Department of Orthodontics and Craniofacial Developmental Biology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima 734-8553, Japan.
Genes Cells. 2012 Feb;17(2):109-21. doi: 10.1111/j.1365-2443.2011.01574.x.
DEC1 and DEC2, members of the basic helix-loop-helix superfamily, are involved in various biological phenomena including clock systems, cell differentiation and metabolism. In clock systems, Dec1 and Dec2 expression are up-regulated by the CLOCK:BMAL1 heterodimer via E-box (CACGTG), exhibiting a circadian rhythm in the suprachiasmatic nucleus (SCN), the central circadian pacemaker and other peripheral tissues. In this study, using assays of luciferase reporters, electrophoretic mobility shift and chromatin immunoprecipitation, we identified novel nuclear receptor response elements, ROR response elements (RORE), in Dec1 and Dec2 promoters. These ROREs responded to the transcriptional activator RORα, but not to the repressor REVERBα, although the Bmal1 promoter responded to both RORα and REVERBα. Therefore, RORα, but not REVERBα, is involved in the regulation of Dec1 and Dec2 expression without significantly affecting their rhythmicity. Since RORα, DEC1 and DEC2 reportedly suppressed adipogenic differentiation, we examined expression of Rorα, Dec1, Dec2 and other clock-controlled genes in differentiating 3T3-L1 adipocytes. The results suggested that RORα suppresses adipogenic differentiation at a later stage of differentiation by RORE-mediated stimulation of Dec1 and Dec2 expression.
DEC1 和 DEC2 是基本螺旋-环-螺旋超家族的成员，参与多种生物学现象，包括时钟系统、细胞分化和代谢。在时钟系统中，DEC1 和 DEC2 的表达受 CLOCK:BMAL1 异二聚体通过 E-box（CACGTG）上调，在视交叉上核（SCN）、中央生物钟起搏器和其他周围组织中表现出昼夜节律。在这项研究中，我们使用荧光素酶报告基因检测、电泳迁移率变动分析和染色质免疫沉淀实验，鉴定了 DEC1 和 DEC2 启动子中的新型核受体反应元件，即 ROR 反应元件（RORE）。这些 RORE 响应转录激活因子 RORα，但不响应抑制剂 REVERBα，尽管 Bmal1 启动子对 RORα 和 REVERBα 都有反应。因此，RORα 参与 DEC1 和 DEC2 的表达调控，而不会显著影响它们的节律性，而 REVERBα 则没有。由于 RORα、DEC1 和 DEC2 据报道抑制脂肪生成分化，我们在分化的 3T3-L1 脂肪细胞中检查了 Rorα、Dec1、Dec2 和其他时钟控制基因的表达。结果表明，RORα 通过 RORE 介导的 Dec1 和 Dec2 表达刺激，在分化的后期抑制脂肪生成分化。
