Figure 1.

Mps3 is related to Sad1 and contains a C-terminal SUN domain. (A) A ClustalW alignment of SUN domains from the indicated proteins shows conserved (red), similar (cyan), and virtually conserved residues (green; in 5 out of 6 SUN proteins included in the alignment). Boxed residues in UNC-84 show the positions of missense mutations that affect nuclear migration (S988F, C994Y, and G1000D), and the arrows show the positions of our ts alleles and a previously described mps3 mutant, nep98-7 (N597K; Nishikawa et al., 2003). The predicted β-strands of the SUN domain are shown by bars above the alignment (Mans et al., 2004). (B) Four SUN domain–containing proteins are depicted: S. cerevisiae Mps3, S. pombe Sad1, C. elegans UNC-84, and H. sapiens Sun1. All contain at least one transmembrane domain (tm), regions of coiled coil (cc), and a SUN domain. Mps3 and Sad1 also contain an acidic N terminus, but the poly-glutamine region (pQ) is unique to Mps3. (C) GAL-MPS3, GAL-SAD1, and vector were transformed into the ts mps3-ΔSUN2 mutant (SLJ1789), and cultures were serially diluted 10-fold and spotted onto plates containing 2% galactose. Plates were incubated at 23 or 37°C for 2 d.