Yoo Seung-Hee, Ko Caroline H, Lowrey Phillip L, Buhr Ethan D, Song Eun-joo, Chang Suhwan, Yoo Ook Joon, Yamazaki Shin, Lee Choogon, Takahashi Joseph S
Department of Neurobiology and Physiology, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA.
Proc Natl Acad Sci U S A. 2005 Feb 15;102(7):2608-13. doi: 10.1073/pnas.0409763102. Epub 2005 Feb 7.
The mouse Period2 (mPer2) locus is an essential negative-feedback element of the mammalian circadian-clock mechanism. Recent work has shown that mPer2 circadian gene expression persists in both central and peripheral tissues. Here, we analyze the mouse mPer2 promoter and identify a circadian enhancer (E2) with a noncanonical 5'-CACGTT-3' E-box located 20 bp upstream of the mPer2 transcription start site. The E2 enhancer accounts for most circadian transcriptional drive of the mPer2 locus by CLOCK:BMAL1, is a major site of DNaseI hypersensitivity in this region, and is constitutively bound by a transcriptional complex containing the CLOCK protein. Importantly, the E2 enhancer is sufficient to drive self-sustained circadian rhythms of luciferase activity in central and peripheral tissues from mPer2-E2::Luciferase transgenic mice with tissue-specific phase and period characteristics. Last, genetic analysis with mutations in Clock and Bmal1 shows that the E2 enhancer is a target of CLOCK and BMAL1 in vivo.
小鼠Period2（mPer2）基因座是哺乳动物昼夜节律钟机制的一个重要负反馈元件。最近的研究表明，mPer2昼夜节律基因表达在中枢和外周组织中均持续存在。在此，我们分析了小鼠mPer2启动子，并鉴定出一个昼夜节律增强子（E2），其具有一个非典型的5'-CACGTT-3' E-box，位于mPer2转录起始位点上游20 bp处。E2增强子是CLOCK:BMAL1对mPer2基因座进行的大部分昼夜节律转录驱动的原因，是该区域DNA酶I超敏反应的主要位点，并被一个包含CLOCK蛋白的转录复合物持续结合。重要的是，E2增强子足以驱动来自具有组织特异性相位和周期特征的mPer2-E2::荧光素酶转基因小鼠的中枢和外周组织中荧光素酶活性的自我维持昼夜节律。最后，对Clock和Bmal1突变的遗传分析表明，E2增强子是体内CLOCK和BMAL1的一个靶点。
