CLOCK regulates Drp1 mRNA stability and mitochondrial homeostasis by interacting with PUF60

Circadian genes such as Clock, Bmal1, Cryptochrome1/2, and Period1/2/3 constitute the precise circadian system. Clock^Δ19 is a commonly used mouse model harboring a circadian clock gene mutation, which lacks the EXON-19-encoded 51 amino acids. Previous reports have shown that Clock^Δ19 mice have severe metabolic abnormalities. Here, we report that the mitochondria of Clock^Δ19 mice exhibit excessive fission and dysfunction. We also demonstrate that CLOCK binds to the RNA-binding protein PUF60 through its EXON 19. Further, we find that PUF60 directly maintains mitochondrial homeostasis through regulating Drp1 mRNA stability, while the association with CLOCK can competitively inhibit this function. In Clock^Δ19 mice, CLOCK^Δ19 releases PUF60, leading to enhanced Drp1 mRNA stability and persistent mitochondrial fission. Our results reveal a direct post-transcriptional role of CLOCK in regulating mitochondrial homeostasis via Drp1 mRNA stability and that the loss of EXON 19 of CLOCK in Clock^Δ19 mice leads to severe mitochondrial homeostasis disorders.