Phosphorylation Of S714 Site In PER1 Regulates Circadian And Feeding Rhythm In Mice

Circadian clock allows an organism to anticipate environmental cyclic changes such as light-dark cycle, availability of food and as a result, provides greater adaptive advantage compared to random processes. The current mammalian clock model is composed of a transcriptional-translational feedback network that includes the PAS(Per-Arnt-Sim) domain-containing helix-loop-helix transcription factors Clock and Bmall, Period genes (Per1, Per2, and Per3), and Cryptochrome genes (Cry] and Cry2). The CLOCK:BMAL1 complex activates the transcription of the Period and Cryptochrome genes by binding to E-boxes in their promoters, whereas the PER:CRY complex closes the negative feedback loop by repressing the activity of CLOCK:BMAL1, resulting in endogenous circadian oscillations of Per and Cry mRNA. Although the basic function of the molecular clock bears remarkable similarity in a wide range of organisms, one of the striking differences between mammalian and drosophila clock is that mammals seem to employ multiple paralogous clock genes. These clock components emerged and expanded in mammalian circadian systems to provide a possibility to meet diverse physiological functions resulting in a high level of functional divergence. Mapping specific functions in each paralogous gene are likely to provide general insights into the understanding of how clock components guide to the vast number of possible physiological processes and how organism adjust clock system to achieve the balance between various clock-dependent mechanism and physiological homeostasis.A particularly interesting example comes the individuals within single-family pedigree apparently carry a dominant mutation of S662G in hPER2 that causes them to wake up very early followed by early morning awakenings (FASPS). The position S662 of hPER2 protein is the first of five serines spaced three amino acids apart and S662G mutation impedes sequential phosphorylation. The SXXS motif is highly conserved in mammalian PER proteins, and this serial phosphorylation of PER2 protein is tightly coupled with day-night cues. We hypothesized that this motif may have arisen before duplications in order to retain the essential time-keeping function and similar selective pressures constraints on this motif, while each PER protein function is likely to be unique. It is possible to observe mutational behavior through the amino-acid change in the first serine of this motif in hPERl protein applying the general principles learned from PER2 regulation. Here, we generated BAC transgenic mice carrying S714G mutation in hPER1, and found that hPER1S714G mutant mice exhibit an advanced feeding rhythm phase and uncoupled food intake with energy expenditure, and therefore developed obesity quickly on a high fat diet challenge. The S714G mutation impeded hPER1 hyperphosphorylation, accelerated hPERl:CRY1 complex nuclear import, and altered the ratio of BMAL1:CRY1 on the E-box to shorten molecular feedback loops in tissue-autonomous oscillators. Both advanced feeding behavior and the accelerating clock were consolidated to invert over 119transcripts in the liver transcriptomes and 28 transcripts in the adipose transcriptomes.Our studies demonstrate that PER1 and PER2 are linked to different downstream pathways and PER1 is a specific molecule that maintains coherence between the circadian clock and energy metabolism.