Abstract
The linker of the nucleoskeleton and cytoskeleton (LINC) complex is composed of two 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) complex 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, Mps2's localization depends on Mps3 but not Csm4. Mps2-mediated t-LINC complex regulates telomere movement and meiotic recombination. By ectopically expressing CSM4 in vegetative yeast cells, we reconstitute the heterotrimeric t-LINC complex and demonstrate its ability to tether telomeres. Our findings therefore reveal the heterotrimeric composition of the t-LINC complex in budding yeast and have implications for understanding variant LINC complex formation.
Highlights
The linker of the nucleoskeleton and cytoskeleton (LINC) complex has emerged as a key regulator for a diverse range of nuclear activities that include chromosome movement, nuclear positioning, and gene expression (Tapley & Starr, 2013; Chang et al, 2015; Burke, 2018)
The canonical LINC complex is composed of two transmembrane proteins, the SUN (Sad1 and UNC-84) protein localized to the inner nuclear membrane (INM) and the KASH (Klarsicht, ANC-1 and Syne/Nesprin homology) protein localized to the outer nuclear membrane (ONM) (Starr et al, 2001; Crisp et al, 2006)
We have demonstrated the heterotrimeric composition of the budding yeast telomereassociated LINC (t-LINC) complex; the KASH-like protein Mps2 bridges Csm4 and Mps3 (Fig 7)
Summary
The linker of the nucleoskeleton and cytoskeleton (LINC) complex has emerged as a key regulator for a diverse range of nuclear activities that include chromosome movement, nuclear positioning, and gene expression (Tapley & Starr, 2013; Chang et al, 2015; Burke, 2018). The canonical SUN-KASH interaction takes place primarily in the perinuclear space; the LINC complex bridges the INM and ONM and connects the cytoskeleton to the nucleoskeleton and chromatin, allowing transduction of mechanical forces through the nuclear envelope (Starr & Fridolfsson, 2010). LINC proteins are believed to form heterodimeric hexamers and possibly higher ordered protein arrays for force transmission (Luxton et al, 2010; Sosa et al, 2012; Wang et al, 2012). How they are assembled in vivo to carry out diverse functions remains to be further determined
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