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4.  Telomere anchoring at the nuclear periphery requires the budding yeast Sad1-UNC-84 domain protein Mps3 
The Journal of Cell Biology  2007;179(5):845-854.
Positioning of telomeres at the nuclear periphery can have dramatic effects on gene expression by establishment of heritable, transcriptionally repressive subdomains. However, little is known about the integral membrane proteins that mediate telomere tethering at the nuclear envelope. Here, we find a previously unrecognized function for the Saccharomyces cerevisiae Sad1-UNC-84 domain protein Mps3 in regulating telomere positioning in mitotic cells. Our data demonstrate that the nucleoplasmic N-terminal acidic domain of Mps3 is not essential for viability. However, this acidic domain is necessary and sufficient for telomere tethering during S phase and the silencing of reporter constructs integrated at telomeres. We show that this is caused by the role of the Mps3 acidic domain in binding and localization of the silent information regulator protein Sir4 to the nuclear periphery. Thus, Mps3 functions as an integral membrane anchor for telomeres and is a novel nuclear receptor for the Sir4 pathway of telomere tethering and gene inactivation.
PMCID: PMC2099192  PMID: 18039933
5.  The Sad1-UNC-84 homology domain in Mps3 interacts with Mps2 to connect the spindle pole body with the nuclear envelope 
The Journal of Cell Biology  2006;174(5):665-675.
The spindle pole body (SPB) is the sole site of microtubule nucleation in Saccharomyces cerevisiae; yet, details of its assembly are poorly understood. Integral membrane proteins including Mps2 anchor the soluble core SPB in the nuclear envelope. Adjacent to the core SPB is a membrane-associated SPB substructure known as the half-bridge, where SPB duplication and microtubule nucleation during G1 occurs. We found that the half-bridge component Mps3 is the budding yeast member of the SUN protein family (Sad1-UNC-84 homology) and provide evidence that it interacts with the Mps2 C terminus to tether the half-bridge to the core SPB. Mutants in the Mps3 SUN domain or Mps2 C terminus have SPB duplication and karyogamy defects that are consistent with the aberrant half-bridge structures we observe cytologically. The interaction between the Mps3 SUN domain and Mps2 C terminus is the first biochemical link known to connect the half-bridge with the core SPB. Association with Mps3 also defines a novel function for Mps2 during SPB duplication.
PMCID: PMC2064310  PMID: 16923827

Results 1-5 (5)