In 5‐azacytidine (5‐AZA)‐resistant leukemia cells, a unique NSUN1/BRD4/RNA‐pol II CTD‐S2P complex is formed, mediating the development of 5‐AZA‐resistant chromatin structures and contributing to 5‐AZA resistance in leukemia. The gene discussed is BRD4; the disease is leukemia.