Project Summary/Abstract Yeast cells need to rapidly control their cell cycle profile, gene expression or protein stability in response to the activation of stress response pathways. It is common for cells to suffer from various attacks to their plasma membrane and cell wall, such as physical damage, pathogen invasion and various environmental perturbations. Here we propose to study that plasma membrane stress inhibits cell growth and DNA replication through a novel cell cycle checkpoint pathway. Eukaryotic cells duplicate their chromosomes. Errors in the DNA replication control could lead to chromosome instability which is a hallmark of cancer. Our long- term goal is to understand the molecular mechanism of DNA replication control in response to stress. In this proposal, three aims will test my hypothesis if plasma membrane damage inhibits polarized cell growth and DNA replication through a novel cell cycle checkpoint pathway. Aim1 will determine how membrane damage drives Pkc1 relocation to inhibit polarized cell growth. Aim2 will determine how plasma membrane stress signal activates Mpk1 to inhibit DNA replication. Aim3 will determine if a yeast GSK-3 kinase Mck1 targets replication proteins upon plasma membrane stress DNA replication and membrane integrity pathways are well conserved from yeast to humans. The results obtained from this study can be applied to understand the molecular mechanism of DNA replication control in response to stress in higher eukaryotes.