Anti-PRDM9 polyclonal antibody

Meiotic recombination is required for correct segregation of chromosomes to gametes and to generate genetic diversity. In mice and humans, DNA double-strand breaks (DSBs) are initiated by SPO11 at recombination hotspots activated by PRDM9-catalyzed histone modifications on open chromatin. However, the DSB-initiating and repair proteins are associated with a linear proteinaceous scaffold called the chromosome axis, the core of which is composed of cohesin proteins. STAG3 is a stromalin subunit common to all meiosis-specific cohesin complexes. Mutations of meiotic cohesin proteins, especially STAG3, perturb both axis formation and recombination in the mouse, prompting determination of how the processes are mechanistically related. Protein interaction and genetic analyses revealed that PRDM9 interacts with STAG3 and REC8 in cooperative relationships that promote normal levels of meiotic DSBs at recombination hotspots in spermatocytes. The efficacy of the Prdm9-Stag3 genetic interaction in promoting DSB formation depends on PRDM9-mediated histone methyltransferase activity. Moreover, STAG3 deficiency has a major effect on DSB number even in the absence of PRDM9, showing that its role is not restricted to canonical PRDM9-activated hotspots. STAG3 and REC8 promote axis localization of the DSB-promoting proteins HORMAD1, IHO1, and MEI4, as well as SPO11 activity. These results establish that PRDM9 and axis-associated cohesin complexes together coordinate and facilitate meiotic recombination by recruiting key proteins for initiation of DSBs, thereby associating activated hotspots with DSB-initiating complexes on the axis.

Saccharomyces cerevisiae Spp1, a plant homeodomain (PHD) finger containing protein, is a critical subunit of the histone H3K4 methyltransferase complex of proteins associated with Set1 (COMPASS). The chromatin binding affinity of the PHD finger of Spp1 has been proposed to modulate COMPASS activity. During meiosis, Spp1 plays another role in promoting programmed double-strand break (DSB) formation by binding H3K4me3 via its PHD finger and interacting with a DSB protein, Mer2. However, how the Spp1 PHD finger performs site-specific readout of H3K4me3 is still not fully understood. In the present study, we determined the crystal structure of the highly conserved Spp1 N-terminal domain (Sc_Spp1(NTD)) in complex with the H3K4me3 peptide. The structure shows that Sc_Spp1(NTD) comprises a PHD finger responsible for methylated H3K4 recognition and a C3H-type zinc finger necessary to ensure the overall structural stability. Our isothermal titration calorimetry results show that binding of H3K4me3 to Sc_Spp1(NTD) is mildly inhibited by H3R2 methylation, weakened by H3T6 phosphorylation, and abrogated by H3T3 phosphorylation. This histone modification cross-talk, which is conserved in the Saccharomyces pombe and mammalian orthologs of Sc_Spp1 in vitro, can be rationalized structurally and might contribute to the roles of Spp1 in COMPASS activity regulation and meiotic recombination.