Dynamics of SREBP1 binding to DNA in mouse liver
To systematically understand how the circadian clock and the nutrient-driven rhythm integrate to regulate SREBP1 activity, we evaluated genome-wide the binding of SREBP1 to its targets along the day in wild-type (WT) C57BL/6mice. The recruitment of SREBP1 to the DNA showed a highly circadian behaviour, with a maximum during the fed status. However, the temporal expression of SREBP1 targets was not always synchronized with its binding. In particular, a different phase of expression was observed for SREBP1 target genes depending on their function, suggesting the involvement of other transcription factors in their regulation. The proper temporal expression pattern of these genes was dramatically changed in Bmal1KO mice upon time-restricted feeding, in spite of the rhythmic, although slightly delayed, binding of SREBP1. Our results show that besides the nutrient-driven regulation of SREBP1 nuclear translocation, a second layer of modulation of SREBP1 transcriptional activity exists and is strongly dependent from the circadian core clock. This system allows to fine tune the expression timing of SREBP1 target genes, thus helping to temporally separate the different physiological processes in which these genes are involved. Overall design: 6 samples examined, 6 SREBP1 samples, as well  as 6 Polr2b and 6 input samples from GEO series GSE35788 CycliX Consortium was a contributor to this submission.