Abstract
Rapid chromosome movements during meiotic prophase are critical for homologous chromosome pairing and proper meiotic progression. These movements are generated by the cytoskeleton and are transmitted to the telomeres via the LINC complex, yet the cytoplasmic components that generate these forces remain poorly defined. In a proteomic screen, we identified candidates of microtubule-associated motor proteins in mouse spermatocytes. Among these, KIF5B and KIF2B emerged as specific interactors of the LINC complex through co-immunoprecipitation and yeast two-hybrid assays using KASH5 as bait. Total internal reflection fluorescence microscopy and microtubule sedimentation assays performed with recombinant proteins suggest direct interaction between purified KASH5 and KIF5B on microtubules. Mapping KIF5B-binding surface of KASH5, revealed that KASH5 N-terminal EF-hand domains mediate the interaction. Further, in vivo KIF5B-KASH5 interaction and KIF5B role in RPMs is evidenced as (1) KIF5B is recruited by KASH5-SUN1 to the nuclear envelope in a cultured somatic cell model, (2) KIF5B is telomere associated and colocalizes with KASH5 and microtubules associated to the nuclear envelope in mouse spermatocytes, (3) inhibition of kinesins reduces telomere-led chromosome motions. Altogether, our findings identify kinesins, particularly KIF5B, as a previously unrecognized component of the force-generating machinery that drives chromosome movement during meiotic prophase I, acting through KASH5 as a specific nuclear membrane adaptor.