Luciferase assay

Luciferase reporter assays were performed using a Dual-Luciferase Reporter Assay System (Promega, Madison, WI, USA) with the pGL3 basic luciferase reporter system. The promoter sequence was chosen by using UCSC database based on the peaks of H3K4Me3 and H3K27AC. The promoter regions were cloned into pGL3-basic plasmid using SmaI and XhoI (Endonucleases were purchased from NEB, MA, USA; T4 DNA ligase was purchased from Promega). Promoter-specific luciferase constructs (the primers used for construction of the plasmid are listed in Additional file 3: Table S1) and empty pGL3-basic were co-transfected with a control Renilla luciferase construct into cells using Lipofectamine 2000 (Invitrogen). The luciferase signal was first normalized to the Renilla luciferase signal and then normalized to the signal from the empty pGL3 plasmid. All experiments were performed independently at least three times.