The role ofbro1p in the maintenance of cell integrity in Saccharomyces cerevisiae

The maintenance of cell integrity in the budding yeast Saccharomyces cerevisiae requires the coordinate regulation of basic cellular processes such as gene expression, vesicular trafficking, and organization of the actin cytoskeleton. One signal required for the maintenance of cell integrity is mediated by a modular mitogen-activated protein (MAP) kinase pathway in which the following protein kinases are activated in series via phosphorylation: Bck1p-Mkk1/2p-Mpk1p. Bck1p is activated through phosphorylation by Pkc1p, yeast homolog of mammalian protein kinase C. Mutations affecting this kinase cascade result in a cell-lysis defect during polarized growth, but the mechanism by which the Pkc1p-MAP kinase pathway promotes the maintenance of cell integrity remains unclear. Although several other genes have been identified in which mutations confer cell-lysis defects and which interact genetically with the Pkc1p-MAP kinase pathway, only two encode proteins which have been implicated in specific processes.;Yeast cells with mutations in BRO1 display growth phenotypes similar to those caused by mutations in components of the cell integrity MAP kinase pathway. In some strain backgrounds, bro1 cells exhibit a temperature-sensitive growth defect that is suppressed by the addition of osmotic stabilizers or Ca...