library_construction_protocol: For mouse skin samples, samples were flash-frozen in liquid N2, followed by dry pulverization of frozen tissue through a cell crusher and douncing. Chromatin was isolated using NUN buffer and fragmented with DNase I, and nascent RNA was biotin-labeled through a run-on reaction. Cell-type-specific nascent RNAs were enriched through GFP pull-down and library preparation steps were then followed as previously described for PRO-seq assay. All input samples were processed without GFP pull-down that served as controls for cell-type specific nascent RNA enrichment. Nascent RNA libraries were generated using the PRO-seq protocol.