The Global Transcriptional Activator of \u3ci\u3eSaccharomyces cerevisiae\u3c/i\u3e, Gcr1p, Mediates the Response to Glucose by Stimulating Protein Synthesis and \u3ci\u3eCLN\u3c/i\u3e-dependent Cell Cycle Progression

Growth of Saccharomyces cerevisiae requires coordination of cell cycle events (e.g., new cell wall deposition) with constitutive functions like energy generation and duplication of protein mass. The latter processes are stimulated by the phosphoprotein Gcr1p, a transcriptional activator that operates through two different Rap1p-mediated mechanisms to boost expression of glycolytic and ribosomal protein genes, respectively. Simultaneous disruption of both mechanisms results in a loss of glucose responsiveness and a dramatic drop in translation rate. Since a critical rate of protein synthesis (CRPS) is known to mediate passage through Start and determine cell size by modulating levels of Cln3p, we hypothesized that CCR1 regulates cell cycle progression by coordinating it with growth. We therefore constructed and analyzed gcr1Δ cln3Δ and gcr1Δ cln1Δ cln2Δ strains. Both strains are temperature and cold sensitive; interestingly, they exhibit different arrest phenotypes. The gcr1Δ cln3Δ strain becomes predominantly unbudded with 1N DNA content (G1 arrest), whereas gcr1Δ cln1Δ cln2Δ cells exhibit severe elongation and apparent M phase arrest. Further analysis demonstrated that the Rap1p/Gcr1p complex mediates rapid growth in glucose by stimulating both cellular metabolism and CLN transcription