David Whitmore, Nicolas Cermakian, Claudia Crosio, Nicholas S. Foulkes, Matthew P. Pando, Zdenka Travnickova, Paolo Sassone-Corsi
A Clockwork Organ
The vertebrate circadian clock was thought to be highly
localized to specific anatomical structures: the
mammalian suprachiasmatic nucleus (SCN), and the
retina and pineal gland in lower vertebrates. However,
recent findings in the zebrafish, rat and in cultured
cells have suggested that the vertebrate circadian timing
system may in fact be highly distributed, with most
if not all cells containing a clock.
Our understanding of the clock mechanism has progressed
extensively through the use of mutant screening
and forward genetic approaches. The first vertebrate
clock gene was identified only a few years ago in
the mouse by such an approach. More recently, using
a syntenic comparative genetic approach, the molecular
basis of the the tau mutation in the hamster was
determined. The tau gene in the hamster appears to
encode casein kinase 1 epsilon, a protein previously
shown to be important for PER protein turnover in the
Drosophila circadian system. A number of additional
clock genes have now been described. These proteins
appear to play central roles in the transcription-translation
negative feedback loop responsible for clock
function. Post-translational modification, protein dimerization
and nuclear transport all appear to be essential
features of how clocks are thought to tick.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 381, 09/2000
Pages: 793 - 800
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