Lesage Guillaume, Shapiro Jesse, Specht Charles A, Sdicu Anne-Marie, Ménard Patrice, Hussein Shamiza, Tong Amy Hin Yan, Boone Charles, Bussey Howard
Department of Biology, McGill University, Montréal (PQ) H3A 1B1, Canada.
BMC Genet. 2005 Feb 16;6:8. doi: 10.1186/1471-2156-6-8.
In S. cerevisiae the beta-1,4-linked N-acetylglucosamine polymer, chitin, is synthesized by a family of 3 specialized but interacting chitin synthases encoded by CHS1, CHS2 and CHS3. Chs2p makes chitin in the primary septum, while Chs3p makes chitin in the lateral cell wall and in the bud neck, and can partially compensate for the lack of Chs2p. Chs3p requires a pathway of Bni4p, Chs4p, Chs5p, Chs6p and Chs7p for its localization and activity. Chs1p is thought to have a septum repair function after cell separation. To further explore interactions in the chitin synthase family and to find processes buffering chitin synthesis, we compiled a genetic interaction network of genes showing synthetic interactions with CHS1, CHS3 and genes involved in Chs3p localization and function and made a phenotypic analysis of their mutants.
Using deletion mutants in CHS1, CHS3, CHS4, CHS5, CHS6, CHS7 and BNI4 in a synthetic genetic array analysis we assembled a network of 316 interactions among 163 genes. The interaction network with CHS3, CHS4, CHS5, CHS6, CHS7 or BNI4 forms a dense neighborhood, with many genes functioning in cell wall assembly or polarized secretion. Chitin levels were altered in 54 of the mutants in individually deleted genes, indicating a functional relationship between them and chitin synthesis. 32 of these mutants triggered the chitin stress response, with elevated chitin levels and a dependence on CHS3. A large fraction of the CHS1-interaction set was distinct from that of the CHS3 network, indicating broad roles for Chs1p in buffering both Chs2p function and more global cell wall robustness.
Based on their interaction patterns and chitin levels we group interacting mutants into functional categories. Genes interacting with CHS3 are involved in the amelioration of cell wall defects and in septum or bud neck chitin synthesis, and we newly assign a number of genes to these functions. Our genetic analysis of genes not interacting with CHS3 indicate expanded roles for Chs4p, Chs5p and Chs6p in secretory protein trafficking and of Bni4p in bud neck organization.
在酿酒酵母中，β-1,4-连接的N-乙酰葡糖胺聚合物几丁质由CHS1、CHS2和CHS3编码的3种专门但相互作用的几丁质合酶家族合成。Chs2p在初级隔膜中合成几丁质，而Chs3p在侧细胞壁和芽颈中合成几丁质，并且可以部分补偿Chs2p的缺失。Chs3p需要Bni4p、Chs4p、Chs5p、Chs6p和Chs7p的途径来实现其定位和活性。Chs1p被认为在细胞分离后具有隔膜修复功能。为了进一步探索几丁质合酶家族中的相互作用，并找到缓冲几丁质合成的过程，我们编制了一个基因相互作用网络，该网络包含与CHS1、CHS3以及参与Chs3p定位和功能的基因表现出合成相互作用的基因，并对它们的突变体进行了表型分析。
在合成遗传阵列分析中使用CHS1、CHS3、CHS4、CHS5、CHS6、CHS7和BNI4中的缺失突变体，我们构建了一个由163个基因之间的316个相互作用组成的网络。与CHS3、CHS4、CHS5、CHS6、CHS7或BNI4的相互作用网络形成了一个密集的邻域，许多基因在细胞壁组装或极化分泌中发挥作用。在单个缺失基因的54个突变体中，几丁质水平发生了改变，表明它们与几丁质合成之间存在功能关系。其中32个突变体触发了几丁质应激反应，几丁质水平升高且依赖于CHS3。CHS1相互作用集的很大一部分与CHS3网络不同，表明Chs1p在缓冲Chs2p功能和更全局的细胞壁稳健性方面具有广泛作用。
基于它们的相互作用模式和几丁质水平，我们将相互作用的突变体分为功能类别。与CHS3相互作用的基因参与细胞壁缺陷的改善以及隔膜或芽颈几丁质的合成，并且我们新确定了一些基因具有这些功能。我们对不与CHS3相互作用的基因的遗传分析表明，Chs4p、Chs5p和Chs6p在分泌蛋白运输中的作用扩大，而Bni4p在芽颈组织中的作用扩大。
