Herein I describe a genetic study that employed a temperature-sensitive allele encoding the Golgi glycosyltransferase sorting receptor VPS74. Through characterizing genes that act as dosage suppressors of the temperature-sensitivity of vps74-1 cells several genes that function in protein trafficking between the ER and Golgi were identified. In addition to trafficking genes, unexpectedly, genes involved in cell cycle regulation were also identified. In this thesis I focused on establishing the functional significance to vps74-1 cells of a subset of the cell cycle genes involved in the spindle assembly checkpoint. Through a succession of genetic studies, pharmacological and cell biological approaches I establish that vps74-1 cells are defective in the processing of glycosylphospha...[ Read more ]

Herein I describe a genetic study that employed a temperature-sensitive allele encoding the Golgi glycosyltransferase sorting receptor VPS74. Through characterizing genes that act as dosage suppressors of the temperature-sensitivity of vps74-1 cells several genes that function in protein trafficking between the ER and Golgi were identified. In addition to trafficking genes, unexpectedly, genes involved in cell cycle regulation were also identified. In this thesis I focused on establishing the functional significance to vps74-1 cells of a subset of the cell cycle genes involved in the spindle assembly checkpoint. Through a succession of genetic studies, pharmacological and cell biological approaches I establish that vps74-1 cells are defective in the processing of glycosylphosphatidylinositol anchored proteins. The defect in the processing of glycosylphosphatidylinositol anchored proteins in vps74-1 cells is a consequence of mutations in two glycosylphosphatidylinositol anchored protein remodelases termed Ted1p and Dcr2p. I have determined defects in the remodeling of glycosylphosphatidylinositol anchored proteins - specifically the removal of phosphoethanolamine from mannose 2 of yeast glycosylphosphatidylinositol anchored proteins results in activation of the spindle assembly checkpoint.