PER1 is a core circadian clock gene that functions as a transcriptional repressor in the molecular circadian feedback loop, forming the negative regulatory limb alongside other Period and Cryptochrome proteins 1. PER1 participates in multiple physiological processes beyond circadian regulation. In cancer biology, PER1 exhibits tumor suppressive properties, with low expression correlating with poor prognosis 1. However, PER1 can also promote oncogenesis through specific pathways, as demonstrated in ocular melanoma where YTHDF2-mediated degradation of m6A-modified PER1 mRNA accelerates tumorigenesis 2. In metabolic regulation, PER1 controls glycolytic activity through HK2-dependent glycolysis with circadian patterns, influencing trastuzumab resistance in gastric cancer 3. PER1 also regulates lipid metabolism in non-alcoholic fatty liver disease through the FOXA3-PER1-SREBP1c axis 4 and mediates ferroptosis in polycystic ovary syndrome via the SREBF2/ALOX15 pathway 5. In reproductive biology, PER1 responds to progesterone signaling during endometrial decidualization, with progesterone receptor directly activating PER1 transcription 6. PER1's therapeutic targeting shows promise, as quercetin-mediated m6A alterations in PER1 can alleviate oxidative stress in periodontal bone defects 7.