ZCWPW1 is recruited to recombination hotspots by PRDM9, and is essential for meiotic double strand break repair

Abstract

AbstractDuring meiosis, homologous chromosomes pair (synapse) and recombine, enabling balanced segregation and generating genetic diversity. In many vertebrates, recombination initiates with double-strand breaks (DSBs) within hotspots where PRDM9 binds, and deposits H3K4me3 and H3K36me3. However, no protein(s) recognising this unique combination of histone marks have yet been identified.We identified Zcwpw1, which possesses H3K4me3 and H3K36me3 recognition domains, as highly co-expressed with Prdm9. Here, we show that ZCWPW1 has co-evolved with PRDM9 and, in human cells, is strongly and specifically recruited to PRDM9 binding sites, with higher affinity than sites possessing H3K4me3 alone. Surprisingly, ZCWPW1 also recognizes CpG dinucleotides, including within many Alu transposons.Male Zcwpw1 homozygous knockout mice show completely normal DSB positioning, but persistent DMC1 foci at many hotspots, particularly those more strongly bound by PRDM9, severe DSB repair and synapsis defects, and downstream sterility. Our findings suggest a model where ZCWPW1 recognition of PRDM9-bound sites on either the homologous, or broken, chromosome is critical for synapsis, and hence fertility.Graphical Abstract LegendIn humans and other species, recombination is initiated by double strand breaks at sites bound by PRDM9. Upon binding, PRDM9 deposits the histone marks H3K4me3 and H3K36me, but the functional importance of these marks has remained unknown. Here, we show that PRDM9 recruits ZCWPW1, a reader of both these marks, to its binding sites genome-wide. ZCWPW1 does not help position the breaks themselves, but is essential for their downstream repair and chromosome pairing, and ultimately meiotic success and fertility in mice.