H3K4-me3 marks are enriched near the binding sites of the hotspot tested. The peak of H3K4-me3 at hotspots is centered near the PRDM9 binding site. Chromatin was prepared using spermatocytes from mice 12 days post-partum and subjected to chromatin immunoprecipitation (ChIP) with antibody directed to H3K4-me3 or normal rabbit IgG. Quantitative PCR was performed for 8 to 9 amplicons distributed across about 10 kb surrounding the hotspot on immunoprecipitated chromatin and an equal amount of MNase-treated, undiluted input DNA to calculate the fraction of chromatin bound at each amplicon. Blue line, B6 × CAST F1; green line, B6; red line, rabbit IgG (negative control). An identical distribution of H3K4-me3 marks for Psmb9 was shown previously by Grey et al. .
Billings et al. Genome Biology 2013 14:R35 doi:10.1186/gb-2013-14-4-r35