by Hongtao Zhang, Wenqing Liang, Meng Li, Yuejun Yang, Lei He, Wencong Nan, Guoteng Liu, Bin Wang, Ye Hong Crossover (CO) formation ensures accurate segregation of homologous chromosomes during the first meiotic division. The pro-crossover proteins are essential for crossover formation and undergo dynamic changes during meiotic prophase I, although the underlying regulatory mechanism is largely unknown. Here, we found that the ubiquitin-proteasome system (UPS) plays a pivotal role in orchestrating pro-crossover protein dynamics and crossover patterning during meiosis in Caenorhabditis elegans . Knockdown of either the ubiquitin-activating enzyme E1 or the proteasome resulted in elevated pro-crossover protein levels and crossover designation. Impairing ubiquitination, but not proteasome activity, led to persistent association of pro-crossover proteins on meiotic chromosomes, a process mediated by the CDC-48 UFD-1/NPL-4 segregase. Utilizing a hypomorphic allele of cosa-1 , a well-charact