Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba Prefecture 277-8562, Japan.
AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory (OPERANDO-OIL), National Institute of Advanced Industrial Science and Technology (AIST), Bldg. Kashiwa Research Complex 2, 5-1-5 Kashiwanoha, Kashiwa, Chiba Prefecture 277-8565, Japan.
J Cell Sci. 2018 Jul 9;131(13):jcs219063. doi: 10.1242/jcs.219063.
The cell wall integrity checkpoint monitors synthesis of cell wall materials during the cell cycle. Upon perturbation of cell wall synthesis, the cell wall integrity checkpoint is activated, downregulating Clb2 transcription. Here, we identified genes involved in this checkpoint by genetic screening of deletion mutants. In addition to the previously identified dynactin complex, the Las17 complex, in particular the Bzz1 and Vrp1 components, plays a role in this checkpoint. We also revealed that the high osmolarity glycerol (HOG) and cell wall integrity mitogen-activated protein kinase (MAPK) signaling pathways are essential for checkpoint function. The defective checkpoint caused by the deficient dynactin and Las17 complexes was rescued by hyperactivation of the cell wall integrity MAPK pathway, but not by the activated form of Hog1, suggesting an order to these signaling pathways. Mutation of Fkh2, a transcription factor important for Clb2 expression, suppressed the checkpoint-defective phenotype of Las17, HOG MAPK and cell wall integrity MAPK mutations. These results provide genetic evidence that signaling from the cell surface regulates the downstream transcriptional machinery to activate the cell wall integrity checkpoint.
细胞壁完整性检查点在细胞周期中监测细胞壁物质的合成。当细胞壁合成受到干扰时，细胞壁完整性检查点被激活，下调 Clb2 转录。在这里，我们通过对缺失突变体的遗传筛选鉴定了参与这个检查点的基因。除了先前鉴定的动力蛋白复合物外，Las17 复合物，特别是 Bzz1 和 Vrp1 成分，在这个检查点中发挥作用。我们还揭示了高渗透压甘油（HOG）和细胞壁完整性丝裂原活化蛋白激酶（MAPK）信号通路对于检查点功能至关重要。由动力蛋白和 Las17 复合物缺陷引起的有缺陷的检查点被细胞壁完整性 MAPK 通路的过度激活所挽救，但不能被 Hog1 的激活形式挽救，这表明这些信号通路存在一个顺序。转录因子 Fkh2 对于 Clb2 表达很重要，其突变抑制了 Las17、HOG MAPK 和细胞壁完整性 MAPK 突变体的检查点缺陷表型。这些结果提供了遗传证据，表明来自细胞表面的信号调节下游转录机制以激活细胞壁完整性检查点。
