Spermatogenic cell fractionation was performed by sedimentation of cells prepared from adult mouse testes through a BSA gradient as previously described (Bryant et al. 2013). Each fractionation experiment used approximately 22 testes. Fractions were analyzed for purity based on cell and nuclear morphology (via DAPI staining) and pooled. Mature spermatozoa were obtained from epididymides of adult mice, and contaminating cell types were eliminated by incubating in somatic cell lysis buffer (0.1% SDS, 0.5% Triton X-100 in DEPC H2O) on ice for 20 minutes. Cells were cross-linked in 1% formaldehyde in PBS for 10 minutes at room temperature. The reaction was quenched with 125mM glycine in PBS for five minutes at room temperature. After cell lysis, lysates were sonicated for 20 minutes with a Covaris S220 sonicator (5% duty cycle, 140 watts peak incident power, 200 cycles per burst). For each IP, 500µg of protein (measured with BCA assay) from the cell lysate, 30uL protein G Dynabeads, and 5µg-10ug of antibody or IgG (Pierce 31235) were used. ChIP libraries for sequencing were prepared using 5ng DNA and the NEBNext Ultra DNA library prep kit for Illumina. Size selection was performed using AMPure XP beads (Beckman Coulter, Inc. #A63881). Libraries were sequenced using a NextSeq 500 machine (Illumina) as per manufacturer's protocols.