Cells were cross-linked in 1% formaldehyde for 10 minutes at room temperature after which the reaction was stopped by addition of 0.125M glycine. Cells were lysed and harvested in ChIP buffer (100 mM Tris at pH 8.6, 0.3% SDS, 1.7% Triton X-100 and 5 mM EDTA) and the chromatin disrupted by sonication using a Diagenode Bioruptor sonicator UCD-200 to obtain fragments of 200-500 bp in size. Suitable amounts of chromatin were incubated with specific antibodies overnight. Antibodies used are: H3K4Me3 (Millipore – Cat. # 07-473), H3K27Ac (Abcam – Cat. # ab4729), H3K4Me1 (Abcam – Cat. # ab8895), MED1 (Bethyl – Cat. # A300-793A), SMC1 (Bethyl – Cat. # A300-005A), Pol2 (Santa Cruz – Cat. # sc-899), Phospho-Rpb1 CTD (Ser2) (Cell Signaling – Cat. # 13499), Phospho-Rpb1 CTD (Ser5) (Cell Signaling – Cat. # 13523), CDK9 (Santa Cruz – Cat. # sc-484) Libraries were generated using NEBNext Ultra DNA Library Prep Kit for Illumina and barcoded using NEBNext Multiplex Oligos for Illumina according to manufacturer recommendation.