The Role of Actin‐Filament Bundling Protein, Fimbrin Sac6, and Type‐V Myosin Myo2, in the Motion of the SUN ‐Domain Protein, Mps3, During Yeast Meiosis

During meiosis, telomere clustering and motion promote the pairing between homologous chromosomes. In budding yeast, actin filaments in the cytoplasm drive the motion of a Linker Nucleoskeleton and Cytoskeleton (LINC) complex with the SUN-domain protein, Mps3, which tethers and moves telomeres to the nuclear envelope (NE). In this study, we analyzed the roles of two actin-binding proteins, essential Type-V myosin (Myo2) and Sac6 fimbrin, which bundles actin filaments in cables, in meiotic Mps3 motion on the NE. Meiosis-specific depletion of MYO2 reduced the motion of Mps3 patches without affecting cytoplasmic actin cables during meiotic prophase I, confirming actin/myosin-dependent Mps3 motion. Moreover, Myo2 plays a critical role in the maintenance of Mps3 clustering and, probably, telomere clustering in the absence of Rec8, a component of the meiotic cohesin. The deletion of SAC6, which is critical for force generation in the cytoplasm, during meiosis largely reduced cytoplasmic actin cables without affecting Mps3 localization and motion. Likely, Sac6-mediated actin filament bundling is not critical for the meiotic motion of Mps3 patches. Our study suggests that actin polymerization and Myo2-mediated force are involved in the meiotic motion of the yeast LINC complex.