Positive Autoregulation Delays the Expression Phase of Mammalian Clock Gene Per2
A simulation result of Per1 and Per2 mRNA expressions calculated by the model schematized in Figure 1A with the ratio of both transcription and degradation rates measured experimentally and applied as parameters. This model simulated the circadian oscillations in 33.8-hour period. After 1000 hours simulation, the first peak of Per1 mRNA was set to simulation time 6. The Per2 expression level was almost 25 times lower than that of Per1 even though its corresponding transcriptional rate was just one-third of the original value, and the Per2 phase was advanced by 5.4 hours, which was inconsistent with the experimentally observed results. Arrows indicate expression peaks.