Fig. 7. Disruption of the CK1δ-PER interaction increases CRY1 enrichment at the E-box region.
a Immunoprecipitation assay using mPER2 antibody showing the levels of CRY1 associated with mPER2 in the WT and Per1−/−; Per2m/m mouse livers. Three independent experiments were performed to validate the results. b CRY1 ChIP assay results showing the relative CRY1 enrichment at the E-box region of the indicated gene promoters at the indicated time points in the WT and Per1−/−; Per2m/m mice. Chromatin samples from mouse livers were analyzed by ChIP using CRY1 antibody. Error bars are standard deviations. *p value < 0.05 and **p value < 0.01 (two-sided t-test). c A model of the coupled CK1-dependent and CK1-independent negative feedback loops in the core mammalian circadian oscillator. During subjective days, the PER levels are low and CLOCK-BMAL is associated with E-box and active. During the subjective night, PER and CRY levels are high. The CK1-dependent negative feedback process (bottom) involving CK1, PER, and CRY that mediates efficient removal CLOCK-BMAL1 from the E-boxes by promoting PER-dependent phosphorylation of CLOCK by CK1. The CK1-independent process (top) results in the repression of the CLOCK-BMAL1 complex transcription activation activity by the PER-CRY complex on DNA. This process also causes slow removal of CLOCK-BMAL1 complex from E-boxes.