• the Korean Society for Brain and Neural Sciences



Exp Neurobiol 2011; 20(1): 18-28

Published online March 31, 2011

© The Korean Society for Brain and Neural Sciences

Mammalian Molecular Clocks

Ilmin Kwon, Han Kyoung Choe, Gi Hoon Son and Kyungjin Kim*

Department of Biological Sciences, Seoul National University and the Brain Research Center for the 21st Century Frontier Program in Neuroscience,Seoul 151-742, Korea

Correspondence to: *To whom correspondence should be addressed.
Tel: 82-2-880-6694/872-9100, Fax: 82-2-872-9108


As a consequence of the Earth's rotation, almost all organisms experience day and night cycles within a 24-hr period. To adapt and synchronize biological rhythms to external daily cycles, organisms have evolved an internal time-keeping system. In mammals, the master circadian pacemaker residing in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus generates circadian rhythmicity and orchestrates numerous subsidiary local clocks in other regions of the brain and peripheral tissues. Regardless of their locations, these circadian clocks are cell-autonomous and self-sustainable, implicating rhythmic oscillations in a variety of biochemical and metabolic processes. A group of core clock genes provides interlocking molecular feedback loops that drive the circadian rhythm even at the single-cell level. In addition to the core transcription/translation feedback loops, post-translational modifications also contribute to the fine regulation of molecular circadian clocks. In this article, we briefly review the molecular mechanisms and post-translational modifications of mammalian circadian clock regulation. We also discuss the organization of and communication between central and peripheral circadian oscillators of the mammalian circadian clock.

Keywords: circadian pacemaker, SCN, feedback loop, mammalian circadian clock