Authors: Yu-Chien Chuang, Gerald R. Smith
During meiosis, appropriate DNA double-strand break (DSB) and crossover distributions are required for proper homologous chromosome segregation in most species. Linear element proteins (LinEs) of Schizosaccharomyces pombe are DSB hotspot determinants. Clusters of LinE-bound hotspots form within ~200 kb chromosomal regions independent of DSB formation. Previous reports showed that LinEs form chromatin-bound, dot-like nuclear foci in nuclear spreads and in fixed cells. Here, we investigated the regulation of LinE configuration and distribution in live cells using super-resolution fluorescence microscopy. In live cells at optimal meiotic temperature (~25°C), LinEs made long linear forms, not previously reported, in both zygotic and azygotic meiosis and shared other characteristics with the synaptonemal complex in other species. LinE structures appeared around the time of replication, underwent a dotty-to-linear-to-dotty configurational transition, and disassembled before the first meiotic division. DSB formation and repair did not detectably influence LinE structure formation, but failure of DSB formation delayed LinE structure disassembly. Several LinE missense mutations formed dotty but not linear LinE configurations. Our study reveals a second, important configuration of LinEs, which suggests that LinE complexes are involved in regulating meiotic events, such as DSB repair, in addition to their established role in DSB formation.