Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, Davis, CA, United States of America.
Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany.
PLoS Genet. 2019 Jan 31;15(1):e1007953. doi: 10.1371/journal.pgen.1007953. eCollection 2019 Jan.
Circadian clocks coordinate time-of-day-specific metabolic and physiological processes to maximize organismal performance and fitness. In addition to light and temperature, which are regarded as strong zeitgebers for circadian clock entrainment, metabolic input has now emerged as an important signal for clock entrainment and modulation. Circadian clock proteins have been identified to be substrates of O-GlcNAcylation, a nutrient sensitive post-translational modification (PTM), and the interplay between clock protein O-GlcNAcylation and other PTMs is now recognized as an important mechanism by which metabolic input regulates circadian physiology. To better understand the role of O-GlcNAcylation in modulating clock protein function within the molecular oscillator, we used mass spectrometry proteomics to identify O-GlcNAcylation sites of PERIOD (PER), a repressor of the circadian transcriptome and a critical biochemical timer of the Drosophila clock. In vivo functional characterization of PER O-GlcNAcylation sites indicates that O-GlcNAcylation at PER(S942) reduces interactions between PER and CLOCK (CLK), the key transcriptional activator of clock-controlled genes. Since we observe a correlation between clock-controlled daytime feeding activity and higher level of PER O-GlcNAcylation, we propose that PER(S942) O-GlcNAcylation during the day functions to prevent premature initiation of circadian repression phase. This is consistent with the period-shortening behavioral phenotype of per(S942A) flies. Taken together, our results support that clock-controlled feeding activity provides metabolic signals to reinforce light entrainment to regulate circadian physiology at the post-translational level. The interplay between O-GlcNAcylation and other PTMs to regulate circadian physiology is expected to be complex and extensive, and reach far beyond the molecular oscillator.
昼夜节律钟协调特定时间的代谢和生理过程，以最大限度地提高生物体的表现和适应性。除了光和温度，它们被认为是昼夜节律钟同步的强信号外，代谢输入现在已成为时钟同步和调节的重要信号。昼夜节律钟蛋白已被确定为 O-GlcNAcylation 的底物，O-GlcNAcylation 是一种营养敏感的翻译后修饰（PTM），时钟蛋白 O-GlcNAcylation 与其他 PTM 之间的相互作用现在被认为是代谢输入调节昼夜生理的重要机制。为了更好地理解 O-GlcNAcylation 在调节时钟蛋白在分子振荡器中的功能的作用，我们使用质谱蛋白质组学鉴定了 PERIOD（PER）的 O-GlcNAcylation 位点，PER 是昼夜转录组的抑制剂，也是果蝇钟的关键生化定时器。PER O-GlcNAcylation 位点的体内功能特征表明，PER(S942) 的 O-GlcNAcylation 减少了 PER 与 CLOCK（CLK）之间的相互作用，CLK 是时钟控制基因的关键转录激活剂。由于我们观察到昼夜节律控制的白天进食活动与 PER O-GlcNAcylation 的更高水平之间存在相关性，因此我们提出白天 PER(S942) 的 O-GlcNAcylation 作用是防止昼夜节律抑制阶段的过早启动。这与 per(S942A) 果蝇的周期缩短行为表型一致。总之，我们的结果支持昼夜节律控制的进食活动提供代谢信号，以加强光同步，在翻译后水平上调节昼夜生理。O-GlcNAcylation 与其他 PTM 之间的相互作用来调节昼夜生理预计将是复杂和广泛的，并且远远超出分子振荡器的范围。
