Khalsa S B, Whitmore D, Bogart B, Block G D
Department of Biology, University of Virginia, Charlottesville 22903, USA.
Am J Physiol. 1996 Nov;271(5 Pt 1):C1646-51. doi: 10.1152/ajpcell.1996.271.5.C1646.
The retinal circadian clock in the isolated in vitro eye of the marine mollusc Bulla gouldiana exhibits a phase-dependent requirement for transcription. The transcription-sensitive phase extends through most of the subjective day and therefore is substantially longer than the previously reported translation-sensitive phase. Lower concentrations of transcription inhibitors yield a significant dose-dependent lengthening of circadian period. Clock motion can be stopped by a high concentration of the transcription inhibitor 5,6-dichlorobenz-imidazole riboside (DRB) when applied during the sensitive phase; after withdrawal of the inhibitor, motion resumes from the phase at which it was stopped. In a double-pulse experiment, phase shifts to light pulses applied after DRB pulses, and not during the translation-sensitive phase, indicate that the inhibition of transcription has immediate effects on the phase of the clock. These data suggest that DRB-induced phase shifts are independent of translation, which implies that the rate of transcription itself plays a significant role in the mechanism underlying the generation of the circadian cycle.
海洋软体动物沟纹泡螺离体体外眼中的视网膜生物钟表现出对转录的相位依赖性需求。转录敏感期贯穿大部分主观日，因此比先前报道的翻译敏感期长得多。较低浓度的转录抑制剂会导致昼夜节律周期显著的剂量依赖性延长。在敏感期应用高浓度的转录抑制剂5,6-二氯苯并咪唑核糖核苷（DRB）可使生物钟运动停止；去除抑制剂后，运动从停止的相位恢复。在双脉冲实验中，向DRB脉冲后而非翻译敏感期施加的光脉冲的相位移动表明，转录抑制对生物钟相位有直接影响。这些数据表明，DRB诱导的相位移动与翻译无关，这意味着转录速率本身在昼夜节律周期产生机制中起着重要作用。
