Hoffmann Julia, Symul Laura, Shostak Anton, Fischer Tamás, Naef Felix, Brunner Michael
Biochemistry Center, University of Heidelberg, Heidelberg, Germany.
Institute of Bioengineering, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
PLoS One. 2014 Jul 9;9(7):e102238. doi: 10.1371/journal.pone.0102238. eCollection 2014.
U2OS cells harbor a circadian clock but express only a few rhythmic genes in constant conditions. We identified 3040 binding sites of the circadian regulators BMAL1, CLOCK and CRY1 in the U2OS genome. Most binding sites even in promoters do not correlate with detectable rhythmic transcript levels. Luciferase fusions reveal that the circadian clock supports robust but low amplitude transcription rhythms of representative promoters. However, rhythmic transcription of these potentially clock-controlled genes is masked by non-circadian transcription that overwrites the weaker contribution of the clock in constant conditions. Our data suggest that U2OS cells harbor an intrinsically rather weak circadian oscillator. The oscillator has the potential to regulate a large number of genes. The contribution of circadian versus non-circadian transcription is dependent on the metabolic state of the cell and may determine the apparent complexity of the circadian transcriptome.
U2OS细胞拥有生物钟，但在恒定条件下仅表达少数节律性基因。我们在U2OS基因组中鉴定出了生物钟调节因子BMAL1、CLOCK和CRY1的3040个结合位点。即使在启动子区域，大多数结合位点也与可检测到的节律性转录水平不相关。荧光素酶融合实验表明，生物钟支持代表性启动子的强劲但低振幅的转录节律。然而，这些潜在的生物钟控制基因的节律性转录被非昼夜节律转录所掩盖，在恒定条件下，非昼夜节律转录覆盖了生物钟较弱的贡献。我们的数据表明，U2OS细胞拥有一个本质上相当弱的生物钟振荡器。该振荡器有调节大量基因的潜力。昼夜节律转录与非昼夜节律转录的贡献取决于细胞的代谢状态，可能决定了昼夜节律转录组的表观复杂性。
