Structural and functional principles underlying germline genome transmission

点击翻译按钮获取中文摘要

Human reproductive success and the development of healthy offspring depend on accurate transmission of genetic material from parent to child. Homologous recombination during meiosis plays a central role in this genetic transmission by ensuring accurate chromosome segregation. Errors in recombination can lead to aneuploidy or mutations in gametes that in turn cause miscarriage or developmental defects in children. Understanding the mechanism and regulation of recombination is thus critical for understanding how meiotic errors affect human fertility and child development, but the molecular principles of recombination remain incompletely understood because of a paucity of biochemical and structural information. Meiotic recombination initiates with DNA double-strand breaks (DSBs) made by the Spo11 protein in collaboration with a suite of accessory factors. We recently overcame longstanding barriers to progress by purifying for the first time recombinant complexes of DSB-promoting proteins. Building on this advance, the Keeney and Patel labs propose to extend their ongoing collaboration to combine biochemical, structural, and single molecule biophysical approaches in vitro with functional experiments in vivo to illuminate the molecular principles that govern how DSB formation by Spo11 occurs. By conducting these studies in parallel on proteins from mouse and Saccharomyces cerevisiae, we will dive deeply into the mechanisms of evolutionarily conserved processes while retaining the ability to explore mammal-specific aspects. Aim 1 will focus on a “core complex” of Spo11 with its direct binding partners TOP6BL (mammals) and Rec102–Rec104–Ski8 (yeast). We will apply cryo-EM, x-ray crystallography, and computational modeling along with biochemical studies to define the structure of Spo11 core complexes and their critical protein-protein and protein-DNA interfaces. We will also test the physiological relevance of our structural and biochemical findings in vivo. To this end, we will use molecular genetic, genomic, and cytological studies in yeast and will employ a novel approach to parallelized genetic screening in mouse by competitively transplanting pools of genetically modified spermatogonial stem cells into testes of germ cell-depleted mice. Aim 2 will focus on the conserved accessory proteins Rec114, Mei4, and Mer2, which are important as a nexus for regulating DSB timing, number and location. We will use NMR spectroscopy, x-ray crystallography, cryo-EM, and computational modeling to define the structures and protein- protein interfaces of heterotrimeric Rec114–Mei4 complexes and of homotetrameric Mer2 complexes. We will use bulk biochemical and single molecule biophysical approaches to define the mechanism and dynamics behind the cooperative assembly of these proteins to form nucleoprotein condensates on DNA, which we hypothesize to be a central feature of their ability to support Spo11 activity. We will also apply a battery of in vivo assays to test functional predictions arising from the structural and biochemical findings.