Exp Neurobiol 2014; 23(3): 191-199
Published online September 30, 2014
© The Korean Society for Brain and Neural Sciences
Euna Lee and Eun Young Kim*
Department of Biomedical Sciences, Department of Brain Science, Ajou University School of Medicine, Suwon 443-380, Korea
Correspondence to: *To whom correspondence should be addressed.
TEL: 82-31-219-4546, FAX: 82-31-219-4530
By means of a circadian clock system, all the living organisms on earth including human beings can anticipate the environmental rhythmic changes such as light/dark and warm/cold periods in a daily as well as in a yearly manner. Anticipating such environmental changes provide organisms with survival benefits via manifesting behavior and physiology at an advantageous time of the day and year. Cell-autonomous circadian oscillators, governed by transcriptional feedback loop composed of positive and negative elements, are organized into a hierarchical system throughout the organisms and generate an oscillatory expression of a clock gene by itself as well as clock controlled genes (ccgs) with a 24 hr periodicity. In the feedback loop, hetero-dimeric transcription factor complex induces the expression of negative regulatory proteins, which in turn represses the activity of transcription factors to inhibit their own transcription. Thus, for robust oscillatory rhythms of the expression of clock genes as well as ccgs, the precise control of subcellular localization and/or timely translocation of core clock protein are crucial. Here, we discuss how sub-cellular localization and nuclear translocation are controlled in a time-specific manner focusing on the negative regulatory clock proteins.
Keywords: circadian rhythms, nuclear translocation, phosphorylation, posttranslational modification, O-GlcNAcylation