Fig. 1.

Molecular clock and temporal expression of clock products. A: Schematic diagram of transcriptional interactions amount clock components. activation; repression. CWO may also mediate repression of output genes (not shown). B: Diurnal expression profiles for clock RNAs and proteins. Black lines represent RNA abundance profiles for per, tim and Clk. Colored lines indicate protein abundance profiles for clock proteins and immunofluorescence signals for Pigment Dispersing Factor (PDF), a clock output peptide. pCLK represents phosphorylated, activated CLK which has a circadian phase hours later than the Clk transcription rhythm. The PDF curve illustrates peptide immunoreactivity in the s-LNv dorsal projections; reduced amounts during the day are presumed to reflect release of the peptide.