Oishi K, Fukui H, Ishida N
Ishida Group of Clock Gene, National Institute of Bioscience and Human Technology, Agency of Industrial Science and Technology, MITI, Higashi 1-1, Tsukuba, Ibaraki, 305-8566, Japan.
Biochem Biophys Res Commun. 2000 Feb 5;268(1):164-71. doi: 10.1006/bbrc.1999.2054.
BMAL1 is a putative clock gene which encodes a basic helix-loop-helix (bHLH)-PAS transcription factor. To examine whether the CLOCK protein is required for the circadian expression of BMAL1 mRNA, in situ hybridization and Northern blot analysis were performed in the suprachiasmatic nucleus (SCN) and peripheral tissues of homozygous Clock mutant mice. In the SCN of Clock mutants, BMAL1 mRNA did not oscillate significantly but apparently expressed with low levels, while in wild-type mice the mRNA was robustly oscillated in a circadian manner. The peak-trough amplitudes of BMAL1 mRNA levels were 6.5-, 8.6-, and 6.7-fold in liver, heart, and kidney of wild-type mice, respectively. In Clock mutants, the amplitudes were extremely damped to 1.2-, 2.1-, and 1.4-fold, respectively. Furthermore, expressions of BMAL1 mRNA in the peripheral of Clock mutant mice were close to the peak level in wild-type mice, whereas mPer2 mRNA levels were severely blunted at trough values. Daily expression of albumin site D-binding protein (DBP), a clock controlled output gene (CCG), was also abolished at trough values by the Clock mutation in all tissues examined. These observations suggest that the circadian expression of BMAL1 mRNA is affected by the CLOCK-induced transcriptional feedback loop in the SCN and peripheral tissues in a different way and that the regulation mechanism appeared to be different from those in mPer2 and DBP expressions in vivo.
BMAL1是一种假定的生物钟基因，它编码一种基本的螺旋-环-螺旋（bHLH）-PAS转录因子。为了研究生物钟蛋白是否是BMAL1 mRNA昼夜节律表达所必需的，我们在纯合Clock突变小鼠的视交叉上核（SCN）和外周组织中进行了原位杂交和Northern印迹分析。在Clock突变体的SCN中，BMAL1 mRNA没有明显的振荡，但明显以低水平表达，而在野生型小鼠中，该mRNA以昼夜节律的方式强烈振荡。野生型小鼠肝脏、心脏和肾脏中BMAL1 mRNA水平的峰谷振幅分别为6.5倍、8.6倍和6.7倍。在Clock突变体中，振幅分别极度衰减至1.2倍、2.1倍和1.4倍。此外，Clock突变小鼠外周组织中BMAL1 mRNA的表达接近野生型小鼠的峰值水平，而mPer2 mRNA水平在谷值时严重减弱。在所有检测的组织中，时钟控制的输出基因（CCG）白蛋白位点D结合蛋白（DBP）的每日表达在谷值时也因Clock突变而被消除。这些观察结果表明，BMAL1 mRNA的昼夜节律表达在SCN和外周组织中受到生物钟诱导的转录反馈环的不同影响，并且调节机制似乎与体内mPer2和DBP的表达不同。
