# Post‐Translational Modifications in Animal Circadian Clocks

## TL;DR

This review explains how post-translational modifications help regulate circadian clocks in animals, enabling them to adapt to daily cycles and environmental changes.

## Contribution

The paper highlights evolutionary convergence in circadian timekeeping mechanisms between Drosophila and mammals through post-translational modifications.

## Key findings

- Post-translational modifications modulate circadian period length and robustness.
- Casein kinase 1 family-dependent phosphorylation is conserved across species.
- PTMs enable circadian clocks to adapt to metabolic and environmental signals.

## Abstract

The circadian clock is a fundamental biological system that synchronizes behavioral and physiological processes such as metabolism and immunity with the 24 h day‐night cycle. Disruption of circadian rhythms, often caused by modern lifestyle factors like shift work and jet lag, is closely associated with metabolic and mental disorders. In both mammals and Drosophila, the molecular oscillator consists of conserved transcriptional‐translational feedback loops (TTFLs) involving positive and negative regulatory elements that generate rhythmic gene expression. Post‐translational modifications (PTMs) of clock proteins play crucial roles in modulating the circadian period length, robustness, and responsiveness to environmental cues. Importantly, casein kinase 1 family‐dependent phosphorylation on both positive and negative elements in animal clocks highlights the evolutionary convergence of circadian timekeeping across species. This review focuses on PTMs and related mechanisms in circadian timekeeping and their roles in adapting to environmental and physiological signals in animals.

Circadian clocks coordinate physiology with daily environmental cycles through conserved transcriptional–translational feedback loops. This review summarizes how post‐translational modifications fine‐tune clock function, highlights the evolutionary convergence of circadian timekeeping in Drosophila and mammals, and emphasizes the central of these modifications in enabling adaptability to metabolic, neural, and environmental challenges.