Institut de Génétique Humaine, CNRS UPR, Montpellier, France.
PLoS Biol. 2011 Oct;9(10):e1001176. doi: 10.1371/journal.pbio.1001176. Epub 2011 Oct 18.
Meiotic recombination generates reciprocal exchanges between homologous chromosomes (also called crossovers, COs) that are essential for proper chromosome segregation during meiosis and are a major source of genome diversity by generating new allele combinations. COs have two striking properties: they occur at specific sites, called hotspots, and these sites evolve rapidly. In mammals, the Prdm9 gene, which encodes a meiosis-specific histone H3 methyltransferase, has recently been identified as a determinant of CO hotspots. Here, using transgenic mice, we show that the sole modification of PRDM9 zinc fingers leads to changes in hotspot activity, histone H3 lysine 4 trimethylation (H3K4me3) levels, and chromosome-wide distribution of COs. We further demonstrate by an in vitro assay that the PRDM9 variant associated with hotspot activity binds specifically to DNA sequences located at the center of the three hotspots tested. Remarkably, we show that mutations in cis located at hotspot centers and associated with a decrease of hotspot activity affect PRDM9 binding. Taken together, these results provide the direct demonstration that Prdm9 is a master regulator of hotspot localization through the DNA binding specificity of its zinc finger array and that binding of PRDM9 at hotspots promotes local H3K4me3 enrichment.
减数分裂重组产生同源染色体之间的相互交换（也称为交叉，COs），这对于减数分裂过程中正确的染色体分离是必不可少的，并且是通过产生新的等位基因组合来产生基因组多样性的主要来源。COs 有两个显著的特性：它们发生在特定的位点，称为热点，这些位点进化迅速。在哺乳动物中，编码一种减数分裂特异性组蛋白 H3 甲基转移酶的 Prdm9 基因最近被确定为 CO 热点的决定因素。在这里，我们使用转基因小鼠表明，仅对 PRDM9 锌指的修饰就会导致热点活性、组蛋白 H3 赖氨酸 4 三甲基化（H3K4me3）水平以及 CO 的全染色体分布发生变化。我们进一步通过体外测定证明，与热点活性相关的 PRDM9 变体特异性结合到三个测试热点中心的 DNA 序列。值得注意的是，我们表明位于热点中心的顺式突变，与热点活性降低有关，会影响 PRDM9 的结合。总之，这些结果直接证明 Prdm9 通过其锌指阵列的 DNA 结合特异性成为热点定位的主要调节剂，并且 PRDM9 在热点处的结合促进了局部 H3K4me3 富集。
