Repression of ribosome and tRNA synthesis in secretion-defective cells is signaled by a novel branch of the cell integrity pathway

The transcription of ribosomal DNA, ribosomal protein (RP) genes, and 5S an d tRNA genes by RNA polymerases (Pols) I, II, and III, respectively, is rap idly and coordinately repressed upon interruption of the secretory pathway in Saccharomyces cerevisiae. We find that repression of ribosome and tRNA s ynthesis in secretion-defective cells involves activation of the cell integ rity pathway. Transcriptional repression requires the upstream components o f this pathway, including the Wsc family of putative plasma membrane sensor s and protein kinase C (PKC), but not the downstream Bck1-Mkk1/2-Slt2: mito gen-activated protein kinase cascade. These findings reveal a novel PKC eff ector pathway that controls more than 85% of nuclear transcription. It is p roposed that the coordination of ribosome and tRNA synthesis with cell grow th may be achieved, in part, by monitoring the turgor pressure of the cell.