Tomishige Nario, Noda Yoichi, Adachi Hiroyuki, Shimoi Hitoshi, Yoda Koji
Department of Biotechnology, University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan.
Yeast. 2005 Jan 30;22(2):141-55. doi: 10.1002/yea.1206.
The fungal GAS1-related genes encode GPI-anchored beta-1,3-glucanosyltransferase, and their loss causes a defect in the assembly of the cell wall. The KEX2 gene encodes a processing protease in the late Golgi compartment and its loss also results in defects in the cell wall. Simultaneous mutations of these genes are lethal in Saccharomyces cerevisiae. To understand the basis of this synthetic lethality, we screened for multicopy suppressors and identified 13 SKG (suppressor of kex2 gas1 synthetic lethality) genes. SKG1 encodes a transmembrane protein that localizes on the inner surface of the plasma membrane at the bud and in the daughter cell. The multicopy SKG1 increases the sensitivity of cells to zymolyase, and the skg1Delta null mutation increases resistance to it. This zymolyase susceptibility corresponds to an increase of alkali-soluble beta-1,3-glucan and a decrease of chitin in the cell wall. Thus SKG1 encodes a novel protein that affects the cell wall polymer composition in the growing region of the cell.
真菌中与GAS1相关的基因编码糖基磷脂酰肌醇（GPI）锚定的β-1,3-葡聚糖基转移酶，这些基因的缺失会导致细胞壁组装缺陷。KEX2基因在高尔基体晚期区室中编码一种加工蛋白酶，其缺失也会导致细胞壁缺陷。这些基因的同时突变在酿酒酵母中是致死的。为了理解这种合成致死性的基础，我们筛选了多拷贝抑制子并鉴定出13个SKG（KEX2 GAS1合成致死性的抑制子）基因。SKG1编码一种跨膜蛋白，定位于芽和子细胞中质膜的内表面。多拷贝的SKG1增加了细胞对溶菌酶的敏感性，而skg1Delta缺失突变则增加了细胞对溶菌酶的抗性。这种对溶菌酶的敏感性对应于细胞壁中碱溶性β-1,3-葡聚糖的增加和几丁质的减少。因此，SKG1编码一种新型蛋白质，它会影响细胞生长区域的细胞壁聚合物组成。
