Figure 7.

Cells lacking rum1 do not delay progression through G1 upon nutritional shift-down experiments. Asynchronous cultures of the indicated strains were grown at 25°C in minimal medium containing 20 mM NH₄Cl supplemented with 0.5% yeast extract and then shifted to minimal medium containing 20 mM l-proline instead of NH₄Cl as a nitrogen source. A small population of G1 cells was detected in the wild type and the cig1⁺ deletion upon the shift. This population increased in cells deleted for cig2⁺ and puc1⁺. In the triple mutant cig1Δ cig2Δ puc1Δ, the percentage of cells in G1 increased to 80%. Deletion of rum1⁺ completely abolished this G1 population.