Integration of molecular rhythms in the mammalian circadian system

The discovery of clock genes and the general principles of their oscillation have made research on biological clocks a highly interesting field in the life sciences. As in other species, the mammalian circadian core oscillator is thought to be composed of an autoregulatory transcription-(post)translation-based feedback loop involving a set of clock genes. The production, phosphorylation, ubiquitination and proteasome-dependent degradation of clock proteins has a key role in generating the clock oscillation. The generation of internal clock time occurs in the hypothalamic suprachiasmatic nucleus (SCN), where clock gene oscillation in each neuron is coupled and amplified. These well synchronized oscillatory signals are spread into the whole brain and to peripheral organs which contain peripheral clocks. The important feature of the circadian system is that the rhythm of gene transcription of dock genes in the SCN reflects the behavioural rhythm almost perfectly. Investigations on biological clocks present the fascinating prospect of analysing the integrational mechanism of 'time' from genes to the living organism.