Abstract #85A

Identification and Analysis of Genes that Interact with the Spindle Pole Body component Mps3. Adriana Martin¹, Charlie Boone², Sue Jaspersen¹. 1) Stowers Institute for Medical Research, Kansas City, MO; 2) Banting & Best Department of Medical Research, Toronto, ON.
   Mps3 is an essential integral membrane protein that localizes to the inner nuclear envelope and to the spindle pole body (SPB) half-bridge. We have shown that Mps3 is the budding yeast member of the SUN (for Sad1-UNC84 homology) family of proteins. Characterized by a 150 amino acid region of homology in their C-termini, SUN domain proteins are thought to bridge the inner and outer nuclear membranes to connect the nucleus with the cytoskeleton. Analysis of mutants in the Mps3SUN domain indicates a defect in the structural integrity of the SPB. As a result, mps3-SUN mutants display defects in SPB duplication. To better understand the function of SUN proteins in the cell as well as to identify Mps3 binding partners and regulators, we performed synthetic genetic analysis using mps3 SUN domain mutants. The genetic interactions we identified showed an enrichment for genes involved in microtubule dynamics and the spindle checkpoint, consistent with Mps3’s known function in SPB duplication and spindle assembly. We also found several classes of chromosome binding proteins, such as histones and histone acetyltransferases/deacetylases, certain kinetochore components, transcriptional regulators and telomere binding proteins. These show genetic interactions with mps3 mutants, suggesting Mps3 may interact with chromosomes and play a role in regulating chromatin structure, transcription and/or DNA segregation in the nucleus. The screen showed that several kinases/phosphatases, proteosome subunits and nuclear pore complex proteins are essential for the viability of mps3-SUN mutants. We are currently testing the role of all interacting genes in Mps3 localization, phosphorylation and stability, and have developed a method to identify Mps3 binding partners by co-immunoprecipitation. Our analysis of Mps3 regulation and binding partners in the genetically tractable yeast system will help us better understand the function of other SUN proteins in higher eukaryotes.

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