By gating cell cycle progression to specific times of the day, the intracellular circadian clock is thought to reduce the exposure of replicating cells to potentially hazardous environmental and endogenous genotoxic compounds. Although core clock gene defects that eradicate circadian rhythmicity can cause an altered in vivo genotoxic stress response and aberrant proliferation rate, it remains to be determined to what extent these cell-cycle-related phenotypes are due to a cell-autonomous lack of circadian oscillations. We investigated the DNA damage sensitivity and proliferative capacity of cultured primary Cry1-/-|Cry2-/- fibroblasts. Contrasting previous in vivo studies, we show that the absence of CRY proteins does not affect the cell-autonomous DNA damage response upon exposure of primary cells in vitro to genotoxic agents, but causes cells to proliferate faster. By comparing primary wild type, Cry1-/-|Cry2-/-, Cry1+/-|Cry2-/- and Cry1-/-|Cry2+/- fibroblasts, we provide evidence that CRY proteins influence cell cycle progression in a cell-autonomous, but circadian clock-independent manner and that the accelerated cell cycle progression of Cry-deficient cells is caused by global dysregulation of Bmal1-dependent gene expression. These results suggest that the inconsistency between in vivo and in vitro observations might be attributed to systemic circadian control rather than a direct cell-autonomous control.
Mammalian cryptochromes impinge on cell cycle progression in a circadian clock-independent manner.
Specimen part
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Histone methyltransferase MLL3 contributes to genome-scale circadian transcription.
Specimen part, Time
View SamplesTotal RNA was isolated from liver samples of C57/BL6 mice over a circadian time course, 3 biological replicate samples per time point were collected and processed individually. RNA from each individual biological replicate sample was extracted using RNeasy mini kit (Qiagen Cat# 74106) and hybridized on an Affymetrix mouse Gene ST1.0 microarray.
Histone methyltransferase MLL3 contributes to genome-scale circadian transcription.
Specimen part, Time
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