A circadian clock translational control mechanism targets specific mRNAs to cytoplasmic messenger ribonucleoprotein granules.
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abstract
Phosphorylation of Neurospora crassa eukaryotic initiation factor 2 (eIF2), a conserved translation initiation factor, is clock controlled. To determine the impact of rhythmic eIF2 phosphorylation on translation, we performed temporal ribosome profiling and RNA sequencing (RNA-seq) in wild-type (WT), clock mutant frq, eIF2 kinase mutant cpc-3, and constitutively active cpc-3c cells. About 14% of mRNAs are rhythmically translated in WT cells, and translation rhythms for 30% of these mRNAs, which we named circadian translation-initiation-controlled genes (cTICs), are dependent on the clock and CPC-3. Most cTICs are expressed from arrhythmic mRNAs and contain a P-body (PB) localization motif in their 5' leader sequence. Deletion of SNR-1, a component of cytoplasmic messenger ribonucleoprotein granules (cmRNPgs) that include PBs and stress granules (SGs), and the PB motif on one of the cTIC mRNAs, zip-1, significantly alters zip-1 rhythmic translation. These results reveal that the clock regulates rhythmic translation of specific mRNAs through rhythmic eIF2 activity and cmRNPg metabolism.
