Regulation of the circadian clock by the metabolic enzyme AHCY

Mammalian circadian rhythms are based on coupled transcriptional-translational feedback loops driven by the transcription factors CLOCK and BMAL1. Chromatin remodeling mechanisms are essential for the proper timing and extent of circadian gene expression. We report that the S-adenosylhomocysteine (SAH) hydrolysing enzyme AHCY binds to CLOCK-BMAL1 at chromatin and drives circadian transcription by promoting cyclic H3K4 trimethylation and recruitment of BMAL1 to chromatin. To study how AHCY affects circadian gene expression we generated AHCY knock out MEF cell lines by performing CRISPR-Cas9 mediated gene editing or treated MEF with a specific inhibitor for AHCY (Dznep). MEF cells were synchronized with dexamethasone and RNA extracted at specific circadian time points (CT). To study the role of AHCY for circadian physiology in vivo, we delivered DZnep or saline into the hypothalamus of mice by direct infusion and extracted RNA from the suprachiasmatic nucleus (SCN) at specific CT.