Roemer T, Paravicini G, Payton M A, Bussey H
Biology Department, McGill University, Montreal, Quebec, Canada.
J Cell Biol. 1994 Oct;127(2):567-79. doi: 10.1083/jcb.127.2.567.
A characterization of the S. cerevisiae KRE6 and SKN1 gene products extends previous genetic studies on their role in (1-->6)-beta-glucan biosynthesis (Roemer, T., and H. Bussey. 1991. Yeast beta-glucan synthesis: KRE6 encodes a predicted type II membrane protein required for glucan synthesis in vivo and for glucan synthase activity in vitro. Proc. Natl. Acad. Sci. USA. 88:11295-11299; Roemer, T., S. Delaney, and H. Bussey. 1993. SKN1 and KRE6 define a pair of functional homologs encoding putative membrane proteins involved in beta-glucan synthesis. Mol. Cell. Biol. 13:4039-4048). KRE6 and SKN1 are predicted to encode homologous proteins that participate in assembly of the cell wall polymer (1-->6)-beta-glucan. KRE6 and SKN1 encode phosphorylated integral-membrane glycoproteins, with Kre6p likely localized within a Golgi subcompartment. Deletion of both these genes is shown to result in a dramatic disorganization of cell wall ultrastructure. Consistent with their direct role in the assembly of this polymer, both Kre6p and Skn1p possess COOH-terminal domains with significant sequence similarity to two recently identified glucan-binding proteins. Deletion of the yeast protein kinase C homolog, PKC1, leads to a lysis defect (Levin, D. E., and E. Bartlett-Heubusch. 1992. Mutants in the S. cerevisiae PKC1 gene display a cell cycle-specific osmotic stability defect. J. Cell Biol. 116:1221-1229). Kre6p when even mildly overproduced, can suppress this pkc1 lysis defect. When mutated, several KRE pathway genes and members of the PKC1-mediated MAP kinase pathway have synthetic lethal interactions as double mutants. These suppression and synthetic lethal interactions, as well as reduced beta-glucan and mannan levels in the pkc1 null wall, support a role for the PKC1 pathway functioning in cell wall assembly. PKC1 potentially participates in cell wall assembly by regulating the synthesis of cell wall components, including (1-->6)-beta-glucan.
酿酒酵母KRE6和SKN1基因产物的特性扩展了先前关于它们在（1→6）-β-葡聚糖生物合成中作用的遗传学研究（Roemer, T., 和H. Bussey. 1991. 酵母β-葡聚糖合成：KRE6编码一种预测的II型膜蛋白，在体内葡聚糖合成和体外葡聚糖合酶活性中是必需的。美国国家科学院院刊。88:11295 - 11299；Roemer, T., S. Delaney, 和H. Bussey. 1993. SKN1和KRE6定义了一对功能同源物，编码参与β-葡聚糖合成的假定膜蛋白。分子细胞生物学。13:4039 - 4048）。预测KRE6和SKN1编码参与细胞壁聚合物（1→6）-β-葡聚糖组装的同源蛋白。KRE6和SKN1编码磷酸化的整合膜糖蛋白，Kre6p可能定位于高尔基体亚区室。这两个基因的缺失导致细胞壁超微结构的显著紊乱。与它们在这种聚合物组装中的直接作用一致，Kre6p和Skn1p都具有COOH末端结构域，与最近鉴定的两种葡聚糖结合蛋白具有显著的序列相似性。酵母蛋白激酶C同源物PKC1的缺失导致裂解缺陷（Levin, D. E., 和E. Bartlett - Heubusch. 1992. 酿酒酵母PKC1基因中的突变体表现出细胞周期特异性的渗透稳定性缺陷。细胞生物学杂志。116:1221 - 1229）。当Kre6p即使轻度过量表达时，也能抑制这种pkc1裂解缺陷。当发生突变时，几个KRE途径基因和PKC1介导的MAP激酶途径成员作为双突变体具有合成致死相互作用。这些抑制和合成致死相互作用，以及pkc1缺失细胞壁中β-葡聚糖和甘露聚糖水平的降低，支持PKC1途径在细胞壁组装中发挥作用。PKC1可能通过调节细胞壁成分（包括（1→6）-β-葡聚糖）的合成来参与细胞壁组装。
