Detection of a circadian enhancer in the mDbp promoter using prokaryotic transposon vector-based strategy.

In mammals, the expression of 5-10% of genes occurs with circadian fluctuation in various organs and tissues. This cyclic transcription is thought to be directly or indirectly regulated through circadian transcriptional/translational feedback loops consisting of a set of clock genes. Among the clock genes in mammals, expression of the Dbp mRNA robustly oscillates both in vivo and in culture cells.

The BMAL1 C terminus regulates the circadian transcription feedback loop.

The circadian clock is driven by cell-autonomous transcription/translation feedback loops. The BMAL1 transcription factor is an indispensable component of the positive arm of this molecular oscillator in mammals. Here, we present a molecular genetic screening assay for mutant circadian clock proteins that is based on real-time circadian rhythm monitoring in cultured fibroblasts.

Rhythmic post-transcriptional regulation of the circadian clock protein mPER2 in mammalian cells: a real-time analysis.

Post-transcriptional/translational mechanisms regulate the circadian clock system of many organisms, including mammals. The level of the essential clock protein mPER2 daily oscillates in peripheral cells as well as in neurons of the master oscillator in the suprachiasmatic nucleus (SCN). Post-translational modifications of mPER2, such as phosphorylation and ubiquitination, are likely involved in the regulation of its stability and intracellular accumulation rhythms, which in turn create an approximately 2-4 h delay from the rhythm of mPer2 mRNA.

A novel mutation in kaiC affects resetting of the cyanobacterial circadian clock.

Light is the most important factor controlling circadian systems in response to day-night cycles. In order to better understand the regulation of circadian rhythms by light in Synechococcus elongatus PCC 7942, we screened for mutants with defective phase shifting in response to dark pulses. Using a 5-h dark-pulse protocol, we identified a mutation in kaiC that we termed pr1, for phase response 1.