Differential effects of two catalytic mutations on full-length PRDM9 and its isolated PR/SET domain reveal a case of pseudo-modularity

The locations of mammalian recombination hotspots are determined by PRDM9, a zinc finger histone methyltransferase that locally trimethylates histone H3 at residues K4 and K36. We previously reported two hypomorphic catalytic mutations, Prdm9-EP and Prdm9-EK, with different phenotypic effects. Prdm9-EP, but not Prdm9-EK, is compatible with female sub-fertility, while both mutations phenocopy the Prdm9-null condition in males. Here we directly compare and contrast the enzymatic effects of the two mutations in vitro and in vivo. We previously performed two biological H3K4me3 ChIP-seq replicates in spermatocytes isolated from Prdm9-EP homozygous males (GSE144144; SRX8588740 and SRX8588741), and re-processed previously reported H3K4me3 ChIP-seq data from spermatocytes isolated from wild-type B6 males (GSE52628; SRX381465 and SRX381466). We used those raw and processed files for this study (GSE144144). We also previously performed one biological H3K4me3 replicate in spermatocytes isolated from Prdm9-EP homozygous males (GSE112110; SRX4136625). We report an additional replicate here, and merged the two replicates for analysis; raw and processed files are reported here. We also performed ChIP-seq for H3K36me3 in both Prdm9-EP and Prdm9-EK homozygous spermatocytes. Raw and processed files are available here. For comparison, we re-mapped and re-analyzed H3K36me3 ChIP-seq data we previously reported from wild-type B6 spermatocytes (GSE76416; SRX1508234); processed files are available here. We performed ChIP-seq with antibodies against H3K4me3 and H3K36me3, using chromatin extracted from C57BL/6J-Prdm9-EP and C57BL/6J-Prdm9-EK homozygous mutant spermatocytes, and combined it with previously generated ChIP-seq data for H3K4me3 in C57BL/6J wild-type and C57BL/6J-Prdm9-EP spermatocytes, for direct comparison between the three genotypes.