Cyclin B transcripts expression and methylation levels of the core promoter was also observed. Our findings suggest that cell cycle progression may be reversibly arrested during aestivation as indicated by the changes in cyclin B expression levels and we propose that DNA methylation is one of the regulatory mechanisms involved in cyclin B transcriptional variation.
仿刺参是研究海洋无脊椎动物环境诱导夏眠的良好模型。夏眠的核心要求之一是抑制细胞周期进程等耗能的细胞过程。本研究确定了细胞周期调节因子细胞周期蛋白B的基因结构，并检测了该基因在年度夏眠-苏醒周期三个阶段的表达水平。此外，还分析了海参非夏眠和深度夏眠阶段细胞周期蛋白B的DNA甲基化特征。我们发现细胞周期蛋白B启动子包含一个CpG岛、三个CCAAT框和三个细胞周期基因同源区域（CHRs）。qRT-PCR分析表明，与非夏眠相比，深度夏眠期间肠道和纵肌中细胞周期蛋白B转录水平显著下调，且在从夏眠苏醒后恢复到基础水平。细胞周期蛋白B核心启动子的甲基化分析显示，其甲基化水平在非夏眠和深度夏眠阶段存在显著差异（p<0.05），有趣的是，还观察到细胞周期蛋白B转录本表达与核心启动子甲基化水平之间呈正相关。我们的研究结果表明，如细胞周期蛋白B表达水平的变化所示，细胞周期进程在夏眠期间可能会可逆性停滞，并且我们提出DNA甲基化是参与细胞周期蛋白B转录变异的调节机制之一。
