Beta-TC6 cells (~40-160 million) were fixed for 30 minutes in 2mM DSG and for 10 minutes in 1% formaldehyde and then either frozen at -80ûC or processed immediately. Nuclei were isolated in buffer containing 1% SDS, 10mM EDTA, 50mM Tris-HCl pH 8.0, and protease inhibitors and sonicated using a Diagenode Bioruptor to shear chromatin to 200-1000bp fragments. Protein-DNA complexes were incubated with antibodies against BMAL1 and CLOCK (affinity-purified guinea pig IgGs as described above), H3K4Me2 (Abcam), H3K27Ac (Active Motif), H2AZ (Active Motif), or PDX1 (Novus Biologicals) and immunoprecipitated with IgG paramagnetic beads (Invitrogen). Eluted chromatin was isolated using MinElute PCR purification columns (Qiagen). Sequencing libraries were generated using KAPA DNA Library Preparation kits (Kapa Biosystems, KK8504) according to manufacturer's instructions. Library concentrations were assessed by both a Bioanalyzer (Agilent) and qPCR-based quantification (Kapa Biosystems)