Figure 9.

Model for TOP-2 function in male meiosis. In wild-type germ lines TOP-2 first localizes along chromosome axes of germ-line nuclei during pachytene and then envelops the highly compact chromosome structure of karyosome nuclei, positioning TOP-2 to interact with DNA during chromosome condensation. TOP-2-mediated chromatin remodeling prepares the chromosomes for segregation during the meiotic divisions. In the top-2(it7ts) mutant, TOP-2 fails to localize along the chromosome tracks of pachytene nuclei and around the karyosome DNA. This results in insufficient chromatin remodeling leading to chromosome-segregation defects. WT, wild type.