A period without PER: understanding 24-hour rhythms without classic transcription and translation feedback loops.

Since Ronald Konopka and Seymour Benzer's discovery of the gene in the 1970s, the circadian rhythm field has diligently investigated regulatory mechanisms and intracellular transcriptional and translation feedback loops involving , and these investigations culminated in a 2017 Nobel Prize in Physiology or Medicine for Michael W. Young, Michael Rosbash, and Jeffrey C. Hall. Although research on 24-hour behavior rhythms started with , a series of discoveries in the past decade have shown us that post-transcriptional regulation and protein modification, such as phosphorylation and oxidation, are alternatives ways to building a ticking clock.