Mps2 links Csm4 and Mps3 to form a telomere-associated LINC complex in budding yeast

The linker of the nucleoskeleton and cytoskeleton (LINC) protein complex is composed of a pair of transmembrane proteins: the KASH-domain protein localized to the outer nuclear membrane and the SUN-domain protein to the inner nuclear membrane. In budding yeast, the sole SUN-domain protein, Mps3, is thought to pair with either Csm4 or Mps2, two KASH-like proteins, to form two separate LINC complexes. Here we show that Mps2 mediates the interaction between Csm4 and Mps3 to form a heterotrimeric telomere-associated LINC (t-LINC) in budding yeast meiosis. Mps2 binds to Csm4 and Mps3, and all three are localized to the telomere. Telomeric localization of Csm4 depends on both Mps2 and Mps3; in contrast, Mps2s localization depends on Mps3 but not Csm4. Mps2-mediated t-LINC regulates telomere movement and meiotic recombination. By ectopically expressing CSM4 in vegetative yeast cells, we reconstitute the heterotrimeric t-LINC and demonstrate its ability to tether telomeres. Our findings therefore reveal the heterotrimeric composition of t-LINC in budding yeast and have implications for understanding LINC variant formation.