Disorder at the heart of a molecular chronosome — insights from the fungal clock protein FRQ

Circadian clocks are conserved timekeeping systems present across the tree of life. Despite sequence divergence, their negative elements share biophysical traits such as intrinsic disorder, phosphorylation clusters, and charged low-complexity regions, suggesting a shared functional logic beyond primary sequence. Using the fungal protein FREQUENCY (FRQ) as a proxy, we review how intrinsic disorder enables temporal regulation. Using computational analysis, we explore the hypothesis that multisite phosphorylation may incrementally reshape FRQ conformational ensemble, with potential consequences for partner engagement over the circadian day. Thus, in this review we consider how, despite poor sequence conservation, circadian negative elements maintain a conserved mechanism rooted in the physical principles of disorder and post-translational modulation, positioning these properties at the very heart of the molecular chronosome.