The Saccharomyces cerevisiae genes KRE6 and SKN1 encode a novel pair of highly homologous proteins involved in cell wall (1$ rightarrow$6)-$ beta$-glucan assembly. Disruption of KRE6 results in a slow growing, killer-toxin resistant mutant possessing reduced levels of structurally wild type (1$ rightarrow$6)-$ beta$-glucan. Although deletion of SKN1 has no effect on killer sensitivity, growth, or (1$ rightarrow$6)-$ beta$-glucan levels, SKN1 appears to overlap in function with KRE6, suppressing kre6 null alleles in a dosage-dependent manner. Strains deleted of both KRE6 and SKN1 possess an exaggerated growth phenotype, enhanced cell wall ultrastructure defects, and more severe (1$ rightarrow$6)-$ beta$-glucan reductions compared with either single disruptant. Moreover, the residual (1$ rightarrow$6)-$ beta$-glucan polymer in kre6 skn1 double mutants is smaller in size and altered in structure. Since single disruptions of either gene lead to structurally wild type (1$ rightarrow$6)-$ beta$-glucan, KRE6 and SKN1 appear to function independently and to act early in the assembly of the polymer, possibly as glucan synthases. Consistent with their direct role in the assembly of this polymer, both Kre6p and Skn1p possess C-terminal domains with significant sequence similarity to two recently identified glucan-binding proteins. / An initial characterization of Kre6p and Skn1p reveal both to be phosphorylated integral-membrane glycoproteins, with Kre6p likely localized to the Golgi apparatus. The topology implied by the post-translational modifications of Kre6p and Skn1p, offers the potential for both proteins to link cytoplasmic regulation with a secretory pathway-based assembly of the (1$ rightarrow$6)-$ beta$-glucan polymer. The observed phosphorylation of both Kre6p and Skn1p prompted an examination for genetic interactions with suspected cell wall regulating kinases. KRE6-dependent suppression of the pkc1 lysis defect, as well as synthetic lethal interactions between several KRE genes and members of the PKC1-mediated MAP kinase pathway, supports a role for the PKC1 pathway in regulating synthesis of cell wall components, including (1$ rightarrow$6)-$ beta$-glucan.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28900 |
| Date | January 1994 |
| Creators | Roemer, Terry |
| Contributors | Bussey, H. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001467856, proquestno: NN05783, Theses scanned by UMI/ProQuest. |
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