CIRP, a cold-inducible RNA-binding protein, modulates circadian gene expression posttranscriptionally

In mammalian tissues circadian gene expression can be driven by local oscillators or systemic signals controlled by the master pacemaker in the suprachiasmatic nucleus. Here we show that simulated body temperature cycles, but not peripheral oscillators, can control the rhythmic expression of Cold-Inducible RNA binding Protein (CIRP) in cultured fibroblasts. In turn, loss-of-function experiments indicate that CIRP is required for high amplitude circadian gene expression. The transcriptome-wide identification of CIRP-bound RNAs by a biotin-streptavidin based CLIP-seq procedure revealed several CIRP-bound transcripts encoding circadian oscillator proteins. One of these, CLOCK, accumulated to particularly low levels in CIRP-depleted fibroblasts. Since ectopic expression of CLOCK improved circadian gene expression in these cells, we surmise that CIRP confers robustness to circadian oscillators via the regulation of CLOCK expression. Overall design: Identification of CIRP-interacting RNA molecules in NIH3T3 cells and RNA expression in NIH3T3 cells treated with Control or CIRP siRNA after incubation of the cells at 33°C for 8 hours