[PDF][PDF] Coactivator-dependent oscillation of chromatin accessibility dictates circadian gene amplitude via REV-ERB loading

B Zhu, LA Gates, E Stashi, S Dasgupta, N Gonzales… - Molecular cell, 2015 - cell.com
B Zhu, LA Gates, E Stashi, S Dasgupta, N Gonzales, A Dean, CC Dacso, B York
Molecular cell, 2015cell.com
A central mechanism for controlling circadian gene amplitude remains elusive. We present
evidence for a" facilitated repression (FR)" model that functions as an amplitude rheostat for
circadian gene oscillation. We demonstrate that ROR and/or BMAL1 promote global
chromatin decondensation during the activation phase of the circadian cycle to actively
facilitate REV-ERB loading for repression of circadian gene expression. Mechanistically, we
found that SRC-2 dictates global circadian chromatin remodeling through spatial and …
Summary
A central mechanism for controlling circadian gene amplitude remains elusive. We present evidence for a "facilitated repression (FR)" model that functions as an amplitude rheostat for circadian gene oscillation. We demonstrate that ROR and/or BMAL1 promote global chromatin decondensation during the activation phase of the circadian cycle to actively facilitate REV-ERB loading for repression of circadian gene expression. Mechanistically, we found that SRC-2 dictates global circadian chromatin remodeling through spatial and temporal recruitment of PBAF members of the SWI/SNF complex to facilitate loading of REV-ERB in the hepatic genome. Mathematical modeling highlights how the FR model sustains proper circadian rhythm despite fluctuations of REV-ERB levels. Our study not only reveals a mechanism for active communication between the positive and negative limbs of the circadian transcriptional loop but also establishes the concept that clock transcription factor binding dynamics is perhaps a central tenet for fine-tuning circadian rhythm.
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