PNNL

Abstract

Ribosome composition can dynamically change depending on cell type, developmental state, or environmental stress. We demonstrate circadian clock-dependent variations in ribosome composition in Neurospora crassa. Using mass spectrometry to analyze ribosomes isolated at different circadian times, six ribosomal proteins and one ribosome-associated protein whose abundance is clock-controlled were identified. Daily rhythmic abundance of eL31-HA was independently validated in purified ribosomes. Deletion of el31 disrupted translation rhythms for nearly half of rhythmically translated mRNAs, indicating its crucial role in circadian translation. eL31 homologs promote translation termination fidelity, and we show that Neurospora eL31 enhances circadian control of translation termination and impacts elongation fidelity. Furthermore, eL31 maintains proper Mg2+ homeostasis, a key factor for accurate translation. Collectively, our findings reveal that the clock orchestrates daily changes in ribosome composition, thereby regulating rhythmic translation and translation fidelity. This mechanism temporally expands the proteome beyond the static genome, aligning cellular processes with circadian time.