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Abstract
Spatial patterning is a ubiquitous feature of biological systems. Meiotic crossovers provide an interesting example, defined by the classic phenomenon of crossover interference. Here we identify a molecular pathway for interference by analysing crossover patterns in budding yeast. Topoisomerase II plays a central role, thus identifying a new function for this critical molecule. SUMOylation (of topoisomerase II and axis component Red1) and ubiquitin-mediated removal of SUMOylated proteins are also required. The findings support the hypothesis that crossover interference involves accumulation, relief and redistribution of mechanical stress along the protein/DNA meshwork of meiotic chromosome axes, with topoisomerase II required to adjust spatial relationships among DNA segments.