Mouse lung tissue was pulverized using Covaris Tissue Smasher model CP02 by following the CryoPrep Dry Pulverization Manuel. Lung tissue was smashed 1-2 times on setting 4 in the tissueTUBE (Covaris #520071). Approximately 50mg of pulverized lung tissue was cross-linked with prewarmed 1% formaldehyde (ThermoScientific #28906 diluted in PBS) for 20 minutes at 37°C. The tissue was spun down at 1,000rpm for 2 minutes and quenched with 0.125M glycine in PBS + 0.5% BSA for 20 minutes at room temperature, spun down at 1,000rpm for 2 minutes and washed with PBS + 2x Protease Inhibitor Cocktail (PIC) (Roche #11873580001) + 5mM Sodium Butyrate (Millipore #19-137) then spun down at 1,000rpm for 2 minutes. The cross-linked tissue was then lysed with 390uL ChIP Lysis Buffer (1% SDS, 10nM EDTA pH8.0, 50mM Tris-HCl pH 8.0, 2x PIC and 5mM Sodium Butyrate) on ice for one hour. The lysate was split into 3 microTUBEs (Covaris #520045) and sheared on the Covaris E210 Series with 5% Duty Cycle, 5 Intensity, 200 Cycles per Burst for a total of 27 minutes. The sheared chromatin was spun down at 14,000rpm for 15 minutes at 4°C. An aliquot of input was saved while the remaining chromatin was snap frozen and stored at -80°C. Input was brought up to 100ul with TE, 10ug of RNAseA (Roche) added and incubated for 30 minutes at 37°C followed by addition of 100ug of Proteinase K (Roche) and incubation at 65°C overnight. Input was purified with Qiagen PCR Purification Kit (#28104) and quantified The prepared chromatin was thawed on ice while 10ug of antibodies against either H3K27ac (Abcam #Ab4729) or H3K27me3 (Cell Signaling #CS9733S) were conjugated to a mix of magnetic Protein A and Protein G coupled beads (Invitrogen #100.02D and #100.04D respectively) in the presence of 0.5% BSA in PBS with rotation at 4°C for 2 hours. Beads were washed 3 times with 0.5%BSA in PBS and either 5ug of chromatin was added to the H3K27ac ChIP or 10ug of chromatin was added to the H3K27me3 ChIP and rotated overnight at 4°C. The beads were washed 2 times with Tris based RIPA buffer (0.1% SDS, 1% Triton X-100, 10mM Tris-HCl pH 7.4, 1mM EDTA pH 8.0, 0.1% Sodium Deoxycholate), 2 times with 0.3M NaCl RIPA (0.1% SDS, 1% Triton X-100, 10mM Tris-HCl pH 7.4, 1mM EDTA pH 8.0, 0.1% Sodium Deoxycholate, 0.3M NaCl), 2 times with LiCl Buffer (250mM LiCl, 0.5% NP-40, 0.5% Sodium Deoxycholate, 1mM EDTA pH 8.0, 10mM Tris-HCl pH 8.0) and 2 times with TE buffer pH 7.6 (Fisher Scientific cat. no. BP2474-1). The beads were resuspended in 100uL of TE and RNAseA and PK digested/reverse crosslinked and purified as described in the chromatin prep.