ChIP Assays

The ChIP assays were carried out using a ChIP assay kit (Cell Signaling Technology, 9005), according to the manufacturer’s instructions. Briefly, the cells were cross-linked with 1% formaldehyde for 10 min and then disrupted in cell lysate buffer. The supernatant was collected after the samples were sonicated to break nuclear membrane. Subsequently, the chromatin was immunoprecipitated with anti-NPAS2 antibody (1:100, Abcam, ab157165) or equal amounts of negative control normal rabbit immunoglobulin G (IgG). Finally, DNA extractions were PCR amplified using primer pairs within the regulatory region of the Hes1. The specific PCR primers are listed in Table S1.